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Highlights Biomimetic polymer composites with micro/nano‐scale brick‐and‐mortar structures show promise for advancing nacre‐like polymer bioinspired nanocomposites. This study used a solvothermal method to graft MIL‐101 onto graphene oxide (GO), forming GO‐g‐MIL‐101. Subsequent heat treatments at 700 and 900°C under inert gas produced magnetic graphene nanosheets (GNS@Fe) with iron oxide particles. Poly(trimethylene terephthalate) (PTT) served as the matrix. PTT/GNS@Fe powders were prepared by coagulation then formed into bioinspired PTT/GNS@Fe and PTT/GNS@Fe‐m composites via solvent casting and hot pressing, yielding brick‐and‐mortar structures with and without magnetic alignment. PTT served as the soft phase and GNS@Fe as the hard phase. Rheological and conductivity analysis of PTT bioinspired composites, based on percolation theory, revealed microstructural changes. Results show that magnetic field assistance enhances GNS@Fe alignment in PTT/GNS@Fe‐m composites. With higher GNS@Fe content, reduced interlayer spacing creates a PTT‐GNS@Fe network, where nanoscale confinement limits PTT chain mobility, impacting crystallization. Low GNS@Fe levels promote crystallization, while high levels hinder it, with PTT unable to crystallize in nacre‐like composites above 40 wt% GNS@Fe. Additionally, we tested the electromagnetic interference (EMI) shielding of the PTT/GNS@Fe bioinspired composite system, finding that the shielding efficiency of PTT/GNS@Fe‐m with 40 wt% filler, though affected in magnetism by processing, approaches commercial application levels. Rheological and conductivity analysis via percolation theory. Percolation analysis revealed microstructures in the nacre‐like composite. Magnetic self‐assembly in PTT/GNS@Fe‐m led to more oriented structures. Higher GNS@Fe content reduced spacing, forming PTT‐GNS@Fe networks. Nanoconfinement and adsorption limited PTT chains, reducing crystallinity. [ABSTRACT FROM AUTHOR]

The evolution of natural armor materials has led to gradient structures with specific architectures to achieve high damage tolerance, thus offering valuable inspiration for the design of man‐made materials. Here, bioinspired gradient composites with a nacre‐like brick‐and‐mortar architecture are fabricated by infiltrating a polymer phase into porous ceramic scaffolds with position‐specific ceramic content. These composites demonstrate an integrated structure with notable several‐fold variations in local hardness and modulus across the thickness. The asymmetric mechanical properties and toughening mechanisms of the composites are investigated and compared to those of uniform composites. Specifically, when loaded along the direction of decreasing stiffness – resembling the typical loading configuration of natural armors, the gradient composites exhibit superior damage tolerance compared to the opposite direction and a uniform composite with equivalent ceramic content. This is attributed to the decreased peak stress, broader stress distribution, and increased deformation capacity, along with enhanced toughening effects that impede crack growth through mechanisms of crack deflection, crack bridging by uncracked ligaments, together with their frictional pull‐out from crack surfaces. This study deepens the understanding of the damage tolerance of gradient materials and offers insights for the bioinspired design of highly damage‐tolerant materials. [ABSTRACT FROM AUTHOR]

Nacre has excellent balanced strength and toughness. In this paper, the mechanical performance of the typical "brick-and-mortar" structure, including the stress–strain and strain at the interface as well as the stress in the bricks, was calculated by a simplified analytical model of the nacre. This paper proposes a new method to control the crack deflection based on the toughening mechanism of the nacre. The crack extension of the "brick-and-mortar" structure was simulated using cohesive elements based on the traction–separation law with elastic and softening stiffness as variables, and it was found that both stiffness could effectively control the crack extension. The strength and toughness of the models with different stiffness combinations were calculated and plotted as a function of elastic stiffness and softening stiffness, showing that elastic stiffness significantly affects strength and softening stiffness is a determinant of toughness. [ABSTRACT FROM AUTHOR]

Bioinspiration offers alternative solutions to overcome the inherent drawbacks of glass, such as low fracture toughness, strength, and impact resistance. Synthetic composites inspired by natural materials, such as nacre, have been recently introduced as an alternative to glasses. However, these have all suffered from trade‐offs between rigidity, optical clarity, fabrication scalability, and complexity. Here, two wave‐based fabrication techniques are presented to create a nacreous structure from glass flakes and polymethyl methacrylate. The glass's surface energy is controlled by adjusting the silane coverage on the glass surface, enabling high levels of structural compactness, mechanical properties, and optical clarity. The scalable glass composite, with a ≈60% glass volume fraction, possesses strength, fracture toughness, and impact resistance values, outperforming annealed glass by 4300%, 350%, and 400%, respectively. It also has a haze level of ≈18%, almost 60% less than that of the similar centrifuged‐based glass composite. This composite is proposed as a potential glass alternative in diverse applications. [ABSTRACT FROM AUTHOR]

This review focus on the current advances of freezing-derived functional materials, involving the design rationale (freezing stratagems and curing methods) of material fabrication and various applications, including mechanical, thermal, energy, environmental, and biomedical applications. The emphasis is put on the correlations among multiscale structures, extraordinary properties and multifarious applications. Promising research directions and challenges about the freezing processing tools are also presented. [Display omitted] Ice-templating, also known as freeze-casting, has emerged as a novel and versatile processing technology in various applications such as strong and tough structured materials, thermal management, energy storage and conversion, biomedical engineering, and so on. By replicating the fractal ice crystal structure, both multiscale hierarchical architectures (from macroscale to micrometer-, and nanometer-scales) and corresponding unique structure-derived functions can be achieved. This review focus on the current advances of freezing-derived functional materials, involving the design rationale (freezing strategies and curing methods) of material fabrication and various applications, including mechanical, thermal, energy, environmental, and biomedical applications. Opportunities (promising research directions and new application scenarios) and challenges about the ice-templating tools are also presented. [ABSTRACT FROM AUTHOR]

The freshwater pearl mussel, Lamellidens marginalis, is widely distributed in India and is cultured for freshwater pearl production. Understanding the biomineralisation process sheds light on the genes responsible for nacre secretion. However, information on the transcriptome of L. marginalis mantle tissue and pearl sac is lacking. This study generated transcriptome resources for L. marginalis, identifying genes involved in biomineralisation. Illumina paired-end sequencing yielded 11.13 million raw reads, assembled into 133,246 contigs and 26,373 unigenes. Of these, 21,033 unigenes exhibited homology with previously reported molluscan proteins. Genes related to biomineralisation, such as pif, perlucin, calreticulin, calmodulin, chitin synthase, chitin dehydrogenase, carbonic anhydrase, tyrosinase, shell matrix protein, dermatopontin isoform X1, chitinase 3, chitinase domain-containing protein 1, and putative chitinase-1were identified. This baseline information will help to compare the expression levels between the phenotypes of high-quality and low-quality pearls. Further investigations, incorporating large sample sizes and phenotype information, could assist in identifying type I genetic markers linked to pearl quality. [ABSTRACT FROM AUTHOR]

Adoration of the Magi (ca. 1695–1700), an enconchado painting attributed to Miguel González, active in Mexico in the late seventeenth century, exemplifies the refinement of the arts produced in Spanish America as a response to the taste for Asian goods during the seventeenth and eighteenth centuries. The painting and its original mother-of-pearl inlaid frame were examined and analyzed using non-invasive and micro-sampling methods, an approach that permitted answering outstanding questions about the stratigraphy, pigments, and the use of shells throughout the painting and frame. The identification of the mother-of-pearl, determined to be from a Pinctada species, was a central focus of this study. In addition to the inlaid shells in the painting and frame, shell fragments were observed mixed with gypsum in the ground preparation of the painting by SEM–EDS. To our knowledge, this is a novel identification of marine shells in the ground of an easel painting. Traces of workmanship in the inlaid shells observed by SEM and optical microscopy are possibly connected to pre-Hispanic methodologies of mother-of-pearl refinement. [ABSTRACT FROM AUTHOR]

