In this paper, the synthesis of alloyed CuInZnxS2+x quantum dots (ZCIS QDs), their transfer into aqueous solution via a polymer coating technique, and the use of these nanocrystals to selectively target HER2-positive cells, are reported. By optimizing first the ZnS shell deposition process onto the CuInS2 core, and next the encapsulation of the dots with the amphiphilic poly(maleic anhydride-alt-1-octadecene) (PMAO) polymer, water-dispersible ZCIS QDs were successfully prepared. The nanocrystals with a photoluminescence quantum yield of 35% were purified via centrifugation and ultracentrifugation and high quality nanoparticles with narrow size distributions and surface charges were obtained. After verifying the biocompatibility of PMO-coated ZCIS QDs, we coupled these nanocrystals with the LTVSPWY peptide and demonstrated via MTT assay that both bare and the peptide-linked QDs exhibit low cytotoxicity. The HER2-mediated delivery of the peptide-linked QDs was confirmed by confocal microscopy. This study indicates that as engineered QDs can efficiently be used as fluorescent nanoprobes for selective labelling of HER2-positive SKBR3 cancer cells
