Degradation Rate Assessment of Biodegradable Magnesium Alloys

Biodegradable magnesium alloys have been widely used in medical implants. But safety concerns were put forward for the high degradation rate of biodegradable magnesium alloy. The optimal biodegradable magnesium alloys that give rise to the desired degradation rate hasn’t yet to be defined. Assessing the degradation rate of biodegradable magnesium alloys involves in vitro testing, in vivo testing, numerical modeling, understanding the factors influencing their degradation in physiological environments, biocompatibility testing, and clinical studies. It is important to standardize analytical tools aimed at assessing the degradation rate of biodegradable magnesium alloys. It is advisable to identify the threshold for safe degradation rate of biodegradable magnesium alloys in biomedical applications.

ZnO nanowires based degradable high-performance photodetectors for eco-friendly green electronics

Disposable devices designed for single and/or multiple reliable measurements over a short duration have attracted considerable interest recently. However, these devices often use non-recyclable and non-biodegradable materials and wasteful fabrication methods. Herein, we present ZnO nanowires(NWs) based degradable high-performance UV photodetectors(PDs) on flexible chitosan substrate. Systematic investigations reveal the presented device exhibits excellent photo response, including high responsivity(55 A/W), superior specific detectivity(4×10^(14) jones), and the highest gain(8.5×10~(10)) among the reported state of the art biodegradable PDs. Further, the presented PDs display excellent mechanical flexibility under wide range of bending conditions and thermal stability in the measured temperature range(5–50 ℃).The biodegradability studies performed on the device, in both deionized(DI) water(pH≈6) and PBS solution(pH=7.4),show fast degradability in DI water(20 mins) as compared to PBS(48 h). These results show the potential the presented approach holds for green and cost-effective fabrication of wearable, and disposable sensing systems with reduced adverse environmental impact.

Eco-friendly biodegradable polyurethane based coating for antibacterial and antifouling performance

Biofouling, which comprises the absorption of proteins and the adhesion of bacteria to the surface of living entities, is a severe concern for the maritime sector since it ultimately leads to hydrodynamic drag,resulting in a higher increase in fuel consumption. As a result, polymer resins are crucial in the marine sector for anti-biofouling coatings. In this work, the poly(caprolactone-ethylene glycol-caprolactone)-p olyurethane(PECL-PU) are prepared through ε-caprolactone(CL), poly(ethylene glycol)(PEG), 4,4'-methylene bis(cyclohexyl isocyanate) and 1,4 butanediol. Our study demonstrate that the PECL-PU copolymer degraded in artificial seawater(5.21%), enzymatic solution(12.63%), and seawater(13.75%)due to the presence of PEG segments in the laboratory-based test under static condition. Because the addition of PEG segments are increased the polymer's amorphous area and decreased the crystallization of the polycaprolactone(PCL) in the copolymer, as demonstrated by differential scanning calorimetry, X-ray diffraction, and water contact angle studies. Therefore, the hydrolysis rates of PECL-PU were higher than the caprolactone-co-polyurethane(CL-PU). The antifouling test showed that PECL-PU3 copolymer had about 90.29% protein resistance, 85.2% Escherichia coli(E. coli) reduction and 94.61% marine diatom Navicula incerta reduction comparison to the control. We have developed an eco-friendly and inexpensive promising degradable polyurethane for reduction of bacterial biofilm, which can preserve the formation of biofouling on marine coating under practical sea conditions.

Compression Mechanical Performance Simulation and Parameter Optimization of Degradable Ureteral Stent Based on ABAQUS

The compression performance of a degradable ureteral stent is analyzed and the parameters are optimized by a finite element modeling method.The degradable ureteral stent explored in this paper is developed from poly(glycolic acid)(PGA)and poly(lactic-co-glycolic acid)(PLGA)degradable materials.Based on the actual measurement of fabric structure parameters,the three-dimensional model of the stent is established with the help of the modeling software.The finite element analysis software is used to simulate the compression process of the degradable ureteral stent.The parameters of materials,interactions and boundary conditions are set according to the compression environment of the stent for modeling and simulation.On this basis,the friction coefficient of yarns,the yarn radius,and the braided angle of the stent are further compared.The comparison test is carried out by a single variable.The experimental results show that the change of yarn friction coefficient has little influence on the compressive stress,while the yarn radius and the braided angle of the stent have a great influence on the compressive stress.

