Researchers have designed a new type of luminescent quantum dot (QD) that could be used for making optical and biomedical devices1. This QD also inhibits the growth of disease-causing bacteria.
QDs have emerged as versatile nanomaterials because of their ability to absorb and emit light. Such QDs can be used to produce optical devices and fluorescent materials for biolabelling. However, most QDs are not biocompatible, being unstable in a physiological environment. In addition, QD preparation involves complex processes.
To overcome these drawbacks, the researchers developed a simple, two-step chemical process to make luminescent QDs. They prepared cadmium telluride QDs and then modified them with amino acid cysteine and chitosan, a biopolymer. Modified QD films became spherical in shape.
When these modified QD films were irradiated with visible light, they emitted blue light. This blue emission suggests that films made from such QDs will be useful for tracking cells and intracellular processes through biosignalling.
The QD films exhibited good swelling properties, which are essential for biomedical applications. The QD films also hindered the growth of three disease-causing bacteria — Staphylococcus aureus , Pseudomonas aurigionasa and Escherichia coli . Positively charged chitosan in the QD films bound to negatively charged bacterial membranes, causing the bacterial cells to rupture.
"Since chitosan used to be used as a DNA delivery system, prepared films can be used to study the processes of drug release and are useful for making devices for diagnostic purposes," says Pradip K. Dutta, a co-author of the study.
The authors of this work are from: Department of Chemistry, Motilal Nehru National Institute of Technology, Allahabad, and Department of Applied Chemistry, Birla Institute of Technology, Deoghar Campus, India.
