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The development of biodegradable bone scaffolds that align with the growth cycle of new bone has become a prominent focus in the field of bone defect repair. The sintered porous hydroxyapatite scaffolds exhibit a high degree of crystallization and demonstrate a slow degradation rate following implantation. The apatite phase with low crystallinity can be obtained following the hydration reaction of the non-sintered calcium phosphate bone cement (CPC) scaffolds. However, this leads to the formation of a weak alkaline environment during degradation, ultimately resulting in unsustainable degradation. The present study focuses on the fabrication of porous pectin/CPC composite scaffolds through two approaches during the preparation process of non-sintered porous CPC scaffolds: uniform composite and surface modification. The degradation performance of porous composite scaffolds exhibited an increase with the rise in pectin content. At a pectin content of 70 mg/mL, the scaffolds demonstrated a degradation rate of 13.79% within a span of 30 days. The mechanical properties of the porous scaffolds were enhanced with an increase in pectin concentration through surface coating. When the pectin concentration was 5 wt%, the scaffold exhibited a compressive strength of 8.72 MPa, an elastic modulus of 0.82 GPa, and experienced a degradation rate of 12.57% after a period of 30 days. The local acidic environment not only facilitates the dissolution of bone-like apatite but also enhances cell proliferation and adhesion. Pectin/apatite porous scaffolds exhibit excellent biocompatibility, offering a novel approach for the development of biodegradable bone replacement scaffolds.

Herein, a novel strategy, namely Vat photopolymerization-assisted template replacement method was developed to achieve elaborate triply periodic minimal surface structure and different pore sizes in biodegradable Zn-based porous scaffolds. The pore structure, microstructure, phase constitution, degradation properties, mechanical performance, in vitro cytocompatibility and antibacterial activity were systematically investigated. As a result, triply periodic minimal surface structures with different pore sizes were successfully obtained in Zn–1Mg porous scaffolds. The actual porosity closely matched the designed porosity, demonstrating the efficacy of the new strategy in achieving precise pore structures with a difference below 2%. Zn–1Mg scaffolds, designed with a pore size of 780 mm, exhibited a uniaxial compressive strength of 59.95 MPa and an elastic modulus of 3.07 GPa. Furthermore, the mechanical integrity was well-maintained even after 28 days of immersion, attributed to the substantial deposition of calcium-phosphate-rich corrosion products within the porous structure. More importantly, a suitable weight loss rate of about 15% were confirmed after 28 days immersion, indicating a period for total degradation of approximately 13 months based on a linear degradation assumption. Further, the experimental scaffolds demonstrated good cytocompatibility with MC3T3-E1 preblast cells and exhibited significant antibacterial activity against both Staphylococcus aureus and Escherichia coli.

Renewable lignocellulosic biomass is a favorable energy resource since its co-pyrolysis with hydrogen-rich plastics can produce high-yield and high-quality biofuel. In contrast to earlier co-pyrolysis research that concentrated on increasing product yield, this study comprehends the synergistic effects of two distinct feedstocks that were not considered earlier. This work focuses on co-pyrolyzing wheat straw (WS) with non-reusable polyethylene terephthalate (PET) for the production of pyrolysis oil. WS and PET were blended in different ratios (100/0, 80/20, 60/40, 40/60, 20/80, and 0/100), and pyrolysis experiments were conducted in a fixed-bed reactor under different temperatures to assess their synergistic effect on oil yield. Synergy rates of up to 7.78 % were achieved on yield for the blends of plastic and biomass at a temperature of 500 °C. In comparison to individual biomass or plastics, co-pyrolyzing PET-biomass blends demonstrated good process interaction and promoted the yields of value-added products. The heating value of the pyrolysis oils was in the range of 16.45–28.64 MJ/kg, which depends on the amount of plastic present in the feedstock. The physical analysis of the oils shows that they can be used for heat production by direct combustion in boilers or furnaces. The correlation between WS and PET was validated with the aid of Fourier transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) analysis. The GC-MS result demonstrated the presence of different compounds such as O-H compounds, esters, carbonyl group elements, acids, hydrocarbons, aromatics, and nitrogenated compounds in the pyrolysis oil, which differed based on the proportions of PET in the feedstock. The increased hydrocarbon and reduced oxygen percentages in the pyrolysis oil were implicitly caused by enhanced hydrocarbon pool mechanisms, in which the breakdown of PET may be supplied as a hydrogen donor. Overall, waste lignocellulosic biomass and plastics can be used to produce biofuels, which helps reduce the amount of solid waste that ends up in landfills. This study also revealed that future research should be focused on the reaction mechanisms of WS and PET co-pyrolysis in order to examine the synergistic interactions.

Biodegradable zinc (Zn) alloys are promising implant materials to restore bone defects in orthopedics. Adding silver (Ag) to Zn not only enhances its mechanical properties but also improves its antibacterial properties. However, the regular pattern of Ag composition on the properties of Zn-xAg alloys remains unclear. In this paper, Zn-Ag alloys with different Ag contents ranging from 0.5 to 6.0% were prepared by casting process and were systematically investigated both in vitro and in vivo. Mechanical tests suggest that the increase of Ag content enhanced the yield strength (YS), ultimate tensile strength (UTS), Vickers hardness, and elongation. Compared with pure Zn, the maximum YS, UTS, Vickers hardness, and elongation were achieved at Zn-6Ag, which were increased by 267%, 295%, 115%, and 172%, respectively. The degradation rate increased and the antibacterial properties were enhanced accordingly. All 25% and most 50% extracts of Zn-Ag alloys significantly promoted the proliferation of MC3T3-E1 cells, except for 50% Zn-6Ag extracts showing cytotoxicity. In the rat femoral condyle model, Zn-2Ag and Zn-4Ag alloys exhibited enhanced osteogenic performance at the early stage of implantation compared with pure Zn. Zn-Ag alloys (especially Zn-2Ag and Zn-4Ag) are identified as promising bone repair materials.

