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Improving the degradation performance and enhancing the biocompatibility are the main challenges of Mg-based biodegradable implants. In this study, a nano-hydroxyapatite-enhanced (nHA) Mg matrix composite was fabricated via friction stir processing and characterised, including microstructure, mechanical, in vitro degradation properties, and cytocompatibility. Hydroxyapatite is renowned for its superior bone compatibility, promoting healing responses and tissue growth. Friction stirring created a gradient grain structure in the alloy, with the stir zone exhibiting the highest grain refinement. The stir zone also contained most of the incorporated nHA and exhibited a strong texture with grains preferentially oriented along the [0001] direction. Immersion and polarisation experiments showed an increase in the FSPed WE43-nHA's corrosion resistance due to the refined microstructure. The treatment also caused a shift in the corrosion mode of the alloy from localized to uniform corrosion despite some localized corrosion associated with the nHA. Cytocompatibility tests in human osteoblast (HOB) cell lines indicated good biocompatibility in the Mg-nHA alloy, with cells exhibiting relatively healthy morphology and increased live cell count. Friction stir processing is a viable manufacturing option for creating Mg-based metal matrix composites with improved corrosion resistance and good biocompatibility.

In recent years, there has been a notable surge of interest in hybrid materials within the biomedical field, particularly for applications in bone repair and regeneration. Ceramic-polymeric hybrid scaffolds have shown promising outcomes. This study aimed to synthesize bioactive glass (BG-58S) for integration into a bioresorbable polymeric matrix based on PDLLA, aiming to create a bioactive scaffold featuring stable pH levels. The synthesis involved a thermally induced phase separation process followed by lyophilization to ensure an appropriate porous structure. BG-58S characterization revealed vitreous, bioactive, and mesoporous structural properties. The scaffolds were analyzed for morphology, interconnectivity, chemical groups, porosity and pore size distribution, zeta potential, pH, in vitro degradation, as well as cell viability tests, total protein content and mineralization nodule production. The PDLLA scaffold displayed a homogeneous morphology with interconnected macropores, while the hybrid scaffold exhibited a heterogeneous morphology with smaller diameter pores due to BG-58S filling. The hybrid scaffold also demonstrated a pH buffering effect on the polymer surface. In addition to structural characteristics, degradation tests indicated that by incorporating BG-58S modified the acidic degradation of the polymer, allowing for increased total protein production and the formation of mineralization nodules, indicating a positive influence on cell culture. [ABSTRACT FROM AUTHOR]

Context: The ensiling process presents losses that are associated with the fermentative profile, resulting in lower nutritional value, and lower aerobic stability of silages. Aims: This study aimed to evaluate the effects of chitosan and microbial inoculants addition in Mombasa grass (Megathyrsus maximus) silage (MGS) fermentation profile and losses, chemical composition, in situ degradation, and aerobic stability. Methods: Forty experimental silos (PVC tubing with 28-cm inner diameter and 25-cm height) were used in a randomised block (n = 5) design to evaluate the following treatments: (1) MGS without additives (control, CON); (2) MGS treated with 5.0 × 104 colony-forming units (CFU) of Lactobacillus buchneri (NCIM 40788) per gram of fresh matter (LBB); (3) MGS treated with 1.6 × 105 CFU of L. plantarum and 1.6 × 105 CFU of Pediococcus acidilactici per gram of fresh matter (LPP); and (4) MGS treated with 6 g/kg DM of chitosan (CHI). Key results: The treatments did not alter the pH, ammonia-N, butyric, and lactic acid concentrations in the silage. The use of LPP reduced the ethanol content, while CHI increased propionic and branched-chain fatty acids compared with other treatments. Fermentation losses and dry-matter recovery were not affected by treatments. Chitosan reduced the organic matter of the MGS in relation to the other treatments, without having an impact on the other variables of chemical composition. The treatments did not influence the in vitro degradation, nor the pH and temperature after aerobic exposure of the silage. Conclusions: Chitosan increases ethanol compared with homofermentative lactic acid bacteria inoculation and does not affect ammonia-N of Mombasa grass silage. In addition, chitosan and microbial inoculants have limited effects on Mombasa grass silage fermentation losses, nutritional value, and aerobic stability. Implications: Chitosan does not reduce fermentation losses or improve the nutritional value of grass silage. The ensiling process presents losses that are associated with the fermentative profile, resulting in lower nutritional value and lower aerobic stability of silages. The study evaluated the effects of adding chitosan and microbial inoculants to Mombasa grass (Megathyrsus maximus) silage. Chitosan altered some variables of the fermentation profile, but the treatments did not show a relevant effect on fermentation losses, chemical composition, and aerobic stability. [ABSTRACT FROM AUTHOR]

The traditional production mode of the sericulture industry is no longer suitable for the development requirements of modern agriculture; to facilitate the sustainable development of the sericulture industry, factory all-age artificial diet feeding came into being. Understanding the structural characteristics and properties of silk fibers obtained from factory all-age artificial diet feeding is an important prerequisite for application in the fields of textiles, clothing, biomedicine, and others. However, there have been no reports so far. In this paper, by feeding silkworms with factory all-age artificial diets (AD group) and mulberry leaves (ML group), silk fibers were obtained via two different feeding methods. The structure, mechanical properties, hygroscopic properties, and degradation properties were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Structurally, no new functional groups appeared in the AD group. Compared with the ML group, the structure of the two groups was similar, and there was no significant difference in mechanical properties and moisture absorption. The structure of degummed silk fibers is dominated by crystalline regions, but α-chymotrypsin hydrolyzes the amorphous regions of silk proteins, so that after 28 d of degradation, the weight loss of both is very small. This provides further justification for the feasibility of factory all-age artificial diets for silkworms. [ABSTRACT FROM AUTHOR]

The aim of the study was to improve the mechanical, biodegradation and in vitro biocompatible characteristics of as received rolled AZ31 (Mg-1%Zn-3%Al) alloy by develop the surface composite of Mg-Titania. The surface composite was developed by friction stir processing (FSP) and it's used for prosthetic applications. The influence of tool rotation speed and number of FSP passes on grain structure, grain refinement, tensile strength, hardness, in vitro degradation rate and in vitro biocompatibility were explored. The obtained results support the capability of FSP in terms of mechanical strengthening, refinement of grain structure, dispersion of reinforcement (i.e. TiO2) and controlled degradation rate. Grain structure at stir zone, advancing side and retreating side were investigated. The large grains in the alloy were reduced to a fine equiaxial grains of average dimension of ≈ 3 μm by 3rd pass of FSP. The process was performed under two different tool rotation speed, i.e. 1550 and 2260 RPM. The addition of second phase in the matrix significantly improve the grain refinement. The results obtained from tensile test revealed the improvement in the percentage elongation without compromising the strength. The micro hardness of specimens of different parametric combination were evaluated and found ≈ 30–50% improvement in the micro hardness. The degradation rate by immersion test in simulated body fluid (SBF) for 3, 6 and 10 days were performed and found a significant reduction in degradation rate. The MTT assay for the biocompatibility performed by indirect method, the results validate the non-toxic behavior of processed specimen. [ABSTRACT FROM AUTHOR]

