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.

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）.

Synthesis and Characterization of Several Degradable Aliphatic Polyanhydrides

The following copolymers based on aliphatic sebacic acid were synthesized through a vacuum-melt polycondensation process:poly(sebacic acid)-b-poly(isophthalic acid)(PSA-PIPH).poly (sebacic acid) -b- (tartaric acid) (PSA-PTTA). poly (sebacic acid) -b-poly (ethylene glycol)(PSA-PEG). copolymers of PSA and copolyether (M1= 1500) of epoxy ethane and (tetrahydrofuran)(PSA-PEG/THF). All these copolymers were characterized by means of 1H or 13C NMR. IR spectrometry. differential scanning calorimetry (DSC). Intrinsic viscosity and melting points were measured to estimate the molecular weights of polymers. DSC measurements indicated that PSA-PEG. PSA-PEG/THF have much lower crystallinity. On the other hand,PSA-PIPH and PSA-PTTA exhibit better film or fibre-forming properties than PSA.

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.

A STUDY OF STRUCTURE AND PROPERTY CHANGES OF BIODEGRADABLE POLYGLYCOLIDE AND POLY(GLYCOLIDE-co-LACTIDE)FIBERS DURING PROCESSING AND IN VITRO DEGRADATION

Structure and properties of bioabsorbable polyglycolide (PGA) and poly(glycolide-co-lactide) (PGA-co-PLA)fibers were investigated during several industrial processing stages and in vitro degradation by means of wide-angle X-raydiffraction (WAXD), dynamic mechanical analysis (DMA) and mechanical property tests. In the orientation stage, the PGAfibers were found to have higher degrees of crystallinity than corresponding PGA-co-PLA samples produced under similarconditions. In the hot-stretching and post-annealing stages, after fibers were braided, PGA samples were found to gain morecrystallinity and higher T_g than PGA-co-PLA samples. The higher crystallinity in PGA fibers resulted in a slower rate ofdegradation. DMA results showed that a great deal of internal stress that was built during orientation and hot-stretchingstages was released in the post-annealing stage for a1l PGA and PGA-co-PLA samples. During earlier stages of in vitrodegradation, both PGA and PGA-co-PLA samples exhibited the typical cleavage-induced crystallization mechanism. Theheat shrinkage in the glass transition area was found to disappear after 6-8 days of degradation for all PGA and PGA-co-PLAsamples, indicating the amorphous portions of the polymers lost orientation after a short period in the buffer solution, mostlikely due to relaxation of the cleaved chains.

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.

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.

Fabrication, Crosslinking and in vitro Biocompatibility of a Novel Degradable Nano-structure Urethral Tubular Scaffold

A degradable poly（lactic-co-glycolic acid, LA：GA=80：20）（PLGA） urethral tubular scaffold was fabricated by electrospinning. In order to enhance the mechanical properties, the scaffold was crosslinked with glutaraldehyde. The structure and properties of the crosslinked scaffolds were investigated by the mechanical property testing, scanning electron microscopy（SEM）, degradability test in vitro and 3-（4,5）-dimethylthiahiazo（-z-yl）-3,5-diphenytetrazo- liumromide（MTT）. The results show that the scaffold has the nano-structure. The pore size and the porosity are suitable for cell seeding, growth and extracellular matrix production. Although influenced by the crosslinking slightly, the pore size and the porosity could still support cell proliferation and tissuse formation. The mechanical properties are remarkably increased by the crosslinking of glutaraldehyde, and it could meet the demands of a urethral stent. The scaffold could completely collapse within 70 d. The results of the biocompatibility test show that the PLGA scaffold had no cytotoxicity.

Degradable Plastics Are Vulnerable to Cracks

A plastic may degrade in response to a trigger.The kinetics of degradation have long been characterized by the loss of weight and strength over time.These methods of gross characterization,however,are misleading when plastic degrades heterogeneously.Here,we study heterogeneous degradation in an extreme form:the growth of a crack under the combined action of chemistry and mechanics.An applied load opens the crack,exposes the crack front to chemical attack,and causes the crack to outrun gross degradation.We studied the crack growth in polylactic acid(PLA),a polyester in which ester bonds break by hydrolysis.We cut a crack in a PLA film using scissors,tore it using an apparatus,and recorded the crack growth using a camera through a microscope.In our testing range,the crack velocity was insensitive to load but was sensitive to humidity and pH.These findings will aid the development of degradable plastics for healthcare and sustainability.