Existing research suggested 300∼600 μm as the optimal pore size range for metallic bone implants. The human bones, however, have numerous pores smaller than 300 μm for bone ingrowth, cell growth and migration, fluid flow, and so forth. The bone implant with such small-sized pores has been rarely manufactured and its property is unclear. In the paper, biodegradable Fe scaffolds of different pore sizes (50 μm, 100 μm, 150 μm, 200 μm, and 300 μm) were fabricated by direct ink writing (DIW) with subsequent sintering. The interconnected pores of all scaffolds are highly precise and have no residual powders. The in-vitro degradation and compression tests were conducted on the scaffolds to evaluate the effect of pore size on degradation and mechanical behaviors, respectively. The results indicate that a decrease in pore size leads to an increase in degradation rate, from 0.0423 ± 0.0014 to 0.0433 ± 0.0035 mm/year, with the exception of the 50 μm scaffolds which exhibit the lowest value of 0.0052 ± 0.0018 mm/year due to clogging by degradation products; meanwhile, both elastic modulus and yield strength rise from 344.8 ± 18.6 MPa to 625.0 ± 52.5 MPa and from 9.5 ± 0.9 MPa to 15.1 ± 0.8 MPa, respectively. The pore size of 100 μm shows the most significant potential for use in Fe bone implants regarding its good degradation and mechanical behaviors. Our work provides new insight into the preferable pore size of metallic bone implants produced by additive manufacturing.

Articular cartilage with limited ability of regeneration remains a grand challenge in the field of tissue engineering. Poly(vinyl alcohol) (PVA) hydrogel with low friction coefficient have been regarded as prior candidate for cartilage substitute, whereas lack of structure performance and bioactivity limited their application. Phosphate glass fiber (PGF) with outstanding mechanical performance and nature of biodegradability presents potential capability to improve mechanical stability of hydrogel and chondrocyte metabolism as well as cell recruitment. Herein, we describe a novel PGF-PVA composites hydrogel incorporated with continuous PGF. The presence of stiff PGF not only improves the mechanical properties of hydrogel with maximum tensile strength of 12.44 MPa and Young's modulus of 68.35 MPa, but also endows the hydrogel molecular structure with the increase of crystallinity and thermal stability via formation of crosslinking points. More importantly, the PVA hydrogel matrix exhibits efficient ions exchange behavior to control ions concentration during PGF degradation, resulting in more suitable metabolic environment for chondrocyte proliferation and induction with enhanced recruitment. Therefore, it is believed that this work provides a kind of fiber reinforced hydrogel material promising excellent properties for cartilage repair.

The graphene-modified composite poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) monofilaments were prepared by melt spinning. The effects of graphene (GR) contents on the microstructural, thermal, dynamic mechanical, and mechanical properties and the degradation behavior of the graphene-modified composite PLA/PBAT monofilaments were studied. Scanning electron microscopy (SEM) confirmed the improved compatibility of the PLA particles in the PBAT matrix, while the transmission electron microscopy (TEM) demonstrated the size and morphology of the GR distribution in the polymer. As the GR content increased, dynamic mechanical analysis (DMA) clarified a decrease of the difference of glass transition temperature (Tg) between PLA and PBAT. In addition, the mechanical properties of the composite monofilaments were significantly enhanced at a GR content of 0.2 wt%. Weight loss rate of the composite monofilaments under soil and sea degradation conditions were obviously related to the GR content.

The repair of segmental bone defects caused by traumatic injury or pathological diseases remains a substantial challenge in clinic. Poly-l-lactic acid (PLLA) is recognized as one potential bone substitute material due to its natural biodegradability and excellent biocompatibility. Nevertheless, it still faces several fundamental puzzles including insufficient mechanical properties, slow degradation and poor osteogenic activity. To address these issues, the corresponding strategies were thoroughly explored in this review. Regulation of molecular weight and crystallization, as well as the control of crack propagation were the mainstream methods to improve the mechanical properties of PLLA, whereas surface medication and polymer blending was commonly adopted to regulate the degradation behavior. To achieve desirable tissue regeneration ability, the combination of physical stimulation (electric and magnetic) brings about a new and attractive solution, since it is able to mimic the electro-magnetic microenvironment of human body. Furthermore, future research directions are proposed from the prospects of fabrication process, dynamic degradation and multifunctional application. This review aims to offer deep insights and meaningful guidelines for future study of PLLA as implants.

Microstructure, degradation behavior in vitro and mechanical property of as-extruded Mg-2Zn-0.2Zr-xSc (x = 0, 0.2, 0.4, 0.6, 0.8, wt.%) alloys was investigated. Fine rod-like Mg(Zn,Sc,Zr) phase in as-extruded ZK-(0.4–0.8)Sc alloys inhibits recrystallized grains growth, resulting in grain refinement. The addition of Sc decreases the degradation rate in vitro and improves the mechanical property of ZK20 alloy. All tested alloys had no cytotoxicity effect on HUVEC and MC3T3-E1 cells. This work provides a better understanding on adding Sc as alloying element for biomedical Mg alloys with superior mechanical property, slower degradation rate and good biocompatibility.

