Weeks Of Degradation Research Articles

Generation of Microplastics from Biodegradable Packaging Films Based on PLA, PBS and Their Blend in Freshwater and Seawater.

Biodegradable polymers and their blends have been advised as an eco-sustainable solution; however, the generation of microplastics (MPs) from their degradation in aquatic environments is still not fully grasped. In this study, we investigated the formation of bio-microplastics (BMPs) and the changes in the physicochemical properties of blown packaging films based on polylactic acid (PLA), polybutylene succinate (PBS) and a PBS/PLA 70/30 wt% blend after degradation in different aquatic media. The tests were carried out in two temperature/light conditions to simulate degradation in either warm water, under sunlight exposure (named Warm and Light-W&L), and cold deep water (named Cold and Dark-C&D). The pH changes in the aqueous environments were evaluated, while the formed BMPs were analyzed for their size and shape alongside with variations in polymer crystallinity, surface and mechanical properties. In W&L conditions, for all the films, the hydrolytic degradation led to the reorganization of the polymer crystalline phases, strong embrittlement and an increase in hydrophilicity. The PBS/PLA 70/30 blend exhibited increased resistance to degradation with respect to the neat PLA and PBS films. In C&D conditions, no microparticles were observed up to 12 weeks of degradation.

Investigation of Degradation and Biocompatibility of Indirect 3D-Printed Bile Duct Stents.

This study proposes a bile duct stent based on indirect 3D printing technology. Four ratio materials were synthesized from lactic acid (LA) and glycolide (GA) monomers by melt polymerization: PLA, PLGA (70:30), PLGA (50:50), and PLGA (30:70). The four kinds of material powders were preliminarily degraded, and the appearance was observed with an optical microscope (OM) and a camera. The weight and appearance of the four materials changed significantly after four weeks of degradation, which met the conditions for materials to be degraded within 4-6 weeks. Among them, PLGA (50:50) lost the most-the weight dropped to 13.4%. A stent with an outer diameter of 10 mm and an inner diameter of 8 mm was successfully manufactured by indirect 3D printing technology, demonstrating the potential of our research. Then, the degradation experiment was carried out on a cylindrical stent with a diameter of 6 mm and a height of 3 mm. The weight loss of the sample was less than that of the powder degradation, and the weight loss of PLGA (50:50) was the largest-the weight dropped to 79.6%. The nano-indenter system measured the mechanical properties of materials. Finally, human liver cancer cells Hep-3B were used to conduct in vitro cytotoxicity tests on the scaffolds to test the biocompatibility of the materials. A bile duct stent meeting commercial size requirements has been developed, instilling confidence in the potential of our research for future medical applications.

Biodegradable poly(lactic acid) blocked polyurethane/carbon nanotubes coated cotton fabric prepared by ultrasonic-assisted inkjet printing for high performance strain sensors

In order to fulfill the demands for degradability, a broad working range, and heightened sensitivity in flexible sensors, biodegradable polyurethane (BTPU) was synthesized and combined with CNTs to produce BTPU/CNTs coated cotton fabric using an ultrasonic-assisted inkjet printing process. The synthesized BTPU displayed a capacity for degradation in a phosphate buffered saline solution, resulting in a weight loss of 25 % after 12 weeks of degradation. The BTPU/CNTs coated cotton fabric sensor achieved an extensive strain sensing range of 0–137.5 %, characterized by high linearity and a notable sensitivity (gauge factor (GF) of 126.8). Notably, it demonstrated a low strain detection limit (1 %), rapid response (within 280 ms), and robust durability, enabling precise monitoring of both large and subtle human body movements such as finger, wrist, neck, and knee bending, as well as swallowing. Moreover, the BTPU/CNTs coated cotton fabric exhibited favorable biocompatibility with human epidermis, enabling potential applications as wearable skin-contact sensors. This work provides insight into the development of degradable and high sensing performance sensors suitable for applications in electronic skins and health monitoring devices.

Preparation and characterization of amphiphilic, biodegradable, waterborne polyurethanes without using organic solvent and catalyst.

