biodegradation

摘要： Cerebral ischemia is a serious disease that triggers sequential pathological mechanisms, leading to significant morbidity and mortality. Although most studies to date have typically focused on the lysosome, a single organelle, current evidence supports that the function of lysosomes cannot be separated from that of the endolysosomal system as a whole. The associated membrane fusion functions of this system play a crucial role in the biodegradation of cerebral ischemia-related products. Here, we review the regulation of and the changes that occur in the endolysosomal system after cerebral ischemia, focusing on the latest research progress on membrane fusion function. Numerous proteins, including N-ethylmaleimide-sensitive factor and lysosomal potassium channel transmembrane protein 175, regulate the function of this system. However, these proteins are abnormally expressed after cerebral ischemic injury, which disrupts the normal fusion function of membranes within the endolysosomal system and that between autophagosomes and lysosomes. This results in impaired “maturation” of the endolysosomal system and the collapse of energy metabolism balance and protein homeostasis maintained by the autophagy-lysosomal pathway. Autophagy is the final step in the endolysosomal pathway and contributes to maintaining the dynamic balance of the system. The process of autophagosome-lysosome fusion is a necessary part of autophagy and plays a crucial role in maintaining energy homeostasis and clearing aging proteins. We believe that, in cerebral ischemic injury, the endolysosomal system should be considered as a whole rather than focusing on the lysosome. Understanding how this dynamic system is regulated will provide new ideas for the treatment of cerebral ischemia.

摘要： Development of functional bioinspired hydrogels that have good releases control character is necessary for the application of these materials in biomedical engineering.Herein,we report a composite hydrogel prepared from several biocompatible carboxymethyl konjac glucomannan(CKGM)/gelatin(G)/tannic acid(TA)functional nano-hydroxyapatite(TA@n-HA),which has good biodegradability and pH sensitivity.The mechanism of interaction between hydrogels was confirmed by Fourier transform infrared spectroscopy,X-ray diffraction,Scanning electron microscopy and Thermogravimetric analysis.The physico-chemical properties of CKGM/G hydrogels have been significantly improved through the incorporation of TA@n-HA within the matrix.Studies in the sustained release of epigallocatechin gallate(EGCG)demonstrated that the TA@n-HA/CKGM/G hydrogels exhibit not only better pH sensitive properties,but also enhanced biocompatibility and encapsulation in comparison to the matrix devoid of TA@n-HA.Consequently,TA@n-HA/CKGM/G hydrogels using EGCG as a drug release model show the potential for drug delivery.

摘要： Magnesium(Mg)-based biomaterials have gained acceptability in fracture fixation due to their ability to naturally degrade in the body after fulfilling the desired functions.However,pure Mg not only degrades rapidly in the physiological environment,but also evolves hydrogen gas during degradation.In this study,Mg0.5Zr and Mg0.5ZrxZn(x=1–5 wt.%)matrix nanocomposites(MNCs)reinforced with different contents(0.1–0.5 wt.%)of graphene nanoplatelets(GNP)were manufactured via a powder metallurgy technique and their mechanical and corrosion properties were evaluated.The increase in GNP concentration from 0.2 wt.%to 0.5 wt.%added to Mg0.5Zr matrices resulted in decreases in the compressive yield strength and corrosion resistance in Hanks’Balanced Salt Solution(HBSS).On the other hand,a higher concentration(4–5 wt.%)of Zn added to Mg0.5Zr0.1GNP resulted in an increase in ductility but a decrease in compressive yield strength.Overall,an addition of 0.1 wt.%GNPs to Mg0.5Zr3Zn matrices gave excellent ultimate compressive strength(387 MPa)and compressive yield strength(219 MPa).Mg0.5Zr1Zn0.1GNP and Mg0.5Zr3Zn0.1GNP nanocomposites exhibited 29%and 34%higher experimental yield strength,respectively,as compared to the theoretical yield strength of Mg0.5Zr0.1GNP calculated by synergistic strengthening mechanisms including the difference in thermal expansion,elastic modulus,and geometry of the particles,grain refinement,load transfer,and precipitation of GNPs in the Mg matrices.The corrosion rates of Mg0.5Zr1Zn0.1GNP,Mg0.5Zr3Zn0.1GNP,Mg0.5Zr4Zn0.1GNP,and Mg0.5Zr5Zn0.1GNP measured using potentiodynamic polarization were 7.5 mm/y,4.1 mm/y,6.1 mm/y,and 8.0 mm/y,respectively.Similarly,hydrogen gas evolution tests also demonstrated that Mg0.5Zr3Zn0.1GNP exhibited a lower corrosion rate(1.5 mm/y)than those of Mg0.5Zr1Zn0.1GNP(3.8 mm/y),Mg0.5Zr4Zn0.1GNP(1.9 mm/y),and Mg0.5Zr5Zn0.1GNP(2.2 mm/y).This study demonstrates the potential of GNPs as effective nano-reinforcement particulates for improving the mechanical and corrosion properties of Mg–Zr–Zn matrices.