Additively manufactured (AM) biodegradable zinc (Zn) alloys have recently emerged as promising porous bone-substituting materials, due to their moderate degradation rates, good biocompatibility, geometrically ordered microarchitectures, and bone-mimicking mechanical properties. While AM Zn alloy porous scaffolds mimicking the mechanical properties of trabecular bone have been previously reported, mimicking the mechanical properties of cortical bone remains a formidable challenge. To overcome this challenge, we developed the AM Zn-3Mg alloy. We used laser powder bed fusion to process Zn-3Mg and compared it with pure Zn. The AM Zn-3Mg alloy exhibited significantly refined grains and a unique microstructure with interlaced α-Zn/Mg 2 Zn 11 phases. The compressive properties of the solid Zn-3Mg specimens greatly exceeded their tensile properties, with a compressive yield strength of up to 601 MPa and an ultimate strain of >60 %. We then designed and fabricated functionally graded porous structures with a solid core and achieved cortical bone-mimicking mechanical properties, including a compressive yield strength of >120 MPa and an elastic modulus of ≈20 GPa. The biodegradation rates of the Zn-3Mg specimens were lower than those of pure Zn and could be adjusted by tuning the AM process parameters. The Zn-3Mg specimens also exhibited improved biocompatibility as compared to pure Zn, including higher metabolic activity and enhanced osteogenic behavior of MC3T3 cells cultured with the extracts from the Zn-3Mg alloy specimens. Altogether, these results marked major progress in developing AM porous biodegradable metallic bone substitutes, which paved the way toward clinical adoption of Zn-based scaffolds for the treatment of load-bearing bony defects. STATEMENT OF SIGNIFICANCE: Our study presents a significant advancement in the realm of biodegradable metallic bone substitutes through the development of an additively manufactured Zn-3Mg alloy. This novel alloy showcases refined grains and a distinctive microstructure, enabling the fabrication of functionally graded porous structures with mechanical properties resembling cortical bone. The achieved compressive yield strength and elastic modulus signify a critical leap toward mimicking the mechanical behavior of load-bearing bone. Moreover, our findings reveal tunable biodegradation rates and enhanced biocompatibility compared to pure Zn, emphasizing the potential clinical utility of Zn-based scaffolds for treating load-bearing bony defects. This breakthrough opens doors for the wider adoption of zinc-based materials in regenerative orthopedics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Calcium silicate can be used as an excellent material for biodegradable bone scaffolds because it can provide bioactive ions to promote bone regeneration. However, the brittleness and rapid degradation of calcium silicate scaffolds have significantly limited their clinical application. In this work, the calcium silicate scaffolds printed by DLP technology were immersed in a gelatin solution under high vacuum condition to obtain calcium silicate/gelatin composite scaffolds with good mechanical and biological properties. Then, genipin was used as a cross-linker for gelatin to control the degradation properties of the composite scaffolds. The initial compressive strength and toughness of the composite scaffolds were 5.0 times and one order of magnitude higher than those of the pure calcium silicate scaffolds, respectively. The gelatin on the surface of the scaffolds could effectively act as a protective layer to regulate the degradation behaviors of the calcium silicate substrate through controlling the crosslinking degree of the gelatin. After degrading for 14 days, the composite scaffolds at 1.0 % genipin concentration exhibited the highest compressive strength of 8.6 ± 0.8 MPa, much higher than that of the pure ceramic scaffold (1.5 ± 0.3 MPa). It can be found that the toughness of the composite scaffolds were almost over 13.2 times higher than that of the pure ceramic scaffold during degradation, despite the higher toughness loss for the former. Furthermore, the composite scaffolds showed enhanced cell biocompatibility and viability. These results demonstrate that the calcium silicate/gelatin composite scaffolds can be a promising candidate in bone tissue regeneration., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.We would like to submit the enclosed manuscript entitled " Calcium silicate/gelatin composite scaffolds with controllable degradation behavior: Fabrication and evaluation”, which we wish to be considered for publication in Ceramics International. We confirm that its publication has been approved by all of us. We also would like to declare that the work described was original research that has not been published previously, and not under consideration for publication elsewhere., (Copyright © 2024. Published by Elsevier Ltd.)

