CdSe@ZnS nanocomposites prepared by a mechanochemical route: No release of Cd2+ ions and negligible in vitro cytotoxicity

• CdSe@ZnS nanocomposites were produced by milling.
• Negligible cadmium leakage was observed.
• No toxicity against living cells was documented.
• The material is suitable for biological imaging.

CdSe@ZnS nanocomposites have been prepared by a two-step solid state mechanochemical synthesis. CdSe prepared from Cd and Se elements in the first step was mixed with zinc acetate and sodium sulphide in the second step of milling to prepare a CdSe@ZnS nanocomposite. In the third step, the obtained nanocomposite was coated with l-cysteine to prepare a biocompatible system. The crystallite size of the new type of nanocomposite was 20–35 nm for cubic CdSe and 3–8 nm for hexagonal ZnS as calculated from XRD, TEM and SEM data. The synthesised samples show good crystallinity and have been tested for dissolution and cytotoxicity. The dissolution of cadmium from CdSe@ZnS was less than 0.05 μg mL−1, whereas a value of 0.8 μg mL−1 was measured for CdSe alone. The binding of ZnS with CdSe in the nanocomposite practically eliminated the release of cadmium into solution. As a consequence, a very low cytotoxic activity has been evidenced for CdSe@ZnS. The nanocomposites coated with l-cysteine have a great potential as fluorescent labels in biomedical engineering.

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