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The purpose of this study was to develop a stable single-dose vaccine based on recombinant hepatitis B surface antigen (HBsAg) in poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres, in which HBsAg was stabilized by a protein stabilizer (trehalose) and an antacid (Mg(OH)2). The microspheres were prepared by the double emulsion method and characterized by scanning electron microscopy. To neutralize the acids liberated by the biodegradable lactic/glycolic acid based polymer, we coincorporated into the polymer an antacid, Mg(OH)2, which neutralized the acidity during degradation of the polymer and also prevented HBsAg structural losses and aggregation. The antigen integrity after encapsulation was examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by silver staining, isoelectric focusing and Western blotting techniques, which confirmed that antigen remained intact after encapsulation. In-vitro release experiments were performed in phosphate-buffered saline (pH 7.4) and the release of antigen was found to be improved by the protein stabilizer (trehalose). In stability studies, performed at 37 degrees C, the microspheres were found to be stable for 16 days. The immunogenicity of stable microsphere formulations bearing HBsAg was compared with the conventional alum-absorbed HBsAg vaccine in a guinea-pig model. The antibody titre indicated that a single injection of stabilized HBsAg-PLGA microspheres produced a better immune response than two injections of alum-formulated HBsAg vaccine. The findings suggest that recombinant HBsAg can be stabilized by use of a protein stabilizer and antacid during entrapment, and this stabilized preparation can be useful for antigen delivery.

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A simple naphthoquinone−dopamine hybrid (2CND) was designed and fabricated as a colorimetric and fluorescence chemosensor for the selective recognition of Sn 2+ in the aqueous medium. This simply accessible chemosensor was prepared by connecting of naphthoquinone acceptor and dopamine donor moieties via Michael-like addition reaction. The chemosensor 2CND showed a turn-on fluorescence response which operated through the inhibited photoinduced electron transfer effect. The sensor probe shows remarkable performance, such as high selectivity, sensitivity, excellent water solubility, and rapid response to Sn 2+ (less than 5 s). The detection mechanism of the 2CND−Sn 2+ complex was supported by FT-IR analysis, 1 H NMR titration, and DFT calculations. Besides, the 1:1 binding stoichiometry was confirmed by the ESI-MS spectral analysis. Furthermore, the chemosensor 2CND has been successfully employed as a fluorescence probe to monitor trace Sn 2+ in live cells and zebrafish. The sensor probe 2CND could serve as an effective fluorescence bioimaging probe for the discriminative detection of diseased and normal human cells.