There has been a considerable increase in the use of face masks in the past years. Managing face mask waste has become a global concern, as the current waste management system is insufficient to deal with such a large quantity of solid waste. The drastic increase in quantity, along with the material's inability to degrade plastic components such as polypropylene, has led to a large accumulation of plastic waste, causing a series of environmental and ecological challenges. In addition, the growing use also imposes pressure on waste management methods such as landfill and incineration, raising concerns about high energy consumption, low value-added utilization, and the release of additional pollutants during the process. This article initially reviews the impact of mask-related plastic waste generation and degradation behavior in the natural environment. It then provides an overview of various recently developed methods for recycling face mask plastic waste. The article also offers forward-looking strategies and recommendations on face mask plastic waste management. The review aims to provide guidance on harnessing the complexities of mask waste and other medical plastic pollution issues, as well as improving the current waste management system's deficiencies and inefficiencies in tackling the growing plastic waste problem., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Guvermectin is a novel biopesticide often used as seed soaking to promote the rice yield. However, its biotoxicity and degradation behavior in soils were still not disclosed, which posed a knowledge gap to guide its rational application. Therefore, the degradation behaviors of guvermectin in four typical soils under aerobic and anaerobic conditions were investigated in the laboratory. The results showed that guvermectin was degraded fast with DT 50 ranging from 0.95 to 10.10 d, and the degradation rate was higher in aerobic condition than that in anaerobic condition. Eight transformation products were screened using UPLC-QTOF/MS. The acute toxicities tests of guvermectin to Coturnix coturnix japonica and Apis mellifera were measured by biological laboratory experiments, and the acute and chronic toxicities of transformation products to Danio rerio, Daphnia magna Straus and Green algae were predicted by ECOSAR software. The results showed that guvermectin has low toxic to quail and honeybee (LD 50  2000 mg a.i./kg body weight, LD 50  ˃ 100 μg a.i./bee), and its transformation products were also low toxic class to Danio rerio, Daphnia magna Straus and Green algae (LC 50 /EC 50  > 100 mg a.i./L). However, the nucleoside-like metabolites may pose a potential risk due to their similarity to genetic material, which should be concerned. The findings provided important environmental risk assessment data for the rational use of guvermectin., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Zinc (Zn)-based composites have received extensive attention as promising biodegradable materials due to their unique combination of moderate biodegradability, biocompatibility, and functionality. Nevertheless, the low mechanical strength of as-cast Zn-based composites impedes their practical clinical application. Here we reported the mechanical properties, corrosion behavior, wear properties, and cytotoxicity of in situ synthesized biodegradable Zn-xMg 2 Ge (x = 1, 3, and 5 wt.%) composites for bone-implant applications. The mechanical properties of Zn-xMg 2 Ge composites were effectively improved by alloying and hot-rolling due to particle reinforcement of the Mg 2 Ge intermetallic phase and dynamic recrystallization. The hot-rolled (HR) Zn-3Mg 2 Ge composite exhibited the best mechanical properties, including a yield strength of 162.3 MPa, an ultimate tensile strength of 264.3 MPa, an elongation of 10.9%, and a Brinell hardness of 83.9 HB. With an increase in Mg 2 Ge content, the corrosion and degradation rates of the HR Zn-xMg 2 Ge composites gradually increased, while their wear rate decreased and then increased in Hanks' solution. The diluted extract (12.5% concentration) of the HR Zn-3Mg 2 Ge composite showed the highest cell viability compared to the other HR composites and their as-cast pure Zn counterparts. Overall, the HR Zn-3Mg 2 Ge composite can be considered a promising biodegradable Zn-based composite for bone-implant applications. STATEMENT OF SIGNIFICANCE: This paper reports the mechanical properties, corrosion behavior, wear properties, and cytotoxicity of in situ synthesized biodegradable Zn-xMg 2 Ge (x = 1, 3, and 5 wt.%) composites for bone-implant applications. Our findings demonstrated that the mechanical properties of Zn-xMg 2 Ge composites were effectively improved by alloying and hot-rolling due to Mg 2 Ge particle reinforcement and dynamic recrystallization. The hot-rolled Zn-3Mg 2 Ge composite showed superior cytocompatibility, satisfying corrosion and degradation rates, and the best mechanical properties including a yield strength of 162.3 MPa, an ultimate tensile strength of 264.3 MPa, and an elongation of 10.9%., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Zinc (Zn)-based metals and alloys are emerging as promising biodegradable implant materials due to their inherent biodegradability and good biocompatibility. However, this class of materials exhibits low mechanical strength and a slow degradation rate, which hinders their clinical application. Here we report the development of a new biodegradable Fe/Zn-3Cu composite fabricated by infiltration casting of a Zn-3Cu alloy into an Fe foam followed by hot-rolling. Our results indicate that the hot-rolled (HR) Fe/Zn-3Cu composite exhibited an α-Zn matrix phase, a secondary CuZn 5 phase, and an α-Fe phase. The HR Fe/Zn-3Cu composite exhibited an ultimate tensile strength of 269 MPa, a tensile yield strength of 210 MPa, and an elongation of 27%. The HR Fe/Zn-3Cu composite showed a degradation rate of 228 µm/year after immersion in Hanks' solution for 30 d The diluted extract of the HR Fe/Zn-3Cu composite exhibited a higher cell viability than that of the HR Zn-3Cu alloy in relation to MC3T3-E1 and MG-63 cells. Furthermore, the HR Fe/Zn-3Cu composite showed significantly better antibacterial ability than that of the HR Zn-3Cu alloy in relation to S. aureus. Overall, the HR Fe/Zn-3Cu composite can be anticipated to be a promising biodegradable implant material for bone-fixation applications. STATEMENT OF SIGNIFICANCE: This work reports a new biodegradable Fe/Zn-3Cu composite fabricated by infiltration casting and followed by hot-rolling for biodegradable bone-fixation application. Our findings demonstrated that the hot-rolled (HR) Fe/Zn-3Cu composite exhibited an ultimate tensile strength of 269.1 MPa, a tensile yield strength of 210.3 MPa, and an elongation of 26.7%. HR Fe/Zn-3Cu composite showed a degradation rate of 227.6 µm/a, higher than HR Zn-3Cu alloy after immersion in Hanks' solution for 30 d The diluted extracts of the HR Fe/Zn-3Cu composite exhibited a higher cell viability than HR Zn-3Cu alloy toward MC3T3-E1 cells. Furthermore, the HR Fe/Zn-3Cu composite showed significantly better antibacterial ability than the HR Zn-3Cu alloy toward S. aureus., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