Nacre‐inspired materials with combined high strength and toughness have been widely developed and utilized for various engineering applications. However, existing preparation techniques suffer from intricate processes, high energy‐consumption, and lack of scalability, all of which collectively impede the efficient production of three‐dimensional materials. Here, a viable strategy is reported for the efficient and scalable production of bulk nacre‐mimetic materials, drawing inspiration from the intricate structures found in both nacre and wood. The prepared millimeter‐thick wooden artificial nacres (WANs) exhibit the presence of multi‐hierarchical lamellar structures, organic bridges, and micro‐asperities. Those features lead to the WANs exhibiting impressive mechanical performances, presenting excellent bending strength (≈93.31 MPa), toughness (≈7.40 MPa m1/2), tensile strength (≈122.59 MPa), and work of fracture (≈4.61 MJ m−3). In addition, owing to the low density (≈1.59 g cm−3), the WANs show much higher specific mechanical properties compared to nacre and related artificial nacre materials. Considering both its production process and exceptional properties, this material holds great promise for practical applications within the realm of engineering and structural fields. [ABSTRACT FROM AUTHOR]

Discoveries of two-dimensional (2D) materials, exemplified by the recent entry of MXene, have ushered in a new era of multifunctional materials for applications from electronics to biomedical sensors due to their superior combination of mechanical, chemical, and electrical properties. MXene, for example, can be designed for specialized applications using a plethora of element combinations and surface termination layers, making them attractive for highly optimized multifunctional composites. Although multiple critical engineering applications demand that such composites balance specialized functions with mechanical demands, the current knowledge of the mechanical performance and optimized traits necessary for such composite design is severely limited. In response to this pressing need, this paper critically reviews structure–function connections for highly mineralized 2D natural composites, such as nacre and exoskeletal of windowpane oysters, to extract fundamental bioinspired design principles that provide pathways for multifunctional 2D-based engineered systems. This paper highlights key bioinspired design features, including controlling flake geometry, enhancing interface interlocks, and utilizing polymer interphases, to address the limitations of the current design. Challenges in processing, such as flake size control and incorporating interlocking mechanisms of tablet stitching and nanotube forest, are discussed along with alternative potential solutions, such as roughened interfaces and surface waviness. Finally, this paper discusses future perspectives and opportunities, including bridging the gap between theory and practice with multiscale modeling and machine learning design approaches. Overall, this review underscores the potential of bioinspired design for engineered 2D composites while acknowledging the complexities involved and providing valuable insights for researchers and engineers in this rapidly evolving field. [ABSTRACT FROM AUTHOR]

Since ancient times, the shells of marine molluscs have been used as a therapeutic and/or prophylactic resource. In Spain, they were part of practical guides for doctors or pharmacists until the 19th century. In general, seashells were prepared by dissolving in vinegar and were part of plasters or powders used as toothpaste, or to treat dyspepsia, heartburn and leprosy. Thus, the nacre or mother-of-pearl of various molluscs was regularly used in the Royal Colleges of Surgery and in hospitals during the times of the Cortes of Cadiz, as a medicine in galenic preparations based on powders. In contemporary Spanish ethnomedicine, seashells, with a high symbolic value, have been used as an amulet to prevent cracks in the breasts and promote their development during lactation, to avoid teething pain in young children, to eliminate stains on the face or to cure erysipelas. But, as in other countries, products derived from seashells have also been empirically applied. The two resources used traditionally have been the cuttlebone, the internal shell of cuttlefish and the nacre obtained from the external shells of some species. Cuttlebone, dried and pulverised, has been applied externally to cure corneal leukoma and in dental hygiene. In the case of nacre, a distinction must be made between chemical and physical remedies. Certain seashells, macerated in lemon juice, were used in coastal areas to remove spots on the face during postpartum. However, the most common practice in Spain mainland was to dissolve mother-of-pearl buttons in lemon juice (or vinegar). The substance thus obtained has been used to treat different dermatological conditions of the face (chloasma, acne), as well as to eliminate freckles. For the extraction of foreign bodies in the eyes, a very widespread traditional remedy has been to introduce small mother-of-pearl buttons under the lid. These popular remedies and practices are compared with those collected in classic works of medicine throughout history, and data on the pharmacological activity and pharmaceutical applications of the products used are provided. The use of cuttlebone powders is supported by different works on anti-inflammatory, immune-modulatory and/or wound healing properties. Nacre powder has been used in traditional medicines to treat palpitations, convulsions or epilepsy. As sedation and a tranquilisation agent, nacre is an interesting source for further drug development. Likewise, nacre is a biomaterial for orthopaedic and other tissue bioengineering applications. This article is a historical, cultural and anthropological view that can open new epistemological paths in marine-derived product research. [ABSTRACT FROM AUTHOR]

The shell of a freshwater mussel (Mollusca: Bivalvia) is a composite biological material that plays an active role in maintaining ecosystem services. Mussel shells have variable structures both within and between species. In this study, the structural and biological characteristics of the shells of Potomida semirugata and Leguminaia wheatleyi were investigated in order to use freshwater mussel shells as a biological material. Close observation of the microstructure of the shells of the two common freshwater bivalves revealed a variation in construction from the outer periostracum to the inner nacreous layer. In P. semirugata, a polygonal arrangement with columnar prisms of different sizes was observed more significantly. In L. wheatleyi the prismatic columns are oval and irregularly polygonal. The nacreous layers of P. semirugata, in which the individual aragonite layers are horizontally overlapped, are more uniformly distributed. The overlapping of the aragonite sheets in L. wheatleyi is more irregular. The presence of calcium carbonate (CaCO3) in the shells was confirmed by the identification of the characteristic carbonate bands at 701.9, 713.5, and 865.8 cm-1. This information was used to classify and distinguish the different layers of the shells, allowing interspecific comparisons and variations in the different layers. The results clearly showed that shell samples were highly biocompatible and nontoxic compared to the control group. This finding suggests that these materials have promising potential for use in various biomedical applications where biocompatibility is a critical factor. The results indicated that the shells of the freshwater bivalves P. semirugata and L. wheatleyi are biological materials with potential multiple applications for human well-being and environmental quality. [ABSTRACT FROM AUTHOR]

Measurements of trace element chemistry, mineralogy, and isotope geochemistry are rarely combined with known environmental data to provide a more complete story about how environmental conditions are recorded in biomineral carbonates. Here, cultured (farmed) pearls serve as relatively pristine time capsules to study these geochemical and mineral-based proxies. Cathodoluminescence (CL) imaging and Raman spectroscopic mapping on the µm-scale reveals that heterogeneous crystal bonding environments, geochemistry, and organic contents across the growth history of a freshwater pearl reflect environmental shifts in Kentucky Lake, TN, USA. A major CL peak at 551 nm aligns with increased manganese and organic contents and correlates with lake conductivity and alkalinity data. These CL features are temporally offset from previous 10-µm-scale aragonite nacre oxygen isotope measurements (δ18O Arg) that record periods of minimum lake temperatures in winter seasons. Thus, we suggest that these trace element and organic features represent autumn or spring rainy seasons that experience lake turnover events and more land runoff rich in Mn and nutrients, increasing aragonite-bound Mn and organic contents in the nacre. This 551 nm signal is absent in Mn-poor saltwater pearl nacre. A second CL peak at 444 nm shows different heterogeneous features likely due to crystal structure shifts, as evidenced by correlations to a Raman map of translational (T): librational (L) mode height ratios typically signaling changes in nacre tablet orientation. Thus, we show that µm-scale CL and Raman mapping may serve as complementary environmental proxies to novel SIMS-based δ18O Arg temperature proxies in order to capture additional information about local lake environments at seasonal to sub-seasonal temporal resolutions. [ABSTRACT FROM AUTHOR]

Osteoporosis is a systemic bone disease characterized by low bone mass and micro- architectural change of bone tissue, leading to an increased bone fragility which can lead to secondary fractures. It has become one of the major factors affecting the quality of life in recent years, especially for the elderly. Currently, treatment drugs have problems with their efficacy and long-term use. Nacre contains osteogenic active substances, which has the potential to be used in osteoporosis and other bone diseases. The characteristics, extraction, and osteogenesis of active components in nacre are reviewed in this paper. [ABSTRACT FROM AUTHOR]

