Cytocompatible Fluorescent Quantum Dot/PEG-Chitosan Bioconjugates for Nanomedicine Applications

In this study, novel nanobioconjugates based on quantum dots and a PEGylated chitosan derivative (PEG-CHI) have been designed and synthesised by a single-step aqueous route at room temperature. Chitosan was chemically modified by PEGylation aiming to significantly improve its water solubility and used as the capping ligand in the preparation of CdS quantum dot (QD) colloidal systems. UV/Vis and photoluminescence spectroscopy, transmission electron microscopy, dynamic light scattering, and the zeta potential were used to characterise the biopolymer-capped semi-conductor nanocrystals and their relative stability. The results clearly demonstrated that the PEG-CHI derivative is remarkably effective in nucleating and stabilising ultra-small colloidal CdS QDs in aqueous suspensions under acidic, neutral and alkaline media with an average size of approximately 2.0-3.0 nm and simultaneously showing luminescent activity in the visible range. In addition, the results of cell viability analysis in vitro using two cell cultures based on MTT bioassays demonstrated no cytotoxicity of the CdS QD/PEG-chitosan bioconjugates. Thus, based on these findings, it can be envisioned that these bioconjugates have potential use as biocompatible fluorescent biomarkers for nanomedicine applications.