A new family of polyester-based copolymers—poly(sorbitol adipate-co-ethylene glycol adipate) (PSAEG), poly(sorbitol adipate-co-1,4 butane diol adipate) (PSABD), and poly (sorbitol adipate-co-1,6 hexane diol adipate) (PSAHD)—was obtained with a catalyst-free melt polycondensation procedure using the multifunctional non-toxic monomer sorbitol, adipic acid, and diol, which are acceptable to the human metabolism. Synthesized polyesters were characterized by FTIR and 1H NMR spectroscopy. The molecular weight and thermal properties of the polymers were determined by MALDI mass spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis. The degradation rate was investigated, at 37 °C, in 0.1M NaOH (pH 13) and in phosphate-buffered solution (PBS) at pH 7.4. It was found that the polymers degraded faster in NaOH (i.e., in a day) compared to their degradation in PBS, which was much slower (in a week). The highest degradation rate was noticed for the PSAEG sample in both media, whereas PSAHD was the most stable polymer at pH 7.4 and 13. A reduced hydrophilicity of the polymers with diol length was indicated by low swelling percentage and sol content in water and DMSO. Mechanical studies prove that all the polymers are elastomers whose flexibility increases with diol length, shown by the increase in percentage of elongation at break and the decrease in tensile stress and Young's modulus. These biodegradable copolymers with adaptable physicochemical characteristics might be useful for a broad variety of biological applications by merely varying the length of the diol. [ABSTRACT FROM AUTHOR]

Biodegradable bone grafts have gained considerable attention in the field of clinical research as they can be used to avoid re-surgery to remove scaffolds. We fabricated biodegradable composite ceramic scaffolds using magnesium oxide and calcium phosphate following the vat photopolymerization technology. We studied the effects of different magnesium oxide content on the process of in vitro degradation of the composite scaffolds and discussed the degradation process by comparing the extent of degradation realized in Tris-HCl buffer and simulated body fluids. We also explored the variations in the mechanical properties of the scaffolds during degradation. The results revealed that the composite scaffolds maintained the strength standard for spongy bone (compressive strength σ: 2–20 MPa) even after 28 d of degradation. Additionally, the strength of the composite scaffold containing 80 wt% magnesium oxide was comparable to the strength standard recommended for cortical bones (σ: 100–200 MPa). Controllable degradation rates were recorded, and acceptable mechanical properties were observed for these scaffolds during degradation. The results reported herein can be potentially used to expand the application prospects of biodegradable scaffolds.

Borosilicate bioactive glasses exhibit excellent bioactivity and degradation properties; however, they suffer from the rapid release of bioactive elements at the initial stage of their degradation. Excessive local concentrations (such as those of B) can affect cell proliferation. Moreover, the degradation and mineralization ability of these glasses deteriorate at the later stages. Aiming to balance the release of bioactive elements during the whole process, herein, a borosilicate bioactive glass 18SiO2–6Na2O–8K2O–8MgO–22CaO–2P2O5–36B2O3 (mol%) was prepared using the melting method. Further, the effects of microcrystallization on the release of bioactive elements and in vitro degradation were studied. Results show that after heat treatment at temperatures over 620 °C, multiple microcrystalline phases, including Ca2SiO4, CaB2O4, and CaMgB2O5, form in the glass. The glass samples heat-treated within the range of 620–640 °C undergo appropriate devitrification degrees, decelerating the rate of pH increase of the immersion solution during the initial stage in comparison to those treated at lower temperatures. This results in a more continuous release of all bioactive elements and allows better control of the overall degradation. Contrarily, the more extensive devitrification degrees of glass samples heat-treated at higher temperatures reverse the pH increase and degradation trends. Since bone marrow mesenchymal stem cells and mouse embryonic osteoblast cells are pH-sensitive, inducing a suitable degree of devitrification proved to favor cell viability and enhance the mineralization capacity. Thus, different microcrystallization degrees provide new approaches for controlling the degradation and release of bioactive elements, resulting in the simultaneous enhancement of biosafety and bioactivity. [ABSTRACT FROM AUTHOR]

The AZ31/1.5TiO2 metal matrix composite is added with different Sn (Tin) weight percentages to study the impacts on in vitro degradation and wear behaviour in simulated body fluid. The AZ31-xSn/1.5TiO2 (x = 0, 3, 6, 9, and 12 wt%) composites were synthesized using stir casting. The microstructure of the alloy and the composites confirmed the existence of the intermetallic compound Mg17Al12 along the grain boundaries. When Sn was added, it dissolved in the Mg matrix and precipitated as an intermetallic compound (Mg2Sn). The Mg(OH)2 protective layer was found on the surface of the alloy and composites during the immersion test in simulated body fluid. As the immersion time increased to 48 hours, the layer started to break down, and corrosion pits appeared. The wear tests revealed that the simulated body fluid's lubrication effect effectively reduced the coefficient of friction (CoF) of the composites compared to dry sliding. But the corrosiveness of simulated body fluid resulted in a higher wear rate than under dry sliding conditions. Increasing the Sn content up to 6% improves wear resistance, and further Sn addition increases wear rate. The results of the worn surface morphology confirmed that abrasion was the dominant wear mechanism in dry sliding and simulated body fluid conditions. The increased oxygen content established the corrosion in simulated body fluid conditions in EDS spectra and corrosion pits on the worn surface morphology. [ABSTRACT FROM AUTHOR]

In order to screen a probiotic strain that has strong stress resistance, inhibits pathogenic bacte‐ ria, produces enzymes and vitamins, and can degrade fungal toxins, a series of studies were conducted on the independently screened Bacillus velezensis（BLS-1） such as optimal temperature, pH, growth curve, enzyme production ability, antibacterial ability and stress resistance, the contents of various enzymes and vitamins in the fermentation broth obtained through fermentation in a fermentation tank were measured, the degradation ability of Bacillus subtilis to various fungal toxins was investigated through in vitro degra‐ dation. The results showed that the independently screened Bacillus velezensis (BLS-1) had good acid re‐ sistance, bile salt resistance, and gastric and intestinal fluid resistance when tested in pH 2.5-3.5, bile salt concentration 0.1%-0.5%, and gastric and intestinal fluid environments; the strain had the highest spore formation rate under the optimal temperature of 37 ℃, optimal pH of 6, and cultivation time of 24- 30 hours,and entered a stable stage of growth and reached its peak in spore count after 28 hours of cultivation; the metabolites and bacteria of the fer‐ mentation broth of the strain had moderately sensi‐ tive inhibition effect on Escherichia coli; the fer‐ mentation broth contained a variety of enzymes, vi‐ tamins and other beneficial substances, and had degradation effects on zearalenone (ZEN), deoxyni‐valenol (DON), aflatoxin B1 (AFB1), fumonisin (FB), and ochratoxi (OT). The Bacillus velezensis（BLS-1） had good biological characteristics and strong stress resistance and could inhibit Escherichia coli, and it had degradation effects on zearalenone, deoxynivalenol, aflatoxin, and fumatoxin at the same time. [ABSTRACT FROM AUTHOR]

The traditional production mode of the sericulture industry is no longer suitable for the development requirements of modern agriculture; to facilitate the sustainable development of the sericulture industry, factory all-age artificial diet feeding came into being. Understanding the structural characteristics and properties of silk fibers obtained from factory all-age artificial diet feeding is an important prerequisite for application in the fields of textiles, clothing, biomedicine, and others. However, there have been no reports so far. In this paper, by feeding silkworms with factory all-age artificial diets (AD group) and mulberry leaves (ML group), silk fibers were obtained via two different feeding methods. The structure, mechanical properties, hygroscopic properties, and degradation properties were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Structurally, no new functional groups appeared in the AD group. Compared with the ML group, the structure of the two groups was similar, and there was no significant difference in mechanical properties and moisture absorption. The structure of degummed silk fibers is dominated by crystalline regions, but α-chymotrypsin hydrolyzes the amorphous regions of silk proteins, so that after 28 d of degradation, the weight loss of both is very small. This provides further justification for the feasibility of factory all-age artificial diets for silkworms.