Biological structures possess excellent damage tolerance, which makes them attractive for ballistic protection applications. This paper develops a finite element modelling framework to investigate the performance of several biological structures that are most relevant for ballistic protection, including nacre, conch, fish scales, and crustacean exoskeleton. Finite element simulations were conducted to determine the geometric parameters of the bio-inspired structures that can survive projectile impact. The performances of the bio-inspired panels were benchmarked against a monolithic panel with the same 4.5 mm overall thickness and projectile impact condition. It was found that the biomimetic panels that were considered possessed better multi-hit resistant capabilities compared to the selected monolithic panel. Certain configurations arrested a fragment simulating projectile with an initial impact velocity of 500 m/s, which was similar to the performance of the monolithic panel. [ABSTRACT FROM AUTHOR]

• A probabilistic crack-bridging model is established accounting for the microstructural randomness of biological composites. • The microstructural randomness can decrease the macroscopic fracture toughness, reflecting the weakest-link principle. • The microscopic crack-bridging mechanism can suppress the negative impact of microstructural randomness. The macroscopic mechanical properties of biological composite materials, such as strength and fracture toughness, are determined by both their constituents and microstructure. Conventional researches often assume that these properties can be modeled using representative volume elements that features microstructural periodicity. However, in reality, such periodicity is absent, and the mechanical and geometric properties of the constituents exhibit spatial randomness, profoundly affecting the material's macroscopic behavior. In this study, we modify the classic crack-bridging model to account for microstructural randomness. Using the brick–mortar microstructure of nacre as an example, we investigate how microstructural randomness influences macroscopic fracture toughness and the mechanical properties of the crack-bridging zone. The results demonstrate that microstructural randomness weakens macroscopic fracture toughness, in line with the classic weakest-link principle. However, the randomness in macroscopic fracture toughness is significantly reduced compared to microstructural randomness, suggesting that the weakening effect induced by microstructural randomness is suppressed. Further analysis reveals that as the length of platelets increases, the weakening effect of microstructural randomness becomes less significant. This indicates that the microstructural stress transfer mechanism is responsible for suppressing the negative impact of microstructural randomness. Beyond the conventional strengthening and toughening effects, our results highlight a new advantage of well-designed microstructures in biological materials, offering deeper insights into how microscopic heterogeneity influences the macroscopic fracture toughness of these materials. [ABSTRACT FROM AUTHOR]

Innovations in impact-resistant materials design inspired by nacre's hierarchical "brick and mortar" structure have ushered a new era of lightweight biomimetics with exceptional strength and toughness. However, the role of microstructure, notably the effect of hierarchy, is hitherto poorly understood. Here, we investigate the impact resistance of graphene-polyethylene nanocomposites that are modeled after nacre's microstructure, capturing the behavior of the stiff (graphene) and soft (polyethylene) phases. Besides the dependence of the impact resistance on the graphene grain size and grafting between the phases, we show that it is the hierarchy that plays the most important role in drastically enhancing impact resistance, with the hierarchical nanocomposite showing up to a three-fold improvement in the ballistic limit without grafting, and a seven-fold increase in the presence of grafting. This research also sheds light on the detailed molecular mechanisms behind these enhancements that can be leveraged for the development of advanced biomimetic materials. [Display omitted] • Atomistic simulations study the microballistic performance of nacre-like graphene-polyethylene composite. • Impact resistance depends on graphene size, microstructure, and grafted polymer chains. • Discuss deformation mechanisms that govern the impact resistance are elucidated. [ABSTRACT FROM AUTHOR]

Due to their extraordinary prospective uses, particularly in the areas of oil–water separation, underwater superoleophobic materials have gained increasing attention. Thus, artificial nacre has become an attractive candidate for oil–water separation due to its superhydrophilicity and underwater superoleophobicity properties. Synthesized artificial nacre has successfully achieved a high mechanical strength that is close to or even surpasses the mechanical strength of natural nacre. This can be attributed to suitable synthesis methods, the selection of inorganic fillers and polymer matrices, and the enhancement of the mechanical properties through cross-linking, covalent group modification, or mineralization. The utilization of nacre-inspired composite membranes for emerging applications, i.e., is oily wastewater treatment, is highlighted in this review. The membranes show that full separation of oil and water can be achieved, which enables their applications in seawater environments. The self-cleaning mechanism's basic functioning and antifouling tips are also concluded in this review. [ABSTRACT FROM AUTHOR]

Organisms hold an extraordinarily evolutionary advantage in forming complex, hierarchical structures across different length scales that exhibit superior mechanical properties. Mimicking these structures for synthesizing high-performance materials has long held a fascination and has seen rapid growth in the recent past thanks to high-resolution microscopy, design, synthesis, and testing methodologies. Among the class of natural materials, nacre, found in mollusk shells, exhibits remarkably high mechanical strength and toughness. The highly organized "brick and mortar" structure at different length scales is a basis for excellent mechanical properties and the capability to dissipate energy and propagation in nacre. Here, we employ large-scale atomistic coarse-grained molecular dynamics simulations to study the mechanical and viscoelastic behavior of nacre-like microstructures. Uniaxial tension and oscillatory shear simulations were performed to gain insight into the role of complex structure-property relationships. Specifically, the role played by the effect of microstructure (arrangement of the crystalline domain) and polymer-crystal interactions on the mechanical and viscoelastic behavior is elucidated. The tensile property of the nanocomposite was seen to be sensitive to the microstructure, with a staggered arrangement of the crystalline tablets giving rise to a 20–30% higher modulus and lower tensile strength compared to a columnar arrangement. Importantly, the staggered microstructure is shown to have a highly tunable mechanical behavior with respect to the polymer-crystal interactions. The underlying reasons for the mechanical behavior are explained by showing the effect of polymer chain mobility and orientation and the load-carrying capacity for the constituents. Viscoelastic responses in terms of the storage and loss moduli and loss tangent are studied over three decades in frequency and again highlight the differences brought about by the microstructure. We show that our coarse-grained models offer promising insights into the design of novel biomimetic structures for structural applications. [ABSTRACT FROM AUTHOR]

Flexible substrates, essential for flexible electronics by providing support and flexibility while influencing sensor stability, still face challenges in achieving mechanical and thermal stability, particularly in large-scale production and cost control. Inspired by the nacre's "brick-and-mortar" hierarchical microstructure, this study introduces PPSN (paper/polydimethylsiloxane (PDMS)/Si₃N₄ nanoparticles), a novel flexible substrate that mimics the "brick-and-mortar" structure. PPSN, with its topological interlocking and assembly technique, provides excellent thermal and mechanical stability, including high-temperature resistance and stress dissipation. An optimized Si₃N₄ content of 1.0 wt% yields a peak elastic modulus of 1245.27 MPa while maintaining hydrophobicity, with a contact angle of 127.1° at 3.0 wt%. The substrate shows excellent fatigue durability, retaining its morphology after 10,000 bending cycles. Thermal analysis indicates a stable CTE below 20 ppm/°C up to 300°C, rising to 200 ppm/°C between 350 and 400°C. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) reveal minimal thermal decomposition with mass loss below 0.5 % from 25 to 300°C and under 3 % at 400°C. Additionally, electrodes were printed on the substrate using screen printing and ion beam deposition (IBD), demonstrating good material adhesion. A flexible temperature sensor was fabricated and exhibited good sensitivity and stability with a TCR of −0.262 % °C⁻¹. PPSN advances traditional materials with superior mechanical strength, thermal stability, and durability, offering significant scientific and practical value for flexible electronics and low-cost biomimetic processes. [Display omitted] • PPSN mimics nacre's structure, offering high thermal and mechanical stability. • Peak elastic modulus at 1.0 wt% Si₃N₄, with hydrophobicity and durability. • Stable CTE below 20 ppm/°C up to 300°C with minimal thermal mass loss. • Excellent performance in flexible sensors with a TCR of −0.262 % °C⁻¹. [ABSTRACT FROM AUTHOR]