摘要： With the growing demand for environmental protection and physical health,food safety is now receiving more and more attention all over the world.However,pesticides are indispensable in agricultural production.Therefore,how to efficiently degrade pesticides and remove their residues in foods has always been a hot research topic in recent decades.This paper not only summarizes the types,degradation mechanism and artificial degradation of organophosphorus pesticides,but also highlights the latest advances in chemical degradation,photocatalytic degradation and biodegradation.

摘要： An in situ groundwater remediation process, termed EGCW, was developed in this study by integrating in-well groundwater electrolysis into groundwater circulation well. Groundwater circulation carries electrolytically generated O2 and H2 into the impacted aquifer for in situ biodegradation of contaminants. In a two-dimensional tank filled with field sandy sediments,simulated trichloroethylene(TCE)-contaminated groundwater was circulated between an injection well with electrodes inside and a pumping well. Results from a 50-day EGCW experiment show that in-well electrolysis oxygenated most region near the injection well, and 10 mg/L TCE was mainly biodegraded aerobically to about 2.7 mg/L(73% removal) by the indigenous microbes. Aerobic TCE degradation was enhanced by the pulsed addition of acetate. Together with the proofs of stable carbon isotope fractionation(enrichment factor:-0.57‰–-1.53‰) and microbial community variation after EGCW treatment, aerobic cometabolism was proposed to be the most likely mechanism for TCE degradation. It is interesting to find that the intrinsic organic carbon in aquifer matrix could fuel the aerobic TCE degradation, particularly at low TCE concentrations. EGCW treatment is advantageous in terms of supplying appropriate dosages of electron acceptor(O_(2)) and donor(H_(2)) for in situ bioremediation because groundwater electrolysis and circulation are expedient and controllable.

摘要： Several important drugs and nutritional supplements are limited by their lack of bioavailability.Nanomaterials display unique beneficial properties that might help improve the bioavailability of drugs and nutritional supplements.Unfortunately,nanomaterials produced from synthetic polymers and metals may have similar difficulties with bioavailability and toxicity.Naturally occurring biopolymers are biodegradable and non-toxic and are adaptable to the synthesis of nanoparticles.Drugs and other substances can be encapsulated or embedded in such particles with an increase in bioavailability.The search for biodegradable nanomaterials is an active research field.This review summarizes the research on nanocrystalline cellulose,starch,lignin,and other biological and environment-friendly nanocomposites which are commonly used as nanocarriers for drugs and nutrients.Further,prospects for the use of biodegradable nanomaterials in targeted therapy,including environmentally responsive therapy,are discussed.

摘要： Present study deals with the biodegradable behavior of individual components and their preforms of nonwoven biocomposites developed from waste wool fibers including coring wool(CW),dorper wool(DW)and recycled polyester fibers(RPET).A respirometric technique was employed to estimate the production of CO_(2) during the biodegradation experiments under soil and aqueous media conditions.Functional groups of test samples before and after biodegradation were analyzed using Fourier transform infrared spectroscopy(FTIR).Leaching chemicals such as formaldehyde(hydrolyzed)and Chromium VI(Cr VI)was also measured.The CO_(2) emission in wool fibers CW and DW indicated 90%and 60%biodegradation in soil burial and aqueous media conditions respectively,for 100 days incubation.RPET fibers,20%and 10%biodegradation in soil burial and aqueous media conditions was measured respectively while the preforms of waste wool and RPET reflected 30%and 25%biodegradation in soil burial and aqueous media conditions,respectively.The degradation of end functional groups such as carbonyl(keto and ester),aldehyde and hydroxyl were also confirmed by FTIR.The DW and CW wool fibers showed higher Cr(VI)concentration as compared to the RPET.The released formaldehyde results showed higher concentration for RPET preforms as compared to waste wool preforms.These results suggest that waste wool preforms are extremely environment friendly as compared to RPET preforms.Thus,waste wool preforms it can be potentially utilized for preparing biocomposite materials and associated biobased products.

