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Spider silks are remarkable materials characterized by superb mechanical properties such as strength, extensibility, and lightweightedness. Yet, to date, limited models are available to fully explore sequence‐property relationships for analysis and design. Here a custom generative large‐language model is proposed to enable the design of novel spider silk protein sequences to meet complex combinations of target mechanical properties. The model, pretrained on a large set of protein sequences, is fine‐tuned on ≈1,000 major ampullate spidroin (MaSp) sequences for which associated fiber‐level mechanical properties exist, to yield an end‐to‐end forward and inverse generative approach that is aplied in a multi‐agent strategy. Performance is assessed through: 1) a novelty analysis and protein type classification for generated spidroin sequences through Basic Local Alignment Search Tool (BLAST) searches, 2) property evaluation and comparison with similar sequences, 3) comparison of resulting molecular structures, and 4) a detailed sequence motif analyses. This work generates silk sequences with property combinations that do not exist in nature and develops a deeper understanding of the mechanistic roles of sequence patterns in achieving overarching key mechanical properties (elastic modulus (E), strength, toughness, failure strain). The model provides an efficient approach to expand the silkome dataset, facilitating further sequence‐structure analyses of silks, and establishes a foundation for synthetic silk design and optimization. [ABSTRACT FROM AUTHOR]

Porous grafts facilitate constructive remodeling of blood vessels. Incorporating multiple biomimetic cues to porous grafts can promote vascular regeneration. However, the fabrication of such medical devices remains challenging. Here, beta‐sheet rich silk nanofibers (BSN) are added to poly(vinyl alcohol) (PVA) solution and aggregated under a cylindric electric field to form circumferentially and axially oriented tubular structures, to simulate the endothelial and media layers of blood vessels. PVA in the aligned tubes is then crystallized through repeat freezing–thawing process to offer mechanical performances. Through tuning the ratio of BSN and PVA, the composite tubes with dual anisotropic microstructures exhibit better mechanical properties than pure PVA vascular grafts. Significantly improved cell adhesion, spreading, proliferation, and alignment are achieved. Both endothelial and smooth muscle cells show improved biological activity on the grafts due to the regulatory roles of the aligned structures. In vivo studies reveal the formation of endothelial layers within four weeks of implantation, ensuring long‐term patency. The endothelial and smooth muscle double layers are regenerated after eight months postimplantation, forming hierarchical microstructures and compositions similar to native vessels. The porous composite grafts with multiple aligned structures guide vascular remodeling to regenerate blood vessels, demonstrating potential for clinical translation. [ABSTRACT FROM AUTHOR]

Different tissues have complex anisotropic structures to support biological functions. Mimicking these complex structures in vitro remains a challenge in biomaterials designs. Here, inspired by different types of silk nanofibers, a composite materials strategy is pursued toward this challenge. A combination of fabrication methods is utilized to achieve separate control of amorphous and beta‐sheet rich silk nanofibers in the same solution. Aqueous solutions containing two types of silk nanofibers are simultaneously treated with an electric field and with ethylene glycol diglycidyl ether (EGDE). Under these conditions, the beta‐sheet rich silk nanofibers in the mixture responded to the electric field while the amorphous nanofibers are active in the crosslinking process with the EGDE. As a result, cryogels with anisotropic structures are prepared, including mimics for cortical‐ and cancellous‐like bone biomaterials as a complex osteoinductive niche. In vitro studies revealed that mechanical cues of the cryogels induced osteodifferentiation of stem cells while the anisotropy inside the cryogels influenced immune reactions of macrophages. These bioactive cryogels also stimulated improved bone regeneration in vivo through modulation of inflammation, angiogenesis and osteogenesis responses, suggesting an effective strategy to develop bioactive matrices with complex anisotropic structures beneficial to tissue regeneration. [ABSTRACT FROM AUTHOR]

Continuous monitoring of biochemical analytes like oxygen is of interest in biomedicine to provide insight into physiology and health. Silk‐protein biomaterials are particularly useful as the scaffold material in oxygen sensors due to silk's unique amphiphilic chemistry, which promotes noncovalent stabilization of the protein and additives in aqueous environments. Silk films containing a water‐insoluble oxygen‐sensing chromophore, Pd (II) tetramethacrylated benzoporphyrin (PdBMAP), are evaluated as optical oxygen sensors in vitro and in vivo. These silk‐chromophore composites are stabilized by the self‐assembled, physically crosslinked protein network. The deaerated phosphorescence lifetime (τm,0 ≈300 µs) of the chromophore in vitro is quenched to 50% of its initial value at ≈31 µm dissolved oxygen, indicating sensing functionality within physiological ranges of oxygen. In vitro enzymatic degradation of the silk films with and without the chromophore is demonstrated. The silk‐chromophore composite films are cytocompatible in vitro, biocompatible in vivo upon implantation in rats, and displayed mechanical properties suitable for subcutaneous implantation. Further, the films maintain oxygen‐sensing function in vivo and demonstrate real‐time sensing capabilities throughout various physiological states (i.e., hyperoxia, normoxia, and hypoxia). [ABSTRACT FROM AUTHOR]

