Large-Scale Preparation of Mechanically High-Performance and Biodegradable PLA/PHBV Melt-Blown Nonwovens with Nanofibers

Biodegradable polylactic acid(PLA)melt-blown nonwovens are attractive candidates to replace nondegradable polypropylene melt-blown nonwovens.However,it is still an extremely challenging task to prepare PLA melt-blown nonwovens with sufficient mechanical properties for practical application.Herein,we report a simple strategy for the large-scale preparation of biodegradable PLA/poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)melt-blown nonwovens with high strength and excellent toughness.In this process,a small amount of PHBV is added to PLA to improve the latter’s crystallization rate and crystallinity.In addition,when the PHBV content increases from 0 to 7.5 wt%,the diameters of the PLA/PHBV melt-blown fibers decrease significantly(with the proportion of nanofibers increasing from 7.7%to 42.9%).The resultant PLA/PHBV(5 wt%PHBV)melt-blown nonwovens exhibit the highest mechanical properties.The tensile stress,elongation,and toughness of PLA/PHBV(5 wt%PHBV)melt-blown nonwovens reach 2.5 MPa,45%,and 1.0 MJm3,respectively.More importantly,PLA/PHBV melt-blown nonwovens can be completely degraded into carbon dioxide and water after four months in the soil,making them environmentally friendly.A general tensile-failure model of melt-blown nonwovens is proposed in this study,which may shed light on mechanical performance enhancement for nonwovens.

Graphene-calcium carbonate coating to improve the degradation resistance and mechanical integrity of a biodegradable implant

Biodegradable implants are critical for regenerative orthopaedic procedures,but they may suffer from too fast corrosion in human-body environment.This necessitates the synthesis of a suitable coating that may improve the corrosion resistance of these implants without compromising their mechanical integrity.In this study,an AZ91 magnesium alloy,as a representative for a biodegradable Mg implant material,was modified with a thin reduced graphene oxide(RGO)-calcium carbonate(CaCO_(3))composite coating.Detailed analytical and in-vitro electrochemical characterization reveals that this coating significantly improves the corrosion resistance and mechanical integrity,and thus has the potential to greatly extend the related application field.

A multi-functional MgF_(2)/polydopamine/hyaluronan-astaxanthin coating on the biodegradable ZE21B alloy with better corrosion resistance and biocompatibility for cardiovascular application

The cardiovascular diseases(CVD)continue to be the major threat to global public health over the years,while one of the effective methods to treat CVD is stent intervention.Biomedical magnesium(Mg)alloys have great potential applications in cardiovascular stents benefit from their excellent biodegradability and absorbability.However,excessive degradation rate and the delayed surface endothelialization still limit their further application.In this study,we modified a Mg-Zn-Y-Nd alloy(ZE21B)by preparing MgF_(2) as the corrosion resistance layer,the dopamine polymer film(PDA)as the bonding layer,and hyaluronic acid(HA)loaded astaxanthin(ASTA)as an important layer to directing the cardiovascular cells fate.The electrochemical test results showed that the MgF_(2)/PDA/HA-ASTA coating improved the corrosion resistance of ZE21B.The cytocompatibility experiments also demonstrated that this novel composite coating also selectively promoted endothelial cells proliferation,inhibited hyperproliferation of smooth muscle cells and adhesion of macrophages.Compared with the HAloaded rapamycin(RAPA)coating,our MgF_(2)/PDA/HA-ASTA coating showed better blood compatibility and cytocompatibility,indicating stronger multi-functions for the ZE21B alloy on cardiovascular application.

Improving corrosion resistance of additively manufactured WE43 magnesium alloy by high temperature oxidation for biodegradable applications

Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples were built with the relativity density reaching 99.9%.High temperature oxidation was performed on the L-PBF samples in circulating air via various heating temperatures and holding durations.The oxidation and diffusion at the elevated temperature generated a gradient structure composed of an oxide layer at the surface,a transition layer in the middle and the matrix.The oxide layer consisted of rare earth(RE)oxides,and became dense and thick with increasing the holding duration.The matrix was composed ofα-Mg,RE oxides and Mg_(24)RE_(5) precipitates.The precipitates almost disappeared in the transition layer.Enhanced passivation effect was observed in the samples treated by a suitable high temperature oxidation.The original L-PBF samples lost 40%weight after 3-day immersion in Hank’s solution,and broke into fragments after 7-day immersion.The casted and solution treated samples lost roughly half of the weight after 28-day immersion.The high temperature oxidation samples,which were heated at 525℃ for 8 h,kept the structural integrity,and lost only 6.88%weight after 28-day immersion.The substantially improved corrosion resistance was contributed to the gradient structure at the surface.On one hand,the outmost dense layer of RE oxides isolated the corrosive medium;on the other hand,the transition layer considerably inhibited the corrosion owing to the lack of precipitates.Overall,high temperature oxidation provides an efficient,economic and safe approach to inhibit the corrosion of WE43 L-PBF samples,and has promising prospects for future clinical applications.