Synthesis and Characterization of Novel Hydrolytically Degradable Polyesters

Six novel hydrolytically degradable polyesters were synthesized from thiodipropionic acid(TDPA)and five diols by melt polycondensation,and characterized by FT-IR,1H NMR,gel permeation chromatography,differential scanning calorimetry and thermogravimetry analysis.The polystyrene-equivalent number-average(Mn)and weight-average molecular weight(Mw)of these polyesters ranged from 4900-11100 Da and 7900-20879 Da,respectively,with PDI values of 1.48-1.98.The melting point varied from 62.3-127.9℃,and the 50%mass-loss temperature ranged between 387-417℃.The degradation of these polyesters was studied in terms of relative weight loss in distilled water at different pH.Weight losses of 14%-26%were obtained at pH 7.0,26%-38%at pH 6.0,and 32%-43%at pH 8.3 over a 20-week period.The ecotoxicity study suggested that safety of the synthesized polyesters for the eisenia foetida.These results indicate that these polyesters have a combination of good thermal and degradability behaviors,which can be tailored through selection of the diol monomers used in the synthesis.

Degradable Foam Tray Based on High-concentration Dispersed Cellulose Fibers Obtained by a Hot-press Baking Process

Degradable industrial packaging foam trays made from cellulose fibers were fabricated using a hot-press baking process.Bleached softwood pulp fibers with a concentration of 30%were dispersed at a high speed under the action of a dispersant.The effects of the dispersant dosage of the fibers on the porosity,foam density,and static compression characteristics were discussed.Furthermore,the effects of the reinforcing adhesive including polyvinyl alcohol(PVA),and cassava starch on the physical and mechanical properties of the foam trays were studied,as well as the relationship between these properties and the microstructure of the foam trays.The dispersant enhanced the rheological and blistering properties of the fiber dispersion.As the dispersant dosage increased from 2%to 4%,the foam density gradually increased and the compressive strain performance and residual compressive strain of the foam trays decreased.Under the condition of constant dosage of dispersant,increasing the fiber proportion from 67%to 77%improved the porosity and foam density and slightly reduced the static compression performance.In additioton,the static compression resistance of the foamed materials was improved by increasing the PVA dosage since PVA was beneficial for improving the strength of the foam trays.

Effect of PEG Incorporation on Physicochemical and in vitro Degradation of PLLA/PDLLA Blends:Application in Biodegradable Implants

Polyethylene glycol(PEG)was added at different concentrations to the blend of poly(L-lactic acid)(PLLA)and poly(D,L-lactic acid)(PDLLA)to tailor the properties.The differential scanning calorimetry(DSC)measurement showed that all blends were miscible due to shifting a single glass transition temperature into a lower temperature for increasing PEG content.The DSC,FTIR,and XRD results implied the crystallinity enhancement for PEG content until 8 wt%,then decreased at 12 wt%PEG.The XRD result indicated the homo crystalline phase formation in all blends and no stereocomplex crystal.The in vitro degradation study indicated that PEG content is proportional to the degradation rate.The highest weight loss after 28 days was achieved at 12 wt%PEG.The FTIR analysis showed a structural evolution overview during hydrolytic degradation,viz.increasing and decreasing crystallinity during 14 days for the blend without and with PEG,respectively.In conclusion,the PEG addition increased crystallinity and degradation rate of the PLLA/PDLLA mixture,but PEG higher amounts led to a decrease in crystallinity,and the weight loss was intensified.This can be useful for tuning PLA-based biomaterials with the desired physicochemical properties and appropriate degradation rates for applications in drug delivery/tissue engineering.

Development and prospects of degradable magnesium alloys for structural and functional applications in the fields of environment and energy

Magnesium and its alloys have such advantages with lightweight, high specific strength, good damping, high castability and machinability,which make them an attractive choice for applications where weight reduction is important, such as in the aerospace and automotive industries.However, their practical applications are still limited because of their poor corrosion resistance, low high temperature strength and ambient formability. Based on such their property shortcomings, recently degradable magnesium alloys were developed for broadening their potential applications. Considering the degradable Mg alloys for medical applications were well reviewed, the present review put an emphasis on such degradable magnesium alloys for structural and functional applications, especially the applications in the environmental and energy fields. Their applications as fracture ball in fossil energy, sacrificial anode, washing ball, and as battery anodes, transient electronics, were summarized. The roles of alloying elements in magnesium and the design concept of such degradable magnesium alloys were discussed. The existing challenges for extending their future applications are explored.