The development of biodegradable Zn matrix composites has been considered a promising approach to achieving enhanced mechanical properties, controllable degradation rate, good biocompatibility, and good osseointegration as orthopedic implants. However, scant literature regarding Zn matrix composites has been reported because of the great difficulty in dispersing the nano-sized bioactive reinforcements uniformly within the Zn matrix. In the present study, a novel and effective method were employed to obtain Zn matrix composites reinforced by uniformly dispersed beta-tricalcium phosphate (β-TCP) via graphene oxide (GO)-assisted hetero-agglomeration and subsequent spark plasma sintering process. A very low-content (0.04 vol%) few-layered GO was used as a coupling reagent to connect the Zn matrix and nano-sized TCP particles. In an appropriate polarity solvent, the negatively charged GO sheets could combine with both the positively charged Zn powder and TCP particles by electrostatic attraction and charge neutralization. Due to the nature of hetero-agglomeration, the flexible GO sheet could adhere to the large Zn powder and attracted a certain amount of TCP particles to form a Zn/GO/TCP sandwich structure by charge neutralization thereby forming a uniform dispersion of TCP particles within Zn matrix. After the spark plasma sintering (SPS) process, the TCP particles incorporated with very thin ZnO layers (thickness of a few dozen nanometers) formed a homogeneous and unique 3D network-like distribution in as-sintered TCP/Zn composites. A unique "snap pea"-like structure was confirmed at the grain boundary of α-Zn grains, which consisted of the TCP particles as "pea" and thin ZnO layer as "pod". Due to the uniform dispersion of bioactive TCP particles and unique structure of the TCP incorporating grain boundary, as-sintered 3TCP/Zn matrix composites possessed yield strength (YS) of 140.8 ± 7.7 MPa, failure strain of 36.0 ± 2.8%, the moderate degradation rate of 19.1 ± 3.3 μm·y -1 and good cytocompatibility to MC3T3-E1 cells. Moreover, osteogenic differentiation activity evaluation revealed that the addition of TCP could significantly improve the expressions of the osteogenic differentiation-related gene (ALP) in MC3T3-E1 cells, thereby resulting in improved osteogenic capability. Therefore, biodegradable 3TCP/Zn matrix composites fabricated by GO-assisted hetero-agglomeration and subsequent SPS process could be a promising material as orthopedic implants., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Biodegradable stents can provide scaffolding and anti-restenosis benefits in the short term and then gradually disappear over time to free the vessel, among which the Mg-based biodegradable metal stents have been prosperously developed. In the present study, a Mg-8.5Li (wt.%) alloy (RE- and Al-free) with high ductility (> 40%) was processed into mini-tubes, and further fabricated into finished stent through laser cutting and electropolishing. In-vitro degradation test was performed to evaluate the durability of this stent before and after balloon dilation. The influence of plastic deformation and residual stress (derived from the dilation process) on the degradation was checked with the assistance of finite element analysis. In addition, in-vivo degradation behaviors and biocompatibility of the stent were evaluated by performing implantation in iliac artery of minipigs. The balloon dilation process did not lead to deteriorated degradation, and this stent exhibited a decent degradation rate (0.15 mm/y) in vitro, but divergent result (> 0.6 mm/y) was found in vivo. The stent was almost completely degraded in 3 months, revealing an insufficient scaffolding time. Meanwhile, it did not induce possible thrombus, and it was tolerable by surrounding tissues in pigs. Besides, endothelial coverage in 1 month was achieved even under the severe degradation condition. In the end, the feasibility of this stent for treatment of benign vascular stenosis was generally discussed, and perspectives on future improvement of Mg-Li-based stents were proposed., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier Ltd.)

Zinc (Zn) and its alloys have been considered promising absorbable metals for medical implants. However, the dynamic interaction between Zn-based materials and human blood after implantation remains unclear. In this study, a modified Chandler-Loop system was applied to assess the blood compatibility and initial degradation behavior of a Zn-4.0Cu (wt%) alloy (Zn-4Cu) and Zn with human peripheral blood under circulation conditions. In this dynamic in vitro model, the Zn-4Cu and Zn showed sufficient blood compatibility. The numbers of erythrocytes, platelets, and leukocytes were not significantly altered, and appropriate activations of the coagulation and complement system were observed. Concerning initial degradation behavior, the product layers formed on the surfaces comprise a mixture of organic and inorganic compounds while the inorganic constituents decrease toward the outer surface. Considering the corrosion morphology and electrochemical behaviors, Zn-4Cu exhibited milder and more uniform degradation than Zn. Additionally, long-term degradation tests of 28 days in human peripheral blood, human serum, and Dulbecco's phosphate-buffered saline (DPBS) demonstrated that the Zn-4Cu showed relatively uniform degradation in blood and serum. On the contrary, in DPBS, severe localized corrosion appeared along the grain boundary of the secondary phase, which was likely attributed to the acceleration of galvanic corrosion. The Zn was found with localized corrosion impeded in the blood albeit with apparently developed deep pitting holes in the serum and DPBS., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Zn-0.8 wt.% Li-0.1 wt.% Mn wire with the diameter of 0.3 mm was fabricated and further processed into gastrointestinal staple, and its in vitro and in vivo biodegradation behavior and biocompatibility were studied systematically. The experimental Zn-Li-Mn alloy staple could deform from the original U-shape to B-shape without fracture, indicating its good mechanical property. Due to the residual stress concentration caused by anastomosis deformation, the feet and leg arc part of the staple were more prone to degradation. The Zn-Li-Mn alloy staple sustained integrity after immersion in Hanks' solution and simulated gastric fluid (SGF) for 28 days, and the degradation rate in SGF was about 4 times of that in Hanks' solution. Furthermore, Zn-Li-Mn alloy staples were utilized for gastrointestinal anastomosis in pig models, with clinically-used titanium alloy staples as a comparison. No anastomotic leakage and severe inflammation were observed after operation. The Zn-Li-Mn alloy staple maintained mechanical integrity within 8 weeks' implantation. The gastrointestinal tissue healed after 12 weeks, and no obvious side effects were detected during the whole implantation period, demonstrating the good biocompatibility of Zn-Li-Mn alloy staple. Thus, Zn-Li-Mn alloy staple fabricated in this work displayed the promising potential in the gastrointestinal anastomosis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