Direct 4D printing of functionally graded hydrogel networks for biodegradable,untethered,and multimorphic soft robots

Recent advances in functionally graded additive manufacturing(FGAM)technology have enabled the seamless hybridization of multiple functionalities in a single structure.Soft robotics can become one of the largest beneficiaries of these advances,through the design of a facile four-dimensional(4D)FGAM process that can grant an intelligent stimuli-responsive mechanical functionality to the printed objects.Herein,we present a simple binder jetting approach for the 4D printing of functionally graded porous multi-materials(FGMM)by introducing rationally designed graded multiphase feeder beds.Compositionally graded cross-linking agents gradually form stable porous network structures within aqueous polymer particles,enabling programmable hygroscopic deformation without complex mechanical designs.Furthermore,a systematic bed design incorporating additional functional agents enables a multi-stimuli-responsive and untethered soft robot with stark stimulus selectivity.The biodegradability of the proposed 4D-printed soft robot further ensures the sustainability of our approach,with immediate degradation rates of 96.6%within 72 h.The proposed 4D printing concept for FGMMs can create new opportunities for intelligent and sustainable additive manufacturing in soft robotics.

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.

Machine Learning Based Virtual Screening for Biodegradable Polyesters

Current biodegradation timelines show that polyesters take over 200 years to break down. A crucial component of several industries, polyesters are relied upon for materials development and thus require sustainable alternatives. Recent works in generative modeling have made it possible to produce large sets of chemical structures, but current molecular screening methods are expensive, not scalable, and are oversimplified. This work evaluates whether a molecule’s biodegradability potential can be accurately predicted by training a model on recent experimental data. Additionally, three chemical descriptors were evaluated on the final molecules for their effects on biodegradability: molecular structure, bond types, and solubility. A Gradient Boosted Machine was trained on a dataset of 600 molecules and their binary labels on biodegradability. The classification model effectively captured the biodegradability property, yielding an Area Under the Receiver Operating Characteristics, AUROC, of 84% and an Area Under the Precision Recall Curve, or AUPRC, of 87%. Additionally, an existing amortized synthetic tree generation model, SynNet, validated each molecule by showing chemical synthesizability and producing simple and interpretable synthesis pathways. This approach of filtering by prediction and chemical rule interpretation is inexpensive, highly scalable and can capture the necessary complexity. Using this method, novel polyester candidates can be polymerized and produced into sustainable fabrics, reducing environmental stress from textile-reliant industries.

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.

Antibacterial mechanism with consequent cytotoxicity of different reinforcements in biodegradable magnesium and zinc alloys: A review

Benefits achieved by the biodegradable magnesium(Mg) and zinc(Zn) implants could be suppressed due to the invasion of infectious microbial, common bacteria, and fungi. Postoperative medications and the antibacterial properties of pure Mg and Zn are insufficient against biofilm and antibiotic-resistant bacteria, bringing osteomyelitis, necrosis, and even death. This study evaluates the antibacterial performance of biodegradable Mg and Zn alloys of different reinforcements, including silver(Ag), copper(Cu), lithium(Li), and gallium(Ga). Copper ions(Cu^(2+)) can eradicate biofilms and antibiotic-resistant bacteria by extracting electrons from the cellular structure. Silver ion(Ag^(+)) kills bacteria by creating bonds with the thiol group. Gallium ion(Ga^(3+)) inhibits ferric ion(Fe^(3+)) absorption, leading to nutrient deficiency and bacterial death. Nanoparticles and reactive oxygen species(ROS) can penetrate bacteria cell walls directly, develop bonds with receptors, and damage nucleotides. Antibacterial action depends on the alkali nature of metal ions and their degradation rate, which often causes cytotoxicity in living cells. Therefore, this review emphasizes the insight into degradation rate, antibacterial mechanism, and their consequent cytotoxicity and observes the correlation between antibacterial performance and oxidation number of metal ions.