Standard care for early stage breast cancer includes tumor resection and local radiotherapy to achieve long-term remission. Systemic chemotherapy provides only low locoregional control of the disease; to address this, self-assembling silk hydrogels that can retain and then deliver doxorubicin locally are described. Self-assembling silk hydrogels show no swelling, are readily loaded with doxorubicin under aqueous conditions, and release drug over 4 weeks in amounts that can be fine-tuned by varying the silk content. Following successful in vitro studies, locally injected silk hydrogels loaded with doxorubicin show excellent antitumor response in mice, outperforming the equivalent amount of doxorubicin delivered intravenously. In addition to reducing primary tumor growth, doxorubicin-loaded silk hydrogels reduce metastatic spread and are well tolerated in vivo. Thus, silk hydrogels are well suited for the local delivery of chemotherapy and provide a promising approach to improve locoregional control of breast cancer. [ABSTRACT FROM AUTHOR]

Biopolymers, a class of fascinating polymers from biomass provide sustainability, biodegradability, availability, biocompatibility, and unique properties. A ubiquitous feature of biopolymers is their hierarchical structure, with the presence of well‐organized structures from the nanoscale to macroscopic dimensions. This structural organization endows biopolymers with toughness, defect resistance, and bucking adaptability. To retain these inherent structural features, nano‐structural assemblies isolated from biomass have been applied as building blocks to construct new biopolymer‐based materials. This top‐down processing strategy is distinct from the more traditional molecular‐level bottom‐up design and assembly approach for new materials. In this review, the hierarchical structures of several representative biopolymers (cellulose, chitin, silk, collagen) are introduced with a focus on these nanoscale building blocks, as well as highlighting the similarities and differences in the respective chemistries and structures. Recent progress in production strategies of these natural building blocks are summarized, covering methods and treatments used for isolations. Finally, approaches and emerging applications of biopolymer‐based materials using these natural nano‐ and meso‐scale building blocks are demonstrated in areas of biomedicine, electronics, environmental, packaging, sensing, foods, and cosmetics. [ABSTRACT FROM AUTHOR]

3D laboratory tissue cultures have emerged as an alternative to traditional 2D culture systems that do not recapitulate native cell behavior. The discrepancy between in vivo and in vitro tissue‐cell‐molecular responses impedes understanding of human physiology in general and creates roadblocks for the discovery of therapeutic solutions. Two parallel approaches have emerged for the design of 3D culture systems. The first is biomedical engineering methodology, including bioengineered materials, bioprinting, microfluidics, and bioreactors, used alone or in combination, to mimic the microenvironments of native tissues. The second approach is organoid technology, in which stem cells are exposed to chemical and/or biological cues to activate differentiation programs that are reminiscent of human (prenatal) development. This review article describes recent technological advances in engineering 3D cultures that more closely resemble the human brain. The contributions of in vitro 3D tissue culture systems to new insights in neurophysiology, neurological diseases, and regenerative medicine are highlighted. Perspectives on designing improved tissue models of the human brain are offered, focusing on an integrative approach merging biomedical engineering tools with organoid biology. [ABSTRACT FROM AUTHOR]

Combinations of hydrogels and solids provide high level functionality for devices such as tissue engineering scaffolds and soft machines. However, the weak bonding between hydrogels and solids hampers functionality. Here, a versatile strategy to develop mechanically robust solid−hydrogel hybrid materials using surface embedded radicals generated through plasma immersion ion implantation (PIII) of polymeric surfaces is reported. Evidence is provided that the reactive radicals play a dual role: inducing surface‐initiated, spontaneous polymerization of hydrogels; and binding the hydrogels to the surfaces. Acrylamide and silk hydrogels are formed and covalently attached through spontaneous reactions with the radicals on PIII activated polymer surfaces without cross‐linking agents or initiators. The hydrogel amount increases with incubation time, monomer concentration, and temperature. Stability tests indicate that 95% of the hydrogel is retained even after 4 months in PBS solution. T‐peel tests show that failure occurs at the tape−hydrogel interface and the hydrogel‐PIII‐treated PTFE interfacial adhesion strength is over 300 N m−1. Cell assays show no adhesion to the as‐synthesized hydrogels; however, hydrogels synthesized with fibronectin enable cell adhesion and spreading. These results show that polymers functionalized with surface‐embedded radicals provide excellent solid platforms for the generation of robust solid−hydrogel hybrid structures for biomedical applications. [ABSTRACT FROM AUTHOR]

