Search

Polylactic acid (PLA) has attracted much attention in bone tissue engineering due to its good biocompatibility and processability, but it still faces problems such as a slow degradation rate, acidic degradation product, weak biomineralization ability, and poor cell response, which limits its wider application in developing bone scaffolds. In this study, Mg(OH)2 nanoparticles were employed as a versatile nanofiller for developing PLA/Mg(OH)2 composite bone scaffolds using fused deposition modeling (FDM) 3D printing technology, and its mechanical, degradation, and biological properties were evaluated. The mechanical tests revealed that a 5 wt% addition of Mg(OH)2 improved the tensile and compressive strengths of the PLA scaffold by 20.50% and 63.97%, respectively. The soaking experiment in phosphate buffered solution (PBS) revealed that the alkaline degradation products of Mg(OH)2 neutralized the acidic degradation products of PLA, thus accelerating the degradation of PLA. The weight loss rate of the PLA/20Mg(OH)2 scaffold (15.40%) was significantly higher than that of PLA (0.15%) on day 28. Meanwhile, the composite scaffolds showed long-term Mg2+ release for more than 28 days. The simulated body fluid (SBF) immersion experiment indicated that Mg(OH)2 promoted the deposition of apatite and improved the biomineralization of PLA scaffolds. The cell culture of bone marrow mesenchymal stem cells (BMSCs) indicated that adding 5 wt% Mg(OH)2 effectively improved cell responses, including adhesion, proliferation, and osteogenic differentiation, due to the release of Mg2+. This study suggests that Mg(OH)2 can simultaneously address various issues related to polymer scaffolds, including degradation, mechanical properties, and cell interaction, having promising applications in tissue engineering. [ABSTRACT FROM AUTHOR]

Macroalgae with nontoxicity, biodegradability and biocompatibility has attracted more attentions as a sustainable alternative towards petroleum-derived plastics. However, brittleness and high affinity towards water has limited marine-based macroalgae films to be widely used. Thus, this paper aims to compare the roles of calcium chloride as ionic cross-linker and acrylic resin as covalent cross-linker in agar-PEG plasticised biofilm composite. Agar biofilm composite with PEG 1000 40% were cross-linked with i) calcium chloride 1, 2, 3 and 4 (CaCl2/agar) wt/wt % at 2 or 4 min immersion time, and ii) acrylic resin at 10, 20, 30, 40 and 50 (acrylic resin/agar) wt/wt %. FTIR and TGA proved that CaCl2 and acrylic resin managed to cross-link agar-PEG films ionically and covalently respectively. In general, films cross-linked with CaCl2 produced highest affinity towards water than films cross-linked with acrylic resin. Highest tensile strength, highest tensile modulus and lowest elongation at break was achieved when films cross-linked with CaCl2. Films cross-linked with CaCl2 has higher degradation rate than films cross-linked with acrylic resin. In conclusion, different mode of cross-linking (ionic or covalent) imparted different properties on the agar-PEG film. [ABSTRACT FROM AUTHOR]

Objective: Reducing the degradation of anthocyanins in blueberry during drying. Methods: The far infrared drying was applied to the drying of blueberries, and compared with traditional hot air drying to explore the degradation characteristics of major anthocyanins and the changes of PPO enzyme activity and antioxidant capacity of blueberries under different drying methods. Results: High retention of two major anthocyanins （D3G and C3G） in blueberries under far-infrared drying, and the second-order mathematical model could better simulate their degradation process. Compared with hot-air drying, the rate constants （k） and entropy values （ΔS） of far-infrared dried blueberry anthocyanins were smaller, and the half-life values （t1/2）, activation energy values （Ea） and enthalpy values （ΔH） were larger. The two drying methods produced similar effects on PPO enzyme activity, but the enzyme activity of the far-infrared drying group was generally lower than that of the hot-air drying group after 4 h. In addition, the highest anthocyanin retention and free radical scavenging ability of dried blueberry fruits were observed under far-infrared 60 ℃ drying conditions. Conclusion: Under the same drying temperature, far-infrared drying can reduce the degradation of anthocyanins and improve the drying quality of blueberries compared with traditional hot air drying.