The toughening mechanism of the nacre was widely investigated in recent decades, which presents a great prospect for designing high performance composite materials and engineering structures with bioinspired structures. To further elucidate which structural parameters and which kinds of morphology of the nacre-inspired structure are the best for improving tensile strength without sacrificing too much toughness is extremely significant for composite materials and engineering structures. The "brick-and-mortar" structure is a classical nacre-inspired bionic structure. Three characteristic structural parameters, including the aspect ratio ρ of the brick length and width, the thickness ratio β between the thickness of brick and mortar, and the spacing ratio τ between the width of brick and mortar, were used as variables to study their effect on tensile strength and toughness. It was found that ρ was the most prominent factor in determining the strength and toughness, and τ could improve the strength and toughness almost simultaneously. Racked and wedged morphology of the structural unit were established based on the structural parameters of the regular staggered unit, and were used to compare tensile behavior. It was found that the model with the wedged unit possessed the highest strength and toughness, and could absorb more strain energy during fracture crack growing. The crack propagation path further illustrated that the crack resisting ability of the wedged unit was the best. Our simulation results presented the connection between three characteristic structural parameters with the strength and toughness, and proved that the wedged staggered unit was the best in improving the strength and toughness. [ABSTRACT FROM AUTHOR]

Nacre is a biomaterial that has shown osteoinductive and osteoconductive properties in vitro and in vivo. These properties make nacre a material of interest for inducing bone regeneration. However, information is very limited regarding the introduction of nacre to dental implant surgery for promoting osteogenesis. This study investigated the potential of nacre powder for peri-implant bone regeneration in a porcine model. Ninety-six dental implants were placed into the tibia of twelve male domestic pigs. The dental implants were coated with nacre powder from the giant oyster before implantation. Implantations without nacre powder were used as control groups. Euthanization took place at 2, 4 and 6 weeks after implantation, after which we measured bone-to-implant contact (BIC) and bone volume density (BVD) of the implanted bone samples using micro-computed tomography (micro-CT), and examined the histology of the surrounding bone using histological sections stained with Stevenel's blue and Alizarin red S. The micro-CT analyses showed that the BIC of dental implantations with nacre powder were significantly higher than those without nacre powder, by 7.60%. BVD of implantations with nacre powder were significantly higher than those without nacre powder, by 12.48% to 13.66% in cortical bone, and by 3.37% to 6.11% in spongy bone. Histological study revealed more peri-implant bone regeneration toward the surface of the dental implants after implantation with nacre powder. This was consistent with the micro-CT results. This study demonstrates the feasibility of using nacre to promote peri-implant bone regeneration in dental implantation. [ABSTRACT FROM AUTHOR]

• Nacre-like composites were prepared with a simple process, including zirconia particles in monoclinic or in tetragonal phase. • A R-curve effect is noted for all samples, mainly driven by crack deflection along the platelet interfaces. • The addition of tetragonal zirconia increases the strength and limits the growth of alumina grains during sintering. • Composites with tetragonal zirconia and no glass phase are potential candidates for high temperature applications. Nacre-like alumina is a class of bio-inspired ceramic composite manufactured by field-assisted sintering of green bodies made primarily of alumina platelets with an anisotropic microstructure. Here we investigate the addition of zirconia particles to enhance the mechanical properties of the composite. The resulting structure is a nacre-like anisotropic structure which features deflection and reinforcement during crack propagation. Monoclinic zirconia has no impact on the mechanical properties of the composite while tetragonal zirconia improves its fracture resistance properties. Both types of zirconia seem to slow down grain growth during sintering. The addition of zirconia stabilised in the tetragonal phase is thus a good option to obtain a composite with a fine microstructure and higher mechanical properties than a standard nacre-like alumina, with a flexural strength of 626 ± 39 MPa and a crack initiation toughness of 6.1 ± 0.6 MPa.m0.5. [ABSTRACT FROM AUTHOR]

The excellent mechanical properties of nacre have attracted the research interest of countless scholars and inspired the optimal design of novel nacre-like materials. In recent years, studies have found that the interface between the mineral platelet and the organic layer of nacre has an uneven micro-topological structure, which has an interlocking effect during the deformation process, and plays a vital role in the mechanical response of nacre. The interlocking structure can increase the sliding resistance of the platelets to increase the fracture toughness. Based on this mechanism, we adapted a crack-bridging model to elucidate the influence of the interlocking angle on the fracture toughness and crack-bridging toughening effect of nacre. The critical interlocking angle and fracture toughness calculated by this model are consistent with the observed and actual experimental results in nacre. This model is of great significance for guiding the interface interlocking design of novel nacre-like materials. [ABSTRACT FROM AUTHOR]

A pearl's distinguished beauty and toughness are attributable to the periodic stacking of aragonite tablets known as nacre. Nacre has naturally occurring mesoscale periodicity that remarkably arises in the absence of discrete translational symmetry. Gleaning the inspiring biomineral design of a pearl requires quantifying its structural coherence and understanding the stochastic processes that influence formation. By characterizing the entire structure of pearls (~3 mm) in a cross-section at high resolution, we show that nacre has medium-range mesoscale periodicity. Self-correcting growth mechanisms actively remedy disorder and topological defects of the tablets and act as a countervailing process to longrange disorder. Nacre has a correlation length of roughly 16 tablets (~5.5 mm) despite persistent fluctuations and topological defects. For longer distances (>25 tablets, ~8.5 mm), the frequency spectrum of nacre tablets follows f-1.5 behavior, suggesting that growth is coupled to external stochastic processes--a universality found across disparate natural phenomena, which now includes pearls. [ABSTRACT FROM AUTHOR]

In an article published in Advanced Functional Materials, Allen Ehrlicher and his team have developed a nacreous glass composite that exhibits high strength, fracture toughness, optical transparency, and scalability in fabrication. The composite, which resembles the microstructure of natural nacre, is created using a mechanical wave-based technique. By fine-tuning the silane coverage on glass flakes, the researchers were able to improve the structural compactness and enhance optical clarity. This research has potential applications in the development of advanced composite materials. [Extracted from the article]

[Display omitted] • Developed a nacre-based calcium orthophosphates composite (NCOC) using a unique two-step self-setting technique, remodelling the human bone matrix. • NCOC showed a superior compression strength of 10 MPa, surpassing the strength of human trabecular bone. • In vitro tests showed the formation of apatite crystals with porous nanostructure, promoting efficient osteoblast attachment, proliferation, and osteogenic differentiation. • NCOC provides superior bone regeneration in critical bone defect models compared to conventional bone substitute apatite. Nacre of Pinctada maxima is a natural biomineralized matrix, appeared 7 million years before hominins. In this study, we converted nacre into a self-setting particle bound with multiple calcium orthophosphates that reassemble mammals' bone mineral matrices for induction of bone regeneration. The nacre-based calcium orthophosphates composite (NCOC) exhibited a compression strength of 10 MPa, which is superior to human trabecular bone. In vitro bioactivity tests revealed the formation of apatite with nano-porous flake-like crystals on the composite surface that mimic HA structure of a human bone matrix. NCOC demonstrated efficient attachment and proliferation of osteoblast cells, promoting osteogenic differentiation by increasing expressions of RUNX2 and OPN. In vivo studies using rabbit back fascia demonstrated that NCOC displays better bone healing and biocompatibility than conventional bone substitute apatite in critical bone defect models. The degradation of calcium carbonate crystal in vivo does not compromise structural integrity of NCOC. Overall, our data showed that NCOC produced through self-setting reactions, presents advantages such as accelerated biodegradation and osteostimulative properties, making it a promising bone substitute for effective bone regeneration. [ABSTRACT FROM AUTHOR]

