Chapter 21 - Quantum Dots for Traceable Therapeutic Delivery

Abstract

Photoluminescent semiconductor nanocrystals, or quantum dots (QDs), hold promise as contrast agents for the diagnosis and characterization of disease using optical imaging. Yet, the diagnostic capabilities of a QD can be extended by coupling therapeutic molecules to its surface to form a theranostic QD. Theranostic QDs act as nanoscale therapeutic delivery vehicles (NDVs), transporting therapeutic molecules selectively to their site of action, while avoiding their interaction with sensitive healthy tissues and their degradation or modification within a biological environment. The optical contrast of the nanocrystal core allows the trafficking and localization of the construct, as well as the dynamics of therapeutic release, to be monitored in a biological environment. By monitoring the therapeutic delivery process, barriers preventing effective therapeutic delivery can be identified and overcome. While theranostic QDs have demonstrated potential in proof-of-concept applications using cultured cells and small animal models, concern surrounding the toxicity of the semiconductor core has prevented their clinical translation. Engineering total body clearance or replacing the semiconductor core with a biocompatible and/or biodegradable nanomaterial prior to clinical translation may facilitate the eventual application of theranostic QDs in human patients. Even if theranostic QDs are never applied clinically, they will still be useful for elucidating the fundamental mechanisms by which NDVs interact with biological systems and in establishing structure-activity relationships to guide NDV design. This chapter explores the design, synthesis, and application of QDs for traceable therapeutic delivery using optical imaging. Emphasis is placed on the delivery of anticancer therapeutics including chemotherapeutics and small interfering RNA.