Introduction and Influence of Water in the Preparation of Crosslinked PVC Foam by Isocyanate

In the preparation process of crosslinked polyvinyl chloride(c-PVC)foam by isocyanate,the formulated mixture is generally required to be carried out under the condition of isolated water,so as to avoid the mixing difficulties caused by the reaction between the introduced water and isocyanate.In this paper,NaHCO_(3) was added to the mixture to indirectly introduce water into the system,and the effects of NaHCO_(3) on the cell structure and curing time of c-PVC foam were investigated.The results showed that NaHCO_(3) not only played a role of foaming agent,but also was a good nucleating agent for cells.At the same time,the introduction of NaHCO_(3) held back the exudation of modified diphenylmethane-4,4'-diisocyanate(MDI)on the cell wall.The effects of NaHCO_(3) on the cell structure and aggregation structure of c-PVC foam were studied by thermogravimetric analysis,infrared spectroscopy and scanning electron microscopy.The results showed that decomposition of NaHCO_(3) occurred during the molding stage,which made small amount of MDI react with water to form polyurea,improved the compatibility of MDI with PVC and inhibited the exudation of MDI.

Influence of residual chirality on the conformation and enzymatic degradation of glycopolypeptide based biomaterials

Glycopolypeptides as analogs of glycoproteins or glycosaminoglycans represent attractive building blocks for the construction of biomimetic biomaterials.However,the effects of amino acid chirality on the conformation and enzymatic degradation of glycopolypeptides are often overlooked.Here,we synthesized and characterized a range of glycopolypeptides composed of galactosylated poly(γ-propargylglutamate)s containing L-and/or D-glutamate residues.Glycopolypeptides containing pure Lglutamate residues were predominantlyα-helical,and the helicity increased over the degree of polymerization of the polypeptide backbones(24 to 44).The glycopolypeptide with pure D-glutamate residues adopted a mirroredα-helical conformation,whilst apparent random coil conformation was observed for the glycopolypeptide with equally mixed enantiomeric residues.The enzymatic degradation rates of the glycopolypeptides were markedly reduced following the introduction of D-glutamate residues into backbones.Galactoside pendants on these glycopolypeptides maintained their binding to peanut agglutinin.These structureproperty relationships provide new insight for the design of biomimetic biomaterials containing glycopolypeptides.

Stimuli-responsive nanocarriers for bacterial biofilm treatment

Bacterial biofilm infections have been threatening the human’s life and health globally for a long time because they typically cause chronic and persistent infections.Traditional antibiotic therapies can hardly eradicate biofilms in many cases,as biofilms always form a robust fortress for pathogens inside,inhibiting the penetration of drugs.To address the issues,many novel drug carriers emerged as promising strategies for biofilm treatment.Among them,stimuli-responsive nanocarriers have attracted much attentions for their intriguing physicochemical properties,such as tunable size,shape and surface chemistry,especially smart drug release characteristic.Based on the microenvironmental difference between biofilm infection sites and normal tissue,many stimuli,such as bacterial products accumulating in biofilms(enzymes,glutathione,etc.),lower pH and higher H_(2)O_(2)levels,have been employed and proved in favor of“on-demand”drug release for biofilm elimination.Additionally,external stimuli including light,heat,microwave and magnetic fields are also able to control the drug releasing behavior artificially.In this review,we summarized recent advances in stimuli-responsive nanocarriers for combating biofilm infections,and mainly,focusing on the different stimuli that trigger the drug release.

Rapid Differentiation of Aconiti Kusnezoffii Radix from Different Geographic Origins Using Ultra-Performance Liquid Chromatography Coupled with Time-of-Flight Mass Spectrometry