Traditionally, waterborne polyurethanes (WPUs) are prepared using toxic organic solvents and catalysts. These WPUs are non-biodegradable and are buried or incinerated after the expiration date. This has adverse effects on the environment and human health, which limits the applications of WPUs. Herein, a special synthetic method was developed for biodegradable waterborne polyurethane (BWPU) by adding hydrophilic prepolymers into WPU prepolymers without using organic solvents and catalysts. Different proportions of polyethylene glycol (PEG) were introduced into polycaprolactone (PCL)-based BWPUs to improve the comprehensive properties. Results showed that as the PEG content was increased from 0 to 16 wt%, the solid content of BWPU increased from 34.8 wt% to 53.1 wt%, while the tensile strength and Young's modulus of BWPU films increased from 21.81 MPa to 56.83 MPa and 8.08 MPa to 19.4 MPa, respectively. However, the elongation at break did not decrease significantly, but still reached 827.17%. With an increase in PEG content, the crystallinity and phase separation decreased, while the hydrophilicity and surface energy increased for BWPU films. In addition, the prepared BWPUs had good biodegradability in PBS/lipase solution. The mass loss of BWPU without PEG reached 6.3 wt% after 4 weeks of degradation, whereas the mass losses of BWPUs with PEG reached 2.3-4.3 wt%. Obviously, the introduction of PEG did not increase biodegradability. Thus, the higher the PCL content, the faster the biodegradation rate. This work would provide an effective method for the preparation of ecofriendly biodegradable BWPU with excellent comprehensive properties.

Degradation Characteristics of Cellulose Acetate in Different Aqueous Conditions.

Cellulose acetate (CA) is widely used in cigarette filters and packaging films, but due to its acetylation, it is difficult to degrade in the natural environment, and the problem of pollution has become a serious challenge. Understanding the degradation behavior and performance of CA in different environments is the basis and prerequisite for achieving its comprehensive utilization and developing efficient degradation methods. In this study, we investigated the degradation performance of CA in different aqueous environments to evaluate the effects of pH, salinity and microorganisms on CA degradation. The CA tows and films were immersed in HCl, NaOH solution, river water, seawater or homemade seawater for 16 weeks and the degradation mechanism was investigated by the changes in weight loss rate, degree of substitution, hydrophilicity, molecular structure and surface morphology. The results showed that the degradation of CA tow and film were the fastest in NaOH solution; the weight loss rates after 16 weeks were 40.29% and 39.63%, respectively, followed by HCl solution, and the degradation performance of CA tow was better than that of film. After 16 weeks of degradation in river water, seawater and homemade seawater, all the weight loss rates were less than 3%. In summary, this study illustrated that the environmental acidity, basicity and high concentration of inorganic salts had a critical promotion effect on the non-enzymatic hydrolysis of CA, whereas the number and type of microorganisms were the key factors affecting the biodegradation of CA.

In-Vitro Degradation Behaviors and Biocompatibility of Sodium Alginate/Platelet-Rich Plasma-Sr2+ Porous Microcarriers

Porous microcarriers as cell carriers have attracted extensive research interest in tissue engineering. In this work sodium alginate (SA) and sodium alginate/platelet-rich plasma (SA/PRP) porous microcarriers cross-linked by SrCl2 (SA-Sr2+ and SA/PRP-Sr2+) were prepared using an emulsion method combined with a freeze-drying method. The in-vitro degradation behaviors of the SA-Sr2+ and SA/PRP-Sr2+ porous microcarriers in phosphate-buffered saline (PBS) were investigated. The cell proliferation ability and osteogenic activity of the SA-Sr2+ and SA/PRP-Sr2+ porous microcarriers were investigated by culturing rat bone marrow mesenchymal stem cells (rBMSCs). During the degradation process, the degradation behaviors, including changes of the pH of the PBS and the weight loss and morphology, of both the SA-Sr2+ and SA/PRP-Sr2+ porous microcarriers showed a similar change. After 6 wk of degradation, parts of both the SA-Sr2+ and SA/PRP-Sr2+ porous microcarriers collapsed. The SA/PRP-Sr2+ porous microcarriers showed higher cell proliferation ability and osteoinductive ability than the SA-Sr2+ porous microcarriers during a culture time of 14 days.

