Tuning the internal compartmentation of single-chain nanoparticles as fluorescent contrast agents

Controlling the internal structures of single-chain nanoparticles (SCNPs) is an important factor for their targeted chemical design and synthesis, especially in view of nanosized compartments presenting different local environments as a main feature to control functionality. We here design SCNPs bearing near-infrared fluorescent dyes embedded in hydrophobic compartments for use as contrast agents in pump–probe photoacoustic (PA) imaging, displaying improved properties by the location of the dye in the hydrophobic particle core. Compartment formation is controlled via single-chain collapse and subsequent crosslinking of an amphiphilic polymer using external crosslinkers in reaction media of adjustable polarity. Different SCNPs with hydrodynamic diameters of 6-12 nm bearing adjustable label densities are synthesized. It is found that the specific conditions for single-chain collapse have a major impact on the formation of the desired core–shell structure, in turn adjusting the internal nanocompartments together with the formation of excitonic dye couples, which in turn increase their fluorescence lifetime and PA signal generation. SCNPs with the dye molecules accumulate at the core also show a nonlinear PA response as a function of pulse energy—a property that can be exploited as a contrast mechanism in molecular PA tomography

High prevalence of multidrug-resistant strains of Vibrio cholerae, in a cholera outbreak in Tehran�Iran, during June�September 2008

Following the occurrence of suspected cases of Vibrio cholerae in Karaj in 2008, this study was conducted in order to determine whether or not the cases were infected with cholera and, if so, to describe the prevalence of serotypes, route of transmission and the antimicrobial resistance profile. In this cross-sectional study, 6505 rectal swabs were collected from patients with acute gastroenteritis. Serotypes and biotypes of the isolates were determined by standard procedures. The antimicrobial susceptibility of 45 Inaba and 30 non-agglutinating (NAG) strains was determined. From 6505 specimens, 110 (1.69) were defined as V. cholerae, including 70 (63.3) V. cholerae O1 serotype Inaba biotype El Tor and 40 (36.4) NAG Vibrios. The case fatality rate was 0.9. Inaba strains were 100 resistant to nalidixic acid and amoxicillin, 95.7 resistant to trimethoprim-sulfamethoxazole, 91.3 resistant to furazolidone while the highest frequency of resistance in NAG Vibrios was 77.4 to erythromycin. The lowest resistance rate belonged to ciprofloxacin to which just one NAG strain was resistant. Results suggests an increase in resistance of V. cholerae to several antibiotics. Ciprofloxacin can still be used as first-line treatment of cholera in this region. © 2010, SAGE Publications. All rights reserved