An electrochemical study of the binding interaction between chitosan and MPA-CdSe QDs for the development of biocompatible theranostic nanoprobe

Abstract

The strength and stability of biopolymer-modified quantum dots (QDs) for designing biocompatible nanoprobes depends on the interaction between QDs and coating of interest. Hence, the quantitative determination of interaction parameters has a crucial role in their development. This paper focuses on an electrochemical approach to determine interaction and binding parameters between the chitosan and hydrophilic Mercaptopropionic acid (MPA) - CdSe QDs. MPA- CdSe QDs were synthesized by the hot injection method and characterized by several techniques. The cyclic voltammetry study revealed the reduction in oxidation peak current of redox solution with the addition of MPA- CdSe QDs (50 × 10−12 M to 350 × 10−12 M); however, the peak current was increased with the addition of chitosan (1 × 10−13 M to 50 × 10−13 M), without any change in the oxidation potential. This may be due to the interaction of the amino group of chitosan with the carboxylate group of MPA-CdSe QDs. The interaction was analyzed in terms of binding constant and no. of binding sites, which was 7.3 × 1015 L Mol−1and 1.3, respectively. Effect of scan rate on oxidation and reduction peak current confirms an irreversible electrode reaction. The interaction was further characterized with UV–Vis/Fluorescence spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Biocompatibility of developed nano-biocomposite further evaluated by standard cell viability assay using Adenocarcinoma human alveolar basal epithelial cell line (A549) and Chinese hamster cell line (V79). Confocal microscopic studies and Z stacking were also performed to explore the efficacy of chitosan-coated MPA-CdSe QDs as a fluorescent agent for cell imaging.