Enzymatic Degradation of PET plastic

Polyethylene terephthalate (PET) plastic is one of the most commonly used polymers worldwide and found in high rates as environmental waste. Previous studies have shown that the degradation of plastics using commercial grade enzymes is possible and highly effective in lab settings. However, the effectiveness and rates of enzymatic plastic degradation at environmentally relevant conditions is less known. In this study, we set up a series of sacrificial incubation experiments using a commercial enzyme, Humicola insolens cutinase (HiC), to examine the effect of various environmental variables, including temperature, pH, and salinity, on the hydrolytic degradation of PET. This was performed by measuring the mass loss at different time points during degradation, dissolved organic carbon produced in solution by PET hydrolysis, the Fourier transform infrared (FTIR) spectra of the PET surfaces, and scanning electron microscope (SEM) images of the PET surfaces. The results indicate that the degradation rate is 15-times faster at 55 °C than at 40 °C at pH 8 (1.93 mg day-1 versus 0.13 mg day-1), giving an initial estimate for the activation energy of PET hydrolysis of 2.2 kJ mol-1. In the 55 °C experiment which ran for 10 days, there was a noticeable decrease in the plastic strength and deformation of the plastic after 1 week of degradation. In the 40 °C experiment (duration 16 weeks), FTIR spectral changes were observed as early as week 6, with peaks of interest at 2,970 cm-1, 2,350 cm-1, 1,240 cm-1 , and between 1,300-1,000 cm-1. Ongoing experiments with pH and salinity will provide insight into their effects on the PET degradation rate. Altogether, these results will provide a comprehensive framework for predicting PET degradation rates, and by extension, other plastics that are degraded by hydrolysis, at environmentally relevant pH, temperature, and salinity conditions. In addition, these results provide insight into the effect of degradation on the chemical spectra of plastics and microplastics.

Understanding the oxidation chemistry of Ti3C2Tx (MXene) sheets and their catalytic performances

Transition metal carbides and nitrides (MXenes) nanosheets are attractive two-dimensional (2D) materials, but they suffer from oxidation/degradation issues during storage and/or applications due to their sensitivity to water and oxygen. Despite the great research progress, the exact oxidation kinetics of Ti3C2Tx (MXene) and their final products after oxidation are not fully understood. Herein, we systematically tracked the oxidation process of few-layer Ti3C2Tx nanosheets in an aqueous solution at room temperature over several weeks. We also studied the oxidation effects on the electrocatalytic properties of Ti3C2Tx for hydrogen evolution reaction and found that the overpotential to achieve a current density of 10 mA cm−2 increases from 0.435 to 0.877 V after three weeks of degradation, followed by improvement to stabilized values of around 0.40 V after eight weeks. These results suggest that severely oxidized MXene could be a promising candidate for designing efficient catalysts. According to our detailed experimental characterization and theoretical calculations, unlike previous studies, black titanium oxide is formed as the final product in addition to white Ti (IV) oxide and disordered carbons after the complete oxidation of Ti3C2Tx. This work presents significant advancements in better understanding of 2D Ti3C2Tx (MXene) oxidation and enhances the prospects of this material for various applications.

Development of isotopically labelled 65Cu embedded PMMA-65CuO nanocomposites for detection and quantification of PMMA bone cement degradation at trace levels

Polymethyl methacrylate (PMMA) bone cement is a popular bone-filling material for biomedical applications. Bone-cement implant failure is a common occurrence, but the consequence of this failure can be prevented/minimised by early detection of degradation. This work utilises a stable isotope labelling approach to monitor PMMA bone cement degradation. Stable isotopically enriched traceable nanoparticles of 65CuO were synthesized and introduced to PMMA bone cement. Accelerated and normal degradation of 65CuO-loaded PMMA bone cement nanocomposite was performed in acetone and simulated body fluid (SBF). 65Cu was detected and quantified upon PMMA bone cement nanocomposite degradation. The results showed a linear correlation between bone cement degradation and tracer release. When the 65CuO-PMMA composite deteriorated by 6.10 ± 3.04% in acetone, 5.6 ± 2.5 µg of tracer was released in 10 min. Similarly, after one week of degradation in SBF, 0.35 ± 0.31 µg of 65Cu tracer was released, translating to a 0.18 ± 0.09% weight loss. The stable isotopic tracer approach allowed us to measure and detect 65Cu under conditions of high background Cu concentration present in the human body upon 0.2% of PMMA nanocomposite degradation. 65CuO nanoparticles addition to PMMA bone cement did not alter the cytocompatibility (proliferation, differentiation, and osteocalcin formation) in MG-63 cells.