In vitro bio-corrosion behaviors of biodegradable AZ31B magnesium alloy under static stresses of different forms and magnitudes

Biomedical degradable materials would be subjected to different degrees and forms of static stress after being implanted in the human body.In this work,the biocorrosion behaviors of AZ31B magnesium alloy under different stress forms with different magnitudes(20~150MPa)were studied.It was found that the corrosion behaviors at stressed conditions were severer than those at unstressed conditions and corrosion rates were obviously accelerated.The biocorrosion behaviors are more sensitive to the effects of tensile loads than to compressive loads.A biocorrosion numerical model on the degradation process of Mg alloy under static loads was established.The corrosion current density(i_(corr))of Mg alloy and the applied static stress(σ)matches a linear relationship of ln i_(corr)~σwell during the early stage(within 24 hrs)while deviated gradually in the latter period of corrosion.This work could provide a guidance and theoretical reference for further researches on the biocorrosion behaviors and practical clinical applications of the biomedical materials subjected to physiological loads.

Low-cost biodegradable lead sequestration film for perovskite solar cells

Despite the high efficiency that has been achieved for the perovskite solar cells(PSCs),the hazardous lead leakage from the perovskite absorber layer is one of the crucial barriers still hindering its penetration into the commercial market for a large-scale installation.Herein,we report a novel low-cost and biodegradable lead sequestration layer with high compatibility for up-scalable encapsulation of PSCs.Through a precisely designed cross-linking reaction of chemical agents,the as-made biodegradable chitosan composite film shows enhanced mechanical strength,chemical stability,and lead adsorption capacity.The designed encapsulation strategy reduces over 99.99% lead leakage to <2 ppb under varied simulations of weather conditions(hail,rain,or flood),which meet the safe level of drinking water set by the US Environmental Protection Agency(EPA).Moreover,the PSC efficiency is improved from 21.91% to22.82% due to the improved light absorption from the printed biodegradable lead absorption film.Finally,we present a prototype process of accumulation and recycling of lead compounds in PSCs derbies via the biodegradation process.Based on the low-cost biodegradable lead sequestration film,this environmental-friendly encapsulation strategy could address the lead leakage issue for further commercialization of PSCs.

Corrosion characteristics of single-phase Mg-3Zn alloy thin film for biodegradable electronics

Biodegradable metals as electrodes, interconnectors, and device conductors are essential components in the emergence of transient electronics, either for passive implants or active electronic devices, especially in the fields of biomedical electronics. Magnesium and its alloys are strong candidates for biodegradable and implantable conducting materials because of their high conductivity and biocompatibility, in addition to their well-understood dissolution behavior. One critical drawback of Mg and its alloys is their considerably high dissolution rates originating from their low anodic potential, which disturbs the compatibility to biomedical applications. Herein, we introduce a single-phase thin film of a Mg-Zn binary alloy formed by sputtering, which enhances the corrosion resistance of the device electrode, and verify its applicability in biodegradable electronics. The formation of a homogeneous solid solution of single-phase Mg-3Zn was confirmed through X-ray diffraction and transmission electron microscopy. In addition, the dissolution behavior and chemistry was also investigated in various biological fluids by considering the effect of different ion species. Micro-tensile tests showed that the Mg-3Zn alloy electrode exhibited an enhanced yield strain and elongation in relation to a pure Mg electrode. Cell viability test revealed the high biocompatibility rate of the Mg-3Zn binary alloy thin film. Finally, the fabrication of a wireless heater demonstrated the integrability of biodegradable electrodes and highlighted the ability to prolong the lifecycle of thermotherapy-relevant electronics by enhancing the dissolution resistance of the Mg alloy.

Understanding the corrosion of Mg alloys in in vitro urinary tract conditions: A step forward towards a biodegradable metallic ureteral stent

Ureteral stents play a fundamental role in modern time urology. However, following the deployment, stent-related symptoms are frequent and affect patient health and quality of life. Using biodegradable metals as ureteral stent materials have emerged as a promising strategy, mainly due to the improved radial force and slower degradation rate expected. Therefore, this study aimed to characterize different biodegradable metals in urinary tract environment to understand their propensity for future utilization as base materials for ureteral stents. The corrosion of 5 Mg alloys - AZ31, Mg-1Zn, Mg-1Y, pure Mg, and Mg-4Ag - under simulated urinary tract conditions was accessed. The corrosion layer of the different alloys presented common elements, such as Mg(OH)_(2), MgO, and phosphate-containing products, but slight variations in their chemical compositions were detected. The corrosion rate of the different metals varied, which was expected given the differences in the corrosion layers. On top of this, the findings of this study highlighted the significant differences in the samples' corrosion and corrosion layers when in stagnant and flowing conditions. With the results of this study, we concluded that Mg-1Zn and Mg-4Ag presented a higher propensity for localized corrosion, probably due to a less protective corrosion layer;Mg-4Ag corroded faster than all the other four alloys,and Mg-1Y stood out due to its distinct corrosion pattern, that showed to be more homogeneous than all the other four samples, making this one more attractive for the future studies on biodegradable metals.

