Prevalence of hepatitis C infection among intravenous drug users in Shanghai

AIM:To characterize the prevalence of hepatitis C virus(HCV)infection among Chinese intravenous drug users(IDUs).METHODS:A total of 432 adult IDUs(95 women and337 men)in Shanghai were included in the study.The third-generation Elecsys Anti-HCV assay(Roche Diagnostics GmbH,Sandhofer Strasse 116,D-68305,Mannheim,Germany)was used to screen for antibodies against HCV.The RIBA strip,a supplemental antiHCV test with high specificity,was performed on all of the samples that tested positive during the initial screening.All of the anti-HCV positive samples were analyzed with a Cobas TaqMan 48 Analyzer(Roche Diagnostics)for direct detection of HCV RNA.All of the HCV RNA-positive samples were sequenced for genotype determination.RESULTS:The preliminary screening identified 262(60.6%)subjects who were seropositive for HCV.Of the 62 females and 200 males seropositive subjects,16(16.7%)and 65(19.3%),respectively,were confirmed by RIBA,yielding an overall HCV seropositive rate of18.8%.Four female(6.5%)and 14 male(7.0%)subjects tested positive for HCV RNA,indicating an active infection rate of 4.2%for the entire study population.The 18 HCV RNA-positive serum samples were genotyped.Seven individuals were genotype 1b,and four were genotype 1a.One individual each was infected with genotypes 2a,2b and 3a.Four subjects were coinfected with multiple strains:two with genotypes 1a and 2a,and two with genotypes 1b and 2a.The active infection rate among HCV-seropositive individuals was22.2%,which was significantly lower than most estimates.CONCLUSION:The prevalence of HCV is relatively low among IDUs in Shanghai,with a spontaneous recovery rate much higher than previous estimates.

Effects on cytotoxicity and antibacterial properties of the incorporations of silver nanoparticles into the surface coating of dental alloys

The aim of this study was to research the changes in cytotoxicity and antibacterial properties after silver nanoparticles （AgNPs） were incorporated into the surface coating of dental alloys. AgNPs were attached to cobalt chromium alloys and pure titanium using a hydrothermal method, according to the reaction： AgNO3＋NaBH4-, Ag＋1/2H2＋1/2B2H6＋NaNO3. A 3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyl tetrazolium bromide （MTT） assay was used to evaluate the cytotoxicity of the alloys when in contact with osteogenic precursor cells （MC3T3-E1） from mice and mesenchymal stem cells （BMSC） from rats. The antibacterial properties of dental alloys incorporating three different concentrations （10, 4, and 2 μmol/L）of AgNPs were tested on Staphylococcus aureus （SA）and Streptococcus mutans （MS）. High cytotoxicity values were observed for all dental alloys that contained 0% of AgNPs （the control groups）. The incorporation of AgNPs reduced cytotoxicity values. No significant difference was observed for antibacterial performance when comparing dental alloys containing AgNPs to the respective control groups. The results demonstrated that the cobalt chromium alloys and pure titanium all had cytotoxicity to MC3T3-E1 and BMSC and that the incorpo- ration of AgNPs could reduce this cytotoxicity. The concentrations of AgNPs adopted in this study were found to have no antibacterial action against SA or MS.

Toxicity testing of four silver nanoparticle-coated dental castings in 3-D LO2 cell cultures

To address the controversial issue of the toxicity of dental alloys and silver nanoparticles in medical ap- plications, an in vivo-like LO2 3-D model was constructed within polyvinylidene fluoride hollow fiber materials to mimic the microenvironment of liver tissue. The use of microscopy methods and the measurement of liver-specific functions optimized the model for best cell performances and also proved the superiority of the 3-D LO2 model when compared with the traditional monolayer model. Toxicity tests were conducted using the newly constructed model, finding that four dental castings coated with silver nanoparticles were toxic to human hepatocytes after cell viability assays. In general, the toxicity of both the castings and the coated silver nanoparticles aggravated as time increased, yet the nanoparticles attenuated the general toxicity by preventing metal ion release, especially at high concentrations.