Fluorescent Quantum Dots, A Technological Marvel for Optical Bio-imaging: A Perspective on Associated In Vivo Toxicity

Abstract

Semiconductor quantum dots (QDs) are one of the technological wonders, known for their excellent photo-physical properties. The recent advances in nanotechnology have made QDs a robust and readily available fluorescent probe for both in vitro and in vivo bio-imaging research. QDs offer great advantages over traditional organic fluorescent dyes and present a number of beneficial characteristics such as size-tunable emission spectra, signal brightness, long life time, photostability, longer multiphoton cross sectioning capabilities and so on. Since its inception, it is being used as excellent fluorescent probe for a wide range of fluorescence microscopy technologies ranging from conventional epifluorescence, confocal, multiphoton to super-resolution microscopy for in vitro cell and tissue imaging to in vivo deep tissue and whole animal imaging. Hence, QDs have opened up plethora of exciting possibilities in bio-imaging research by enabling the researchers to probe and visualize the invisible biological processes from the whole organism level (macroscale) down to the cellular and in molecular level (nanoscale). Despite its enormous potential in bio-imaging, the involvement of heavy metals and the colloidal instability of QDs have led to legitimate concerns about toxicity. These issues have impeded the widespread adoption of QDs, especially in biomedical and in vivo bio-imaging. This chapter mainly focuses on the QD-based fluorescence bio-imaging applications from biological point of view and discuss relevant toxicity issues associated with using QDs in in vivo investigations.