Quantum dot and Its nanocomposites : interactions with biosystems and biomedical applications

Abstract

Quantum dot (QD) has been studied as an effectively alternative or complementary tool to replace traditional organic dyes in biosensors, cell imaging and in vivo animal tracking. In spite of its various merits, the use of QDs as antimicrobial materials and the development of biocompatible QD-based nanocomposites for various biomedical applications remain great challenges. This PhD research project investigates the antimicrobial activity of CdTe QDs and its mechanism, the fabrication of biocompatible QD nanocomposites for cell imaging and the shape effects of specific designed QD nanocomposites on phagocytosis. The bactericidal activity and mechanism of CdTe QDs against Escherichia coli (E. coli) were investigated. The QDs effectively kill bacteria in a concentration-dependent manner. The QDs bind with bacteria and impair the functions of a cell’s anti-oxidative system, including down-regulations of antioxidative genes and decreases of antioxidative enzymes activities. The mechanism of the bactericidal activity of CdTe QDs involves QDs-bacteria association and a reactive oxygen species-mediated pathway. Besides the bactericidal effects, QD-induced cell growth inhibition effect and its photophysical mechanism were investigated. The QDs block cell division to inhibit the growth of bacteria. A photophysical mechanism involving a polypeptide or amino acid adsorption-mediated fluorescence and reactive oxygen species quenching process is elucidated. CdTe QDs have the potential to be formulated as a novel antimicrobial material with excellent optical properties.