Application of solid-state fermentation using mushrooms for the production of animal feed.

The increasing growth of agroindustrial activity resulting in excessive amounts of agriwaste has led to the accumulation of a large quantity of lignocellulosic residues all over the world, in particular in deforestation initiatives for the removal of invasive trees in South Africa. These lignocellulosic residues are rich in energy resources and consist of a mixture of natural polymers based on lignin, cellulose, and hemicellulose. The use of lignolytic fungi such as mushrooms in solid-state fermentation could sufficiently degrade the indigestible lignocellulosic components and add medicinal and nutritional value to otherwise unusable, high-energy waste material, which in turn could yield a new method of producing energy-rich fodder for ruminant animals. The digestive type of animal for which the potential feed is developed must be identified and considered before deciding on the bioconversion method and process, as the outcomes for obtaining potentially high-quality feeds for nonruminant and ruminant animals are different. The current study presents data on the bioconversion of lignocellulosic substrate using solid-state fermentation with edible and medicinal mushrooms, Ganoderma lucidumand Pleurotus ostreatus, and a possible new species, to increase digestibility and nutritional value to be applied as ruminant animal feed. The solid-state fermentation process was optimized and the resulting product was analyzed for the degradation of the lignocellulosic components. Results indicated that the solid-state fermentation duration and mushroom species were key components in achieving significant degradation. Data obtained after 18 weeks of degradation indicated a significant (p < 0.05) reduction in the acid detergent fiber, acid detergent lignin, and neutral detergent fiber fractions of the biomass, with up to a 20% reduction in indigestible components. This increase in digestibility could contribute to increased energy availability for ruminant animals.

Cerium Oxide and Chondroitin Sulfate Doped Polyurethane Scaffold to Bridge Tendons.

Tendon disorders are common medical conditions, which can be greatly debilitating as they are often accompanied by great pain and inflammation. The techniques used nowadays for the treatment of chronic tendon injuries often involve surgery. However, one critical aspect of this procedure involves the scar tissue, characterized by mechanical properties that vary from healthy tissue, rendering the tendons inclined to reinjury or rupture. Synthetic polymers, such as thermoplastic polyurethane, are of special interest in the tissue engineering field as they allow the production of scaffolds with controlled elastic and mechanical properties, which could guarantee an effective support during the new tissue formation. The aim of this work was the design and the development of tubular nanofibrous scaffolds based on thermoplastic polyurethane and enriched with cerium oxide nanoparticles and chondroitin sulfate. The scaffolds were characterized by remarkable mechanical properties, especially when tubular aligned, reaching values comparable to the ones of the native tendons. A weight loss test was performed, suggesting a degradation in prolonged times. In particular, the scaffolds maintained their morphology and also remarkable mechanical properties after 12 weeks of degradation. The scaffolds promoted the cell adhesion and proliferation, in particular when in aligned conformation. Finally, the systems in vivo did not cause any inflammatory effect, representing interesting platforms for the regeneration of injured tendons.