Biodegradable mulch films are recognized as a promising substitute of polyethylene (PE) films to alleviate the “white pollution”. Biodegradable mulch films with optimum degradation rates increase crop yield even compared to PE films. However, the mechanisms underlying this yield-increasing effect remains elusive. In this study, three biodegradable film treatments (BFM1, BFM2 and BFM3) and one PE film treatment (PFM) were used to evaluate their effects on soil and winter potatoes, and a partial least squares path model (PLS-PM) was constructed to investigate their relationships. The degradation rates of films under different treatments were ranked as BFM3 > BFM2 >BFM1 > PFM, and presented distinctive effects on soil properties and nutrients, structure of soil bacterial community, and yield traits of winter potatoes. The PLS-PM showed that mulch treatments affected potato yield through effects on soil properties (soil water and temperature) and soil nutrients (TOC, DOC, TN and NO3--N). The disintegration of the biodegradable films decreased soil water content and temperature, and reduced the loss of soil nutrients in the topsoil at the later growth stage of winter potatoes compared to PE films. Additionally, the elevated content of soil TN and NO3--N under treatment BFM1 may play a key role in its yield-increasing effect on potatoes compared to treatments PFM and BFM2. Thus, biodegradable mulch films with proper degradation rates regulate soil TN and NO3--N through their effects on soil water and temperature, and subsequently improve the yield of winter potatoes compared to PE mulch films.

In order to improve and alleviate environmental pollution caused by the disposal of seedling pots, a rice straw fiber-based headed vegetable seedling pot material, which is suitable for mechanical transplantation and biodegradable, was studied. Used rice straw as the main raw material, a five-factor and five-level (1/2 full implementation) quadratic regression orthogonal rotation central of rotation combination test method. The experimental factors included the beating degree of rice straw fiber, quantity, the proportion of rice fiber, neutral sizing agents, and wet strength agent mass fraction. The performance evaluation index included dry and wet tensile strength, burst strength, tear strength, air permeance, and degradation period. The results showed that when the parameter combination of the beating degree of rice straw fiber was 50 ± 1°SR, the quantity was 87.5 ± 4 g/m2, the proportion of fiber in rice was 70%, the neutral sizing agents mass fraction was 1 ± 0.25%, and the wet strength agent mass fraction was 1.5 ± 0.1%. The dry tensile strength was ≥ 1.8 kN·m−1, the wet tensile strength was ≥ 0.7 kN·m−1, the burst strength was ≥ 140 kPa, the tear strength was ≥ 350 m·N, the air permeance was ≤ 1.33 μm/Pa·s, and the degradation period was ≤ 80 d. The dry tensile strength reduction rate was 0.0274 kN/(m·d) and the wet tensile strength reduction rate was 0.0113 kN/(m·d), during the nursery period [30, 40], while the dry tensile strength was ≥ 1 kN·m−1 and the wet tensile strength was ≥ 0.4 kN·m−1 during the transplanting period. [ABSTRACT FROM AUTHOR]

Copyright of Food & Machinery is the property of Food & Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To reduce the oxidative degradation of citral and improve its antimildew performance, citral was modified with natural antioxidants such as tea polyphenols, ascorbic acid, and theaflavin in the present study. Additionally, the effects of these natural antioxidants on the citral degradation rate and DPPH radical-scavenging rate, as well as the effectiveness of antioxidant-modified citral in the antimildew treatment of bamboo were investigated. Ascorbic acid, theaflavin, and tea polyphenols improved the antioxidant performance of citral to some extent, and the tea polyphenols exhibited the best antioxidant performance. When the amount of tea polyphenols added to citral reached 1.0%, the oxidative degradation of citral was effectively prevented. Compared with citral, tea-polyphenol-modified citral could reduce the efficacy of the bamboo antimildew treatment against all four mildews and the effectiveness of the antimildew treatment reached 100%. Citral modification with antioxidants reduced the amount of citral required in the treatment, thereby reducing the treatment cost for bamboo mildew. [ABSTRACT FROM AUTHOR]