In this study, the effects of Mg addition on the organization refinement and mechanical properties of the alloys were investigated by designing Zn-Mg binary alloys with different compositions. Solution treatment and cold drawing successfully prepared fine wire materials with smooth surface and uniform organization. The material’s mechanical properties were further improved by treating the fine wires with an optimized annealing process. Electrochemical tests and in vitro degradation experiments showed that the degradation properties of the alloy in simulated body fluids were closely related to the alloy composition and microstructure. Cytotoxicity tests showed that the prepared Zn-Mg alloys were significantly cytotoxic to tumor cells. The corrosion weight loss analysis revealed the corrosion behavior of the alloy and its trend with time. Overall, this study provides critical experimental data and theoretical basis for preparing biodegradable biomedical metal-zinc alloys with excellent performance, and lays a solid foundation for future clinical applications.

L-ornithine and L-glutamine are amino acids used for ammonia and nitrogen transport in the human body. Novel biodegradable synthetic poly(lactic-co-glycolic acid) derivatives were synthesized via conjugation with L-ornithine or L-glutamine, which were selected due to their biological importance. L-ornithine or L-glutamine was integrated into a PLGA polymer with EDC coupling reactions as a structure developer after the synthesis of PLGA via the polycondensation and ring-opening polymerization of lactide and glycolide. The chemical, thermal, and degradation property–structure relationships of PLGA, PLGA-L-ornithine, and PLGA-L-glutamine were identified. The conjugation between PLGA and the amino acid was confirmed through observation of an increase in the number of carbonyl carbons in the range of 170–160 ppm in the 13C NMR spectrum and the signal of the amide carbonyl vibration at about 1698 cm−1 in the FTIR spectrum. The developed PLGA-L-ornithine and PLGA-L-glutamine derivatives were thermally stable and energetic materials. In addition, PLGA-L-ornithine and PLGA-L-glutamine, with their unique hydrophilic properties, had faster degradation times than PLGA in terms of surface-type erosion, which covers their requirements. L-ornithine- and L-glutamine-linked PLGAs are potential candidates for development into biodegradable PLGA-derived biopolymers that can be used as raw materials for biomaterials. [ABSTRACT FROM AUTHOR]

β-tricalcium phosphate has good biodegradability and biocompatibility; it is widely perceived as a good material for treating bone deficiency. In this research, different contents of strontium (Sr) and silver (Ag) ion-doped β-tricalcium phosphate powders were prepared using the sol–gel method. After obtaining the best ratio of pore-forming agent and binder, the as-synthesized powders were sintered in a muffle for 5 h at 1000 °C to obtain the samples. Then, these samples were degraded in vitro in simulated body fluids. The samples were tested using a series of characterization methods before and after degradation. Results showed that the amount of Sr and/or Ag doping had an effect on the crystallinity and structural parameters of the samples. After degradation, though the compressive strength of these samples decreased overall, the compressive strength of the undoped samples was higher than that of the doped samples. Notably, apatite-like materials were observed on the surface of the samples. All the results indicate that Sr and/or Ag β-TCP has good osteogenesis and proper mechanical properties; it will be applied as a prospective biomaterial in the area of bone repair. [ABSTRACT FROM AUTHOR]

In this study, as a first step toward the development of novel candidate for absorbable suture materials based on poly(glycolide-co-ɛ-caprolactone), we synthesized a poly(glycolide-co-ɛ-caprolactone-co-l-lactide) block copolymer with ABA block structure via a two-step polymerization process and prepared the final PGCLA suture using a pilot-scale melt spinning machine. Then, to understand the mechanism on the early degradation stage of the PGCLA suture, we systematically investigated the mechanical, morphological properties and microstructural changes of the PGCLA suture through in vitro degradation. As a result, it was observed that, during the in vitro degradation process, the mechanical properties of PGCLA sutures exhibited an overall linear decrease and retained only 32% of its initial strength at 2 weeks of degradation. In addition, it was confirmed that, from FE-SEM analysis, internal degradation and structural changes, including longitudinal cracks on the suture surface, were noticeably appeared at 2 weeks of degradation. Interestingly, the results obtained from 1H-NMR and WAXS analyses exhibited clearly that PGCLA sutures undergo simultaneous degradation of glycolide units and l-lactide units present in the amorphous region during in vitro degradation. Therefore, based on these findings, we concluded that in the early stage of in vitro degradation of PGCLA suture, simultaneous degradation of glycolide units and l-lactide units in the amorphous region occurs, leading to chemical and structural changes such as erosion and cracking of the suture, as well as a decrease in its mechanical properties. [ABSTRACT FROM AUTHOR]

In this work, electrospun nanofibers based on polylactic acid, PLA, reinforced with ZnO nanoparticles have been studied, considering the growing importance of electrospun mats based on biopolymers for their applications in different fields. Specifically, electrospun nanofibers based on PLA have been prepared by adding ZnO nanoparticles at different concentrations, such as 0.5, 1, 3, 5, 10 and 20 wt%, with respect to the polymer matrix. The materials have been characterized in terms of their morphological, mechanical, and thermal properties, finding 3 wt% as the best concentration to produce PLA nanofibers reinforced with ZnO nanoparticles. In addition, hydrolytic degradation in phosphate buffer solution (PBS) was carried out to study the effect of ZnO nanoparticles on the degradation behavior of PLA-based electrospun nanofiber mats, obtaining an acceleration in the degradation of the PLA electrospun mat. [ABSTRACT FROM AUTHOR]

A new family of polyester-based copolymers—poly(sorbitol adipate-co-ethylene glycol adipate) (PSAEG), poly(sorbitol adipate-co-1,4 butane diol adipate) (PSABD), and poly (sorbitol adipate-co-1,6 hexane diol adipate) (PSAHD)—was obtained with a catalyst-free melt polycondensation procedure using the multifunctional non-toxic monomer sorbitol, adipic acid, and diol, which are acceptable to the human metabolism. Synthesized polyesters were characterized by FTIR and 1H NMR spectroscopy. The molecular weight and thermal properties of the polymers were determined by MALDI mass spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis. The degradation rate was investigated, at 37 °C, in 0.1M NaOH (pH 13) and in phosphate-buffered solution (PBS) at pH 7.4. It was found that the polymers degraded faster in NaOH (i.e., in a day) compared to their degradation in PBS, which was much slower (in a week). The highest degradation rate was noticed for the PSAEG sample in both media, whereas PSAHD was the most stable polymer at pH 7.4 and 13. A reduced hydrophilicity of the polymers with diol length was indicated by low swelling percentage and sol content in water and DMSO. Mechanical studies prove that all the polymers are elastomers whose flexibility increases with diol length, shown by the increase in percentage of elongation at break and the decrease in tensile stress and Young’s modulus. These biodegradable copolymers with adaptable physicochemical characteristics might be useful for a broad variety of biological applications by merely varying the length of the diol.