Rational design, synthesis and prospect of biodegradable magnesium alloy vascular stents

Biodegradable magnesium(Mg) alloys are expected to be promising materials for cardiovascular stents(CVS), which can avoid the longterm clinical problems of current CVS, such as in-stent restenosis, late stent thrombosis, etc. Mg alloy stents exhibit superior biocompatibility and tunable biodegradability, compared with conventional permanent metallic stents. However, the poor formability and non-uniform corrosion of Mg alloy stents hinder their clinical application of CVS. This review focuses on the development of Mg alloys for CVS in recent years.According to the results of bibliometric analysis, we analyzed different biodegradable Mg alloy systems. Moreover, the structural design strategies for Mg alloy stents that can reduce the stress concentration, as well as the surface modification methods to control the corrosion behavior and biological performance of Mg alloy stents are also highlighted. At last, this review systematically discussed the potential directions and challenges of biodegradable magnesium stents(BMgS) in cardiovascular fields.

Safety and Efficacy of Biodegradable Patent Foramen Ovale Occluder in Patients with Migraine:A Clinical Trial

Background:Transcatheter closure of patent foramen ovale(PFO)has been widely accepted as a highly effective way to treat high-risk PFO-related diseases.However,traditional non-degradable occluders made of metal alloys will permanently exist in the body,resulting in thrombosis,valve damage,hemolysis,arrhythmia,or other complications.The biodegradable PFO occluder developed by Shanghai Mallow Medical Instrument Co.,Ltd.,China can be fully absorbed and degrade into nontoxic ingredients,reducing postoperative complications.Objectives:To study the safety and efficacy of biodegradable PFO occluders in treating PFO.Methods:This single-center clinical trial collected 30 patients treated with a biodegradable PFO occluder.The follow-up period lasted 12 months to analyze the echocardiographic characteristics and headache relief through HIT-6 scores.Results:The immediate success rate was 100%,with no intraoperative severe occlusion-related complications.The contrast transcranial Doppler(cTCD)at 12 months showed that all patients’right-to-left shunts(RLS)were grade I or 0 with no serious postoperative complications,indicating the overall success rate was 100%.The biodegradable PFO occluder mostly degraded six months after the occlusion.Conclusion:PFO closure with a Mallow biodegradable occluder is safe and effective and has no severe complications.

Hydroxyapatite-containing PEO-coating design for biodegradable Mg-0.8Ca alloy: Formation and corrosion behaviour

In this study, the biocompatible protective coating was formed using plasma electrolytic oxidation(PEO) on bioresorbable Mg-0.8Ca alloy. The composition of the formed coating was studied using XRD, SEM-EDX analysis, and micro-Raman spectroscopy. The uniform distribution of hydroxyapatite over the thickness of protective PEO-layer was established. Using traditional(EIS, PDP, OCP) and local scanning electrochemical methods(SVET, SIET with H^(+)-selective microelectrode), the level of protective properties of PEO-layer in a biological environment(mammalian cell culture medium, MEM) was determined. It was established that modification of Mg-0.8Ca alloy surface by PEO contributes to a significant increase in the corrosion resistance of the surface layer, making it possible to control the process of material‘s biodegradation. The maximum local electrochemical activity was recorded after 72 h of testing, while for the uncoated sample,intense corrosion degradation was recorded in the first 12 min of exposure to the cell culture medium. Formation of the PEO-coating results in a twofold decrease in the corrosion current density(2.8·10^(-6)A cm^(-2)) and an increase in the impedance modulus measured at a low frequency(1.7·10^(4)Ω cm^(2)) in comparison with the uncoated material(9.5·10^(-6)A cm^(-2);8.1·10^(3)Ω cm^(2)). The mechanism of material bioresorption was established and a model for biodegradation process of Mg-0.8Ca alloy with hydroxyapatite-containing PEO-coating in MEM was proposed. Analysis of these results and comparing with others obtained by various scientific groups indicate the prospects for application of biocompatible PEO-coating on Mg-Ca alloy in implant surgery.