Synthesis and properties of biodegradable aliphatic–aromatic polyesters derived from 4‐hydroxybenzaldehyde

AbstractA novel biphenyl monomer, diethyl 6,6′‐dimethoxy‐[1,1′‐bipheny]‐3,3′‐dicarboxylate (DDBD), was synthesized from 4‐hydroxybenzaldehyde, a phenolic compound derived from lignin. A series of polyesters were prepared by polycondensation of the biphenyl monomer with hydroquinone bis(2‐hydroxyethyl) ether and aliphatic diacids via a two‐step melt polycondensation method. It was shown that the properties of the polyesters can be tuned by varying the length and the structure of the spacer in the aliphatic diacid monomers. Structure–property relations for these materials were investigated by Fourier‐transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. GPC analysis showed that the weight‐average molecular weight (Mw) of the samples varied from 4.2–5.0 × 104 g/mol, while thermal analysis yielded Tg values of 51–120°C, and 5% decomposition temperatures (Td,5%) of 327–389°C. All the samples exhibited a high yield strength (56–87 MPa). After 30 weeks of degradation in soil, the copolyesters had mass losses of up to 4.4%, and an investigation of the ecotoxicity of the copolyesters with Eisenia fetida yielded a survival rate of over 80% after 14 days for the different copolyesters, suggesting low toxicity in the environment. Overall, these copolyesters have good properties and would be suitable to replace petroleum‐based commercial poly(ethylene terephthalate) packaging materials.

Irrigating degradation properties of silk fibroin–collagen type II composite cartilage scaffold in vitro and in vivo

Silk fibroin-collagen type II scaffolds are promising in cartilage tissue engineering due to their suitable biological functionality to promote proliferation of chondrocytes in vitro. However, their degradation properties, which are of crucial importance as scaffold degradation should consistent with the new tissue formation process, are still unknown. In this study, degradability of silk fibroin-collagen type II cartilage scaffolds was probed both in vitro and in vivo. In vitro degradation experiments show that the scaffolds decreased 32.25 % ± 0.62 %, 34.27 % ± 0.96 %, 36.27 % ± 2.39 % in weight after 8 weeks of degradation at the irrigation velocity of 0 mL/min, 7.89 mL/min and 15.79 mL/min. The degradation ratio, which increases with time and increasing irrigation velocity, is described by combining the built mathematic model and finite element modeling method. The scaffolds after 8 weeks of degradation in vitro keep their mechanical structural integrity to support new tissues. In vivo degradation experiments conducted in rabbits further show that the scaffolds degrade gradually, be absorbed with time and finally collapse in structure. The degradation process is accompanied by the growth of fibrous tissues and the scaffold is filled by fibrous tissues after 12 weeks of implantation. Immunohistology analysis shows that the inflammation caused by scaffolds is controllable and gradually alleviates with time. To sum up, silk fibroin-collagen type II cartilage scaffolds, which show suitable mechanical properties and biocompatibility during degradation in vitro and in vivo, have great potential in cartilage repair. The novelty of the study is that it not only introduces a mathematical model to predict the irrigation degradation ratio, but also provides experimental degradation data support for clinical application of silk fibroin-collagen type II cartilage scaffolds.

Degradation of biobased poly(ethylene 2,5‐furandicarboxylate) and polyglycolide acid blends under lipase conditions

AbstractBio‐based polymer materials are considered to have function of protecting the environment, and improving the degradation performance of bio‐based polymer materials is of great significance to realize the green cycle of production‐use‐degradation of plastic products. This present work is focused on the investigation of the degradation behavior of bio‐based polymer blend poly(ethylene 2,5‐furandicarboxylate) /polyglycolide acid (PEF/PGA) with different composition ratios in phosphate‐buffered saline (PBS solution, pH = 7.4) with 0.5 mg/mL of lipase from porcine pancreas. The results observed that the thermal decomposition temperatures at 5% weight loss of both the PEF/PGA blends are higher than 310°C, which reflected that the PEF/PGA blends possessed excellent thermal stability. The water absorption of the PEF/PGA blends continued to increase with increasing the PGA content. This trend is consistent with the mass loss of blends in the degradation process. The systematic degradation study revealed that the neat PEF showed no mass loss in both PBS solution with and without lipase, while the PEF/PGA blends possessed a faster rate under enzymatic degradation circumstance in the first 4 weeks, and the weight loss in the same degradation period increase with increasing the PGA content due to the erosion of lipase on the polymer chain. In particular, the weight loss of PEFGA40 blend was more than 18.33% after 8 weeks of degradation in enzyme solution. 1H NMR results showed that in addition to PGA component as a major component of degradation, a small amount of PEF component was also involved in the mass loss of the blend during degradation. At the same time, the short‐chain segment produced during the degradation had a clear plasticizing effect on the PEFGA blends, which is reflected in that the Tg of PEFGA40 blend decreased first and then increased with the increase of degradation time.