The Application Effects of Truly Biodegradable Mulch in Potato Farmlands

[Objective] The aim was to explore application effects of truly biodegradable mulch in farmlands and provide data support for large area spreading on southern potato fields. [Method] The field plot experiments were conducted to investigate mulch film＇s weight loss and the effects of using truly biodegradable mulch film on potato yield and agronomic characters. [Result] The emergence rates of truly biodegradable mulch film and black plastic mulch film kept 9.71% and9.27% higher compared with the open field, and yield increased by 30.84% and36.81%. In the potato harvest period, the truly biodegradable mulch films already broke, and mulch film＇s weight loss rate was 58.62%. It can be completely degraded in the field after some time, and following crops would not be affected. [Conclusion] Truly biodegradable mulch performs significantly in increasing yield and keeps higher in weight-loss rate, so that it has a promising future.

Photolytic Model of Six Degradable Mulch Plastic Films

[Objective] This study aimed to solve the mulch plastic film pollution problems in Xinjiang, in order to provide reliable theoretical basis for the research on the degradation mechanism of biodegradable plastic films. [Method] The effect of illumination intensity on the decomposition of decomposable mulching films was investigated through simulating the field condition in laboratory. Regression analysis was employed to fit the processes of film decompositions. [Result] The weight loss ratios of different types of plastic films were closely related with the illumination. There was no sundry produced during the degradation process, but the weight was reduced, indicating that degradation produced gas, thus, ultraviolet rays had destructive effect on mulch plastic films. Different types of plastic films showed significant differences in the degradation speeds, and under the same conditions, the degradation speed of S4# with the induction period of 30 d was the fastest. With the extension of uv illumination time, the degradation became cumulative degradation process. [Conclusion] Under the uv rays, the weight loss ratio and illumination hours is regarded as a positive correlation relationship. The significant inspection shows that the data fitted degradation model can be described by the logistic model of Y = a/（1＋b×e -ct）, and all the parameters show significant differences （P0.01）.

Studies on Mechanical Properties of Full-Biodegradable Starch-PVA-Polyester Films

A kind of full biodegradable film material is discussed in this article. The film material is composed of starch, PVA, degradable polyesters(PHB, PHB V, PCL) with built plasticizer, a cross linking reinforcing agent and a wet strengthening agent. It contains a high percentage of starch, costs cheap and is excellent in weather fastness, temperature resistance and waterproof and it could be completely biodegraded. The present paper deals mainly with a new technical route using a new type of electromagnetic dynamic blow molding extruder and some effects on mechanical properties of the system.

Downstaging disease in patients with hepatocellular carcinoma outside up-to-seven criteria: Strategies using degradable starch microspheres transcatheter arterial chemo-embolization

AIM: To evaluate the downstaging rates in hepatitis C virus-patients with hepatocellular carcinoma(HCC), treated with degradable starch microspheres transcatheter arterial chemoembolization(DSM-TACE), to reach new-Milan-criteria(nM C) for transplantation. METHODS: This study was approved by the Ethics Committee of our institution. From September 2013 to March 2014 eight patients(5 men and 3 women) with liver cirrhosis and multinodular HCC, that did not meet n MC at baseline, were enrolled in this study. Patients who received any other type of treatment such as termal ablation or percutaneous ethanol injection were excluded. DSM-TACE was performed in all patients using Embo Cept? S and doxorubicin. Baseline and follow-up computed tomography or magnetic resonance imaging was assessed measuring the longest enhancing axial dimension of each tumor according to the modified Response Evaluation Criteria In Solid Tumors measure-ments, and medical records were reviewed.RESULTS: DSM-TACE was successfully performed in all patients without major complication. We treated 35 lesions(mean 4.3 per patient). Six of eight patients(75%) had their HCC downstaged to meet nM C. Every patient whose disease was downstaged eventually underwent transplantation. The six patients who received transplant were still living at the time of this writing, without recurrence of HCC. Baseline age(P = 0.25), Model for End-stage Liver Disease score(P = 0. 77), and α-fetoprotein level(P = 1.00) were similar between patients with and without downstaged HCC. CONCLUSION: DSM-TACE represents a safely and effective treatment option with similar safety and efficacy of conventional chemoembolization and could be successfully performed also for downstaging disease in patients without n MC, allowing them to reach liver transplantation.