Effect of Media on the in vitro Degradation of Biodegradable Ureteral Stent

The biodegradable ureteral stent should retain their supporting properties for defined period and then gradually degrade to small particles with the flow of urine. The mechanism and process of the stent's degradation should be investigated and understood well due to its direct impact on the stents' usage. An enhanced braidbased degradable ureteral stent composed of poly-glycolic acid(PGA) and the copolymer of lactic and glycolic acid(PGLA) was evaluated in vitro in this study with four kinds of degradable media:human urine(HU,pH = 7. 4),artificial urine(AU,pH = 5. 8),and phosphate buffer solutions( PBS,pH = 5. 8 and 7. 4) so as to compare the effects of media on the degradation of stents. The mechanical properties and morphology were observed at different degradaing time intervals of 0,7,14,21,28,and 35 d. The in vitro degradation behaviors of stents in four kinds of media were extremely different. The degradation rate of stents in HU was the highest. The impact of media's pH to the degradation is not obvious while the components in the media contribute much to the difference.

Preparation, Characterization, and in vitro Release of Biodegradable Erythromycin-gelatin Microspheres

Blank and erythromycin-loaded gelatin microspheres were successfully fabricated via emulsion chemical- crosslinking technique. The surface morphology of the microspheres was characterized by scanning electron microscope（SEM） and optical microscope. The results show that the microspheres were spherical and smooth. The particle average size of erythromycin-loaded microspheres was found to be 20.6 μm, with a high purity of more than 90% and with a good dispersibility. The microspheres could be obtained in a high yield. Erythromycin released from the microspheres was monitored in buffer and artificial body fluid at 37 ℃. Average drug content was 27.2%, and erythromycin-loaded gelatin microspheres showed good release profiles with a nearly constant release during 4-8 h in artificial body fluid in vitro degradation studies. These gelatin microspheres are useful for studying and developing various drug-delivery systems.

Enhanced mechanical properties and degradation rate of Mg-Ni-Y alloy by introducing LPSO phase for degradable fracturing ball applications

In this work,as-cast Mg-Ni-Y alloys were proposed to develop a feasible material for fracturing balls,and their mechanical performance and corrosion behavior were systematically investigated.Long period stacking order(LPSO)phase was firstly introduced to improve both the mechanical properties and degradation rate of magnesium alloys.With the increase of LPSO phase,the compressive strength was improved significantly,while the elongation of the alloys decreased owing to the relatively brittle nature of LPSO phase.Due to the higher corrosion potential of LPSO phase,the LPSO phase can accelerate the corrosion process by providing more micro-couples.However,the LPSO phase would serve as the corrosion barrier between the corrosion medium and the matrix when the contents of LPSO phase are too high in Mg92.5Ni3Y4.5 and Mg87.5Ni5Y7.5 alloys.As-cast Mg97.5Ni1Y1.5 alloy with satisfactory mechanical properties and rapid degradation rate was successfully developed,exhibiting a high degradation rate of 6675 mm/a(93℃)in 3 wt.%KCl solution and a favorable ultimate compressive strength of 410 MPa.The degradation rate of Mg97.5Ni1Y1.5 alloy is 2-5 times of the current commercial magnesium alloy fracturing materials.

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.

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.

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.

Interaction between Live Yeast and Dietary Rumen Degradable Protein Level: Effects on Diet Utilization in Early-Lactating Dairy Cows

Four early lactating Holstein cows were used to study the effect of live yeast (LY, Actisaf&reg;CNCM I-4407, Lesaffre Feed Additives, Marcq en Baroeul, France) supplementation on diet digestive utilization of dairy cows receiving concentrated corn silage-based diets with two rumen-degradable protein (RDP) levels. For a 33 d period, cows were fed a total mixed ration (TMR) containing an adequate level (AL) of RDP or a low level (LL, 30% below AL) by using soybean meal or tanned soybean meal, respectively: for 21 d with no LY addition followed by 12 d during which LY was added to the diet. The pH and redox potential (Eh) were recorded and ruminal fluid samples were collected over 3 consecutive days. Feces were collected individually over 48 h and individual dry matter intake (DMI) was measured for determining apparent nutrient digestibility. The effective degradability of individual feed ingredients composing both diets was evaluated with nylon bags technique. Structure of the ruminal bacterial community was studied and diversity index was calculated. Digestibility of organic matter (OM) and crude protein (CP) were lower for LL than those for AL. With LY, digestibility of OM and CP was increased: +2.4 and +0.8 points, for AL, and +3.7 and +5.9 points for LL, respectively. Live yeast reduced dietary N ruminal degradation with both AL and LL. Ruminal pH and Eh were lower with AL compared to LL: 5.95 and –167 mV vs. 6.13 and –144 mV. Live yeast increased ruminal total volatile fatty acids (VFA) (+8.6%), C2 (+10%), and C4 (+35%) contents for LL and decreased that of C3 (?9.8%) for AL. Neither the structure of bacterial populations of the rumen nor the diversity index (Shannon) was altered by treatments. Those results suggested a specific interest in using LY in RDP deficient diets for early lactating cows.

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.

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.