Influence of hydrocarbons on the virulence and antibiotic sensitivity associated with Pseudomonas aeruginosa

The bacterium, Pseudomonas aeruginosa has the potential for use in bioremediation. However, this organism is an opportunistic pathogen and is highly resistant to disinfectants and antibiotics. P. aeruginosa has been known to cause a wide variety of infections in humans, especially in immunocompromised persons. The purpose of this study was to assess the influence of hydrocarbons on the virulence of P. aeruginosa as it degrades these hydrocarbons. The expression of virulence factors associated with 12 different hydrocarbon-degrading strains of P. aeruginosa was evaluated. Virulence factors including hemolytic activity, antibiotic sensitivity, cell adherence, and exopolysaccharide capsule formation were tested in the presence of 0.1% glucose and the appropriate hydrocarbon. No differences were found in hemolytic activity or antibiotic resistance in the presence of glucose or hydrocarbon. Growth on glucose significantly enhanced adherence, while growth on a hydrocarbon enhanced capsule formation. The results of this study indicate that, overall, growth in the presence of hydrocarbons such as hexadecane does not enhance the virulence characteristics of P. aeruginosa.     

Enzymes involved in the metabolism of valproate

This article provides a short overview of enzymes involved in activation, transport and oxidation ( and) of valproate and other fatty acids.     

Biodegradable DNA-enabled poly(ethylene glycol) hydrogels prepared by copper-free click chemistry

Significant research has focused on investigating the potential of hydrogels in various applications and, in particular, in medicine. Specifically, hydrogels that are biodegradable lend promise to many therapeutic and biosensing applications. Endonucleases are critical for mechanisms of DNA repair. However, they are also known to be overexpressed in cancer and to be present in wounds with bacterial contamination. In this work, we set out to demonstrate the preparation of DNA-enabled hydrogels that could be degraded by nucleases. Specifically, hydrogels were prepared through the reaction of dibenzocyclooctyne-functionalized multi-arm poly(ethylene glycol) with azide-functionalized single-stranded DNA in aqueous solutions via copper-free click chemistry. Through the use of this method, biodegradable hydrogels were formed at room temperature in buffered saline solutions that mimic physiological conditions, avoiding possible harmful effects associated with other polymerization techniques that can be detrimental to cells or other bioactive molecules. The degradation of these DNA-cross-linked hydrogels upon exposure to the model endonucleases Benzonase^® and DNase I was studied. In addition, the ability of the hydrogels to act as depots for encapsulation and nuclease-controlled release of a model protein was demonstrated. This model has the potential to be tailored and expanded upon for use in a variety of applications where mild hydrogel preparation techniques and controlled material degradation are necessary including in drug delivery and wound healing systems.     

Biostable,antidegradative and antimicrobial restorative systems based on host-biomaterials and microbial interactions

Objectives

Despite decades of development and their status as the restorative material of choice for dentists, resin composite restoratives and adhesives exhibit a number of shortcomings that limit their long-term survival in the oral cavity. Herein we review past and current work to understand these challenges and approaches to improve dental materials and extend restoration service life.

聚己酸内酯及其在医药领域的应用

目前，对聚己酸内酯的性质和应用的研究日益增多。本文综述了聚己酸内酯材料的制备、一般理化性质、降解吸收性质和在临床及给药系统中的应用等。聚己酸内酯一般由开环聚合得到，为半结晶性聚合物，有较好的柔韧性。该材料降解属于水解反应，不在体内积蓄，排泄完全；可以作为手术缝线、骨折固定材料、药物载体等使用。由于它安全、低毒、可生物降解，所以在医药领域得到广泛应用。     

可吸收聚乳酸接骨板的动物实验初步报道

本文报道了可吸收聚乳酸接骨板用于动物实验的初步结果。聚乳酸接骨板为四孔板，抗拉强度３６．２６ｍＰａ，抗弯强度７９．０９ｍＰａ，抗压强度为４９．８８ｍＰａ。用于１８只家兔股骨骨折的结果表明：全部实验动物伤口愈合好，在２－１０周不同观察期内均有聚乳酸接骨板变形、骨折移位现象，其原因可能是聚乳酸接骨板在体内降解较快，尚不能在骨折愈合前起到有效的固定作用。     