Effect of polycaprolactone impregnation on the properties of calcium silicate scaffolds fabricated by 3D printing

Calcium silicate (CS) is a suitable substrate for bone tissue engineering because it can provide bioactive ions like Si4+ and Ca2+ to promote bone regeneration. However, the rapid degradation of CS leads to pH problems and does not match the rate of osteogenesis. The 3D printed CS scaffolds were immersed in Polycaprolactone (PCL) solution to obtain PCL-coated scaffolds with improved mechanical and biological properties. Finite element method (FEM) analysis found that PCL impregnation has the effect of stress shielding and defect healing, effectively improving the mechanical properties of CS porous scaffolds. The degradation rate of PCL-coated scaffolds was significantly slowed down in Tris buffer. After 4 weeks of degradation, the compressive strength of PCL-coated scaffolds remained at 23.34 MPa, maintaining reliable mechanical properties. PCL coating significantly reduced the degradation rate of CS scaffolds, and the pH value and Si ion concentration of Dulbecco's modified Eagle's medium (DMEM) soaked by PCL-coated scaffolds were more favorable for cell survival. The results show that PCL-coated scaffolds enhance cell proliferation and osteogenic differentiation, demonstrating the potential applicability of bone tissue engineering applications.

A Complex In Vitro Degradation Study on Polydioxanone Biliary Stents during a Clinically Relevant Period with the Focus on Raman Spectroscopy Validation.

Biodegradable biliary stents are promising treatments for biliary benign stenoses. One of the materials considered for their production is polydioxanone (PPDX), which could exhibit a suitable degradation time for use in biodegradable stents. Proper material degradation characteristics, such as sufficient stiffness and disintegration resistance maintained for a clinically relevant period, are necessary to ensure stent safety and efficacy. The hydrolytic degradation of commercially available polydioxanone biliary stents (ELLA-CS, Hradec Králové, Czech Republic) in phosphate-buffered saline (PBS) was studied. During 9 weeks of degradation, structural, physical, and surface changes were monitored using Raman spectroscopy, differential scanning calorimetry, scanning electron microscopy, and tensile and torsion tests. It was found that the changes in mechanical properties are related to the increase in the ratio of amorphous to crystalline phase, the so-called amorphicity. Monitoring the amorphicity using Raman spectroscopy has proven to be an appropriate method to assess polydioxanone biliary stent degradation. At the 1732 cm−1 Raman peak, the normalized shoulder area is less than 9 cm−1 which indicates stent disintegration. The stent disintegration started after 9 weeks of degradation in PBS, which agrees with previous in vitro studies on polydioxanone materials as well as with in vivo studies on polydioxanone biliary stents.

Electrospun hybrid nanofibrous meshes with adjustable performance for potential use in soft tissue engineering

Electrospun nanofibrous scaffolds have gained extensive attention in the fields of soft tissue engineering and regenerative medicine. In this study, a series of biodegradable nanofibrous meshes were fabricated by electrospinning poly(ε-caprolactone) (PCL) and poly( p-dioxanone) (PPDO) blends with various mass ratios. All the as-developed PCL/PPDO nanofibrous meshes possessed smooth and highly aligned fiber morphology. The mean fiber diameter was 521.5 ± 76.6 nm for PCL meshes and 485.8 ± 88.9 nm for PPDO meshes, and the mean fiber diameter seemed to present a decreasing tendency with the increasing of the PPDO component. For pure PCL meshes, the contact angle was about 117.5 ± 1.6°, the weight loss ratio was roughly 0.2% after 10 weeks of degradation, and the tensile strength was 41.2 ± 2.3 MPa in the longitudinal direction and 4.2 ± 0.1 MPa in the transverse direction. It was found that the surface hydrophilicity and in vitro degradation properties of PCL/PPDO meshes apparently increased, but the mechanical properties of PCL/PPDO meshes obviously decreased when more PPDO component was introduced. The biological tests showed that 4:1 PCL/PPDO nanofibrous meshes and 1:1 PCL/PPDO nanofibrous meshes could obviously promote the adhesion and proliferation of human adipose derived mesenchymal stem cells more than pure PCL and PPDO meshes and 1:4 PCL/PPDO meshes. The results demonstrated that it is feasible to adjust the surface hydrophilicity, degradation profile, and mechanical properties as well as biological properties of as-obtained nanofibrous meshes by blending PCL and PPDO components. This study provides meaningful reference and guidance for the design and development of PCL/PPDO hybrid nanofibrous scaffolds for soft tissue engineering research and application.