Designing biomimetic scaffolds with in vivo–like microenvironments using biomaterials is an essential component of successful tissue engineering approaches. The intestinal smooth muscle layers exhibit a complex tubular structure consisting of two concentric muscle layers in which the inner circular layer is orthogonally oriented to the outer longitudinal layer. Here, a 3D bi‐layered tubular scaffold is presented based on flexible, mechanically robust, and well aligned silk protein microfibers to mimic the native human intestinal smooth muscle structure. The scaffolds are seeded with primary human intestinal smooth muscle cells to replicate intestinal muscle tissues in vitro. Characterization of the tissue constructs reveals good biocompatibility and support for cell alignment and elongation in the different scaffold layers to enhance cell differentiation and functions. Furthermore, the engineered smooth muscle constructs support oriented neurite outgrowth, a requisite step to achieve functional innervation. These results suggest these microfiber scaffolds as functional templates for in vitro regeneration of human intestinal smooth muscle systems. The scaffolding provides a crucial step toward engineering functional human intestinal tissue in vitro, as well as engineering other types of smooth muscles in terms of their similar phenotypes. Such utility may lead to a better understanding of smooth muscle associated diseases and treatments. [ABSTRACT FROM AUTHOR]

Development and maturation of vascular and neuronal tissues occurs simultaneously in utero, and are regulated by significant crosstalk. Here, the development of a 3D tissue system to model neurogenesis and recapitulate developmental signaling conditions is reported. Human umbilical vein endothelial cells (HUVECs) are seeded inside channels within collagen gels to represent nascent vascular networks. Axons extending from chicken dorsal root ganglia grow significantly longer and preferentially toward the HUVEC seeded channels with respect to unloaded channels. To replicate these findings without the vascular component, channels are loaded with brain‐derived neurotrophic factor (BDNF), the principle signaling molecule in HUVEC‐stimulated axonal growth, and axons likewise are significantly longer and grow preferentially toward the BDNF‐loaded channels with respect to controls. This 3D tissue system is then used as an in vitro replicate for peripheral nerve injury, with neural repair observed within 2 weeks. These results demonstrate that the 3D tissue system can model neural network formation, can repair after laceration injuries, and can be utilized to further study how these networks form and interact with other tissues, such as skin or skeletal muscle. A 3D tissue system is developed to model neurogenesis and understand the development, maturation, and repair of neural networks. Neural networks are patterned on collagen gels and align along channel dimensions from neurotrophic cues embedded within the gel. A laceration injury model is described to study mechanisms involved in neural repair and regeneration. [ABSTRACT FROM AUTHOR]

Abstract: Biomineralization at the organic–inorganic interface is critical to many biology material functions in vitro and in vivo. Recombinant silk–silica fusion peptides are organic–inorganic hybrid material systems that can be effectively used to study and control biologically mediated mineralization due to the genetic basis of sequence control. However, to date, the mechanisms by which these functionalized silk–silica proteins trigger the differentiation of human mesenchymal stem cells (hMSCs) to osteoblasts remain unknown. To address this challenge, silk–silica surfaces are analyzed for silica–hMSC receptor binding and activation, and the intracellular pathways involved in the induction of osteogenesis on these bioengineered biomaterials. The induction of gene expression of αVβ3 integrin, all three mitogen‐activated protein kinsases, as well as c‐Jun, runt‐related transcription factor 2, and osteoblast marker genes is demonstrated upon growth of the hMSCs on the silk–silica materials. This induction of key markers of osteogenesis correlates with the content of silica on the materials. Moreover, computational simulations are performed for silk/silica‐integrin binding which show activation of αVβ3 integrin in contact with silica. This integrated computational and experimental approach provides insight into interactions that regulate osteogenesis toward more efficient biomaterial designs. [ABSTRACT FROM AUTHOR]