Hot deformation behavior, the corresponding microstructure evolution, and degradation properties of a weak-textured Mg-Er-Ni alloy containing a high-volume fraction of Ni-LPSO phases, have been investigated. Hot deformation behavior has been carried out in the temperatures range of 370 ∼ 460 °C and strain rates range of 0.001 ∼ 1 s−1. Flow stress-strain curves of high strain rate cases show a continuous increase trend without a steady or a peak stage, while that of low strain rate cases show an obvious dynamic softening after peak stress. Based on flow stress-strain curves, materials constants calculated by an Arrhenius-type constitutive equation, show a high n and Q compared to those of high-volume fraction α-Mg matrix Mg alloys. Optimal processing windows, based on the dynamic material model, is determined as high temperature domains. As for microstructure evolution, a complete recrystallization and dispersive Ni-LPSO fragments for high temperature & low strain rates while a restricted recrystallization and a streamline distribution LPSO phase for high temperature & high strain rates are observed. Varying degrees of continuous dynamic recrystallization, particle induced nucleation mechanism, as well as coordinated deformation of LPSO through kinking and bending account for the strain-rate-dependence hot deformation mechanism. As a result, dispersive Ni-LPSO fragments at low strain rates provide more degradation channels for the α-Mg matrix and thus possess better a degradation rate than the streamlined LPSO at high strain rates. • High strain rate cases show a continuous increase trend while low strain rate cases show an obvious dynamic softening. • A restricted DRX and a streamline distribution Ni-LPSO phases for high temperature & high strain rates are observed. • A complete DRX and dispersive Ni-LPSO fragments for high temperature & low strain rates are observed. • Dispersive LPSO fragments provide more degradation channels for the α-Mg and thus a faster degradation rate. [ABSTRACT FROM AUTHOR]

The micro-arc oxidation (MAO) coatings were fabricated on the surface of the microwave sintered Ti-15Mg metal-metal composite (MMC). The surface morphologies, phase composition, degradation properties and cytocompatibility of the MAO treated Ti-15Mg MMC were investigated. The XRD and XPS results show that the MAO coatings are mainly composed of anatase and rutile TiO2 crystal phases and amorphous MgO and SiO2 with some –OH groups. There are some differences between MAO pore structure in Ti region and Mg region, but both of the pore sizes increase and the number of pores decreases with increasing the applied voltages. The degradation rate of Ti-15Mg MMC is reduced by the MAO coatings, and with increasing the applied voltages, the degradation rates of the MAO treated samples decrease first, reaching the minimum value at 300 V, and then increase. After immersed in SBF solution for 250 h, the calcium-deficient apatite containing CO32− is detected on the surface of the MAO treated and untreated Ti-15Mg MMC. The results of cell viability and alkaline phosphatase activity show that the MAO treated Ti-15Mg MMCs are more conducive to the proliferation and differentiation of MG-63 cells.

Iron (Fe) has attracted great attention as bone repair material owing to its favorable biocompatibility and mechanical properties. However, it degrades too slowly since the corrosion product layer prohibits the contact between the Fe matrix and body fluid. In this work, zinc sulfide (ZnS) was introduced into Fe bone implant manufactured using laser additive manufacturing technique. The incorporated ZnS underwent a disproportionation reaction and formed S-containing species, which was able to change the film properties including the semiconductivity, doping concentration, and film dissolution. As a result, it promoted the collapse of the passive film and accelerated the degradation rate of Fe matrix. Immersion tests proved that the Fe matrix experienced severe pitting corrosion with heavy corrosion product. Besides, the in vitro cell testing showed that Fe/ZnS possessed acceptable cell viabilities. This work indicated that Fe/ZnS biocomposite acted as a promising candidate for bone repair material. [ABSTRACT FROM AUTHOR]

