Nanobiotechnology for health care
Chitosan capped CuInS2 and CuInS2/ZnS by wet stirred media milling: in vitro verification of their potential bio-imaging applications
Dutková, E.1, Lukáčová Bujňáková, Z.1, Kello, M.2, Mojžiš, J.2,       Shpotyuk, O.3,4
1Institute of Geotechnics, Slovak Academy of Sciences, 04001 Košice, Slovakia,
E-mail: dutkova@saske.sk 
2Faculty of Medicine, P.J. Šafárik University, 04011 Košice, Slovakia
3 Vlokh Institute of Physical Optics, 79005 Lviv, Ukraine
4Institute of Physics, Jan Dlugosz University, 42200 Czestochowa, Poland

Recently, research works on CuInS2 and CuInS2/ZnS nanocrystals have gained much importance in scientific community due to their non-toxic behavior and ecofriendly properties and for their various applications, such as solar cells, polymer hybrid solar cells, as absorbing materials in solar cell structures, etc. Besides, CuInS2 and CuInS2/ZnS nanocrystals were already tested for bio-imaging applications. For using inorganic nanocrystals in biomedicine, it is necessary to cover them by organic, biocompatible material. Various methods have been reported for producing stable colloidal nanoparticles. 
The wet mechanochemical synthesis was also successfully used for producing of stable nanosuspensions in several previous papers published by our research group. In this work, the mechanochemically synthesized CuInS2 and CuInS2/ZnS samples were capped with chitosan by wet stirred media milling in order to obtain nanosuspensions suitable for testing of their bio-imaging properties. Their stability was studied using a particle size-distribution and zeta potential measurements. The nanosuspension of CuInS2/ZnS was stable only for 1 week, on the other hand, CuInS2 was stable for 37 weeks. The dissolution of copper and zinc ions in a physiological solution was investigated. The optical properties were also studied using UV-Vis and PL spectroscopies. The potential bio-imaging applications were verified in vitro on four cancer cell lines with no toxicity risk in a case of CuInS2 sample. The cells were more visible in comparison with non-treated ones under the fluorescence microscope. They stayed in cytoplasm and surrounded the nucleus. Granularity and metabolic activity of the cells were strongly influenced. On the other hand, CuInS2/ZnS nanocrystals affected cell metabolism and survival and they seem not suitable for bio-imaging applications particularly in high concentrations. Futher concentration screening and testing must be taken into consideration.