Abstract: Well‐designed micropatterns present in native tissues and organs involve changes in extracellular matrix compositions, cell types and mechanical properties to reflect complex biological functions. However, the design and fabrication of these micropatterns in vitro to meet task‐specific biomedical applications remains a challenge. A de novo design strategy to code and synthesize functional micropatterns is presented to engineer cell alignment through the integration of aqueous‐peptide inkjet printing and site‐specific biomineralization. The inkjet printing provides direct writing of macroscopic biosilica selective peptide‐R5 patterns with micrometer‐scale resolution on the surface of a biopolymer (silk) hydrogel. This is combined with in situ biomineralization of the R5 peptide for site‐specific growth of silica nanoparticles on the micropatterns, avoiding the use of harsh chemicals or complex processing. The functional micropatterned systems are used to align human mesenchymal stem cells and bovine serum albumin. This combination of peptide printing and site‐specific biomineralization provides a new route for developing cost‐effective micropatterns, with implications for broader materials designs. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogels are the focus of extensive research due to their potential use in fields including biomedical, pharmaceutical, biosensors, and cosmetics. However, the general weak mechanical properties of hydrogels limit their utility. Here, pristine silk fibroin (SF) hydrogels with excellent mechanical properties are generated via a binary‐solvent‐induced conformation transition (BSICT) strategy. In this method, the conformational transition of SF is regulated by moderate binary solvent diffusion and SF/solvent interactions. β‐sheet formation serves as the physical crosslinks that connect disparate protein chains to form continuous 3D hydrogel networks, avoiding complex chemical and/or physical treatments. The Young's modulus of these new BSICT–SF hydrogels can reach up to 6.5 ± 0.2 MPa, tens to hundreds of times higher than that of conventional hydrogels (0.01–0.1 MPa). These new materials fill the “empty soft materials' space” in the elastic modulus/strain Ashby plot. More remarkably, the BSICT–SF hydrogels can be processed into different constructions through different polymer and/or metal‐based processing techniques, such as molding, laser cutting, and machining. Thus, these new hydrogel systems exhibit potential utility in many biomedical and engineering fields. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogels are the focus of extensive research due to their potential use in fields including biomedical, pharmaceutical, biosensors, and cosmetics. However, the general weak mechanical properties of hydrogels limit their utility. Here, pristine silk fibroin (SF) hydrogels with excellent mechanical properties are generated via a binary‐solvent‐induced conformation transition (BSICT) strategy. In this method, the conformational transition of SF is regulated by moderate binary solvent diffusion and SF/solvent interactions. β‐sheet formation serves as the physical crosslinks that connect disparate protein chains to form continuous 3D hydrogel networks, avoiding complex chemical and/or physical treatments. The Young's modulus of these new BSICT–SF hydrogels can reach up to 6.5 ± 0.2 MPa, tens to hundreds of times higher than that of conventional hydrogels (0.01–0.1 MPa). These new materials fill the “empty soft materials' space” in the elastic modulus/strain Ashby plot. More remarkably, the BSICT–SF hydrogels can be processed into different constructions through different polymer and/or metal‐based processing techniques, such as molding, laser cutting, and machining. Thus, these new hydrogel systems exhibit potential utility in many biomedical and engineering fields. [ABSTRACT FROM AUTHOR]

The production of structural and functional materials with enhanced mechanical properties through the integration of soft and hard components is a common approach to Nature's material design. However, directly mimicking these optimized design routes in the lab for practical applications remains challenging. For example, graphene and silk are two materials with complementary mechanical properties that feature ultrahigh stiffness and toughness, respectively. Yet, no simple and controllable approach is developed to homogeneously integrate these two components into functional composites, mainly due to the hydrophobicity and chemical inertness of graphene. In this study, well-dispersed and highly stable graphene/silk fibroin (SF) suspension systems are developed, which are suitable for processing to fabricate polymorphic materials, such as films, fibers, and coatings. The obtained graphene/SF nanocomposites maintain the electronic advantages of graphene, and they also allow tailorable mechanical performance to form including ultrahigh stretchable (with a strain to failure to 611 ± 85%), or high strength (339 MPa) and high stiffness (7.4 GPa) material systems. More remarkably, the electrical resistances of these graphene/SF materials are sensitive to material deformation, body movement, as well as humidity and chemical environmental changes. These unique features promise their utility as wearable sensors, smart textiles, intelligent skins, and human-machine interfaces. [ABSTRACT FROM AUTHOR]

Elastomeric, robust, and biocompatible hydrogels are rare, while the need for these types of biomaterials in biomedical-related uses remains high. Here, a new family of genetically engineered silk-elastin-like proteins (SELPs) with encoded enzymatic crosslinking sites is developed for a new generation of stimuli-responsive yet robust hydrogels. Input into the designs is guided by simulation and realized via genetic engineering strategies. The avoidance of gamma irradiation or chemical crosslinking during gel fabrication, in lieu of an enzymatic process, expands the versatility of these new gels for the incorporation of labile proteins and cells. In the present study, the new SELP hydrogels offer sequence-dependent, reversible stimuli-responsive features. Their stiffness covers almost the full range of the elasticity of soft tissues. Further, physical modification of the silk domains provides a secondary control point to fine-tune mechanical stiffness while preserving stimuli-responsive features, with implications for a variety of biomedical material and device needs. [ABSTRACT FROM AUTHOR]

