Ligand-assisted synthesis and cytotoxicity of ZnSe quantum dots stabilized by N-(2-carboxyethyl)chitosans

Here we report a green synthesis of ZnSe quantum dots (QDs) in aqueous solution of polyampholyte chitosan derivative - N-(2-carboxyethyl)chitosan (CEC) with substitution degrees (DS) from 0.7 to 1.3 and molecular weight (MW) of 40 kDa and 150 kDa. We have shown that the maximum intensity of photoluminescence (PL) is exhibited by ZnSe QDs synthesized in solutions of CEC with DS 1 at Se:Zn molar ratio 1:2.5. The defect-related band was predominant in the PL spectra of ZnSe QDs obtained at room temperature; however, hydrothermal treatment at 80-150 °C during 1-2 h significantly increased contribution of exciton emission to the spectra. Cytotoxicity of ZnSe QDs was investigated by MTT assay using cancer cell lines SKOV-3; SkBr-3; PANC-1; Colon-26 and human embryonic kidney cell line HEK293. Cytotoxicity of ZnSe QDs did not depend on MW or DS of CEC but significantly depended on the cell line, being the lowest for normal human cells HEK293 and breast cancer cell line SKOV-3. The hydrothermally treated ZnSe QDs showed higher toxicity toward both normal and cancer cell lines. Since ZnSe QDs were toxic for most of the investigated cancer cell lines, they cannot be used as inert tracers for bioimaging, but can be promising for further investigation for anticancer therapy.