The structural integrity of MXene and MXene-based materials is important across applications from sensors to energy storage. While MXene processing has received significant attention, its structural integrity for real-world applications remains challenging due to its flake-like structure. Here the mechanical response of layered MXene-polymer nanocomposites (MPC) with high MXene concentration (>70 %) and bioinspired nacre-like brick-and-mortar architecture is investigated to offer insights for MPC design and processing. An automated finite element analysis (FEA) framework is developed to analyze MPC models with randomized geometries and multiple combinations of the parameter space. Specifically, the influence of concentration, aspect ratio (AR), flake thickness, flake distribution, and interfacial strength is investigated. The results reveal property trends such as increasing elastic modulus, strength, and toughness with increasing cohesive strength and concentration for lower AR (=40, 60) but a decreasing trend at higher AR of 75. Local structural features like flake distribution, overlapping MXene lengths, and interconnected polymers in adjacent layers was found a critical determinant of performance. For example, stronger cohesive interaction showed 6X high toughness (291 ± 226 K J / m 3) compared to weaker case (50 ± 24 K J / m 3), but the large scatter highlighted the impact of microstructural features. The results are compared and validated with theoretical, computational, and experimental work. The findings provide valuable guidance for optimizing MPC design and their processing. Finally, the automation of the framework allows the design to be extended beyond the current system and chosen material combinations. [ABSTRACT FROM AUTHOR]

Résumé: Pour améliorer la prévention des cancers, la nutrition dans son ensemble (alimentation, consommation d'alcool, activité physique, surpoids/obésité) est un des facteurs essentiels sur lesquels il est possible d'agir. Les médias diffusent régulièrement des messages sur le sujet, parfois erronés, et la littérature scientifique regorge de données, parfois contradictoires. Des expertises collectives nationales (Institut National du Cancer et Réseau National Nutrition Cancer) et internationales (World Cancer Research Fund et Centre International de Recherche sur le Cancer) permettent de faire régulièrement le point des avancées scientifiques en respectant une méthodologie rigoureuse et élaborer des recommandations basées sur des niveaux suffisants de preuve scientifique. Dans le cas du cancer colorectal, plusieurs facteurs nutritionnels ont ainsi été identifiés comme associés au risque de survenue de ce cancer avec un niveau de preuve « convaincant » ou « probable » : le surpoids et l'obésité, les boissons alcoolisées, la consommation de viandes rouges ou de viandes transformées. À l'inverse, certains facteurs auraient un rôle protecteur : l'activité physique, les aliments riches en fibres et les produits laitiers. Des données scientifiques probantes manquent encore pour confirmer le rôle d'autres facteurs. Suivre les recommandations émises par le Haut Conseil de la Santé Publique et l'Institut National du Cancer pourrait permettre de diminuer le développement de plus de la moitié des cancers colorectaux. Diffuser ces messages auprès des professionnels de Santé et de la population est donc essentiel. In order to improve cancer prevention, nutrition (including: diet, alcohol consumption, physical activity, body fatness) is one of the key factors that can be modified. The media regularly broadcast messages on the topic, sometimes erroneous and the scientific literature is full of data, but sometimes contradictory also. National and international collective expertises regularly review scientific advances using a rigorous methodology to enable recommendations to be made based on sufficient levels of scientific evidence. In the case of colorectal cancer, several nutritional factors have been identified as associated with the risk of developing this cancer with a level of evidence defined as "probable" or "convincing": overweight and obesity, consumption of red and of processed meats, alcoholic beverages. On the other hand, some factors would have a protective role: physical activity, foods containing fibre and dairy products. There is still a lack of scientific evidence to confirm the role of other factors. To follow the recommendations of the French High Council of Public Health and the French National Cancer Institute could reduce the development of more than half of colorectal cancers. Spreading these messages to health professionals and to the public is therefore essential. [ABSTRACT FROM AUTHOR]

Recently, several types of nacre-like materials have been developed using various methods. However, the resulting materials exhibit a significant randomness and defects compared to natural nacre. Therefore, evaluating the influence of these microstructural variations on the material's mechanical behavior is of high interest for the development of nacre-like materials and their industrial scale-up. In this work, we present an original method that allows the modeling of complex morphology of brick and mortar materials, by combining Discrete Element Method and Electron Backscatter Diffraction images. Using different realistic microstructures we studied the effect of the microstructural variations on crack propagation and damage resistance. The obtained results were compared to the regular microstructure of nacre and showed a non-negligible decrease of mechanical properties. [ABSTRACT FROM AUTHOR]

BACKGROUND: Seawater cultured gray Akoya pearls have become popular as jewelry in the recent years. In the early stage, some research focused mainly on investigating the cultured environment of seawater or freshwater pearls, element occurrence characteristics of each structural unit, irradiation treatment and the identification method of irradiated pearls. OBJECTIVES: To further study the gemological characteristics and fine microstructure of a type of gray pearl with a white nucleus. METHODS: Ultraviolet - visible reflection spectrum, micro - infrared spectrum and scanning electron microscope methods were used. RESULTS: A brown transition layer of orgamc matter between the nacre and nucleus was discovered, which measures several microns in thickness. A layer with no fixed morphology composed of calcite and vaterite m the nacre near the brown transition layer was also discovered. Quasi plates of aragonite exist in the nacre near the surface of the pearl. The morphology of these aragonite tablets in the middle area of the nacre was more regular, the thickness of individual aragonite plate gradually decreased in the direction from the nucleus to the surface of the pearls. The reflectance spectrum of the entire pearl surface was consistent with the spectral characteristics of the outer single nacre. The brown transition layer had no direct effect on the UV - Vis reflectance spectrum of the entire pearl. Therefore, whether or not the brown transition layer affected the gray appearance of the pearl needs further discussion. CONCLUSIONS: The research work has important guiding significance for the coloring mechanism of gray Akoya pearls and the identification of the formation attributes. It can also aid in the recognition of the fine structure and mineralization characteristics of pearls with a thin layer of nacre of 0. 3mm to 0. 6mm. [ABSTRACT FROM AUTHOR]

Recently, there has been a proliferation of studies focused on traceological analyses of shell tools, most of which have been carried out using high magnifications. In contrast, wear patterns identified in other types of shell objects, such as ornaments, are usually analyzed at low magnifications. A new approach to the technological and functional analysis of Paleolithic Homalopoma sanguineum shell beads is proposed here. This taxon has been considered especially problematic in archaeomalacology for several reasons. First, it is a very rare species in on current coasts, so conducting perforation and suspension experiments is logistically difficult. This leaves two unique routes for the acquisition of data: analogous experiments on other seashells, which is not recommended based on the characteristics of the internal structure of this species, or directly through the study of archaeological specimens. Secondly, it has been considered impossible to successfully perform use-wear analyses due to the physical characteristics of this species. Lastly, the high reflective capacity of the species' inner nacreous layer can make its study via optical microscopy difficult. Given these issues, the goal of this study is to compare the advantages and disadvantages of the microscopy equipment conventionally used for use-wear analysis. By comparing multiple microscopes' accuracy in identifying polishing, striation, and micro-chipping patterns, a set of criteria has been generated which can be used not only in analyses of H. saguineum , but in a wide range of nacreous ornaments. [ABSTRACT FROM AUTHOR]

The C1q-domain-containing (C1qDC) proteins are a family of proteins characterized by a globular C1q (gC1q) domain in their C-terminus which hold the potential function in the shell formation as shell matrix proteins. In this study, a C1qDC protein was identified and characterized in pearl oyster (Pinctada fucata martensii) (PmC1qDC) to explore its function in nacre formation. The PmC1qDC-deduced protein sequence carried a typical globular C1q (gC1q) domain that possessed the typical 10-stranded β-sandwich fold with a jelly-roll topology common to all C1qDC family members and shared high homology with other gC1q domains. Homologous analysis of PmC1qDC presented it contained conserved secondary structure and Phe135, Phe155, Tyr166, Phe173, Tyr181, Phe183, and Phe256 amino acid residues. Expression pattern analysis showed that PmC1qDC expressed in all the detected tissues and exhibited a significantly higher expression level in nacre formation-associated tissues. After the shell notching, the expression level of PmC1qDC showed significantly up-regulation after 12 h in the central zone of mantle (MC). PmC1qDC expression significantly decreased in the MC after RNA interference (RNAi). Furthermore, disordered crystals with evident rough surface and irregular crystal tablets were observed in the nacre after RNAi. Results suggested that PmC1qDC affects the shell nacre formation, which is significant to improve the pearl production of pearl oyster. • PmC1qDC expressed significantly higher in nacre formation associated tissues. • PmC1qDC was involved in shell regeneration after injury. • PmC1qDC affected the shell nacre formation. [ABSTRACT FROM AUTHOR]