Functional vascularization is critical for the clinical regeneration of complex tissues such as kidney, liver, or bone. The immobilization or delivery of growth factors has been explored to improve vascularization capacity of tissue-engineered constructs; however, the use of growth factors has inherent problems such as the loss of signaling capability and the risk of complications including immunological responses and cancer. Here, a new method of preparing water-insoluble silk protein scaffolds with vascularization capacity using an all-aqueous process is reported. Acid is added temporally to tune the self-assembly of silk in the lyophilization process, resulting in water-insoluble scaffold formation directly. These biomaterials are mainly noncrystalline, offering improved cell proliferation than previously reported silk materials. These systems also have an appropriate softer mechanical property that could provide physical cues to promote cell differentiation into endothelial cells, and enhance neovascularization and tissue ingrowth in vivo without the addition of growth factors. Therefore, silk-based degradable scaffolds represent an exciting biomaterial option, with vascularization capacity for soft tissue engineering and regenerative medicine. [ABSTRACT FROM AUTHOR]

Recent use of biopolymers as interface materials between planar, inorganic electronics and biological tissues has required the adaptation of micro- and nanofabrication techniques for use with these nontraditional materials. In this work, a method which builds on this principle for spatial control of adhesion in multilayer silk fibroin laminates is investigated. This is accomplished through the addition of a spatially patterned amorphous silk adhesive layer in between the films to be adhered, before thermally processing them with heat (120 °C) and pressure (80 Psi) according to established procedures. A one-step method for rapid, high-throughput fabrication is demonstrated, which establishes a strong (1100 kPa) bond between the layers independent of the initial processing conditions of the films. The adhesive layers can be patterned using existing silk fabrication techniques, allowing for the assembly of complex geometries including bilayers and microbubbles. Additionally, the utility of this method is demonstrated for potential applications in drug delivery and transient electronics. This approach provides a versatile method for construction of complex multilayer structures in silk, which with future work may ultimately improve the utility of this material as a bridge between high technology and the biomedical sciences. [ABSTRACT FROM AUTHOR]

Elastomeric, fully degradable, and biocompatible biomaterials are rare, with current options presenting significant limitations in terms of ease of functionalization and tunable mechanical and degradation properties. A new method for covalently crosslinking tyrosine residues in silk proteins, via horseradish peroxidase and hydrogen peroxide, to generate highly elastic hydrogels with tunable properties, is reported. These materials offer tunable mechanical properties, gelation kinetics, and swelling properties. In addition, these new polymers withstand shear strains on the order of 100%, compressive strains greater than 70% and display stiffness between 200-10 000 Pa, covering a significant portion of the properties of native soft tissues. Molecular weight and solvent composition allow control of material mechanical properties over several orders of magnitude while maintaining high resilience and resistance to fatigue. Encapsulation of human bone marrow derived mesenchymal stem cells (hMSC) shows long term survival and exhibits cell-matrix interactions reflective of both silk concentration and gelation conditions. Further biocompatibility of these materials is demonstrated with in vivo evaluation. These new protein-based elastomeric and degradable hydrogels represent an exciting new biomaterials option, with a unique combination of properties, for tissue engineering and regenerative medicine. [ABSTRACT FROM AUTHOR]

The need for dynamic, elastomeric polymeric biomaterials remains high, with few options with tunable control of mechanical properties, and environmental responses. Yet the diversity of these types of protein polymers pursued for biomaterials-related needs remains limited. Robust high-throughput synthesis and characterization methods will address the need to expand options for protein-polymers for a range of applications. Here, a combinatorial library approach with high throughput screening is used to select specific examples of dynamic protein silk-elastin-like polypeptides (SELPs) with unique stimuli responsive features, including tensile strength and adhesion. Using this approach, 64 different SELPs with different sequences and molecular weights are selected out of over 2000 recombinant E. coli colonies. New understanding of sequence-function relationships with this family of proteins is gained through this combinatorial-screening approach and can provide a guide to future library designs. Further, this approach yields new families of SELPs to match specific material functions. [ABSTRACT FROM AUTHOR]