Polycaprolactone and poly-l-lactide-co-caprolactone are promising degradable biomaterials for many medical applications. Their mechanical properties, especially a low elastic modulus, make them particularly interesting for implantable devices and scaffolds that target soft tissues like the small intestine. However, the specific environment and mechanical loading in the intestinal lumen pose harsh boundary conditions on the design of these devices, and little is known about the degradation of those mechanical properties in small intestinal fluids. Here, we perform tensile tests on injection molded samples of both polymers during in vitro degradation of up to 70 days in human intestinal fluids. We report on yield stress, Young's modulus, elongation at break and viscoelastic parameters describing both materials at regular time steps during the degradation. These characteristics are bench-marked against degradation studies of the same materials in other media. As a result, we offer time dependent mechanical properties that can be readily used for the development of medical devices that operate in the small intestine. [ABSTRACT FROM AUTHOR]

Zn alloys have lately captivated the attention of the scientific community as possible materials for cardiovascular applications, showing a corrosion behavior and mechanical properties in between of those of Mg and Fe alloys. To better understand the different aspects of the interaction of Zn with body fluids, the basic corrosion pattern and the degradation products' formation were investigated considering the effect of CO2 amount in the atmosphere and different pseudo-physiological media; that is Hanks' balanced salt (HSS), Dulbecco's phosphate-buffered saline (PSS) and physiological saline solution (NSS), through a 14-day static immersion study. A mixed degradation layer mainly composed of ZnO with Zn3(PO4)2·4H2O and Zn(CO3)2 precipitates was found on surfaces immersed in both HSS and PSS, independently of the atmosphere, while a ZnO/ZnCl2 layer was found on the surface immersed in NSS, which also revealed the higher corrosion rate due to the effect of Cl− ions. Samples tested under a CO2-rich atmosphere showed a more compact passivating layer, higher dimensions crystals and less cavities when tested in HSS, PSS and NSS, respectively. [ABSTRACT FROM AUTHOR]

Additive manufacturing, in particular the fused deposition method, is a quite new interesting technique used to obtain specific 3D objects by depositing layer after layer of material. Generally, commercial filaments can be used in 3D printing. However, the obtention of functional filaments is not so easy to reach. In this work, we obtain filaments based on poly(lactic acid), PLA, reinforced with different amounts of magnesium, Mg, microparticles, using a two-step extrusion process, in order to study how processing can affect the thermal degradation of the filaments; we additionally study their in vitro degradation, with a complete release of Mg microparticles after 84 days in phosphate buffer saline media. Therefore, considering that we want to obtain a functional filament for further 3D printing, the simpler the processing, the better the result in terms of a scalable approach. In our case, we obtain micro-composites via the double-extrusion process without degrading the materials, with good dispersion of the microparticles into the PLA matrix without any chemical or physical modification of the microparticles. [ABSTRACT FROM AUTHOR]

Production of biocompatible composite scaffolds shifts towards additive manufacturing where thermoplastic biodegradable polymers such as poly(lactic acid) (PLA) are used as matrices. Differences between industrial- and medical-grade polymers are often overlooked although they may affect properties and degradation behaviour as significantly as the filler addition. In the present research, composite films based on medical-grade PLA and biogenic hydroxyapatite (HAp) with 0, 10, and 20 wt.% of HAp were prepared by solvent casting technique. The degradation of composites incubated in phosphate-buffered saline solution (PBS) at 37 °C after 10 weeks showed that the higher HAp content slowed down the hydrolytic PLA degradation and improved its thermal stability. Morphological nonuniformity after degradation was indicated by the different glass transition temperatures (Tg) throughout the film. The Tg of the inner part of the sample decreased significantly faster compared with the outer part. The decrease was observed prior to the weight loss of composite samples. [ABSTRACT FROM AUTHOR]

Biodegradable polymers play a significant role in medical applications, especially internal devices because they can be broken down and absorbed into the body without producing harmful degradation products. In this study, biodegradable polylactic acid (PLA)-polyhydroxyalkanoate (PHA)-based nanocomposites with various PHA and nano-hydroxyapatite (nHAp) contents were prepared using solution casting method. Mechanical properties, microstructure, thermal stability, thermal properties, and in vitro degradation of the PLA-PHA-based composites were investigated. PLA-20PHA/5nHAp was shown to give the desired properties so it was selected to investigate electrospinnability at different applied high voltages. PLA-20PHA/5nHAp composite shows the highest improvement of tensile strength at 36.6 ± 0.7 MPa, while PLA-20PHA/10nHAp composite shows the highest thermal stability and in vitro degradation at 7.55% of weight loss after 56 days of immersion in PBS solution. The addition of PHA in PLA-PHA-based nanocomposites improved elongation at break, compared to the composite without PHA. PLA-20PHA/5nHAp solution was successfully fabricated into fibers by electrospinning. All obtained fibers showed smooth and continuous fibers without beads with diameters of 3.7 ± 0.9, 3.5 ± 1.2, and 2.1 ± 0.7 µm at applied high voltages of 15, 20, and 25 kV, respectively. [ABSTRACT FROM AUTHOR]

Scaffolding biomaterials are gaining great importance due to their beneficial properties for medical purposes. Targeted biomaterial engineering strategies through the synergy of different material types can be applied to design hybrid scaffolding biomaterials with advantageous properties for biomedical applications. In our research, a novel combination of the bioactive agent Manuka honey (MHo) with 2-hydroxyethyl methacrylate/gelatin (HG) hydrogel scaffolds was created as an efficient bioactive platform for biomedical applications. The effects of Manuka honey content on structural characteristics, porosity, swelling performance, in vitro degradation, and in vitro biocompatibility (fibroblast and keratinocyte cell lines) of hybrid hydrogel scaffolds were studied using Fourier transform infrared spectroscopy, the gravimetric method, and in vitro MTT biocompatibility assays. The engineered hybrid hydrogel scaffolds show advantageous properties, including porosity in the range of 71.25% to 90.09%, specific pH- and temperature-dependent swelling performance, and convenient absorption capacity. In vitro degradation studies showed scaffold degradability ranging from 6.27% to 27.18% for four weeks. In vitro biocompatibility assays on healthy human fibroblast (MRC5 cells) and keratinocyte (HaCaT cells) cell lines by MTT tests showed that cell viability depends on the Manuka honey content loaded in the HG hydrogel scaffolds. A sample containing the highest Manuka honey content (30%) exhibited the best biocompatible properties. The obtained results reveal that the synergy of the bioactive agent, Manuka honey, with 2-hydroxyethyl methacrylate/gelatin as hybrid hydrogel scaffolds has potential for biomedical purposes. By tuning the Manuka honey content in HG hydrogel scaffolds advantageous properties of hybrid scaffolds can be achieved for biomedical applications. [ABSTRACT FROM AUTHOR]