Transarterial chemoembolization using degradable starch microspheres and iodized oil in the treatment of advanced hepatocellular carcinoma: evaluation of tumor response, toxicity, and survival

BACKGROUND: In a multidisciplinary conference patients with advanced non-resectable hepatocellular carcinoma (HCC) were stratified according to their clinical status and tumor extent to different regional modalities or to best supportive care. The present study evaluated all patients who were stratified to repeated transarterial chemoembolization (TACE) from 1999 until 2003 in terms of tumor response, toxicity, and survival. A moderate embolizing approach was chosen using a combination of degradable starch microspheres (DSM) and iodized oil (Lipiodol) in order to combine anti-tumoral efficiency and low toxicity. METHODS: Fourty-seven patients were followed up prospectively. TACE treatment consisted of cisplatin (50 mg/m2), doxorubicin (50 mg/m2), 450-900 mg DSM, and 5-30 ml Lipiodol. DSM and Lipiodol were administered according to tumor vascularization. Patient characteristics,toxicity, and complications were outlined. In multivariate regression analyses of pre-treatment variables from a prospective database, predictors for tumor response and survival after TACE were determined. RESULTS: 112 TACE courses were performed (2.4±1.5 courses per patient). Mean maximum tumor size was 75 (± 43) mm, in 68% there was bilobar disease. Best response to TACE treatment was: progressive disease (PD) 9%, stable disease (SD) 55%, partial remission (PR) 36%, and complete remission (CR) 0%. Multivariate regression analyses identified tumor size ≤75 mm, tumor number ≤5, and tumor hypervascularization as predictors for PR. The overall 1-, 2-, and 3-year-survival rates were 75%, 59%, and 41%, respectively, and the median survival was 26 months. Low α-fetoprotein levels (<400 ng/ml) (Odds ratio=3.3) and PR as best response to TACE (Odds ratio=6.7) were significantly associated with long term survival (>30 months, R2=36%). Grade 3 toxicity occurred in 7.1% (n=8), and grade 4 toxicity in 3.6% (n=4) of all courses in terms of reversible leukopenia and thrombocytopenia. The incidence of major complications was 5.4% (n=6). All complications were managed conservatively. The mortality within 6 weeks after TACE was 2.1% (one patient). CONCLUSIONS: DSM and Lipiodol were combined successfully in the palliative TACE treatment of advanced HCC resulting in high rates of tumor response and survival at limited toxicity. Favourable tumor response was associated with tumor extent and vascularization. TACE using DSM and Lipiodol can be considered a suitable palliative measure in patients who might not tolerate long acting embolizing agents.

Biodegradable Mg alloys for orthopedic implants——A review

The last decade has seen a significant growth in the market for alloys used for implants,especially for those intended for orthopedic implants.Research into biodegradable magnesium-based alloys has made great strides in this period,so huge progress has been made in their use in the medical industry.The important factors that led to the intensification of research in this regard,were social but also economic,wanting to improve the quality of life,by reducing the use of conventionally permanent metallic implants(stainless steel,cobalt-based alloys,and titanium alloys)which involve the second implant removal surgery and other undesirable effects(stress shielding and metal ion releases),with a negative impact on the emotional and physical condition of patients,and by significantly reducing the costs for both the patient and the health system in the field of orthopedics.This paper refers to the impact and importance of biodegradable Mg alloys,reviewing the beginning of their development,the significant characteristics that make them so desirable for such applications(orthopedic implants)but also the characteristics that must be modulated(corrosion rate and mechanical properties)to arrive at the ideal product for the targeted application.It highlights,in detail,the mechanism and aspects related to the corrosion behaviour of Mg alloys,electrochemical characterization techniques/methods,as well as strategies to improve the corrosion behaviour and mechanical properties of these types of biodegradable alloys.The means of optimization,the category and the effect of the alloying elements,the design criteria,the requirements that the implants of biodegradable alloys Mg-based must meet and the aspects related to their efficiency are also presented.Finally,the potential applications in the specialized clinics,as well as the final products currently used and made by important prestigious companies in the world are approached.

