Elucidating the Impact of Hydrophilic Segments on 19F MRI Sensitivity of Fluorinated Block Copolymers.

A major challenge in the preparation of polymeric 19F magnetic resonance imaging (MRI) contrast agents (CAs) is signal attenuation caused by reduced segmental mobility of partly fluorinated polymers possessing large numbers of fluorine atoms. Previous studies have thus mainly focused on the development of fluorinated segments for improved 19F MRI; however, detailed investigations of the role of hydrophilic segments on imaging performance remain scarce. In this study, three hydrophilic and biocompatible monomers, i.e., 2-(methylsulfinyl)ethyl acrylate (MSEA), oligo(ethylene glycol) methyl ether acrylate (OEGA), and oligo(2-methyl-2-oxazoline) acrylate (OMOXA), were used to prepare perfluoropolyether (PFPE)-containing amphiphilic block polymers through reversible addition-fragmentation chain-transfer (RAFT) polymerization. The effect of the different hydrophilic segments on 19F imaging performance was explored. The three polymers could be readily dissolved in aqueous solutions, forming assemblies with the hydrophobic PFPE as the core and the hydrophilic chains as the shell. Molecular dynamics simulations demonstrate that the POMOXA chains adopt a rigid, extended conformation, leading to a relatively short 19F NMR spin-spin relaxation time (T2), lower NMR detectable 19F spins (i.e., visibility), and the least intense 19F MRI signal. In contrast, although PMSEA-PFPE has a shorter 19F NMR T2 than POEGA-PFPE, the much higher 19F spin visibility enhances its MRI signal intensity. The result confirms the importance of maintaining both high fluorine visibility and long T2 relaxation time to prepare effective CAs and highlight the key role of the nonfluorinated hydrophilic segments in determining these parameters.

Enhanced mechanical, thermal and antimicrobial properties of poly(vinyl alcohol)/graphene oxide/starch/silver nanocomposites films.

In the present work, synthesis of poly(vinyl alcohol)/graphene oxide/starch/silver (PVA/GO/Starch/Ag) nanocomposites films is reported. Such films have been characterized and investigated for their mechanical, thermal and antimicrobial properties. The exfoliation of GO in the PVA matrix occurs owing to the non-covalent interactions of the polymer chains of PVA and hydrophilic surface of the GO layers. Presence of GO in PVA and PVA/starch blends were found to enhance the tensile strength of the nanocomposites system. It was found that the thermal stability of PVA as well as PVA/starch blend systems increased by the incorporation of GO where strong physical bonding between GO layers and PVA/starch blends is assumed to cause thermal barrier effects. Antimicrobial properties of the prepared films were investigated against Escherichia coli and Staphylococcus aureus. Our results show enhanced antimicrobial properties of the prepared films where PVA-GO, PVA-Ag, PVA-GO-Ag and PVA-GO-Ag-Starch showed antimicrobial activity in ascending order.

Liquid crystals based sensing platform-technological aspects.

In bulk phase, liquid crystalline molecules are organized due to non-covalent interactions and due to delicate nature of the present forces; this organization can easily be disrupted by any small external stimuli. This delicate nature of force balance in liquid crystals organization forms the basis of Liquid-crystals based sensing scheme which has been exploited by many researchers for the optical visualization and sensing of many biological interactions as well as detection of number of analytes. In this review, we present not only an overview of the state of the art in liquid crystals based sensing scheme but also highlight its limitations. The approaches described below revolve around possibilities and limitations of key components of such sensing platform including bottom substrates, alignments layers, nature and type of liquid crystals, sensing compartments, various interfaces etc. This review also highlights potential materials to not only improve performance of the sensing scheme but also to bridge the gap between science and technology of liquid crystals based sensing scheme.

Mixed cryoglobulinemia secondary to interferon therapy for hepatitis C: case report & review of the literature.

Mixed cryoglobulinemia is a systemic vasculitis associated with hepatitis C infection. We present a case of mixed cryoglobulinemia induced by interferon-alpha therapy for hepatitis C infection and review previous cases in which cryoglobulinemic symptom exacerbations were caused by interferon-alpha.