Borosilicate bioactive glasses exhibit excellent bioactivity and degradation properties; however, they suffer from the rapid release of bioactive elements at the initial stage of their degradation. Excessive local concentrations (such as those of B) can affect cell proliferation. Moreover, the degradation and mineralization ability of these glasses deteriorate at the later stages. Aiming to balance the release of bioactive elements during the whole process, herein, a borosilicate bioactive glass 18SiO2–6Na2O–8K2O–8MgO–22CaO–2P2O5–36B2O3 (mol%) was prepared using the melting method. Further, the effects of microcrystallization on the release of bioactive elements and in vitro degradation were studied. Results show that after heat treatment at temperatures over 620 °C, multiple microcrystalline phases, including Ca2SiO4, CaB2O4, and CaMgB2O5, form in the glass. The glass samples heat-treated within the range of 620–640 °C undergo appropriate devitrification degrees, decelerating the rate of pH increase of the immersion solution during the initial stage in comparison to those treated at lower temperatures. This results in a more continuous release of all bioactive elements and allows better control of the overall degradation. Contrarily, the more extensive devitrification degrees of glass samples heat-treated at higher temperatures reverse the pH increase and degradation trends. Since bone marrow mesenchymal stem cells and mouse embryonic osteoblast cells are pH-sensitive, inducing a suitable degree of devitrification proved to favor cell viability and enhance the mineralization capacity. Thus, different microcrystallization degrees provide new approaches for controlling the degradation and release of bioactive elements, resulting in the simultaneous enhancement of biosafety and bioactivity.

Poly(glycerol-dodecanoate) (PGD) has aroused increasing attention in biomedical engineering for its degradability, shape memory and rubber-like mechanical properties, giving it potential to fabricate intelligent implants for soft tissues. Adjustable degradation is important for biodegradable implants and is affected by various factors. The mechanical load has been shown to play an important role in regulating polymer degradation in vivo. An in-depth investigation of PGD degradation under mechanical load is essential for adjusting its degradation behavior after implantation, further guiding to regulate degradation behavior of soft tissue implants made by PGD. In vitro degradation of PGD under different compressive and tensile load has proceeded in this study and describes the relationships by empirical equations. Based on the equations, a continuum damage model is designed to simulate surface erosion degradation of PGD under stress through finite element analysis, which provides a protocol for PGD implants with different geometric structures at varied mechanical conditions and provides solutions for predicting in vivo degradation processes, stress distribution during degradation and optimization of the loaded drug release. [ABSTRACT FROM AUTHOR]

A copolymer of polyglycolide (PGA) and trimethylene carbonate (TMC) used to fabricate a surgical suture with a trade name Maxon was investigated. Mach–Zehnder interferometer equipped to a suture drawing device was used to measure the optical and mechanical properties of PGA/TMC copolymer. These properties were investigated for the degradable samples during the incubation periods from 4 to 32 days. The pH level of buffer solution, crystallinity percent, swelling rates percent and weight retention of a PGA/TMC copolymer were measured. The results indicate that there was an overall decreasing for the mechanical properties with increasing the incubation time. The PGA/TMC suture maintained approximately 55% from its original mechanical properties after 32 days of incubation. An empirical formula was calculated to simulate the effect of a degradation process on of PGA/TMC suture and predict Young's modulus values during whole periods of degradation. It is found that the incubated sutures will be completely absorbed after approximately 8 weeks. [ABSTRACT FROM AUTHOR]

A comparative study on the degradation properties of fully biodegradable Mg wire/poly(lactic acid) (PLA) composite rods with rod diameter of 5 mm and 6 mm (Φ5-HP and Φ6-HP) at the same Mg wire volume content was performed. Control groups of PLA rods with the same diameter (Φ5-PLA and Φ6-PLA) were also studied. The results indicated the sample diameter significantly influenced the degradation performance. For Φ5-HP, after 3-week immersion, the pH value of immersion fluid, the mass loss rate and bending strength decline of the sample was 9.3, 22.3 and 26.8%, respectively, while the viscosity-average molecular weight of PLA matrix decreased to 3.65 × 104 g/mol with a decline amplitude of 36.0%. The changes in Φ5-HP were more obvious than those in Φ6-HP, indicating the faster degradation at a smaller diameter. According to the molecular dynamics simulation results after degradation for 1 week at 50 °C, the diffusion coefficients of H2O (DH2O) in Φ5-HP and Φ6-HP were 8.1 × 10−6 and 5.8 × 10−6 cm2/s, respectively. The DH2O in Φ5-PLA and Φ6-PLA was 2.6 × 10−5 and 1.9 × 10−5 cm2/s, respectively, while the DH2O of water itself was 1.5 × 10−4 cm2/s. The results clarified the influence mechanism of radial diffusion distance of degradation medium on degradation performances of the samples. Furthermore, the life cycle assessment method was used to calculate the carbon emission of Mg wire/PLA composite rods during their preparation and degradation process. [ABSTRACT FROM AUTHOR]

In the transition from the laboratory to the clinic, the sterilization of medical devices becomes a fundamental and mandatory step to ensure patient safety. This work evaluates the impact of three different sterilization methods - autoclave, ethylene oxide and gamma irradiation - on the physicochemical properties and degradation kinetics of 3D-printed polycaprolactone\calcium deficient hydroxyapatite (PCL\CDHA) scaffolds for bone regeneration. The in vitro degradation test was performed in phosphate buffer saline solution at 47 °C for 18 weeks by recording the evolution of pH, scaffold morphology, swelling degree, mass loss as well as polymer content, molecular weight and crystallinity. The results showed that under thermally accelerated degradation, the scaffolds underwent hydrolytic bulk degradation without altering the pH of the soaking medium nor compromising the morphology and integrity of the constructs. Although the structural integrity of the scaffolds was maintained, autoclaving severely deteriorated the properties of the polymer, resulting in a faster degradation pattern, confirming that it is not an appropriate sterilization method for PCL\CDHA scaffolds. While ethylene oxide had no significant effect on degradation, gamma irradiation slightly accelerated hydrolysis by chain scission. However, due to the porous nature of the scaffolds, the use of ethylene oxide is inadvisable due to the risk of gas trapping in the pores. Therefore, gamma irradiation, a non-toxic, effective, predictable and reproducible sterilization method, is considered the most appropriate. • The effect of sterilization method on the polymer phase of a composite bone scaffold is analysed. • The in vitro degradation of the PCL phase depends on the sterilization method. • Despite structural integrity preservation, steam sterilization degrades the PCL phase. • Gamma irradiation slightly accelerates the hydrolysis due to chain scission. [ABSTRACT FROM AUTHOR]

Biodegradable metals such iron-based materials, are studied as temporary implants in the orthopedic field due to their adequate mechanical properties, non-toxic degradation products, and the possibility of avoiding a second surgical intervention to remove the device. One strategy to overcome the slow degradation rate of pure Fe is the addition of alloying elements. The aim of this work is to characterize the in vitro behavior of a new FeMnCSi alloy (Fe 26.5Mn 0.5C 1.14Si 0.03P 0.01S), and compare it with the performance of pure iron in simulated body fluid. The alloy performance was characterized in terms of chemical composition, microstructure, hemocompatibility and electrochemical responseIt has been found that FeMnCSi alloy presented a marked and progressive degradation in simulated body fluid after 14 days of immersion, significantly larger than pure Fe. The presence of phosphate-based compounds was confirmed on the surface of the alloy after 1 day of immersion while only after 14 days of immersion was detected on Fe. Additionally, the FeMnCSi alloy demonstrates improved blood compatibility compared to pure iron, indicating its suitability for applications in irrigated areas such as bones. • The addition of Si in the FeMnCSi alloy promotes γ-austenite and reduces magnetism. • FeMnCSi alloy displays earlier bioactivity than pure iron. • The presence of Mn and Si contributes progressive degradation in SBF after 14 days. • FeMnCSi alloy demonstrates better blood compatibility than pure iron. [ABSTRACT FROM AUTHOR]

