Ferroxidase-like and antibacterial activity of PtCu alloy nanoparticles.

Many metal nanoparticles are reported to have intrinsic enzyme-like activities and offer great potential in chemical and biomedical applications. In this study, PtCu alloy nanoparticles (NPs), synthesized through hydrothermal treatment of Cu2+ and Pt2+ in an aqueous solution, were evaluated for ferroxidase-like and antibacterial activity. Electron spin resonance (ESR) spectroscopy and colorimetric methods were used to demonstrate that PtCu NPs exhibited strong ferroxidase-like activity in a weakly acidic environment and that this activity was not affected by the presence of most other ions, except silver. Based on the color reaction of salicylic acid in the presence of Fe3+, we tested the ferroxidase-like activity of PtCu NPs to specifically detect Fe2+ in a solution of an oral iron supplement and compared these results with data acquired from atomic absorption spectroscopy and the phenanthroline colorimetric method. The results showed that the newly developed PtCu NPs detection method was equivalent to or better than the other two methods used for Fe2+ detection. The antibacterial experiments showed that PtCu NPs have strong antibacterial activity against Staphylococcus aureus and Escherichia coli. Herein, we demonstrate that the peroxidase-like activity of PtCu NPs can catalyze H2O2 and generate hydroxyl radicals, which may elucidate the antibacterial activity of the PtCu NPs against S. aureus and E. coli. These results showed that PtCu NPs exhibited both ferroxidase- and peroxidase-like activity and that they may serve as convenient and efficient NPs for the detection of Fe2+ and for antibacterial applications.

Further evaluation of the pertussis component vaccine produced by apoceruloplasmin affinity chromatography.

The heat-treated apoceruloplasmin (Apocp) is a useful protein as an affinity ligand for the purification of pertussis toxin (PT). The amounts of Apocp in the purified antigens or the pertussis component vaccine were determined. Anti-Apocp antibodies were not detected by the passive cutaneous anaphylaxis (PCA) test in rats. No anti-Apocp antibody was detected after hyperimmunization of rabbits with the vaccine. Apocp was not detected in PT and filamentous hemagglutinin (FHA) by ELISA using rabbit anti-Apocp IgG. In the experiments using 125I-labelled Apocp, 125I-Apocp was not detected in either PT or FHA which were purified by 125I-labeled Apocp-Sepharose, DEAE Sepharose, and cellulose sulfate chromatography. The contents of human DNA were also determined to be less than 10 pg per 1 mg of Apocp, by the dot-blot hybridization method using the 32P-labeled DNA probe of Alu sequence. In the tests for the presence of inapparent viruses, HBs antigen and HTLV-III antibody, no contamination was found in either the Apocp or in the vaccine. Large amounts of various viruses, which were intentionally added to the Apocp (spiking test), were completely inactivated by heating at 65 degrees C for 18 hr. Both the Apocp and the vaccine passed the general pharmacology and acute toxicity tests. From these results, the heat-treated Apocp was considered to be a suitable affinity ligand for the purification of the antigens for the pertussis component vaccine.