There is great need for soft biomaterials that match the stiffness of human tissues for tissue engineering and regeneration. Hydrogels are frequently employed for extracellular matrix functionalization and to provide appropriate mechanical cues. It is challenging, however, to achieve structural integrity and retain bioactive molecules in hydrogels for complex tissue formation that may take months to develop. This work aims to investigate mechanical and biochemical characteristics of silk hydrogels for soft tissue engineering, specifically for the nervous system. The stiffness of 1 to 8% silk hydrogels, measured by atomic force microscopy, is 4 to 33 kPa. The structural integrity of silk gels is maintained throughout embryonic chick dorsal root ganglion (cDRG) explant culture over 4 days whereas fibrin and collagen gels decrease in mass over time. Neurite extension of cDRGs cultured on 2 and 4% silk hydrogels exhibit greater growth than softer or stiffer gels. Silk hydrogels release <5% of neurotrophin-3 (NT-3) over 2 weeks and 11-day old gels show maintenance of growth factor bioactivity. Finally, fibronectin- and NT-3-functionalized silk gels elicit increased axonal bundling suggesting their use in bridging nerve injuries. These results support silk hydrogels as soft and sustainable biomaterials for neural tissue engineering. [ABSTRACT FROM AUTHOR]

In the field of regenerative medicine there is a need for scaffolds that support large, critically-sized tissue formation. Major limitations in reaching this goal are the delivery of oxygen and nutrients throughout the bulk of the engineered tissue as well as host tissue integration and vascularization upon implantation. To address these limitations, the development of a porous scaffold platform made from biodegradable silk protein that contains an array of vascular-like structures that extend through the bulk of the scaffold was previously reported. Here, the hollow channels play a pivotal role in enhancing cell infiltration, delivering oxygen and nutrients to the scaffold bulk, and promoting in vivo host tissue integration and vascularization. The unique features of this protein biomaterial system, including the vascular structures and tunable material properties, render this scaffold a robust and versatile tool for implementation in a variety of tissue engineering, regenerative medicine, and disease modeling applications. [ABSTRACT FROM AUTHOR]

Neural engineering provides promise for cell therapy by integrating the host brain with brain-machine-interface technologies in order to externally modulate functions. Long-term interfaces with the host brain remain a critical challenge due to insufficient graft cell survivability and loss of brain electrode sensitivity over time. Here, integrated neuron-electrode interfaces are developed on thin flexible and transparent silk films as brain implants. Mechanical properties and surface topography of silk films are optimized to promote cell survival and alignment of primary rat cortical cells. Compartmentalized neural cultures and co-patterned electrode arrays are incorporated on the silk films with built-in wire connections. Electrical stimulation via electrodes embedded in the films activated surrounding neurons to produce evoked calcium responses. In mice brains, silk film implants show conformal contact capable of modulating host brain cells with minimal inflammatory response and stable indwelling for weeks. The approach of combining cell therapy and brain electrodes could provide sustained functional interfaces with ex vivo control with spatial precision. [ABSTRACT FROM AUTHOR]

The goals of the present study are to establish an in vitro co-culture model of osteoblast and osteoclast function and to quantify the resulting bone remodeling. The bone is tissue engineered using well-defined silk protein biomaterials in 2D and 3D formats in combination with human cells. Parathyroid hormone (PTH) and glucose-dependent insulinotropic peptide (GIP) are selected because of their roles in bone remodeling for expression in tethered format on human mesenchymal stem cells (hMSCs). The cell-modified biomaterial surfaces are reconstructed from scanning electron microscopy images into 3D models for quantitative measurement of surface characteristics. Increased calcium deposition and surface roughness are found in 3D surface models of silk protein films remodeled by co-cultures containing tethered PTH, and decreased surface roughness is found for the films remodeled by tethered GIP co-cultures. Increased surface roughness is not found in monocultures of hMSCs expressing tethered PTH, suggesting that osteoclast-osteoblast interactions in the presence of PTH signaling are responsible for the increased mineralization. These data point towards the design of in vitro bone models in which osteoblast-osteoclast interactions are mimicked for a better understanding of bone remodeling. [ABSTRACT FROM AUTHOR]

Tunable protein composites are important for constructing extracellular matrix mimics of human nerve tissues with control of charge, structural, and mechanical properties. Molecular interaction mechanisms between silk fibroin protein and recombinant human tropoelastin, based on charge, are utilized to generate a new group of multifunctional protein alloys with different net charges. These new biomaterials are then utilized as a biomaterial platform to control neuron cell response. With a +38 net charge in water, tropoelastin molecules provide extraordinary elasticity and selective interactions with cell surface integrins. In contrast, negatively charged silk fibroin protein (net charge −36) provides remarkable toughness and stiffness with morphologic stability in material formats via autoclaving-induced beta-sheet crystal physical crosslinks. The combination of these properties in alloy format extends the versatility of both structural proteins, providing a new biocompatible, biodegradable, and charge-tunable biomaterial platform for neural repair. The data point to these protein alloys as an alternative to commonly used charged synthetic polymers, particularly with regard to the versatility of material formats (e.g., gels, sponges, films, fibers). The results also provide a practical example of physically designed protein materials with control of net charge to direct biological outcomes, in this case for neuronal tissue engineering. [ABSTRACT FROM AUTHOR]