Biodegradable zinc (Zn) based materials have been regarded as promising candidates for orthopedic applications owing to their suitable biodegradability. However, pure Zn exhibited poor mechanical performance and inadequate biofunctionality, which restricted its biomedical applications. Herein, biodegradable Zn-Mg-Cu alloys were developed to enhance the mechanical strength of the Zn matrix and endow the alloys with antibacterial activity. The effect of Cu addition on corrosion behavior, biocompatibility and antibacterial activity of biodegradable Zn-3Mg-xCu alloys was systematically investigated. In vitro immersion test revealed that Zn-3Mg-1Cu exhibited an increasing corrosion rate of 0.0504 mm y ^−1 . The relative cell availability of MC3T3-E1 cells was over 70% after co-culture with 2-fold diluted extracts of the Zn-3Mg-xCu alloy for 3 d, indicating acceptable cytotoxicity. The Cu addition could enhance the antibacterial activity of the Zn-3Mg matrix, and Zn-3Mg-1Cu alloy exhibited the highest inhibition zone diameter (IZD) values of 10.4 mm and 6.0 mm against S. aureus and E. coli , respectively. Overall, the Zn-3Mg-1Cu could be recognized as a promising biodegradable orthopedic material owing to favorable degradation behavior, satisfying biocompatibility, and substantial antibacterial ability.

A too slow degradation of iron (Fe) limits its orthopedic application. In this study, calcium chloride (CaCl2) was incorporated into a Fe-based biocomposite fabricated by laser additive manufacturing, with an aim to accelerate the degradation. It was found that CaCl2 with strong water absorptivity improved the hydrophilicity of the Fe matrix and thereby promoted the invasion of corrosive solution. On the other hand, CaCl2 could rapidly dissolve once contacting the solution and release massive chloride ion. Interestingly, the local high concentration of chloride ion effectively destroyed the corrosion product layer due to its strong erosion ability. As a result, the corrosion product layer covered on the Fe/CaCl2 matrix exhibited an extremely porous structure, thus exhibiting a significantly reduced corrosion resistance. Besides, in vivo cell testing proved that the Fe/CaCl2 biocomposite also showed favorable cytocompatibility.

Biopolymer products that is biodegradable presently attracting an attention from researchers and industry. The biodegradable packaging based on polylactic acid (PLA), durian skin fibre (DSF), epoxidized palm oil (EPO) and incorporated with cinnamon essential oil (CEO) as antimicrobial agent have been developed and showed to be a promising field of research. This paper reported the effects of supercritical carbon dioxide on the degradation and antimicrobial properties of PLA biocomposite films produced via solvent casting. The biocomposites underwent supercritical carbon dioxide (SCCO2) treatment at two different conditions under 40 °C temperature and at 100 bar and 200 bar pressure. Water absorption test showed that the untreated PLA biocomposite absorbed most water as compared to treated PLA biocomposite with SCCO2 at 5.1%. This is due to the hydrophilic nature of the fibre that absorbed water molecules. Soil burial test showed that the treated PLA biocomposite possessed the highest value of weight losses after 80 days with 97.8%. Biocomposite with the presence of CEO demonstrated antimicrobial activity against both gram-positive and gram-negative bacteria. This showed that SCCO2 significantly improved the properties of PLA biocomposite films. The supercritical fluid treatment of PLA biocomposite could be an alternative for active packaging industries to ensure that the packaging product meets the requirement by consumers as well as being an eco-friendly product. ABSTRAK: Produk biopolimer yang biodegradasi pada masa ini menarik perhatian dari penyelidik dan industri. Pembungkusan biodegradasi berasaskan polilaktik asid (PLA), serat kulit durian (DSF), minyak kelapa sawit terepoksi (EPO) dan ditambah dengan minyak pati kayu manis (CEO) sebagai agen antimikrobial telah dibangunkan dan menjadi bidang penyelidikan. Artikel ini melaporkan kesan karbon dioksida superkritikal terhadap sifat-sifat degradasi dan antimikrobik dari filem biokomposit PLA yang dihasilkan melalui pemutus pelarut. Biokomposit telah menjalani rawatan superkritikal karbon dioksida (SCCO2) pada dua keadaan yang berbeza di bawah suhu 40 °C pada 100 bar dan 200 tekanan bar. Ujian penyerapan air menunjukkan bahawa biocomposite PLA yang tidak dirawat menyerap kebanyakan air berbanding komposisi lain dengan 5.1%. Ini disebabkan sifat hidrofilik serat yang menyerap molekul air. Ujian penanaman dalam tanah menunjukkan bahawa biocomposite PLA yang dirawat mempunyai nilai kehilangan berat tertinggi setelah 80 hari dengan 97.8%. Biokomposit dengan kehadiran CEO menunjukkan aktiviti antimikrobial terhadap bakteria gram-positif dan gram-negatif. Ini menunjukkan bahawa SCCO2 meningkatkan sifat-sifat filem biocomposite PLA. Rawatan cecair superkritikal PLA biocomposite boleh menjadi alternatif bagi industri pembungkusan untuk memastikan produk pembungkusan memenuhi keperluan pengguna serta menjadi produk mesra alam.