• Nacre-like GO-PTA paper is prepared by evaporation-induced self-assembly method. • Fire sensor-based GO-PTA exhibits ultrasensitive and durable warning response. • Enhancement in fire resistance of GO is attributed to in situ phosphorus doping. A novel nacre-like flame-retardant paper based on graphene oxide (GO), and phytic acid (PTA) is fabricated via evaporation-induced self-assembly. This facile method is time saving and low energy consuming. A facile approach is proposed to improve thermal oxidative stability of GO paper by in situ phosphorus doping during flame exposure. Then fire-alarm system is designed based on the high-temperature thermal reduction characteristic of GO. The GO paper functionalized with PTA (GO-PTA) can provide ultrasensitive, reliable and longtime fire early-warning signal. Fire alarm can be triggered at approximately 0.50 s when GO-PTA samples are attacked by fire. Phosphorus atoms are in situ doped into graphene layers during fire exposure, endowing GO-PTA paper with outstanding thermal oxidative stability, and thus alarm duration time of GO is greatly improved. The work develops advanced fire detection and early-warning sensors that provide reliable and continuous signals, which provide more available time for fire evacuation. [ABSTRACT FROM AUTHOR]

Although research in bioinspired nanocomposites is delivering mechanically superior nanocomposite materials, there remain gaps in understanding some fundamental design principles. This article discusses how the mechanical properties of nacre‐mimetic polymer/nanoclay nanocomposites with nanoconfined polymer layers are controlled by the thermo‐mechanical polymer properties, that is, glass transition temperature, Tg, using a series of poly(ethylene glycol methyl ether methacrylate‐co‐N,N‐dimethylacrylamide) copolymers with tunable Tg from 130 to −55 °C. It is elucidated that both the type of copolymer and the nanoconfined polymer layer thickness control energy dissipation and inelastic deformation at high fractions of reinforcements in such bioinspired nanocomposites. [ABSTRACT FROM AUTHOR]

Higher systematics and evolutionary history of Protobranchia, a subclass of Bivalvia, have long been controversial due to paucity of prominent shell characters and difficulties in collecting live material for diverse taxa. Here, we evaluate the reliability of shell microstructure for protobranch higher systematics by reconstructing a molecular phylogeny of the subclass. Relationships were assessed using the nuclear (18S rRNA, 28S rRNA and histone H3) and mitochondrial (16S rRNA and cytochrome c oxidase subunit 1) gene sequences from 89 in‐group species. Maximum likelihood reconstruction with the nuclear markers recognized five superfamilies (Nuculoidea, Solemyoidea, Manzanelloidea, Nuculanoidea and Sareptoidea) as the in‐group clades of the monophyletic Protobranchia. Sareptoidea is herein redefined to comprise Sarepta and Setigloma in the sole family Sareptidae, whereas Pristigloma and its monotypic Pristiglomidae are transferred from this superfamily to Nuculanoidea, both in the order Nuculanida. Mapping of shell microstructure characters on the tree confirmed their conservativeness at superfamily level when only living species were taken into account. The Nuculoidea have shells with the outer prismatic and middle/inner nacreous structures; Solemyoidea are characterized by either the radially elongate simple prismatic structure or the reticulate structure in the outer shell layer; Manzanelloidea, Nuculanoidea and Sareptoidea have shells of homogeneous, fibrous prismatic and/or fine complex crossed lamellar structures, all of which lack large structural units. Our Bayesian time calibration, on the contrary, suggested frequent loss of nacre in the Paleozoic and Mesozoic history of Protobranchia, at least once each in Nuculoidea, Manzanelloidea, Solemyoidea and Sareptoidea in the Paleozoic, and perhaps multiple times in Nuculanoidea by the Mesozoic. [ABSTRACT FROM AUTHOR]

In this study, a novel matrix protein (teosin) was isolated from Hyriopsis cumingii. Gene expression analysis showed that teosin is mainly expressed in the mantle and blood, and a hybridization signal was found in dorsal epithelial cells of the mantle pallial by in situ hybridization. Moreover, teosin expression during pearl formation indicated its participation in initial nacreous layer biomineralization, and suppressing teosin expression resulted in irregular crystal morphology and disordered arrangement in RNAi assay. In vitro crystallization assays indicated teosin could increase the size of calcite. By turning the sample stage about 15°, we got the high-resolution TEM images of the crystals' edges. This is a novel method to observe the crystal which is over 200 nm under TEM. In the control experiment group, the calcite show the character of long range order. The calcite induced by teosin were composed of nano-grains, and the polycrystal character were confirmed by EDS. These results suggested that teosin is involved in regulating crystal morphology regulation and inducing polycrystal formation during nacreous-layer formation. [ABSTRACT FROM AUTHOR]

Nacre like graphene based composite films (GCFs) have been developed over the last decade. Although the progress in ultrastrong GCFs is remarkable, fabricating GCFs with excellent integrated properties of strength, flexibility, and toughness still remains a challenge. Here, a ternary GCF of reduced graphene oxide (rGO), polydopamine (PDA) and multi-walled carbon nanotubes (MWCNTs) was developed. The MWCNTs were modified by PDA to form PDA@MWCNTs which were then compounded with GO to fabricate the rGO-PDA@MWCNT films by evaporation-induced assembly and chemical reduction. The preparation was simple, cheap and environmentally-friendly. The PDA increased the dispersion of MWCNTs in the rGO-PDA@MWCNT films, crosslinked the rGO sheets, and enhanced the entanglement of MWCNTs and the interactions between MWCNTs and rGO sheets. Benefiting from the synergistic effect of PDA and MWCNTs, the rGO-PDA@MWCNT films exhibited excellent integrated properties by increasing strength, tensile fracture strain and toughness to 579 ± 35 MPa, 12.03 ± 0.56%, and 34.03 ± 1.60 MJ/m3, which were 2.26, 2.02 and 4.94 times that of pure rGO films, respectively. The rGO-PDA@MWCNT films also exhibited a high conductivity of 612 ± 68 S/cm and excellent structural stability under extreme environments. These excellent integrated properties of the rGO-PDA@MWCNT films will promote their applications in aerospace engineering, flexible electrical devices and artificial muscle. Image 1 • A ternary nacre like graphene based composite film (GCF) is developed by a simple, cheap and green method. • This GCF is synergistically toughened and reinforced by polydopamine wrapped carbon nanotubes. • This GCF exhibits good mechanical properties, electrical conductivity and structural stability under extreme environments. [ABSTRACT FROM AUTHOR]

To examine variations in nacre color and thickness in Pteria penguin oysters obtained from Tonga and Japan, a novel approach with a focus on their potential for mabé pearl production was used. Detailed analyses of color and microstructure revealed that the middle position of the right-valve nacre (position 1) primarily showed a reduction in yellow pigmentation. This was indicated by a decrease in the yellowness index (YI) and an increase in the whiteness index (WI). In contrast, the anterior and middle positions of the left-valve nacre (positions 2 and 3) consistently displayed a higher level of yellow pigmentation. A comparison of oysters from different geographical origin found that Tonga wild-caught oysters had significantly thicker nacre than Tonga culture-site oysters, suggesting the influence of probable genetic diversity and environmental factors on nacre formation. Notably, nacre at position 1 was generally thinner, while at positions 2 and 3 it was thicker, which would influence the resultant pearl quality and attributes. We demonstrate the significance of the nacre position on the valve for mabé pearl production: position 1 tended to produce white pearls with pronounced interference colors, whereas position 2 tended to yield gold pearls. Furthermore, our findings highlight the significant impact of the oysters' geographic origin on mabé pearl color and quality. This study emphasizes the importance of considering the position of shell nacre and the potential influences of the oysters' genetic origins and environmental factors on mabé pearl formation. • Advanced colorimetric techniques can surpass conventional visual assessment of nacre quality. • Right-valve nacre middle position had the most intense interference color but the least yellow pigment. • Left-valve nacre anterior and middle positions had greater yellow pigmentation, befitting gold mabé pearls. • Geographic origin influenced pearl coloration, with Japanese oysters producing white pearls. [ABSTRACT FROM AUTHOR]

