耐氯聚酰胺复合纳滤膜的制备与性能

采用哌嗪(PIP)与均苯三甲酰氯(TMC)为单体以界面聚合制备聚酰胺复合纳滤膜,用戊二醛(GA)对聚酰胺复合纳滤膜进行交联处理,再浸入间氨基乙酰苯胺中进行接枝反应得到具有耐氯性的改性复合纳滤膜。通过红外光谱和固体表面电位Zeta电位分析仪表征,证明间氨基乙酰苯胺接枝到活性层表面,降低了复合膜的荷负电性,扫描电子显微镜显示改性膜呈现无孔和更加粗糙的状态,接触角测量表明改性提高了复合膜表面的亲水性。耐氯测试表明,室温下,在pH=4,浓度1g/L的NaClO溶液中浸泡10h后,改性膜的截留率由94.04%下降至91.81%,PIP-TMC复合纳滤膜的截留率由94.60%下降至78.85%。

In vitro and in vivo degradation behavior of Mg-2Sr-Ca and Mg-2Sr-Zn alloys

Magnesium alloys with integration of degradability and good mechanical performance are desired for orthopedic implants.In this paper,Mg-2Sr-Ca and Mg-2Sr-Zn alloys were prepared and the degradation as well as the bone response were investigated.Compared with the binary Mg-2Sr alloys,the addition of Ca and Zn improved the in vitro and in vivo corrosion resistance.Mg-2Sr-Ca and Mg-2Sr-Zn alloys exhibited more uniform corrosion and maintained the configuration of the implants 4 weeks post-implantation.The in vivo corrosion rates were 0.85 mm/yr for Mg-2Sr-Zn and 1.10 mm/yr for Mg-2Sr-Ca in comparison with 1.37 mm/yr for Mg-2Sr.The in vitro cell tests indicated that Mg-2Sr-Ca and Mg-2Sr-Zn alloys exhibited higher MG63 cell viability than Mg-2Sr alloy.Furthermore,these two alloys can promote the mineralization and new bone formation without inducing any significant adverse effects and this sound osteogenic properties suggest its attractive clinical potential.

A surface-eroding poly(1,3-trimethylene carbonate)coating for magnesium based cardiovascular stents with stable drug release and improved corrosion resistance

Magnesium alloys with integration of degradability and good mechanical performance are desired for vascular stent application.Drug-eluting coatings may optimize the corrosion profiles of magnesium substrate and reduce the incidence of restenosis simultaneously.In this paper,poly(trimethylene carbonate)(PTMC)with different molecular weight(50,000 g/mol named as PTMC5 and 350,000 g/mol named as PTMC35)was applied as drug-eluting coatings on magnesium alloys.A conventional antiproliferative drug,paclitaxel(PTX),was incorporated in the PTMC coating.The adhesive strength,corrosion behavior,drug release and biocompatibility were investigated.Compared with the PLGA control group,PTMC coating was uniform and gradually degraded from surface to inside,which could provide long-term protection for the magnesium substrate.PTMC35 coated samples exhibited much slower corrosion rate 0.05μA/cm^(2)in comparison with 0.11μA/cm^(2)and 0.13μA/cm^(2)for PLGA and PTMC5 coated counterparts.In addition,PTMC35 coating showed more stable and sustained drug release ability and effectively inhibited the proliferation of human umbilical vein vascular smooth muscle cells.Hemocompatibility test indicated that few platelets were adhered on PTMC5 and PTMC35 coatings.PTMC35 coating,exhibiting surface erosion behavior,stable drug release and good biocompatibility,could be a good candidate as a drug-eluting coating for magnesium-based stent.

Fluid-induced corrosion behavior of degradable zinc for stent application

The influence of laminar flow on the corrosion of pure zinc(Zn) and cell response was investigated and compared with the static measurements.The results revealed that laminar flow accelerated the corrosion and enhanced the localized corrosion of pure Zn.The dynamic corrosion rate was 0.184 mm/yr after 168 h corrosion.More corrosion products were formed under flow condition,which were mainly composed of Zn_(3)(PO_(4))_(2)·4 H_(2) O,Ca_(3)(PO_(4))_(2),ZnO and Zn_(5)(OH)_(6)(CO_(3))_(2).Moreover,the adhered rat aortic endothelial cells(RAEC) on Zn samples exhibited notably cell loss and round configuration under laminar flow.

Continuous Detection of pH-responsive Drug Delivery System in Cells in situ by Confocal Laser Scanning Microscopy

Mesoporous silica nanoparticles （MSN） were coated by pH-responsive polymer chitosan-poly （methacrylic acid） （CS-PMAA）. This nano drug delivery system showed good application prospects and the polymer-coated microspheres were promising site-specific anticancer drug delivery carriers in biomedical field. A continuous detection of pH-responsive drug delivery system in cells in situ, utilizing MSN/CS-PMAA composite microspheres, was pro- posed. Two kinds of different cell lines, tumor cell line （Hela） and normal somatic cells （293T）, were used to inves- tigate the behaviours of the drug loaded system in the cells. Conclusions could be drawn from the fluorescent im- ages obtained by confocal laser scanning microscopy （CLSM）, modified drug-loaded microspheres （MSN/CS-PMAA） were ingested into cells more easily, the uptake of DOX@FITC-MSN/CS-PMAA by HeLa/293T cells were performed at pH 7.4/pH 6.8, DOX was released during the ingestion process, fluorescence intensity de- creased with time because of efflux transport and photo-bleaching. Fluoresence detection by flow cytometry was performed as comparison. The continuous fluorescent observation in situ could be widely used in the pH-responsive releasing process of drug delivery system in the cells.

In vitro and in vivo evaluation of micro-alloyed magnesium for potential application in alveolar bone fixation screws

Alveolar bone augmentation with fixation screws has difficulties such as non-degradable materials that could lead to secondary surgery and insufficient osseointegration due to the subgingival environment in dental practice.With degradability and a high degree of osteogenesis,Mg alloy is a successful biodegrad-able material for orthopedic applications,and its application in dentistry has made certain progress.How-ever,considering the unique subgingival healing properties of oral implants,there is still a gap between the desired material properties for clinical applications and available materials.Indeed,studies on the use of Mg-based fixation screws for dentistry applications are still rare.In this study,we reported a magnesium alloy with low combined addition of strontium and lanthanum.The mechanical properties,degradation behavior,osteogenesis,and gingival compatibility were systematically investigated for assess-ing its potential application in alveolar bone fixation screws.With the alloying element content restricted to 0.3 wt.%,Mg-Sr-La alloy still exhibited good mechanical properties,with yield tensile and compressive strength twice higher than those of pure Mg.The in vitro degradation rate of this alloy was 0.10 mm y-1,which was slightly slower than high-purity Mg.The indirect and direct cell assay confirmed the elevated osteoblastic differentiation of MC3T3-E1 and migration of HGF-1 cells.Moreover,Mg-Sr-La alloy demon-strated a relatively slow degradation in the maxillary bone of Beagles.A remarkable promotion of the bone-implant contacts and significantly decreased fibrous encapsulation was observed in the subgingival environment,implying superior osseointegration of the experimental alloy than the titanium control.The empirical findings here reveal the great potential of Mg-Sr-La alloy for the application in alveolar bone fixation devices.

Remark on Gauss curvature equations on punctured disk

We give a new argument on the classification of solutions of Gauss curvature equation on R2,which was first proved by W.Chen and C.Li[Duke Math.J.,1991,63(3):615-622].Our argument bases on the decomposition properties of the Gauss curvature equation on the punctured disk.