Objective:There are different geographic origins of Aconiti Kusnezoffii Radixs(AKRs)sold in the market with different quality.This study aims to establish a rapid analysis method to distinguish the different geographic origins of AKRs and to realize the rapid evaluation of their quality.Methods:An ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry(UPLC-Q-TOF MS)method was utilized to acquire the constituents'information of AKRs from different geographic origins.MSE data and Progenesis QI software were employed to identify the chemical constitutes.Principal component analysis(PCA)was applied to comparing MS data to find the chemical markers of AKRs from different geographic origins.Results:Twenty-three components were detected and 17 out of them were identified,including diester-diterpenoid alkaloids,monoester-diterpenoid alkaloids,and amine-diterpenoid alkaloids.Three pairs of isomers were detected and two of them were distinguished by the retention time of standard samples.Thirteen chemical markers were screened out through PCA and orthogonal partial least square discriminant analysis.Through detecting Napelline or isomer of Napelline(m/z 360.2530)and Aconifine(m/z 662.3170),AKRs from inner Mongolia autonomous could be screened.According to the existence of benzoylaconine(m/z 604.3108)and Indaconitine(m/z 630.3159),it could be confirmed that the AKRs are from Xinjiang Uygur autonomous.AKRs that cannot detect compounds above-mentioned could be from Liaoning or Shanxi Province.Conclusions:The chemical profile could be used not only to distinguish the AKRs from different geographic origins but also to identify the true and false of AKRs.This study lays a foundation for the study of efficacy and toxic of AKRs.

β-CuGaO_(2):a ferroelectric semiconductor with narrow band gap as degradation catalyst for wastewater environmental remediation

As a narrow band gap semiconductor,wurtziteβ-CuGaO_(2)has drawn increasing attention in the area of solar energy.Althoughβ-CuGaO_(2)has been theoretically predicted to possess ferroelectric polarization,its experi-mental ferroelectric characterization and practical appli-cations have not yet been presented.Herein,firstly we experimentally confirmed its ferroelectric property via hysteresis loop measurement.The result showed a rema-nent polarization value of 10.20μC·cm^(-2) with low coer-cive electricfield of 6.45 kV·cm^(-1) at 20 Hz at room temperature,while the leakage current density(J)value was found to be 1.188 A·cm^(-2),which suggested the property of a larger remnant polarization with low coercive electricfield than current value if the compactness was strengthened.Then,the synergistic effect of ferroelectric and semiconductor was comparatively highlighted by the experiment of pollutant degradation.Within 30 min,methyl orange degradation efficiency had reached 30.73%only in the case of spontaneous polarization(electricity),while it could reach 67.58%under the effect of pre-po-larizedβ-CuGaO_(2)powder due to the modulating orienta-tion of ferroelectric domains.Once irradiated(light),it was up to 92%within 30 min;in comparison,it merely took 16 min up to 92%degradation efficiency under both illu-mination and pre-polarization.If without illumination,it was 92.01%with 30 min in the condition of ordinary ultrasonic vibration(force)while under both illumination and ultrasonic vibration,only 11 min was spent to reach 92.79%degradation efficiency.All these results felici-tously indicated thatβ-CuGaO_(2)had fascinating potential in energy harvesting(such as electricity,light,force)and transformation as wastewater environment remediation catalyst.

Biocompatible in situ-forming glycopolypeptide hydrogels

A lack of biological activity hinders the application of synthetic hydrogels in tissue engineering and regenerative medicine.However,the use of glycopolypeptides in hydrogel synthesis may provide the materials with the desired biological activities.Herein,we prepared three in situ-forming hydrogels from various phenol-functionalized glycopolypeptides.The gelation time,mechanical properties,degradation properties,and biocompatibility of the hydrogels were assessed.Gelation time ranged from 11 to 380s,depending on the concentration of horseradish peroxidase.The galactose-modified polypeptide hydrogel showed the highest storage modulus with an obvious stress relaxation phenomenon.The prepared hydrogels exhibited good degradation properties and compatibility to cells and tissues.Furthermore,the rate of immune cell accumulation around the mannosemodified polypeptide hydrogel was the fastest among the hydrogels.

Recent advances in polymeric biomaterials-based gene delivery for cartilage repair

Untreated articular cartilage damage normally results in osteoarthritis and even disability that affects millions of people.However,both the existing surgical treatment and tissue engineering approaches are unable to regenerate the original structures of articular cartilage durably,and new strategies for integrative cartilage repair are needed.Gene therapy provides local production of therapeutic factors,especially guided by biomaterials can minimize the diffusion and loss of the genes or gene complexes,achieve accurate spatiotemporally release of gene products,thus provideing long-term treatment for cartilage repair.The widespread application of gene therapy requires the development of safe and effective gene delivery vectors and supportive gene-activated matrices.Among them,polymeric biomaterials are particularly attractive due to their tunable physiochemical properties,as well as excellent adaptive performance.This paper reviews the recent advances in polymeric biomaterial-guided gene delivery for cartilage repair,with an emphasis on the important role of polymeric biomaterials in delivery systems.