Nacre-like polymer/clay nanocomposites are a fascinating material thanks to its superior mechanical property. However, it has been a great challenge to incorporate hydrophobic polymer components due to highly hydrophilic nature of clay, which limits further improvement of water-resistance and addition of various functionalities. To overcome this problem, we developed a method to form regular nacre-like layered structure from a hydrophobic polymer and hydrophilic clay by a combination of surface modification of clay and selective click reaction between the polymer and clay surfaces. Natural clay, montmorillonite, was modified with a hydrophobic surfactant bearing an ethenyl group and subsequently reacted in situ with a thiol-functionalized hydrophobic polysiloxane. The layered structure, as well as its formation process, mechanical property, physical stability in water, and self-adhesion property of the nanocomposites were investigated. In situ thiol-ene click reaction between surface-modified clay and polymer led to self-alignment of clay platelets into a regular layered structure. The resultant nacre-like nanocomposites not only showed the good mechanical property but also had excellent stability in water and self-adhesion ability, both of which originated from the characteristics of the polymer used. These findings widen the possibility of functional nacre-like nanocomposites by expanding the range of applicable polymers to hydrophobic ones. [ABSTRACT FROM AUTHOR]

Nacre-like alumina manufactured using spark plasma sintering shows a strikingly different mechanical behaviour compared to conventional alumina. A range of sintering conditions were applied to micron-sized alumina platelet powders to form alumina with different nacre-like microstructures, density, grain size and flexural strength. We show that a microstructure of aligned sintered platelets not only mitigates the typical issue of brittleness, but also has extraordinary energy absorption capabilities. It can withstand an impact with up to three times the kinetic energy required to break monolithic alumina while maintaining structural integrity. The high-rate compressive strength is shown to be more than 50% higher than that of monolithic alumina and we show energy absorption mechanisms such as crack deflection and branching to be present. Our approach provides a fast and effective way of manufacturing aligned nacre-like ceramic microstructures that maintain structural integrity through energy dissipation and interlocking mechanisms. [ABSTRACT FROM AUTHOR]

Vignesh, T.S.; Suja, C.P., and Geetha, S., 2019. Fabrication of tissue engineering scaffolds using marine bioactive materials for diverse applications. In: Jithendran, K.P.; Saraswathy, R.; Balasubramanian, C.P.; Kumaraguru Vasagam, K.P.; Jayasankar, V.; Raghavan, R.; Alavandi, S.V., and Vijayan, K.K. (eds.), BRAQCON 2019: World Brackishwater Aquaculture Conference. Journal of Coastal Research, Special Issue No. 86, pp. 170–176. Coconut Creek (Florida), ISSN 0749-0208. Scaffolds are polymeric matrices employed in delivering cells and drugs into human body. The scaffold matrices can be fabricated using natural or chemical polymers. In the present study, natural polymers and biomineralized materials extracted from marine sources have been used in the fabrication of the scaffolds. Marine biomaterials are highly biocompatible and they have been used for medicinal purposes. Hence the study focuses on fabricating a novel molluscan nacre incorporated scaffold, using biomaterials like κ-carrageenan from Kappaphycus alvarezii, collagen from Sepia lycidas and chitosan from shrimp shell by freeze-drying method. Due to the osteogenic and dermal regeneration properties of nacre, this novel scaffold can be used for tissue engineering applications. The extracted natural polymers used in fabricating the scaffolds were analyzed by Fourier Transform Infrared Spectroscopy (FTIR). The FTIR analysis of the sulfated polysaccharide κ-carrageenan showed strong absorbance peaks along 926 cm-1 and 1250 cm-1 which correspond to 3,6 anhydro-d-galactose and sulphur bonds respectively whereas the deacetylated polysaccharide chitosan showed peaks along the 3428 cm-1 and 1635 cm-1 corresponding to OH groups and secondary amine groups. FTIR analysis of collagen exhibited characteristic peaks along 3432 cm-1 and 1641 cm-1 indicating the presence of the amine groups and hydrogen bonds. The structural morphology of the fabricated scaffold has been analyzed by Scanning Electron Microscopy (SEM). These scaffolds have wide scope in diverse areas and will be a useful model of 3D cell culture for engineering edible meat, tissues and organs. [ABSTRACT FROM AUTHOR]

Srinivasa Raghavan, V.; Jayasankar, V.; Suja, C.P., and Laxmilatha, P., 2019. Cell culture and gene expression studies in relation to biomineralization in the black-lip pearl oyster, Pinctada margaritifera. In: Jithendran, K.P.; Saraswathy, R.; Balasubramanian, C.P.; Kumaraguru Vasagam, K.P.; Jayasankar, V.; Raghavan, R.; Alavandi, S.V., and Vijayan, K.K. (eds.), BRAQCON 2019: World Brackishwater Aquaculture Conference. Journal of Coastal Research, Special Issue No. 86, pp. 156–163. Coconut Creek (Florida), ISSN 0749-0208. Nacre is composed of aragonite platelets and organic material formed by molluscs as inner shell layer through biomineralization process, and mantle epithelial cells control nacre formation. A primary culture of granulated epithelial cells was established from mantle tissue of Pinctada margaritifera, through a process of continuous sub-culturing at 28°C in yeast supplemented sea water culture medium. Nuclear beads were placed in culture wells containing semi-solid agar medium and incubated in vitro with cultured granulated epithelial cells in order to evaluate the nacre secretion. On visual observation, a brown coloration was observed on the surface of the bead after 7-10 days. Evaluation of the surface of the nuclear beads by scanning electron microscopy (SEM) after 60 days of incubation revealed a good brick and mortar pattern, characteristic of nacreous layer formation. A lustrous hue was also seen to develop on bead surfaces after this stage. SEM images of a cross section of the nacre-coated bead showed a pattern of arrangement of aragonite tablets similar to that seen in cross sections of the nacre layer of shell of molluscs. The functional ability of cultured granulated epithelial cells was further confirmed by detecting gene expression of two matrix proteins, nacrein and amorphous calcium carbonate binding proteins (ACCBP), which play an important role in formation of the nacreous layer, in both cultured cells and in native mantle tissue. Amplification products for nacrein (480 bp) and ACCBP (500 bp) genes were obtained in both native mantle tissue and in vitro cultured mantle epithelial cells. There was good correlation between the expression patterns of the two genes in in vitro cultured cells and in native mantle tissue, signifying that cultured mantle epithelial cells retain their functional characteristics of biomineralization. [ABSTRACT FROM AUTHOR]

Biological mineralized tissues are hybrid materials with complex hierarchical architecture composed of biominerals often embedded in an organic matrix. The atomic-scale comprehension of surfaces and organo-mineral interfaces of these biominerals is of paramount importance to understand the ultrastructure, the formation mechanisms as well as the biological functions of the related biomineralized tissue. In this communication we demonstrate the capability of DNP SENS to reveal the fine atomic structure of biominerals, and more specifically their surfaces and interfaces. For this purpose, we studied two key examples belonging to the most significant biominerals family in nature: apatite in bone and aragonite in nacreous shell. As a result, we demonstrate that DNP SENS is a powerful approach for the study of intact biomineralized tissues. Signal enhancement factors are found to be up to 40 and 100, for the organic and the inorganic fractions, respectively, as soon as impregnation time with the radical solution is long enough (between 12 and 24 h) to allow an efficient radical penetration into the calcified tissues. Moreover, ions located at the biomineral surface are readily detected and identified through 31P or 13C HETCOR DNP SENS experiments. Noticeably, we show that protonated anions are preponderant at the biomineral surfaces in the form of HPO 4 2− for bone apatite and HCO 3 2− for nacreous aragonite. Finally, we demonstrate that organo-mineral interactions can be probed at the atomic level with high sensitivity. In particular, reliable 13C-{31P} REDOR experiments are achieved in a few hours, leading to the determination of distances, molar proportion and binding mode of citrate bonded to bone mineral in native compact bone. According to our results, only 80% of the total amount of citrate in bone is directly interacting with bone apatite through two out of three carboxylic groups. Image 1 • DNP SENS is powerful to characterize the surface and hybrid interface of biominerals. • HPO 4 2− and HCO 3 − are the main anionic components of bone apatite and nacre aragonite. • 50% of the total amount of citrate is interacting with bone apatite. [ABSTRACT FROM AUTHOR]