β-tricalcium phosphate has good biodegradability and biocompatibility; it is widely perceived as a good material for treating bone deficiency. In this research, different contents of strontium (Sr) and silver (Ag) ion-doped β-tricalcium phosphate powders were prepared using the sol–gel method. After obtaining the best ratio of pore-forming agent and binder, the as-synthesized powders were sintered in a muffle for 5 h at 1000 °C to obtain the samples. Then, these samples were degraded in vitro in simulated body fluids. The samples were tested using a series of characterization methods before and after degradation. Results showed that the amount of Sr and/or Ag doping had an effect on the crystallinity and structural parameters of the samples. After degradation, though the compressive strength of these samples decreased overall, the compressive strength of the undoped samples was higher than that of the doped samples. Notably, apatite-like materials were observed on the surface of the samples. All the results indicate that Sr and/or Ag β-TCP has good osteogenesis and proper mechanical properties; it will be applied as a prospective biomaterial in the area of bone repair.

In this work, electrospun nanofibers based on polylactic acid, PLA, reinforced with ZnO nanoparticles have been studied, considering the growing importance of electrospun mats based on biopolymers for their applications in different fields. Specifically, electrospun nanofibers based on PLA have been prepared by adding ZnO nanoparticles at different concentrations, such as 0.5, 1, 3, 5, 10 and 20 wt%, with respect to the polymer matrix. The materials have been characterized in terms of their morphological, mechanical, and thermal properties, finding 3 wt% as the best concentration to produce PLA nanofibers reinforced with ZnO nanoparticles. In addition, hydrolytic degradation in phosphate buffer solution (PBS) was carried out to study the effect of ZnO nanoparticles on the degradation behavior of PLA-based electrospun nanofiber mats, obtaining an acceleration in the degradation of the PLA electrospun mat.

As a new kind of biodegradable metal, Zn possesses promising features, i.e. suitable biodegradability and biocompatibility, lower energy consumption for melting, better recyclability, and processing size tolerance. Such features provide some new insights for manufacturing medical implants. However, cast pure Zn usually contains coarsening microstructures, which brings about poor syngenetic controlling between mechanical strength and degradation rate. In the present work, a significant grain refinement was achieved in the Zn alloys through combination of solidification and rolling, followed by exploration of the mechanical response and in vitro degradation. Specifically, the grain refiner (i.e. Zn–Al master alloy) was firstly prepared and, then, added into cast pure Zn during solidification. Fine equiaxed grains were obtained due to the constitutional supercooling (CS)-driven interdependence effects. Then, the cast Zn alloys were subjected to hot rolling at 200 °C, which gives rise to further reduction in the grain size of Zn alloys. Thereafter, the mechanical properties and the in vitro immersion testing were carried out not only in the as-rolled Zn–Al alloys, but also in the purely cast Zn–Al alloys for comparison. The {0001} basal plane texture became dominant in all the as-rolled Zn–Al alloys; however, the weak {112¯0} prismatic plane texture occurred in the high alloying Zn–Al alloys (>1.5wt% Al). Finally, the mechanisms behind the mechanical improvement and the in vitro degradation were discussed. These work shield new light on synergic tunning between the biodegradable rate and mechanical strength of Zn alloys.

In this study, poly(glycolide-co—caprolactone) (PGCL) block copolymers, which have an ABA block structure, were prepared by a two-step polymerization process, and their microstructures, thermal properties and in vitro degradation properties according to introducing a small amount of L-lactide as a comonomer in the first step of the polymerization process were systematically investigated. Through our study, it was confirmed that the introduction of L-lactide in the first step of the polymerization process had a great effect on the microstructure of the random PGCL prepolymer (B block) as well as the final PGCL block copolymer (ABA block). Specifically, with the introduction of L-lactide, the average sequence length of glycolide segments on the PGCL prepolymer decreased from 3.32 to 2.40. In addition, it was observed that there is a relatively large difference in the average sequence length of glycolide segments in the final PGCL block copolymers. As a result, these microstructural changes of the PGCL prepolymer originated from the L-lactide comonomer affected significantly the thermal properties and in vitro degradation properties on the final PGCL block copolymers. Compared with the PGCL block copolymer without L-lactide, melting temperature and crystallization temperature of the PGCL block copolymer with L-lactide decreased, as well as their thermal degradation temperature. In addition, the introduction of a small amount of L-lactide comonomer accelerated the hydrolytic degradation of the PGCL block copolymer. Overall, by introducing L-lactide copolymer in the first step of the two-step manufacturing process for the PGCL block copolymer, changes of various properties on the PGCL block copolymer originated from the changes in the microstructure of random PGCL prepolymer were confirmed. [ABSTRACT FROM AUTHOR]

The semi-solid Ca-gels were prepared from low-methoxyl pectins (methoxylation degree DM 4-36 %) of Oberna behen, Potamogeton natans, Tanacetum vulgare, Comarum palustre, Bergenia crassifolia, and Heracleum sosnowskyi. Pectins are characterized by Mw of 77-556 kDa and different content of HG and RG-I. The gels were prepared by addition of Ca 2+ ions at varying stoichiometric ratios, R = 2 × [Ca 2+ ]/[COO - ], of 0.2-0.6, and a fixed pectin concentration of 10 g/L. It was shown that the presence of certain sets of structural characteristics in low-methoxyl pectins from different sources leads to the formation of gels with similar rheological properties. Pectins with Mw 77-98 kDa, DM 6-14 % form stiffer Ca-gels than pectins with Mw 218-253 kDa, DM 24-36 % at the same R. Pectins with Mw 346-556 kDa form the strongest Ca-gels. Their high Mw compensates for the influence of DM on the properties of Ca-gels. The stability of gels in PBS (pH 7.4) is determined mainly by proportion of 1,4-linked non-methoxylated GalA in pectins. Pectins with DM 4-14 % form more stable Ca-gels in PBS than pectins with DM 21-36 %., 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 Elsevier B.V. All rights reserved.)

Polycaprolactone and poly-l-lactide-co-caprolactone are promising degradable biomaterials for many medical applications. Their mechanical properties, especially a low elastic modulus, make them particularly interesting for implantable devices and scaffolds that target soft tissues like the small intestine. However, the specific environment and mechanical loading in the intestinal lumen pose harsh boundary conditions on the design of these devices, and little is known about the degradation of those mechanical properties in small intestinal fluids. Here, we perform tensile tests on injection molded samples of both polymers during in vitro degradation of up to 70 days in human intestinal fluids. We report on yield stress, Young’s modulus, elongation at break and viscoelastic parameters describing both materials at regular time steps during the degradation. These characteristics are bench-marked against degradation studies of the same materials in other media. As a result, we offer time dependent mechanical properties that can be readily used for the development of medical devices that operate in the small intestine.