Cellulose nanocrystals isolated from water hyacinth fiber (WHF) have been studied as a reinforcement for polyvinyl alcohol (PVA)-gelatin nanocomposite. Central composite design was used to study and optimize effects of the PVA, gelatin and cellulose nanocrystal (CNC) concentration on tensile strength and elongation of formed films. The results of this study showed that WHF CNC had a diameter range of 20-50 nm produced films reaching 13.8 MPa tensile strength. Thermal stability of the films was improved from 380 °C to 385 °C in addition of CNCs and maximum storage modulus of 3 GPa were observed when 5 wt% CNC was incorporated. However, water absorption, water vapour permeability (WVP) and moisture uptake of the films decreased in addition of CNC to the PVA-gelatin blends. Moisture uptake decreased from 22.50% to 19.05% while the least WVP when 10 wt% CNC added was 1.64 × 10 -6 g/(m • h • Pa). These results show possibility for industrial application of WHF CNC and PVA-gelatin blends in biodegradable films for on-the-go food wrappers. [ABSTRACT FROM AUTHOR]

Iron (Fe) has attracted great attention as bone repair material owing to its favorable biocompatibility and mechanical properties. However, it degrades too slowly since the corrosion product layer prohibits the contact between the Fe matrix and body fluid. In this work, zinc sulfide (ZnS) was introduced into Fe bone implant manufactured using laser additive manufacturing technique. The incorporated ZnS underwent a disproportionation reaction and formed S-containing species, which was able to change the film properties including the semiconductivity, doping concentration, and film dissolution. As a result, it promoted the collapse of the passive film and accelerated the degradation rate of Fe matrix. Immersion tests proved that the Fe matrix experienced severe pitting corrosion with heavy corrosion product. Besides, the in vitro cell testing showed that Fe/ZnS possessed acceptable cell viabilities. This work indicated that Fe/ZnS biocomposite acted as a promising candidate for bone repair material.

A new type of unsaturated poly ester-amide was prepared by melt polycondensation and characterized completely. Influence of heat treatment conditions and cross-linking content on mechanical and degradation properties of unsaturated polyester-amide were studied. Results suggested that the newly synthesized unsaturated poly(ester-amide) possessed good heat stabilization properties. Mechanical and degradation properties of cross-linked poly (ester-amide) were determined by heat treatment conditions and cross-linker content. Different initiation-accelerating agent systems and their content differences have an insignificant influence on the cross-linking time at Room Temperature (RT). Increasing heat treatment time increased the retention rate of mechanical properties during the degradation process and decreased hydrolysis rate in alkaline solution.

Several different bioabsorbable polymeric coil materials are currently used with the goal of improving treatment outcomes of endovascular embolization of intracranial aneurysms. However, little is known about the correlation between polymer degradation profiles and concomitant tissue responses in a blood vessel. The authors describe in vitro degradation characteristics of nine different polymeric materials and their corresponding tissue responses induced in rabbit carotid arteries. Mass loss and molecular weight loss of nine commercially available bioabsorbable sutures were evaluated in vitro up to16 weeks. The same nine materials, as well as platinum coils, were implanted into blind-end carotid arteries (n = 44) in rabbits, and their tissue reactions were evaluated histologically 14 days after the implantation.Five of the nine polymers elicited moderate to strong tissue reactions relative to the remaining materials. While polymer mass loss did not correlate with their histologic findings, polymers that showed a faster rate of molecular weight loss had a tendency to present more active tissue reactions such as strong fibrocellular response around the implanted material with a moderate inflammatory cell infiltration. Maxon exhibited the fastest rate of molecular weight loss and poly-l-lactic acid the slowest.The rate of molecular weight loss may be an important factor that is associated with the degree of bioactivity when bioabsorbable polymers are implanted into blood vessels. For further quantitative analysis, additional experiments utilizing established aneurysm models need to be conducted.

