Ultrafine biocompatible chitosan nanoparticles encapsulating multi-coloured quantum dots for bioapplications.

Owing to their excellent optical properties, luminescent semi-conductor quantum dots (QDs) have proven themselves to be an attractive choice in biological labeling. However, there exists the concern of cytotoxicity in using these heavy metal-based nanoparticles as molecular probes. In order to improve their general biocompatibility, CdSe/ZnS QDS are encapsulated in the natural biopolymer chitosan, forming monodisperse chitosan nanoparticles in the range of 60 nm in 1 single step. This straight forward method also allows for the synthesis of chitosan nanoparticles encapsulating multi-coloured QDs. In vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity tests on primary myoblast cells suggest that the cytotoxicity of the QDs is greatly reduced after chitosan encapsulation. At the same time, fluorescence confocal microscopy studies also prove that nanoparticles are small enough to be internalized into the myoblast cells. Our results show the ease of synthesizing biocompatible, nanometer-sized chitosan nanoparticles encapsulating QDs and their promise in biological applications such as ultra-sensitive bio-detection and labeling of biomolecules.