Repair of bile duct defect with degradable stent and autologous tissue in a porcine model

AIM： To introduce and evaluate a new method to re- pair bile duct defect with a degradable stent and au- tologous tissues. METHODS： Eight Ba-Ma mini-pigs were used in this study, Experimental models with common bile duct （CBD） defect （0,5-1,0 cm segment of CBD resected） were established and then CBD was reconstructed by duct to duct anastomosis with a novel degradable stent made of poly [sebacic acid-co-（1,3-propanediol）-co- （1,2-propanediol）]. In addition, a vascularized greater omentum was placed around the stent and both ends of CBD. Cholangiography via gall bladder was per- formed for each pig at postoperative months 1 and 3 to rule out stent translocation and bile duct stricture. Complete blood count was examined pre- and post- operatively to estimate the inflammatory reaction. Liver enzymes and serum bilirubin were examined pre- and post-operatively to evaluate the liver function. Five pigs were sacrificed at month 3 to evaluate the healing of anastomosis. The other three pigs were raised for one year for long-term observation. RESULTS： All the animals underwent surgery success- fully. There was no intraoperative mortality and no bile leakage during the observation period, The white blood cell counts were only slightly increased on day 14 and month 3 postoperatively compared with that before operation, the difference was not statistically significant （P = 0.652）. The plasma level of alanine aminotrans- ferase on day 14 and month 3 postoperatively was also not significantly elevated compared with that before operation （P = 0.810）. Nevertheless, the plasma level of y-glutamyl transferase was increased after opera- tion in both groups （P = 0.004）, especially 2 wk after operation. The level of serum total bilirubin after opera- tion was not significantly elevated compared with that before operation （P = 0.227）, so did the serum direct bilirubin （P = 0.759）. By cholangiography yia gall blad- der, we found that the stent maintained its integrity of shape and was stillin situ at month 1, and it disap- peared completely at month 3. No severe CBD dilation and stricture were observed at both months 1 and 3. No pig died during the 3-too postoperative observation period. No sign of necrosis, bile duct stricture, bile leak- age or abdominal abscess was found at reoperation at month 3 postoperatively. Pigs had neither fragments of stent nor stones formed in the CBD. Collagen deposit was observed in the anastomosis by hematoxylin and eosin （HE） and Masson＇s trichrome stains. No severe cholestasis was observed in liver parenchyma by HE staining. Intestinal obstruction was found in a pig 4 mo after operation, and no bile leakage, bile duct stricture or biliary obstruction were observed in laparotomy. No sign of bile duct stricture or bile leakage was observed in the other two pigs. CONCLUSION： The novel method for repairing bile duct defect yielded a good short-term effect without postoperative bile duct stricture. However, the long- term effect should be further studied.

Development of degradable pre-formed particle gel(DPPG)as temporary plugging agent for petroleum drilling and production

Temporary plugging agent(TPA)is widely used in many fields of petroleum reservoir drilling and production,such as temporary plugging while drilling and petroleum well stimulation by diverting in acidizing or fracturing operations.The commonly used TPA mainly includes hard particles,fibers,gels,and composite systems.However,current particles have many limitations in applications,such as insufficient plugging strength and slow degradation rate.In this paper,a degradable pre-formed particle gel(DPPG)was developed.Experimental results show that the DPPG has an excellent static swelling effect and self-degradation performance.With a decrease in the concentration of total monomers or cross-linker,the swelling volume of the synthesized DPPG gradually increases.However,the entire self-degradation time gradually decreases.The increase in 2-acrylamide-2-methylpropanesulfonic acid(AMPS)in the DPPG composition can significantly increase its swelling ratio and shorten the self-degradation time.Moreover,DPPG has excellent high-temperature resistance(150°C)and high-salinity resistance(200,000 mg/L NaCl).Core displacement results show that the DPPG has a perfect plugging effect in the porous media(the plugging pressure gradient was as high as 21.12 MPa),and the damage to the formation after degradation is incredibly minor.Therefore,the DPPG can be used as an up-and-coming TPA in oil fields.