Zinc (Zn) and its alloys are receiving great attention as promising biodegradable materials due to their suitable corrosion resistance, good biocompatibility, and highly desirable biofunctionality. Nevertheless, the low mechanical strength of pure Zn impedes its practical clinical application and there have been calls for further research into the Zn alloys and thermomechanical processes to enhance their mechanical properties and biocompatibility. Here, we report on the alloying efficacy of rare earth elements (REEs) including erbium (Er), dysprosium (Dy), and holmium (Ho) on the microstructure, mechanical properties, corrosion and wear behavior, and in vitro biological properties of Zn-1Mg-0.1RE alloys. Microstructural characterization revealed that the addition of 0.1 wt.% REEs had a significant refining effect on the grain size of the α-Zn matrix and the second phases of the alloys. Alloying of the REEs and hot-rolling effectively improved the mechanical properties due to both precipitation strengthening of the second phases of ErZn 5 , DyZn 5 , and Ho 2 Zn 17 and grain-refinement strengthening. The highest ultimate tensile strength of 259.4 MPa and yield strength of 234.8 MPa with elongation of 16.8% were achieved in the hot-rolled Zn-1Mg-0.1Ho. Alloying of REEs also improved the wear and corrosion resistance, and slowed down the degradation rate in Hanks' solution. Zn-1Mg-0.1Er showed the highest cytocompatibility of MC3T3-E1 cells cultured directly on the alloy surface and of MG-63 cells cultured in the alloy extract. Zn-1Mg-0.1Dy showed the best anticoagulant property among all the alloys. Overall, these Zn-1Mg-0.1RE (Er, Dy, and Ho) alloys can be considered promising biodegradable metallic materials for orthopedic applications., Competing Interests: Declaration of competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

Calcium phosphate cements (CPCs) have been used to treat bone defects and support bone regeneration because of their good biocompatibility and osteointegrative behavior. Since their introduction in the 1980s, remarkable clinical success has been achieved with these biomaterials, because they offer the unique feature of being moldable and even injectable into implant sites, where they harden through a low-temperature setting reaction. However, despite decades of research efforts, two major limitations concerning their biological and mechanical performance hamper a broader clinical use. Firstly, achieving a degradation rate that is well adjusted to the dynamics of bone formation remains a challenging issue. While apatite-forming CPCs frequently remain for years at the implant site without major signs of degradation, brushite-forming CPCs are considered to degrade to a greater extent. However, the latter tend to convert into lower soluble phases under physiological conditions, which makes their degradation behavior rather unpredictable. Secondly, CPCs exhibit insufficient mechanical properties for load bearing applications because of their inherent brittleness. This review places an emphasis on these limitations and provides an overview of studies that have investigated the biological and biomechanical performance as well as the degradation characteristics of different CPCs after implantation into trabecular bone. We reviewed studies performed in large animals, because they mimic human bone physiology more closely in terms of bone metabolism and mechanical loading conditions compared with small laboratory animals. We compared the results of these studies with clinical trials that have dealt with the degradation behavior of CPCs after vertebroplasty and kyphoplasty., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships, (Copyright © 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

An Mg-Zn-Ca-Y alloy operative clip was developed to overcome the drawbacks of the Ti clips such as ion dissolution inflammation, interference imaging diagnosis, and the potential harm that permanent retention brings to the patient. The structure optimization design of the hemostatic clip was carried out by the finite element numerical simulation method to realize the matching between the structure design and the material properties. Hot extrusion and wire cutting process was used to prepare the Mg-Zn-Ca-Y alloy operative clip. Corrosion degradation behavior of Mg-Zn-Ca-Y alloy in vitro was investigated using electrochemical noise (EN) and immersion test in Simulated body fluid (SBF). The carotid artery of SD rats was clipped using the Mg-Zn-Ca-Y operative clip to evaluate occlusion safety and the complete corrosion degradation behavior and biocompatibility of Mg-Zn-Ca-Y alloy clip in vivo were investigated using micro-computed tomography, histological analysis, and blood biochemical indicators. It was found that the newly designed Mg-Zn-Ca-Y clip can successfully ligate the carotid artery, and no blood leakage occurred after surgery. After eight months, the Mg-Zn-Ca-Y clip degraded utterly. Histological analysis and various blood biochemical parameters in SD rat serum samples collected at different time periods showed no tissue inflammation around the clips., Competing Interests: Declaration of competing interest The authors declared that they have no conflicts of interest to this work. We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Biodegradable zinc (Zn) and its alloys have great potential to be used for orthopedic applications due to their suitable degradation rate and good biocompatibility. However, pure Zn has insufficient mechanical properties, such as low strength and hardness, and poor plasticity, which limits its clinical applications. Here, we report on a new series of ternary Zn-3Ge-0.5X (X=Cu, Mg, and Fe) alloys aiming to achieve good corrosion resistance and biocompatibility, and enhanced mechanical properties via micro-alloying with copper (Cu), magnesium (Mg), and iron (Fe). Hot-rolling has also been applied to the new ternary alloys to further enhance their mechanical properties. Mechanical testing results indicate that both the strength and hardness of hot-rolled Zn-3Ge are significantly improved with micro-alloying of Cu, Mg, and Fe; of which the hot-rolled Zn-3Ge-0.5Mg exhibits the highest ultimate tensile strength of 253.4 MPa and yield strength of 208.5 MPa among all the alloys, 25.9% and 44.7% higher than those of the hot-rolled Zn-3Ge. The degradation rate of the as-cast alloys is lower than that of the hot-rolled alloys in Hanks' solution for 1 month and the hot-rolled Zn-3Ge-0.5Mg alloy exhibits the highest degradation rate of 0.075 mm/y. CCK-8 assay using MG-63 cells indicates that the diluted extracts of Zn-3Ge-0.5X (X=Cu, Mg, and Fe) alloys with concentrations of 12.5% and 25% exhibit no or slight cytotoxicity, and the diluted extracts of Zn-3Ge-0.5Cu alloys show high cell viability of over 100%, showing the best cytocompatibility., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