There is critical clinical demand for tissue-engineered (TE), 3D constructs for tissue repair and organ replacements. Current efforts toward this goal are prone to necrosis at the core of larger constructs because of limited oxygen and nutrient diffusion. Therefore, critically sized 3D TE constructs demand an immediate vascular system for sustained tissue function upon implantation. To address this challenge the goal of this project was to develop a strategy to incorporate microchannels into a porous silk TE scaffold that could be fabricated reproducibly using microfabrication and soft lithography. Silk is a suitable biopolymer material for this application because it is mechanically robust, biocompatible, slowly degrades in vivo, and has been used in a variety of TE constructs. Here, the fabrication of a silk-based TE scaffold that contains an embedded network of porous microchannels is reported. Enclosed porous microchannels support endothelial lumen formation, a critical step toward development of the vascular niche, while the porous scaffold surrounding the microchannels supports tissue formation, demonstrated using human mesenchymal stem cells. This approach for fabricating vascularized TE constructs is advantageous compared to previous systems, which lack porosity and biodegradability or degrade too rapidly to sustain tissue structure and function. The broader impact of this research will enable the systemic study and development of complex, critically-sized engineered tissues, from regenerative medicine to in vitro tissue models of disease states. [ABSTRACT FROM AUTHOR]

The reliability of chronic, brain-penetrating electrodes must be improved for these -neural recording technologies to be viable in widespread clinical applications. One approach to improving electrode reliability is to reduce the foreign body response at the probe-tissue interface. In this work, silk fibroin is investigated as a candidate material for fabricating mechanically dynamic neural probes with enhanced biocompatibility compared to traditional electrode materials. Silk coatings are applied to flexible cortical electrodes to produce devices that transition from stiff to flexible upon hydration. Theoretical modeling and in vitro testing show that the silk coatings impart mechanical properties sufficient for the electrodes to penetrate brain tissue. Further, it is demonstrated that silk coatings may reduce some markers of gliosis in an in vitro model and that silk can encapsulate and release the gliosis-modifying enzyme chondroitinase ABC. This work establishes a basis for future in vivo studies of silk-based brain-penetrating electrodes, as well as the use of silk materials for other applications in the central nervous system where gliosis must be controlled. [ABSTRACT FROM AUTHOR]

Effective treatment of infections in avascular and necrotic tissues can be challenging due to limited penetration into the target tissue and systemic toxicities. Controlled-release polymer implants have the potential to achieve the high local concentrations needed while also minimizing systemic exposure. Silk biomaterials possess unique characteristics for antibiotic delivery, including biocompatibility, tunable biodegradation, stabilizing effects, water-based processing, and diverse material formats. The functional release of antibiotics spanning a range of chemical properties from different material formats of silk (films, microspheres, hydrogels, coatings) is reported. The release of penicillin and ampicillin from bulk-loaded silk films, drug-loaded silk microspheres suspended in silk hydrogels and bulk-loaded silk hydrogels is investigated and the in vivo efficacy of the ampicillin-releasing silk hydrogels is demonstrated in a murine infected-wound model. Silk sponges with nanofilm coatings are loaded with gentamicin and cefazolin, and release is sustained for 5 and 3 days, respectively. The capability of silk antibiotic carriers to sequester, stabilize, and then release bioactive antibiotics represents a major advantage over implants and pumps based on liquid drug reservoirs, where instability at room or body temperature is limiting. The present studies demonstrate that silk biomaterials represent a novel, customizable antibiotic platform for focal delivery of antibiotics using a range of material formats (injectable to implantable). [ABSTRACT FROM AUTHOR]

The mechanical properties of spider silks drive interest as sources of new materials. However, there remains a lot to learn regarding the relationships between sequence, structure, and mechanical properties. In order to predict the types of sequence-functional relationships, synthesis-characterization-computation are integrated using recombinant spider silk-like block copolymers. Two designs are studied, both with origins from the spider Nephila clavipes. These proteins are studied both experimentally and in silico to understand the relationships between sequence chemistry, processing, structure, and materials function. Films formed from the two proteins are thoroughly characterized. In parallel, molecular modeling is used to assess the propensity of the two sequences to form β-sheets or crystalline structures. The results demonstrate that the modeling predicts the structural differences between the two silk-like polymers and these features can also be related to differences in functional outcomes. With this example of relating sequence design (hydrophobic-hydrophilic domains), experiment (genetic design and synthesis), processing (film and fiber formation) and modeling (predictions of crystallinity), synergy among these methods is demonstrated for predictable material outcomes. This approach offers a robust discovery path when looking towards next generation approaches to targeted materials outcomes. [ABSTRACT FROM AUTHOR]

