Metal nanoparticles (NPs), such as gold (Au) and silver (Ag), are important for chemistry, physics, and biology due to their unique optical, electrical, and photothermal properties. Such NPs are widely used for immobilization of various bioactive substances, including peptides, enzymes, antibodies and DNA. The synthesis of silver and gold nanoparticles was carried out by reduction of silver nitrate by glucose and reduction of tetrachloroauric acid by sodium citrate, respectively. The size and structure of the AgNPs and AuNPs were characterized using TEM, AFM and XRD methods. The average size of the AgNPs and AuNPs was between 8 and 15 nm. Recombinant arginase I was immobilized using the carbodiimidepentafluorophenol method on the surface of NPs functionalized with ω-mercaptohexadecanoic acid. It was shown that recombinant human liver arginase I isolated from the yeast Hansenula polymorpha maintains satisfactory stability after immobilization on both NPs. The immobilized arginase retained 40% of its activity on the surface of AuNPs and 25% on AgNPs compared to the free arginase after storage at +4 ºC during 25 days. The immobilized enzyme can be used for assay of arginine in pharmaceuticals, in food products and in blood

Last decades various imaging techniques have been applied in biological and biomedical research, such as magnetic resonance imaging, different types of tomography, fluorescence/bioluminescence, ultrasound, as well as multimodality approaches. Fluorescence imaging, especially in combination with nanoscale materials, is a very prospective tool for experiments in vivo and clinical applications due to its high temporal and spatial resolutions. Fluorescent n anoparticles (NPs), having ability to interact with biomolecules both on the surface of and inside the cells, may revolutionize the cell imaging approaches for diagnostics and therapy. In our investigation we report about new method of cell imaging with fluorescent bi-metallic NPs synthesized by chemical reduction of the relevant ions. As the model of living organism, the cells of yeast Hansenula polymorpha were used. All NPs in minimal concentration (up to 0.05 mM) was proved to be nontoxic for yeast cells. The NPs and NPs -modified cells were characterized with the methods of UV-VIS spectroscopy, scanning electron microscopy, atom force microscopy, transmission electron m icroscopy and fluorescence microscopy. The bimetallic NPs, possessing the stable fluorescence in solution and inside the cells, allow to observe the phenomenon of NPs transferring from parental to daughter cells through at least three generations followed by releasing from the modified cells. The fluorescent NPs synthesized being small, non-toxic and fluorescent was shown to be perspective tool for cell imaging. KeywordsNanoparticles of noble metals· Fluorescence ·Toxicity of nanoparticles · Yeast Hansenula polymorpha ·Cell imaging .