Runt related transcription factors as trans-acting elements play critical roles in the developmental control of cell fate, hematopoiesis, bone formation and cancers. In previous study, the homologue of runt related transcription factor PmRunt has been identified from pearl oyster Pinctada fucata martensii and considered to play an important role in nacre formation. In this study, we used the same samples to perform RNA-seq to detect the global effects after the decrease of PmRunt expression. The transcription levels of several nacre shell matrix protein (NSMP) genes were significantly changed and the potential compensatory effect could happen internal gene families. Downregulation of PmRunt could also influence the biosynthesis of NSMPs through affecting amino acid metabolism, translation, protein processing and export. The inhibition of PmRunt also possibly affected the expression of caspases, IAPs and C1qs that related to apoptosis and immune. In addition, PmRunt highly expressed at 12 h and 12 d after transplantation in hemolymph, which was corresponded to transplantation immunity immune response and the morphology of pearl sac, suggested the cross-talk of biomineralization-immune regulation in hemocytes. Furthermore, a lincRNA (LncRunt) that co-located with PmRunt was identified and showed a significantly relative expression with PmRunt , which suggested the potential regulation. Therefore, these findings provided new idea to find the regulation targets of runt-related transcription factors and offers evidence of lncRNAs in potential biomineralization-immune regulation. • The global effects of PmRunt were explored by RNAi combined with RNA-seq. • A lincRNA co-located with PmRunt was identified and designated as LncRunt. • PmRunt co-expressed with lncRunt in mantle tissue. [ABSTRACT FROM AUTHOR]

Hard biological materials such as nacre, bone, and teeth exhibit high values of toughness although it is meanly made of a ceramic material. Ceramic materials are brittle and fail in a catastrophic manner therefore they have low values of toughness. Researchers have been curious in examining the reasons behind such performance. It has been found that the staggered structure of these materials, that is brittle tablets embedded into a soft matrix, is the main reason that allows for multiple toughening mechanisms to operate at different length scales. In addition, it has been shown that the tablets are not flat. There is some waviness that generates hardening and spreading of nonlinear deformation leading to high values of toughness. The effect of waviness was not included in previous analytical toughness models. In the present work, a toughness model based on J-integral approach is developed that considers the waviness. Crack resistance curve, denoted by R-curve, is obtained that agrees with the experimental results. The developed toughness model aids in the design and optimization of nacre-like materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Biological materials have consistently intrigued researchers due to their remarkable properties and intricate structure–property-function relationships. Deciphering the pathways through which nature has bestowed its exceptional properties represents a complex challenge. The hierarchical architectures of biomaterials are recognized as the basis for mechanical robustness. Moreover, it is well-established that the intriguing properties of biomaterials arise primarily from the architecture at the nanoscale, particularly the abundant carefully designed interfaces. Driven by the diverse functionality and the increasing comprehension of the underlying design mechanisms in biomaterials, substantial endeavors have been directed toward emulating the architectures and interactions in synthetic materials. By reviewing atomistic modeling of nacre, wood, and coconut endocarp, in this work, we aim at highlighting the significant role of atomistic modeling in revealing nanoscale strengthening and toughening mechanisms of biomaterials, subsequently advancing the development of bioinspired material. [ABSTRACT FROM AUTHOR]

Abstract Many types of tissues in living organisms exhibit a combination of different properties to fulfil their mechanical functions in complex environments. Nacre with more than 90% brittle and hard phase and a little protein matrix, exhibits high strength and toughness, which is difficult to achieve in artificial materials. Researchers have shown that the toughness of nacre is related to the cracking process. Most of them, however, assume an obvious pre-existing crack on the model and the initiation of the microscopical pre-existing crack is not considered yet. Based on fracture mechanics with the cohesive zone model, we reveal the mechanism of the crack initiation and propagation pattern in staggered biomaterials without any pre-existing crack. The simulation result shows that there are two crack propagation modes: localized mode and unlocalized mode. A crack initiates and propagates in a small area in the localized mode, while cracks initiate at different points and propagate in various paths in the unlocalized mode. The crack initiation mechanism from the intrinsic properties of the material is clarified using energy based stability analysis. The result shows that the shear interfacial mechanism significantly delays the crack initiation. [ABSTRACT FROM AUTHOR]

Abstract The position and arrangement of nuclei is the most important technical aspect of mabé pearl (half-pearl) production. This study examined the effects of nucleus arrangement, profile (height) and position, on quality, nacre thickness and shape of mabé pearls produced by Pteria penguin. Oysters implanted with three nuclei produced a greater proportion of saleable mabé pearls with more regular shapes than oysters implanted with five nuclei. Use of low profile nuclei resulted in mabé pearls with increased nacre thickness and produced mabé pearls of significantly higher quality, with more regular shapes than high profile nuclei. Nucleus position significantly influenced mabé pearl quality, nacre thickness and shape. The posterior-ventral position of the left shell valve produced mabé pearls of the highest quality with the thickest nacre and was the best location for mabé pearl culture. Based on the results of this study, it is recommended that P. penguin is implanted with a maximum of three nuclei to increase the production of regular-shaped mabé pearls, and that low profile nuclei are used to improve quality and nacre thickness of mabé pearls produced in less favourable nucleus positions. An optimal nucleus arrangement for P. penguin of 130–150 mm dorso-ventral height would include one high profile nucleus in the posterior-ventral position of the left shell plus additional low profile nuclei in both the anterior-ventral position of the left shell valve and, the center of the right shell. Based on the quality grading system used in this study, a minimum commercial nacre thickness of 0.25 mm is recommended for mabé pearl production using P. penguin. Highlights • Factors influencing mabé pearl quality in Pteria penguin were assessed. • Oysters implanted with fewer nuclei produced a greater proportion of regular-shaped mabé pearls. • Low profile nuclei improved mabé pearl quality, shape and nacre thickness. • Nucleus position influenced nacre thickness, quality and shape of mabé pearls. • Nucleus arrangements that maximise mabé pearl quality are suggested. [ABSTRACT FROM AUTHOR]

Abstract In this study, we use the coextrusion process to make high volume-fraction, nacre-like brick-and-mortar alumina structures with <10% nickel between the ceramic bricks. We perform strength and toughness tests on these compliant-phase aluminas at temperatures up to 900 °C, both to explore the evolution of toughening with changes in the mortar plasticity and to evaluate the viability of these materials at elevated temperatures. We find that temperature plays an important role in the mechanical performance of these materials. Specifically, we observe that crack-growth resistance can be improved at higher temperatures due to enhanced ductility in the metallic mortar. Graphical abstract High volume fraction “brick-and-mortar” alumina ceramic structures in the image of naturally occurring nacre, containing a metallic nickel mortar, were processed using coextrusion. The damage-tolerant properties of these bioinspired ceramics were evaluated at temperatures up to 900 °C, both to explore the evolution of toughening with changes in mortar plasticity and to evaluate the viability of these materials at high temperature. The “nacre-like” alumina was found to display significantly higher toughness at elevated temperatures up to 800 °C due to enhanced ductility and interphase failure within the metallic mortar. Unlabelled Image [ABSTRACT FROM AUTHOR]