Microplastic (MP) pollution is a significant environmental concern due to the persistence of MPs and their potential adverse effects on biota. Most scientific studies have examined the distribution, ingestion, fate, behavior, amount, and effect of MPs. However, few studies have described the development of methods for the removal and remediation of MPs. Therefore, in this review, we summarize the recent literature regarding the microbial-mediated degradation of MPs and discuss the associated degradation characteristics and mechanisms. Different types and combinations of microorganisms, such as bacteria, fungi, bacterial consortia, and biofilms, that can degrade different MPs are categorized. This article summarizes approximately 50 recent papers. Twelve and 6 papers reported that bacteria and fungi, respectively, can degrade MPs. Nine articles indicated that bacterial consortia have the ability to degrade MPs, and 6 articles found that biofilms can also utilize MPs. Furthermore, to evaluate their associated degradation effects, the corresponding structural changes (i.e., macro size, surface morphology, and functional groups) in MPs after microbial degradation are examined. In addition, MP biodegradation is affected by microbial characteristics and environmental factors; therefore, the environmental factors (i.e., temperature, pH and strain activity) influencing MP degradation and the associated degradation effects (i.e., weight loss, degradation rate, and molecular weight change) are generalized. Furthermore, the mechanisms associated with the microbial-mediated degradation of MPs are briefly discussed. Finally, prospects for the degradation of MPs using microbes and future research directions are envisioned. This review provides the first systematic summary of the microbial-mediated degradation of MPs and provides a reference for future studies investigating effective means of MP pollution control., Competing Interests: Declaration of competing interest All the authors declared that they have no conflicts of interest to this work. And we declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The poor interfacial bonding and resultant agglomeration of nanoparticles in polymer-based composite severely deteriorated their reinforcement effect. In this work, MgO nanoparticles (MgO-NPs) were surface modified with Poly (L-lactic acid-co-malic acid) (PLMA) to improve the interfacial compatibility in Poly-l-lactic acid (PLLA) scaffold manufactured by selective laser sintering. PLMA possess a hydrophilic end with carboxyl group (comes from the malic acid) and an l-lactic acid chain. On one hand, the carboxyl group was able to form hydrogen bonding with the hydroxyl groups of MgO-NPs. On the other hand, the l-lactic acid chain containing the hydroxyl groups could react with the carboxyl group of PLLA. Results revealed that the scaffold exhibited significantly enhanced compressive strength and modulus by 47.1% and 237.7%, respectively, which could be ascribed to the enhanced interfacial bonding between PLLA and MgO-NPs, as well as the rigid particle reinforcement. In addition, the scaffold was favorable for cell adhesion, proliferation and differentiation, owing to the improved hydrophilic and suitable pH environment. It was suggested the scaffold was a promising material for bone repair application., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Tetracycline hydrochloride (TCH), as a typical antibiotic-pollutant, is desired to enhance its removal from public environment, due to its toxicity and persistence. Microbial electrochemical technology (MET) is a series complex microorganisms-driven processes with characteristics of simultaneous wastewater treatment and electricity generation. The study was presented to evaluate the TCH removal behavior and power generation performance through the co-metabolism under constant glucose with different TCH concentrations using MET. It was found that the TCH removal efficiency arrived at 40% during the first 6 h, when TCH concentrations ranged from 1 to 50 mg/L. It was interesting that TCH degradation rate increased to a maximum of 4.15 × 10 -2 h -1 with its concentrations varying from 1 to 20 mg/L, however, the further increase to 50 mg/L in TCH concentration resulted in a reverse 66% reduction. In the meantime, the generated bioelectricity declared a similar fluctuation trend with a maximum power density of 600 mW/m 2 under the condition of 20 mg/L TCH co-degradation with glucose. What's more, the TCH inhibition effect fitted well with Haldane's model, indicating that the microbial electrochemical system had a better potency toward TCH toxicity than that reported (EC 50  = 2.2 mg/L). Thauera as mainly functional aromatics-degrading bacteria and Bdellovibrio against bacterial pathogens, only existed in the mixed cultures with TCH and glucose, indicating extremely remarkable changes in bacterial community with TCH addition. In summary, a new approach for the anaerobic biodegradation of TCH was explored through co-metabolism with glucose using MET. The results should be useful for antibiotics wastewater disposal of containing TCH., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The degradation behavior of Mg-4 wt% Zn alloy with three different microstructures was examined in Hank's solution at 37 °C by electrochemical measurements and immersion tests in this study. The results show that the sample with cellular structure exhibits a more positive corrosion potential, lower corrosion current density, larger impedance and more protective film than samples with columnar dendritic and equiaxed dendritic structure. The higher corrosion resistance is attributed to the preferred orientation, eliminating susceptible grain boundaries and reduced secondary phases., (Copyright © 2019. Published by Elsevier B.V.)