Improved Corrosion Behavior of Biodegradable Mg-4Zn-1Mn Alloy Modified by Sr/F co-doped CaP Micro-arc Oxidation Coatings

The Sr/F co-doped CaP(Sr/F-CaP)coatings were prepared by micro-arc oxidation(MAO)under different voltages to modify the microstructure and corrosion behavior of Mg-4Zn-1Mn alloy.The surface and interface characteristics investigated using scanning electron microscopy(SEM)and energy dispersive X-ray spectrometer(EDS)showed that the MAO coatings displayed uneven crater-like holes and tiny cracks under lower voltage,while they exhibited relatively homogeneous crater-like holes without cracks under higher voltage.The thickness of MAO coatings increased with increasing voltage.The corrosion behavior of Mg-4Zn-1Mn alloy was improved by the MAO coatings.The MAO coatings prepared under 450 V and 500 V voltages possessed the best corrosion resistance with regard to the electrochemical corrosion tests and immersion corrosion tests,respectively.The MAO coatings fabricated under 450-500 V could provide a better corrosion protection effect for the substrate.

煤矿矿井水水质形成及演化的水动力场-水化学场-微生物场耦合作用与数值模拟

煤矿矿井水的水质形成与演化过程机理复杂,受水动力场、水化学场和微生物场等多场作用影响显著。深入研究并揭示煤矿矿井水水质形成机理与演化趋势、阐明采空区封闭后矿井水的多场耦合作用机制是矿井水污染防控与修复的理论基础。以鄂尔多斯盆地某煤矿采空区为水文地质原型,在前期研究的基础上,进一步建立了煤矿采空区积水水位回升、蓄满后水动力-水化学-微生物场(HCB)多场耦合室内相似模拟和数值模型。采空区水动力场研究结果表明基质-裂隙双孔隙模型能有效模拟采空区水位回升过程,模拟误差为9.9%,其模拟精度远高于理论预测和单孔隙模型。水化学场模拟结果与试验较为吻合,SO_(4)^(2-)、HCO_(3)-和p H模拟相对误差分别为3.0%、21.0%和6.2%,模拟结果较为可靠。模拟结果显示采空区蓄水过程中水岩反应和微生物作用不明显;而蓄满后水动力几乎停滞,但水化学场和微生物场较为活跃,2号煤和3号煤层中黄铁矿的氧化反应使得SO_(4)^(2-)质量浓度提升约24.6%;后期采空区水环境演化为弱酸性、厌氧还原条件,微生物降解作用凸显,将SO_(4)^(2-)有一定的“自净”能力。通过调整微生物代谢速率常数,可将SO_(4)^(2-)降解比例提高到61.6%。实际工程场景中可通过补充碳源、人工建立密闭厌氧环境等强化手段实现这一目标。将多场耦合室内试验和数值模拟技术拓展到煤矿采空区积水水质形成与演化规律研究,研究结论可为煤矿区矿井水污染防治提供指导。

黄曲霉毒素对畜禽危害和脱毒方法的研究进展

黄曲霉毒素是一种重要饲料安全风险因子,污染范围非常广泛,对动物健康造成严重伤害。本文综述了黄曲霉毒素的理化性质、污染现状、对畜禽的危害及有效去除黄曲霉毒素的方法,为有效控制饲料中黄曲霉毒素对动物危害提供参考。

MABR好氧喹啉和苯酚降解驱动反硝化脱氮研究

以喹啉和苯酚为含氮杂环类和酚类污染物为代表的废水是典型的强毒性难降解有机废水。该课题采用无泡膜曝气生物膜反应器(MABR)实现了好氧反硝化驱动喹啉和苯酚降解生物强化过程。反应器在不同工况条件下,完成了对喹啉、苯酚和硝酸盐分别为(82.6±10.2)%、(84.5±11.9)%、(67.3±10.6)%的去除率以及(11.1±1.4)、(3.1±1.2)、(1.91±0.4)g/(m^(2)·d)的去除负荷。胞外聚合物含量的增加有助于提高生物膜对高喹啉进水负荷的抵抗能力。通过解析生物膜菌群结构,发现生物膜能够有效富集Rhodococcus等典型好氧喹啉降解菌;通过q-PCR功能基因定量分析发现以oxoO为代表的喹啉降解基因和napA好氧反硝化指示基因存在同一菌群,说明了好氧反硝化驱动喹啉和苯酚降解菌群的存在。通过宏基因组学分析,进一步核定Pseudomonas和Raineyella是主要的好氧喹啉和苯酚降解协同反硝化功能的关键菌群。本课题证实了MABR生物膜在好氧条件下完成对喹啉和苯酚的高效降解和好氧反硝化耦合过程,为拓展MABR在含氮杂环和酚类有机废水处理的应用提供必要的理论参考。