Biodegradable magnesium fixation screw for barrier membranes used in guided bone regeneration

An ideal fixation system for guided bone (GBR) regeneration in oral surgery must fulfil several criteria that includes the provision of adequate mechanical fixation, complete resorption when no longer needed, complete replacement by bone, as well as be biocompatible and have a good clinical manageability. For the first time, a biodegradable magnesium fixation screw made of the magnesium alloy WZM211 with a MgF2 coating has been designed and tested to fulfill these criteria. Adequate mechanical fixation was shown for the magnesium fixation screw in several benchtop tests that directly compared the magnesium fixation screw with an equivalent polymeric resorbable device. Results demonstrated slightly superior mechanical properties of the magnesium device in comparison to the polymeric device even after 4 weeks of degradation. Biocompatibility of the magnesium fixation screw was demonstrated in several in vitro and in vivo tests. Degradation of the magnesium screw was investigated in in vitro and in vivo tests, where it was found that the screw is resorbed slowly and completely after 52 weeks, providing adequate fixation in the early critical healing phase. Overall, the magnesium fixation screw demonstrates all of the key properties required for an ideal fixation screw of membranes used in guided bone regeneration (GBR) surgeries.

More Precise Control of the In Vitro Enzymatic Degradation via Ternary Self-Blending of High/Medium/Low Molecular Weight Poly(trimethylene carbonate)

To more precisely control the degradation rate of poly(trimethylene carbonate) (PTMC), self-blending films were prepared via the ternary self-blending of pure PTMC with a molecular weight of 334, 152, and 57 kg/mol. The in vitro enzymolysis degradation of the ternary self-blending films was performed in lipase solutions. The results showed that ternary self-blending could control the degradation of PTMC by adjusting the mass ratio of high/medium/low molecular weight PTMC in the composition, and the PTMC334/PTMC152/PTMC57 films with a mass ratio of 1/4/16 showed mass loss of 85.96% after seven weeks of degradation, while that of PTMC334/PTMC152/PTMC57 films with a mass ratio of 1/1/1 was 96.39%. The former and latter’s degradation rate constant was 13.263 and 23.981%/w, respectively, and the former presented better morphology stability than the latter. The strategy of ternary self-blending could simultaneously bestow PTMC with a lower degradation rate and good morphology stability, indicating that ternary self-blending is an efficient way to control the degradation performance of PTMC more precisely.

An assessment of magnesium AZ31 coronary stents manufacture

AZ31 magnesium coronary stents were studied through a manufacturing process chain involving laser cutting, acid pickling, and dip coating. The purpose of this study was to evaluate surface thickness and geometrical dimensions of stents after processing. Stents were dip coated in a solution using PCL with 1% of TiO2. Additionally, AZ31 coronary stents were dynamically tested using a degradation system based on peristaltic pumps. Our results indicate that coated stents degraded slower than AZ31 uncoated control stents. After 4 weeks of dynamic degradation under flowing Hank’s solution, coated stents lost only ∼9% in weight while uncoated stents lost ∼27% in weight. Stents were qualitatively evaluated after four weeks of degradation. Our results demonstrate the formation of micro-pores after one and two weeks of degradation for coated stents. Lamination was observed after three weeks of degradation, meanwhile, uncoated stents resulted with notches and an irregular surface caused by degradation.