Plastic film is an important resource in agricultural production, but it takes hundreds of years to degrade completely in natural environment. The large-scale use of plastic film will inevitably lead to serious environmental pollution. One way to solve the problem is to develop a substitutable mulching film, such as a biodegradable film that can ultimately be decomposed to water, carbon dioxide, and soil organic matter by micro-organisms. In this study, a 2-year experiment was conducted to determine the degradation properties of a biodegradable plastic film, including degradation rate, surface microstructure, tensile strength and elongation at break, and the effects of different mulching treatments on soil temperature and maize yield. The mulching experiment was conducted with three different biodegradable plastic films with different degradation rates, using a common plastic film and a non-mulched treatment as control. With the addition of the additives for degradation in the biodegradable plastic films, the degradation rates increased significantly, which were 7.2%-17.8% in 2017 and 18.1%-35.2% in 2018 after maize harvesting. However, the degradation occurred mainly on the ridge side. The decrease in tensile strength and elongation was proportional to the degradation rate of the degradable film. The SEM results indicated that the surface microstructures of the biodegradable films were loose and heterogeneous after maize harvesting. Biodegradable plastic film mulching increased the soil temperature at soil depths of 5 cm, 15 cm, and 25 cm, over the maize's entire growth period, by 3.1°C-3.2°C in 2017 and 1.2°C-2.1°C in 2018 compared with the non-mulched treatment. The biodegradable plastic film increased the maize yield by 10.4%-14.3% in 2017 and 11.6%-24.7% in 2018. The soil temperature and maize yield increases were statistically significant; however, with respect to maize qualities, there were no statistically significant increases among the five treatments. This study shows that biodegradable plastic film can be used as a substitute for common plastic film. However, the ingredients in biodegradable plastic films should be improved further to ensure that they can be degraded completely after crop harvest. [ABSTRACT FROM AUTHOR]

Biodegradable mulch films are recognized as a promising substitute of polyethylene (PE) films to alleviate the "white pollution". Biodegradable mulch films with optimum degradation rates increase crop yield even compared to PE films. However, the mechanisms underlying this yield-increasing effect remains elusive. In this study, three biodegradable film treatments (BFM1, BFM2 and BFM3) and one PE film treatment (PFM) were used to evaluate their effects on soil and winter potatoes, and a partial least squares path model (PLS-PM) was constructed to investigate their relationships. The degradation rates of films under different treatments were ranked as BFM3 > BFM2 >BFM1 > PFM, and presented distinctive effects on soil properties and nutrients, structure of soil bacterial community, and yield traits of winter potatoes. The PLS-PM showed that mulch treatments affected potato yield through effects on soil properties (soil water and temperature) and soil nutrients (TOC, DOC, TN and NO 3 --N). The disintegration of the biodegradable films decreased soil water content and temperature, and reduced the loss of soil nutrients in the topsoil at the later growth stage of winter potatoes compared to PE films. Additionally, the elevated content of soil TN and NO 3 --N under treatment BFM1 may play a key role in its yield-increasing effect on potatoes compared to treatments PFM and BFM2. Thus, biodegradable mulch films with proper degradation rates regulate soil TN and NO 3 --N through their effects on soil water and temperature, and subsequently improve the yield of winter potatoes compared to PE mulch films. • Biodegradable mulch films with an optimum degradation rate increased the yield of winter potatoes compared to PE films. • Different mulch treatments significantly affected soil water and temperature. • Different mulch treatments altered the structure of soil bacterial community. • The yield-increasing effects of biodegradable mulch films were associated with soil TN and NO 3 --N. [ABSTRACT FROM AUTHOR]

The physical and degradation properties of polylactic (PLA)/thermoplastic starch (TPS) blends after TPS modification with citric acid (CA) were investigated. The interfacial adhesion between the PLA and TPS was expected to improve, thus enhancing the physical properties of the PLA/TPS blends. The tensile strength and Young's modulus for PLA/TPS blends at (60/40) and (40/60) blends ratio were found to increase after modification with CA. On the other hand, the elongation at break of the (60/40) blend decreased, while elongation at break of the (40/60) blend increased. Meanwhile, an additional peak at 1721 cm-1 was detected by the FTIR spectroscopic analysis, which indicated that the TPS had chemically interacted with the CA. The biodegradability properties of PLA/TPS blends were also improved after treatment with CA. The deterioration of PLA/TPS blends was attributed to the incorporation of CA; O2 from the soil was attracted to the PLA/TPS blends, thus speeding up the degradation process of the blends. [ABSTRACT FROM AUTHOR]