鼻中隔软骨细胞组织工程法构建预定形态软骨

目的探讨利用人鼻中隔软骨细胞组织工程方法构建预定形态软骨的可能性。方法将人鼻中隔软骨细胞播种在聚乙醇酸（polyglycolicacid,PGA）无纺网支架材料上,制成片状和管状结构,埋入裸鼠体内,经4、6、8周后取材作大体及组织学观察。结果大体观察见裸鼠体内形成了预定的片状和管状软骨。组织学观察6周时软骨细胞基本成熟,Masson三色染色显示胶原形成,番红花-“O”染色证实其基质中存在糖氨多糖。对照组于6周时PGA纤维基本消失。结论人鼻中隔软骨细胞与PGA无纺网复合可在裸鼠体内形成预定形态软骨。     

Biodegradation of Titanium Implants After Long-Time Insertion Used for the Treatment of Fractured Upper and Lower Jaws Through Osteosynthesis: Element Analysis by Electron Microscopy and EDX or EELS

Twelve patients underwent an osteosynthesis with titanium to treat upper and lower jaw fractures. Six to 12 months later, the miniplates were removed. Tissue samples were analyzed by light and electron microscopy for detection of a metallosis. The analysis showed new bone formation like callus tissue around the miniplates. In some cases small, rounded deposits and accumulation of colloid-like particles located next to bigger titanium artifacts were detected in the cytoplasm of histiocytes and in the matrix of connective tissue. The titanium was identified by elemental analysis using EDX in SEM as well as by EELS and electron diffraction in TEM. Both kinds of particles contain titanium, but they seem to be different in composition and derivation. The bigger particles seem to consist of metallic titanium and sourced by working on the metallic implants during the implantation itself. On the other hand, the colloidal-like, small, rounded particles in tissue macrophages and outside the cells in the matrix of connective tissue are presumably of other origin; for example, they could be derived from biodegradation and chemical conversion of the metallic implants. The titanium miniplates were examined before and after implantation by using ESCA technique and revealed metallic titanium and different compositions with other elements. The amount of titanium load of the tissue was very low in most cases and presumably not of biomedical relevance.     

不同分子量壳聚糖膜性质的研究

分别以分子量为130，000、220，000、300，000、550，000道尔顿的壳聚糖制备壳聚糖膜，并研究了各膜的表面结构、结晶性、力学特性、渗透性、透光透气性、吸附性、生物降解性等。结晶表明壳聚糖膜的各种特性和壳聚糖的分子量相关，高分子量的壳聚糖膜表面较为光滑，透光性较好，透气性、渗透性和生物降解性较差；低分子量的壳聚糖膜表面较为粗糙，透气性、渗透性和生物降解性较好，但透光性较差。经分析认为膜的结晶性和超微结构决定了不同分子量壳聚糖膜具有不同的性质。     

Influence of Mechanical Stimulation in the Development of a Medial Equivalent Tissue-Engineered Vascular Construct using a Gelatin-g-Vinyl Acetate Co-Polymer Scaffold

Abstract

Vascular regeneration in the area of small diameter (<6 mm) vessels via the tissue-engineering approach has been in focus for some time now. In this study, we report the development and evaluation of a tissue-engineered medial equivalent using gelatin-g-vinyl acetate co-polymer (GeVAc) as the scaffold material. GeVAc was synthesized by co-polymerizing gelatin and vinyl acetate monomer in the presence of AIBN as the initiator and subjected to physico-chemical characterization. A porous 3-D scaffold with open interconnected pores was then produced from GeVAc. The scaffold is non-cytotoxic with good smooth muscle cell proliferative capacity and high cell viability. Influence of smooth muscle cell phenotype in response to these scaffolds has been studied under mechanical stimulation. It was found that the cell-seeded tubular GeVAc constructs under mechanical stimulation preferentially supported the contractile phenotype of smooth muscle cells, as evidenced by the elevated expression of contractile protein markers such as alpha-SMA, calponin and SM22α. The mechanical properties and the ECM secretion were also increased on applying the mechanical stimulation. Hence, the results showed the promising potential of the GeVAc scaffolds in the regeneration of the medial equivalent tissue-engineered vascular construct.