Although silk is an ancient material, it is highly versatile and can be processed into various material formats to accommodate new and emerging applications. On page 58, David L. Kaplan and co ‐ workers demonstrate that self ‐ assembling silk hydrogels can serve as a valuable local delivery platform for cancer research. [ABSTRACT FROM AUTHOR]

Animal silks, consisting of pure protein components, offer an extraordinary combination of strength, elongation, and toughness, exceeding most engineered materials. The secret to this success is their unique nanoarchitectures formed through the hierarchical self‐assembly of silk proteins. This natural process contrasts the production of artificial silk materials, which usually are directly constructed as bulk structures from silk fibroin (SF) molecules. A variety of fabrication strategies to control nanostructures of silks or to create functional materials from silk nanoscale building blocks have been developed in the recent years. These emerging fabrication strategies offer an opportunity to tailor the structure of SF at the nanoscale and provide a promising route to produce structurally and functionally optimized silk nanomaterials. Herein, the critical roles of silk nanoarchitectures in property and function of natural silk fibers are reviewed and the strategies of utilization of these silk nanobuilding blocks are outlined. Further, the state‐of‐the‐art techniques to create silk nanoarchitectures and to generate silk‐based nanocomponents are summarized. An effective approach to constructing sophisticated silk functional nanocomposites with promising applications in regenerative medicine, drug delivery, and optical and electronic device designs is provided. Further, such insights suggest templates to consider for other material systems. A critical summary of the state of the art in the field of design, fabrication, and function of silk‐based nanomaterials is provided in this review. The structure–property–function relationships of nanobuilding blocks in silk fibers and the emerging strategies for fabrication and use of natural and regenerated silk fibroin–based nanomaterials are highlighted. [ABSTRACT FROM AUTHOR]

A ubiquitous feature of natural silk fibers is the presence of well‐organized mesostructures, including microfibrils, nanofibrils, and nanoparticles. These mesoscale building blocks are typically well organized into sophisticated arrangements and contribute robust mechanical performance and functions as part of natural silk fibers. However, it remains a major challenge to directly isolate these mesostructures for engineering applications. Here, an environmentally friendly and scalable "partial dissolution and physical dispersion" strategy is developed to exfoliate silk fibers into different mesostructures, including microfibrils, nanofibrils, nanorods, and nanoparticles. On the basis of the advantages of these mesosilks in tunable sizes, sharp size distributions, high modulus, excellent redispersibility, as well as versatile processability, the applications of these mesosilks in electronic and environmental fields are further explored, including water treatment, recycling organic solvent, paper sensors, and nanofertilizers. These explorations open a new avenue for silk fiber applications while also providing a pathway to help address critical issues in electronic and environmental fields. An environmentally friendly and scalable "partial dissolution and physical dispersion" strategy is designed to exfoliate silk fibers into different mesostructures, including microfibrils, nanofibrils, nanorods, and nanoparticles. These silk mesostructures can be further assembled into polymorphic materials, showing promising applications in electronic and environmental fields. [ABSTRACT FROM AUTHOR]

Well‐designed micropatterns present in native tissues and organs involve changes in extracellular matrix compositions, cell types and mechanical properties to reflect complex biological functions. However, the design and fabrication of these micropatterns in vitro to meet task‐specific biomedical applications remains a challenge. A de novo design strategy to code and synthesize functional micropatterns is presented to engineer cell alignment through the integration of aqueous‐peptide inkjet printing and site‐specific biomineralization. The inkjet printing provides direct writing of macroscopic biosilica selective peptide‐R5 patterns with micrometer‐scale resolution on the surface of a biopolymer (silk) hydrogel. This is combined with in situ biomineralization of the R5 peptide for site‐specific growth of silica nanoparticles on the micropatterns, avoiding the use of harsh chemicals or complex processing. The functional micropatterned systems are used to align human mesenchymal stem cells and bovine serum albumin. This combination of peptide printing and site‐specific biomineralization provides a new route for developing cost‐effective micropatterns, with implications for broader materials designs. Coding cell micropatterns through peptide inkjet printing for arbitrary biomineralized architectures is demonstrated here. The functional micropatterned systems are used to align human mesenchymal stem cells and bovine serum albumin in vitro, avoiding the use of harsh chemicals or complex processing, while providing potential applications in developing cost‐effective micropatterns to meet task‐specific biomedical applications. [ABSTRACT FROM AUTHOR]