Zn-based alloys as biodegradable materials for cardiovascular stents have drawn more and more attention in recent years. However, the hot plastic deformation of Zn-based alloys does not get enough attention. In this study, Zn-3Cu-0.5Fe alloy was prepared and then hot extruded at 140, 180, 220 and 260 °C. Effects of extrusion temperature on the microstructure, mechanical properties and degradation behavior were investigated. Nano-scaled particles precipitated during extrusion and the quantity decreased with the increasing of extrusion temperature. As the extrusion temperature increased from 140 to 260 °C, the grain size increased from 1.15 to 4.38 μm, the yield strength and ultimate tensile strength increased from 203 ± 3.23 and 221 ± 1.56 MPa to 269 ± 2.65 and 302 ± 8.01 MPa, increased by 32.5% and 45%, while the degradation rate was decreased gradually from 62.8 ± 0.72 μm/year to 49.9 ± 3.35 μm/year, decreased by 20.5%. In addition, the degradation behavior changes from a relatively uniform degradation mode to a localized degradation mode with the increase of the grain size. Dislocation gliding is replaced by grain-boundary movement and dynamic recrystallization (DRX) in the room temperature tensile deformation process. Lower extrusion temperature is beneficial for higher elongation and degradation rate as well as relatively uniform degradation mode, which is better suitable for the clinical application of cardiovascular stents., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In this study, we prepared Mg wire/poly(lactic acid) composite rods by hot pressing (HP) and hot drawing (HD) processes, which show desirable application potential as a biodegradable implant in orthopedics. The influences of the volume content of Mg wires and processing steps on the degradation behavior of composite rods as well as the mutual influence between Mg and poly(lactic acid) (PLA) during degradation were investigated. During degradation, the improved interface bonding between Mg and PLA by micro-arc oxidation can effectively inhibit the diffusion of the medium from the ends to the central part, supported by XR-CT results, which show the degradation cracks in PLA initiated and propagated along the radial direction of the rod rather than the axial direction. When compared with the hot pressed rod, the three passes hot drawn rod had lower degradation rate and better strength retention during long-time immersion. This is ascribed to the higher crystallinity of the PLA matrix by HD. For both hot pressed and hot drawn rods, more Mg content of the wires will result in an increase in the degradation rate of PLA due to alkaline catalytic hydrolysis. Therefore, we can not only predict the degradation period by the present degradation mathematical model but also further control degradation rate by adjusting processing steps and wire volume content. This will be helpful for future material design and indication selection. STATEMENT OF SIGNIFICANCE: We investigated the influence of interface microstructure, self-reinforced PLA matrix, and wire volume content on the degradation behavior and clarified the differences in the degradation mechanism of composite rods. The 3D morphology of cracks in composite rods enlightened us a clear understanding about the emergence and evolution of cracks, which revealed the reason for the failure of composite rods. The degradation model can be used to predict the degradation period and provide valuable information for their future application., (Copyright © 2019. Published by Elsevier Ltd.)

The orthopedic application of Zn is limited owing to the poor strength and low plasticity. In this study, a novel strategy by combining rapid solidification obtained by selective laser melting (SLM) and alloying with Mg was proposed to improve the mechanical properties of Zn. The microstructures, mechanical properties, as well as in vitro cytocompatibility of SLM processed Zn-xMg (x = 0-4 wt%) were studied systematically. Results shown that SLM processed Zn-xMg alloys consisted of fine equiaxed α-Zn grains with homogeneously precipitated Mg 2 Zn 11 along grain boundaries. More importantly, the grains size of α-Zn was decreased from 104.4 ± 30.4 µm to 4.9 ± 1.4 µm with Mg increasing. And Mg mainly dissolved in α-Zn developing into supersaturated solid solution due to rapid solidification effect. As a consequence, the ultimate tensile strength and elongation were enhanced by 361% and 423%, respectively, with Mg containing up to 3 wt%. Meanwhile, alloying with Mg enhanced the corrosion resistance of Zn, with the degradation rate decreasing from 0.18 ± 0.03 mm year -1 to 0.10 ± 0.04 mm year -1 . Furthermore, SLM processed Zn-xMg exhibited good biocompatibility. This research suggested that SLM processed Zn-3Mg alloy was a potential biomaterial for orthopedic applications., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

With the goal of developing new biodegradable implant materials, we have investigated the degradation behavior of (Ca, Mg)-based intermetallic compounds. The degradation behavior of the compounds within the Ca-Mg-Zn system was roughly classified into four groups, and their behaviors were strongly influenced by the compositions of the compounds. For example, the Ca3MgxZn(15-x) compound exhibited a large solubility region with varying the Mg/Zn ratio, and the Ca3Mg12Zn3 phase alloy with the lowest Zn content was rapidly broken apart within 6h of immersion. Alternatively, the Ca3Mg4.6Zn10.4 phase alloy with the highest Zn content retained the bulk shape even after 250 h of immersion. These varying degradation behaviors were ascribed to the difference in the formability of Zn oxide as a protective layer against corrosion on the specimen surfaces, depending on the Zn content. The gained results suggest that there is a feasibility on developing new biodegradable materials based on intermetallic compounds in which the degradation rate can be controlled by their compositions., (Copyright © 2014 Elsevier B.V. All rights reserved.)