The overly-fast degradation rates of magnesium-based alloys in the biological environment have limited their applications as biodegradable bone implants. In this study, rare earth element yttrium (Y) was introduced into AZ61 magnesium alloy (Mg-6Al-1Zn wt %) to control the degradation rate by laser rapid melting. The results showed that the degradation rate of AZ61 magnesium alloy was slowed down by adding Y. This was attributed to the reduction of Mg17Al12 phase and the formation of Al2Y phase that has a more active potential, which decreased galvanic corrosion resulting from its coupling with the anodic matrix phase. Meanwhile, the hardness increased as Y contents increased due to the uniform distribution of the Al2Y and Mg17Al12 phases. However, as the Y contents increased further, the formation of excessive Al2Y phase resulted in the increasing of degradation rate and the decreasing of hardness due to its agglomeration. [ABSTRACT FROM AUTHOR]

Preliminary studies were undertaken to assessment the impact of thermal treatment of commercial gelatin solution on the physicochemical properties of electrospun gelatin fibrous mats. The gelatin (dry granules) was dissolved in aqueous solution and heated up to boiling then was dried at 40 °C. The electro spinning process and cross-linking of electrospun mats using glutaraldehyde (GTA) vapor were achieved. The results revealed that thermal treatment of raw gelatin solution before electro spinning process enhanced the quality of electrospun gelatin fibrous mats, especially in terms of fibers sizes, degradation time, and swelling degree that could provide a basis for improving electrospun gelatin fibers for medical applications. [ABSTRACT FROM AUTHOR]

The in-situ stress field in deeply incised valleys is an important factor to be considered in major construction projects on the Qinghai-Tibet Plateau. The resulting in-situ stress has a complex distribution and large magnitude due to rapid river erosion. Considering that the few actual measured in-situ stress values are insufficient to meet the needs of understanding the regional in-situ stress field and its evolution, this research proposes a method, the Svisc model, to study the distribution and evolution characteristics of the in-situ stress field and applies it to a case study of the Jinping-I Hydropower Station. The results show that the Svisc model, which considers the rheological and degradation properties of the rock mass, applies strength parameters that change from peak to residual values rather than remaining constant with rock mass degradation during the downcutting process of valleys. The stress adjustment depth obtained is deeper, and the current in-situ stress field values are higher overall according to the Svisc model. This model is more effective than conventional methods to simulate the long-term evolution of valleys. • The Svisc model is proposed to study the distribution and evolution characteristics of in-situ stress field. • The rheological and degradation properties of rock mass are fully considered in valley evolution. • The adjustment depth and value of stress obtained by the Svisc model are deeper and higher overall. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this work was to develop and study new biodegradable thermoplastics with improved mechanical properties for potential use as temporary implantable biomaterials. Linear poloxamer and star-shaped poloxamine have been used as macroinitiators for the ring-opening polymerization (ROP) of lactide to yield high molecular weight PLA-based thermoplastic block copolymers. The influence of the nature of the macroinitiator, PLA crystallinity and initial molecular weight on the copolymers properties was investigated by performing a 7-week degradation test in PBS. The evaluation of water uptakes and molecular weights during the degradation pointed out an early hydrolytic degradation of the 100-kg∙mol−1 copolymers compared to the 200-kg∙mol−1 ones (molecular weight decrease of ca. 40% and 20%, respectively). A dramatic loss of tensile mechanical properties was also observed for the 100-kg∙mol−1 copolymers, whereas the 200-kg∙mol−1 copolymers showed stable or even slightly improved properties with Young's moduli around 500MPa and yield strains around 3% to 4%. Finally, the cytocompatibility of the more stable 200kg∙mol−1 copolymers was confirmed by murine mesenchymal stem cells (MSCs) culture. [Copyright &y& Elsevier]

