CdTe quantum dots linked to Glutathione as a bridge for protein crosslinking

Abstract

We have optimized a synthetic method for the preparation of water soluble CdTe quantum dots (QDs), capped with glutathione (GSH) molecules, chemically bound to the nanoparticle surface (GSH-CdTe QDs). These QDs have been prepared by a co-precipitation reaction, in the presence of GSH. Modulating the temperature (from 90 to 145 °C) and the heating time (from 1 to 9 hours) we have obtained QDs of different sizes with a narrow size distribution, high water solubility and a fluorescent emission of a relatively high quantum yield (QY). Absorption and position of the fluorescent emission band show a strong dependence on QD size. The percentage of GSH linked to the QD surface has been estimated from chemical analysis and confirmed by thermogravimetry. The capping using this peptide, via the thiol group, converts these QDs in powerful tools as biomarkers for selective, fast and sensitive imaging in Biomedicine. The ability of these QDs to be biofunctionalized with a protein (a fundamental step for their use as biological probes) has been demonstrated. Surface functionalization of QDs is the fundamental aspect in the design of QDs for biomedical applications. In this work, the GSH-CdTe QDs have been efficiently bioconjugated with a protein extract from Dermatophagoides pteronyssinus. We have demonstrated that the GSH capping is a valuable means for subsequent protein crosslinking. Based on our results, we can conclude that proteins from Dermatophagoides pteronyssinus can be linked to GSH-CdTe QDs terminal groups. These results reveal that these GSH-capped QD probes, with high fluorescent intensity and a well functionalized surface that can be crosslinked to proteins, can have potential applications in targeted cell imaging.