High rumen degradable starch decreased goat milk fat via trans-10,cis-12 conjugated linoleic acid-mediated downregulation of lipogenesis genes,particularly,INSIG1

Background:Starch is an important substance that supplies energy to ruminants.To provide sufficient energy for high-yielding dairy ruminants,they are typically fed starch-enriched diets.However,starch-enriched diets have been proven to increase the risk of milk fat depression(MFD)in dairy cows.The starch present in ruminant diets could be divided into rumen-degradable starch(RDS)and rumen escaped starch(RES)according to their different degradation sites(rumen or intestine).Goats and cows have different sensitivities to MFD.Data regarding the potential roles of RDS in milk fat synthesis in the mammary tissue of dairy goats and in regulating the occurrence of MFD are limited.Results:Eighteen Guanzhong dairy goats(day in milk=185±12 d)with similar parity,weight,and milk yield were selected and randomly assigned to one of three groups(n=6),which were fed an LRDS diet(Low RDS=20.52%),MRDS diet(Medium RDS=22.15%),or HRDS diet(High RDS=24.88%)for 5 weeks.Compared with that of the LRDS group,the milk fat contents in the MRDS and HRDS groups significantly decreased.The yields of short-,mediumand long-chain fatty acids decreased in the HRDS group.Furthermore,increased RDS significantly decreased ruminal B.fibrisolvens and Pseudobutyrivibrio abundances and increased the trans-10,cis-12 conjugated linoleic acid(CLA)and trans-10 C18:1 contents in the rumen fluid.A multiomics study revealed that the HRDS diet affected mammary lipid metabolism down-regulation of ACSS2,MVD,AGPS,SCD5,FADS2,CERCAM,SC5D,HSD17B7,HSD17B12,ATM,TP53RK,GDF1 and LOC102177400.Remarkably,the significant decrease of INSIG1,whose expression was depressed by trans-10,cis-12 CLA,could reduce the activity of SREBP and,consequently,downregulate the downstream gene expression of SREBF1.Conclusions:HRDS-induced goat MFD resulted from the downregulation of genes involved in lipogenesis,particularly,INSIG1.Specifically,even though the total starch content and the concentrate-to-fiber ratio were the same as those of the high-RDS diet,the low and medium RDS diets did not cause MFD in lactating goats.

A novel biodegradable Mg-1Zn-0.5Sn alloy:Mechanical properties,corrosion behavior,biocompatibility,and antibacterial activity

To meet the growing demand for antibacterial implants for bone-implant-associated infection therapy and avoid the adverse effects of secondary surgery,a degradable platform with pH responsiveness and ion-associated antibacterial properties was constructed.A small amount of Sn added to Mg-1Zn alloy reduces the biocorrosion rate,which can be attributed to Sn participation in outer-layer film formation,significantly reducing the biocorrosion rate and hydrogen evolution rate after implantation in vivo.These Mg alloys,which are susceptible to degradation in the acidic bacterial microenvironment,degrade by releasing Mg,Zn and Sn,producing favorably alkaline and antibacterial conditions.Samples with the composition of Mg-1Zn-0.5Sn were found to be beneficial for promoting initial cell adhesion and proliferation,resulting in improved biocompatibility and biosafety.The biocompatibility of this alloy was confirmed by the healthy behavior of animals and the absence of acute or chronic toxicity in the liver,spleen,and kidneys.Our results demonstrate that Mg-1Zn-0.5Sn is safe for biological systems,enabling its efficacious use in biomedical applications.

Pyrolysis Characteristics and Thermal Kinetics of Degradable Films

Developing degradable films is an important means for resolving the problem of film pollution; however, in recent years, there have been only few studies related to the thermal analysis of degradable plastic films. This research detailed the composition and pyrolysis of one kind of ordinary and three kinds of degradable plastic films using the differential thermal analysis （DTA） technique. The results showed that degradable films and ordinary film had similar DTA curves, which reflected their similar compositions; however, small differences were measured, which were due to the added constituents of the degradable films. The pyrolysis reaction orders of each film were about 0.93. The pyrolysis activation energies and pre-exponential factors followed the order of ordinary film 〉 photodegradable film 〉 photodegradable calcium carbonate film 〉 biodegradable film. The results of this research laid the foundation for new theories for harnessing soil pollution caused by plastic films.