摘要： Magnesium and its composites as biodegradable materials offer especial capabilities to be used as bio-absorbable implants.However,their poor corrosion and fatigue properties in the physiological environment can restrict their applications.In this study,corrosion-fatigue tests have been performed on the extruded magnesium and magnesium/hydroxyapatite(Mg/HA)composites in a high cycle regime.To produce the composites,pure magnesium was reinforced by 2.5 wt.%and 5 wt.%of hydroxyapatite submicron particles using an electromagneticmechanical stirring method and hot extrusion process.The experimental density measurement exhibits that the porosity increases in the extruded samples with more hydroxyapatite particles.To investigate the corrosion and corrosion-fatigue behavior of the specimens,simulated body fluid(SBF)was used during in vitro tests.The results of the potentiodynamic polarization corrosion test show that the composite with 2.5 wt.%of hydroxyapatite(Mg/2.5 wt.%HA)and the pure magnesium specimen exhibit the highest and the lowest corrosion resistance,respectively.Regarding the elemental mapping analysis of the corroded samples,this behavior could be due to the formation of strong phosphorus-calcium based layers on the composite surface.The results obtained from the mechanical tests indicate that Mg/5 wt.%HA offered the highest tensile and compressive yield strengths,as well as the most promising high cycle fatigue behavior.During the corrosionfatigue test,the simultaneous effects of fatigue and corrosion damages led to a similar corrosion-fatigue behavior in both composites.The fracture surfaces of the corrosion-fatigue samples suggest that the cracks are initiated in the corroded regions of the samples surface,which reduces the crack initiation step and subsequently decreases the fatigue life.In comparison with the pure magnesium,both composites exhibit more promising corrosion and corrosion-fatigue behaviors with a significant fatigue life improvement in the physiological environment.

摘要： Lignin is the most abundant heteropolymer based on aromatic subunits in nature.Large quantities of lignin are annually produced from pulping processes and biorefinery industries.Its unclearly defined structure and difficult biodegradation mainly limit its utilization.This work focused on the effect of hydroxylation of lignin on its microbial degradation.Butyloxy carbonyl-modified lignin,and hydroxylated-lignin were synthesized with di-tert-butyl dicarbonate and hydrogen peroxide,respectively,using lignin as raw material.The degradation of the modifiedlignins both by P.chrysosporium and B.subtilis were analyzed using UV-vis spectroscopy.Results revealed that the lignin degradation velocity raises with the increase hydroxylation level of lignin.Moreover,FTIR and 1H NMR analysis of the biodegradation products of lignin further indicated that higher content of hydroxyl groups in lignin facilitated the demethylation combined with the aromatic ring cracking in the presence of fungus and bacteria.

摘要： Synthetic grafting needs improvements to eliminate secondary surgeries for the removal of implants after healing of the defected tissues.Tissue scaffolds are engineered to serve as temporary templates,which support the affected tissue and gradually degrade through the healing period.Beside mechanical function to withstand the anatomic loading conditions,scaffolds should also provide a decent biological function for the diffusion of nutrients and oxygen to the cells,and excretion of the wastes from the cells to promote the new tissue growth and vascularization.Moreover,the degradation byproducts of the scaffolds should be safe to the human body.Development of such multifunctional scaffolds requires selection of the right material,design,and manufacturing method.Mg has been recognized as the prominent biodegradable metal with regards to its mechanical properties matching to that of human bone,degradability in the body fluid,and its ability to stimulate new tissue growth.Scaffolds with intricate porous structures can be designed according to the patient-specific anatomic data using computer aided designs.Additive manufacturing(AM)is the right method to materialize these models rapidly with reasonably acceptable range of dimensional accuracy.Thus,the recent research trend is to develop ideal scaffolds using biodegradable Mg through AM methods.This review compiles and discusses the available literature on the AM of biodegradable Mg parts from the viewpoints of material compositions,process conditions,formation quality,dimensional accuracy,microstructure,biodegradation,and mechanical properties.The current achievements are summarized together,and future research directions are identified to promote clinical applications of biodegradable Mg through the advancement of AM.