Zn alloys have lately captivated the attention of the scientific community as possible materials for cardiovascular applications, showing a corrosion behavior and mechanical properties in between of those of Mg and Fe alloys. To better understand the different aspects of the interaction of Zn with body fluids, the basic corrosion pattern and the degradation products’ formation were investigated considering the effect of CO2 amount in the atmosphere and different pseudo-physiological media; that is Hanks’ balanced salt (HSS), Dulbecco’s phosphate-buffered saline (PSS) and physiological saline solution (NSS), through a 14-day static immersion study. A mixed degradation layer mainly composed of ZnO with Zn3(PO4)2·4H2O and Zn(CO3)2 precipitates was found on surfaces immersed in both HSS and PSS, independently of the atmosphere, while a ZnO/ZnCl2 layer was found on the surface immersed in NSS, which also revealed the higher corrosion rate due to the effect of Cl− ions. Samples tested under a CO2-rich atmosphere showed a more compact passivating layer, higher dimensions crystals and less cavities when tested in HSS, PSS and NSS, respectively.

Objective: To evaluate the chemical quality and in vitro fermentative characteristics of Panicum maximum cv. Guinea grass, in order to determine its optimum cutting point under four fertilization schemes. Methodology: Guinea grass was fertilized with chemicals (F1), vermicompost (F2), compost (F3), and compost + leachate (F4). The grass was cut at 20, 35, 50, 50, 65, 80, and 105 days. The neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP) contents were determined, along with the dry matter (DMD), NDF (NDFD), and ADF (ADFD) degradations, as well as the in vitro gas production. The experimental design was a 4×6 factorial arrangement within a completely randomized design; fertilization and cutting days were used as factors. Results: F3-65 d, F1-65 d, F4-80 d, and F1-8 d had higher NDF content; F1-65 d, higher ADF; F1-20 d, higher CP (p<0.05); F4-50 d and F2-50 d, higher gas production; F4-20, F4-35, F4-50, F2-20, F2-35, F1-20 d, higher DMD, F2-20 and F4-20 d, higher NDFD; F4-20, F4-35, F4-65, and F2-20 d, higher ADFD (p<0.05). Limitations/Implications: The lack of previous research studies about the organic fertilization of Guinea grass. Conclusions: Fertilization with vermicompost or compost + leachate improves chemical content, in vitro gas production, and degradation of Guinea grass. [ABSTRACT FROM AUTHOR]

BACKGROUND: Hemostasis is an important part of clinical treatment. Fast and effective hemostasis is necessary to ensure the safety of surgical patients.OBJECTIVE: To prepare a kind of plant polysaccharide hemostatic microsphere with porous structure and its performance evaluation. METHODS: Porous hemostatic microspheres were prepared from potato starch by gelatinization, emulsification crosslinking, cleaning, and drying technique. The hemostatic performance of the hemostatic microspheres was improved by improving the gelatinization and crosslinking processes of the starches, setting the grouping: group A(gelatinization for 1 hour, crosslinking for 6 hours, group B（gelatinization for 1 hour, crosslinking for 12 hours）, group C（gelatinization for 1 hour, crosslinking for 18 hours）, group D（gelatinization for 2 hours, crosslinking for 6 hours）, group E（gelatinization for 2 hours, crosslinking for 12 hours）, and group F（gelatinization for 2 hours and crosslinking for 18 hours）. The listed absorbable hemostatic microspheres were used as controls to examine the microtopography, pH, porosity and in vitro degradation of microspheres in each group. According to the above experimental results, suitable microspheres were selected for hemostasis of liver and spleen in New Zealand rabbits, comparing the sample dosage, hemostasis amount with hemostasis time.RESULTS AND CONCLUSION:（1） Scanning electron microscope showed that group B and group E formed porous microspheres with a stable structure of 50-200 μm in diameter, and the spherical morphology and porosity were better than those of the control group. Except for groups C and E, the pH values of the other samples were in the range of 6.5-7.5, which met the pH requirements. The same quality of samples, the cross-linking time growth and degradation time increased significantly（P < 0.01）. Based on the examination of morphological structure, porosity, pH and in vitro degradation in the previous stage, groups A, B, E and the control group were selected for hemostasis experiments.（2） Under the same hemostatic effect, the hemostatic time of microspheres in group E was shorter and less used compared with that in the control group, and the hemostatic effect in group B was not significantly different from that in the control group.（3） The results showed that the porous starch microspheres prepared after gelatinization at 60 °C for 2 hours, emulsification for 45 minutes, and cross-linking for 12 hours had the best hemostatic effect and its degradation time was also relatively short, and its performance was superior to that of listed products. [ABSTRACT FROM AUTHOR]

Novel ternary Zn–Ca–Cu alloys were studied for the development of absorbable wound closure device material due to Ca and Cu's therapeutic values to wound healing. The influence of Ca and Cu on the microstructure, mechanical and degradation properties of Zn were investigated in the as-cast state to establish the fundamental understanding on the Zn–Ca–Cu alloy system. The microstructure of Zn-0.5Ca-0.5Cu, Zn-1.0Ca-0.5Cu, and Zn0.5Ca-1.0Cu is composed of intermetallic phase CaZn13 distributed within the Zn–Cu solid solution. The presence of CaZn13 phase and Cu as solute within the Zn matrix, on the one hand, exhibited a synergistic effect on the grain refinement of Zn, reducing the grain size of pure Zn by 96%; on the other hand, improved the mechanical properties of the ternary alloys through solid solution strengthening, second phase strengthening, and grain refinement. The degradation properties of Zn–Ca–Cu alloys are primarily influenced by the micro-galvanic corrosion between Zn–Cu matrix and CaZn13 phase, where the 0.5% and 1.0% Ca addition increased the corrosion rate of Zn from 11.5 μm/y to 19.8 μm/y and 29.6 μm/y during 4 weeks immersion test.

Additive manufacturing, in particular the fused deposition method, is a quite new interesting technique used to obtain specific 3D objects by depositing layer after layer of material. Generally, commercial filaments can be used in 3D printing. However, the obtention of functional filaments is not so easy to reach. In this work, we obtain filaments based on poly(lactic acid), PLA, reinforced with different amounts of magnesium, Mg, microparticles, using a two-step extrusion process, in order to study how processing can affect the thermal degradation of the filaments; we additionally study their in vitro degradation, with a complete release of Mg microparticles after 84 days in phosphate buffer saline media. Therefore, considering that we want to obtain a functional filament for further 3D printing, the simpler the processing, the better the result in terms of a scalable approach. In our case, we obtain micro-composites via the double-extrusion process without degrading the materials, with good dispersion of the microparticles into the PLA matrix without any chemical or physical modification of the microparticles.

Biodegradable polymers play a significant role in medical applications, especially internal devices because they can be broken down and absorbed into the body without producing harmful degradation products. In this study, biodegradable polylactic acid (PLA)-polyhydroxyalkanoate (PHA)-based nanocomposites with various PHA and nano-hydroxyapatite (nHAp) contents were prepared using solution casting method. Mechanical properties, microstructure, thermal stability, thermal properties, and in vitro degradation of the PLA-PHA-based composites were investigated. PLA-20PHA/5nHAp was shown to give the desired properties so it was selected to investigate electrospinnability at different applied high voltages. PLA-20PHA/5nHAp composite shows the highest improvement of tensile strength at 36.6 ± 0.7 MPa, while PLA-20PHA/10nHAp composite shows the highest thermal stability and in vitro degradation at 7.55% of weight loss after 56 days of immersion in PBS solution. The addition of PHA in PLA-PHA-based nanocomposites improved elongation at break, compared to the composite without PHA. PLA-20PHA/5nHAp solution was successfully fabricated into fibers by electrospinning. All obtained fibers showed smooth and continuous fibers without beads with diameters of 3.7 ± 0.9, 3.5 ± 1.2, and 2.1 ± 0.7 µm at applied high voltages of 15, 20, and 25 kV, respectively.