Abstract: Biodegradable poly(sebacic anhydride-co-caprolactone) (PSA-co-PCL) multi-block copolymers were prepared by condensation of acylated PSA and PCL prepolymers with different weight ratios. The homopolymer and copolymers were characterized by 1H-NMR, gel permeation chromatography (GPC), differential scanning calorimeter (DSC) and atom force microscope (AFM). 1H-NMR and GPC has indicated the formation of PSA-co-PCL multi-block copolymers, in which PSA and PCL segments are randomly distributed. The incorporation of PCL segments into the molecule chains even at a content of 20wt% could significantly decrease the molecular weight distribution of the copolymer and increase its weight average molecular weight, as compared with PSA homopolymer. DSC has revealed that the melting temperature and degree of crystallinity for both SA and CL components are strongly composition dependent, implying the hindrance effect of the two components on crystallinity of each other. AFM observation has shown the difference in crystalline structures between PSA and PCL phases in the copolymers. In-vitro degradation tests performed at 37°C in PBS buffer solution (pH 7.4, 0.1M) have demonstrated the acceleration of degradation rate of the sample with increasing SA content in the copolymer. [Copyright &y& Elsevier]

Polyactive® 1000PEOT70PBT30 (a segmented block copolymer of poly(ethylene oxide terephtalate)/poly(butylene terephtalate) with 70/30 PEOT/PBT ratio) was processed into three different types of samples: injection molded to rods, hot-pressed to films and to composite membranes made by hot-pressing a tubular mesh of poly-l,d-lactide 96/4 between two films of Polyactive®. The molecular weight of Polyactive® was not influenced by processing, but γ-sterilization seemed to increase the weight average molecular weight (Mw). Mechanical properties of the rods and films decreased rapidly in hydrolytic conditions due to the hydrogel nature of the polymer, swelling and degradation. Mesh reinforcement increased the mechanical properties, but the components separated during soaking. In vitro the molecular weight of the rods and films started to decrease immediately, but the PEOT (or PEO) proportion remained relatively constant for 26 weeks. Macroscopically, all the wet devices remained intact, but fragmented on drying. Microscopically, topographical formations of polymer were found on the surfaces and small sodium-rich spots were precipitated onto and inside the polymer. Thermal measurements showed that polymer consisted of amorphous PEOT segments and both amorphous and crystalline PBT segments. [Copyright &y& Elsevier]

Bone repair failure caused by implant-related infections is a common and troublesome problem. In this study, an antibacterial scaffold was developed via selective laser sintering with incorporating nano magnesium oxide (nMgO) to poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The results indicated the scaffold exerted high antibacterial activity. The antibacterial mechanism was that nMgO could cause oxidative damage and mechanical damage to bacteria through the production of reactive oxygen species (ROS) and direct contact action, respectively, which resulted in the damage of their structures and functions. Besides, nMgO significantly increased the compressive properties of the scaffold including strength and modulus, due to its excellent mechanical properties and uniform dispersion in the PHBV matrix. Moreover, the degradation tests indicated nMgO neutralized the acid degradation products of PHBV and benefited the degradation of the scaffold. The cell culture demonstrated that nMgO promoted the cellular adhesion and proliferation, as well as osteogenic differentiation. The present work may open the door to exploring nMgO as a promising antibacterial material for tissue engineering., Competing Interests: No conflict of interest was reported by the authors. The authors gratefully acknowledge the following projects and funds for the financial support: (1) The Natural Science Foundation of China (51575537, 81572577, 51705540); (2) Overseas, Hong Kong, and Macao Scholars Collaborated Researching Fund of National Natural Science Foundation of China (81428018); (3) Hunan Provincial Natural Science Foundation of China (2016JJ1027); (4) The Project of Innovationdriven Plan of Central South University (2016CX023); (5) The Open-End Fund for the Valuable and Precision Instruments of Central South University; (6) The fund of the State Key Laboratory of Solidification Processing at NWPU (SKLSP201605); (7) The Project of State Key Laboratory of High Performance Complex Manufacturing, Central South University, and (8) National Postdoctoral Program for Innovative Talents (BX201700291)., (Copyright: © 2018 Shuai C, et al.)