Production of biocompatible composite scaffolds shifts towards additive manufacturing where thermoplastic biodegradable polymers such as poly(lactic acid) (PLA) are used as matrices. Differences between industrial- and medical-grade polymers are often overlooked although they may affect properties and degradation behaviour as significantly as the filler addition. In the present research, composite films based on medical-grade PLA and biogenic hydroxyapatite (HAp) with 0, 10, and 20 wt.% of HAp were prepared by solvent casting technique. The degradation of composites incubated in phosphate-buffered saline solution (PBS) at 37 °C after 10 weeks showed that the higher HAp content slowed down the hydrolytic PLA degradation and improved its thermal stability. Morphological nonuniformity after degradation was indicated by the different glass transition temperatures (Tg) throughout the film. The Tg of the inner part of the sample decreased significantly faster compared with the outer part. The decrease was observed prior to the weight loss of composite samples.

Magnesium scaffolds are biodegradable, biocompatible, bioactive porous scaffolds, which find applications within tissue engineering. The presence of porosity increases surface area and enhances cell proliferation and tissue ingrowth. These characteristics make Mg scaffolds key materials to enhance the healing processes of tissues such as cartilage and bone. However, along with the increment of porosity, the corrosion of magnesium within a physiological environment occurs faster. It is, therefore, necessary to control the degradation rate of Mg scaffolds in order to maintain their mechanical properties during the healing process. Several studies have been performed to increase Mg scaffolds' corrosion resistance. The different approaches include the modification of the Mg surface by conversion coatings or deposited coatings. The nature of the coatings varies from ceramics such as hydroxyapatite and calcium phosphates to polymers such as polycaprolactone or gelatin. In this work, we propose a novel approach to generating a protective bilayer coating on the Mg scaffold surface composed of a first layer of naturally occurring Mg corrosion products (hydroxide and phosphates) and a second layer of a homogeneous and biocompatible coating of polylactic acid. The Mg scaffolds were fabricated from Mg powder by means of powder metallurgy using ammonium bicarbonate as a space holder. The size and amount of porosity were controlled using different size distributions of space holders. We addressed the influence of scaffold pore size on the conversion and deposition processes and how the coating process influences the in vitro degradation of the scaffolds. [ABSTRACT FROM AUTHOR]

In this article, the mechanical properties and physicochemical indexes of a poly(l‐lactic acid) (PLLA) braided stent during in vitro degradation in bile for 270 days are characterized to investigate its applications in treating biliary strictures. The PLLA braided stent always maintains structural integrity well macroscopically without cracks or pits microscopically. During degradation, radial compressive force and chronic outward force are increased by 25.1% and 14.3%, respectively, bending stiffness and axial force are increased by 3.0% and 4.9%, respectively. These results indicate that PLLA braided stent can keep sufficient radial force and good bending performance during degradation in bile for 270 days, showing promising application prospects in treating severe benign biliary strictures demanding support for over half a year. Furthermore, almost no mass loss and 42.4% attenuation in molecular weight indicate the degradation mechanism of bulk erosion without obvious autocatalysis, causing decrease in bile pH. Degradation rate constant is 0.002 day−1 and crystallinity is increased by 8%. These results explain that PLLA braided stent can keep high mechanical properties during degradation in bile for 270 days, which is in the early stage of degradation. This study may bring new ideas into the applications of PLLA braided stents in treating biliary strictures. [ABSTRACT FROM AUTHOR]

In this study, whey protein isolate (WPI) solution (12% w/v) was mixed with alginate or carrageenan at a concentration of 2.5 mg mL− 1 and then enriched with CaCl2 (30 mM) to prepare mixed hydrogels with modulated functional properties and high stability to gastrointestinal degradation. The mixed gels enriched with CaCl2 had higher hardness (approximately sixfold) and lower water holding capacity (WHC) compared to the other hydrogel samples (P < 0.05). The highest (100%) and lowest (about 70%) WHC were observed for gel made of WPI/carrageenan and gel made of WPI/CaCl2, respectively. The WPI-alginate/carrageenan composite gels showed more homogenous and compact structure with lower pore sizes than the CaCl2-enriched pairs. According to the X-ray diffraction analysis, intermolecular interactions between WPI and alginate/carrageenan and CaCl2 were occurred in the amorphous phase. Furthermore, the results revealed that the binary hydrogels made of WPI and carrageenan/alginate had lower swelling degree and protein degradation rate under simulated gastric and small intestinal conditions. Generally, the results of this study suggested that the mixed WPI-polysaccharide (alginate/carrageenan) based hydrogels can be used for the site-specific delivery of bioactive molecules and designing of novel functional foods with modulable technological functionalities. [ABSTRACT FROM AUTHOR]

The present work aims at exploring the influence of laser welding on the functional behaviour of a Fe-20Mn-0.6C (wt.%) bioabsorbable alloy. At first, the selection of the most suitable process speed (40 mm/s) was done in order to obtain a full penetration joint with limited taper. Then, microstructural and mechanical analyses of welded sheets confirmed suitable performance of the joint, without porosity, thus preserving chemical composition, mechanical resistance and ductility even after welding. In particular, the base material comprised both γ austenite and ε martensite, while the welded samples showed a further type of martensite, namely α’. Moreover, ultimate tensile strength (1095 MPa and 1104 MPa in base and welded material, respectively) and elongation to failure (61.3% and 60.9%, respectively) were almost not influenced by the welding process. Considering the absorbable nature of these alloys, static immersion degradation tests were carried out, and confirmed that the surface of the welded bead did not exhibit a significant variation of the material degradation rate after 14 days in modified Hanks’ solution. Finally, a significant accumulation of degradation products, mainly (Fe,Mn)CO3, was observed along the joining line.

Only little is known about degradation of methacrylate monomers. Therefore, using in vitro chemical and saliva degradation this study aimed to identify the degradation products of organic compounds present in resin-based dental materials. Ten dental monomers and nine polymerized dental resin-based materials were immersed for 24 h in chemical media (0.1 M HCl, 0.1 M NaOH) and human pooled saliva in order to identify leached monomers and degradation products from chemical and saliva degradation. Samples were analyzed using liquid chromatography coupled to high-resolution mass spectrometry to identify previously unknown degradation products. During in vitro chemical degradation, uncured monomers were rapidly hydrolyzed into mono- and demethacrylated degradation products. During chemical degradation in alkaline conditions of polymerized materials, considered the worst-case scenario, only degradation products could be detected. In acidic conditions, monomers and their degradation products were detected. In addition, different additives such as EDMAB, DMPA and HMBP were present in acidic degradation samples. Degradation in human pooled saliva for 24 h to mimic the in vivo situation, resulted in the identification of both monomers and their degradation products. Using state-of-the-art high-resolution mass spectrometry previously unknown degradation products of commonly used monomers were identified for the first time. Results show that patients may be exposed to monomers and their degradation products in the first 24 h after restorative procedures. The results provide a base for further research on the degradation of resin-based dental composites in order to assess their safety using elution and toxicity studies. [ABSTRACT FROM AUTHOR]