Optical Contrast Agents for Imaging, Biosensing, and Therapy

Abstract

Over the past few decades, there has been a wide variety of optical contrast agents developed for various imaging, biosensing, and therapeutic applications. In the move toward clinical translation, research efforts have been heavily focused on improving various aspects of such contrast agents, such as sensitivity, specificity, toxicity, water solubility, and targeting efficacy. In this review, we focus on some of the notable optical contrast agents typically employed for imaging, biosensing, and therapy. The first section provides a brief discussion on the typical organic dyes used in fluorescence imaging, with a specific focus on indocyanine green, which is an important near‐infrared dye widely used for clinical applications. The second section focuses on specially designed nanotags used in surface‐enhanced Raman spectroscopy, a highly sensitive molecular biosensing technique with multiplexing capabilities. Multifunctional theranostic nanosensitizers concurrently used in imaging and therapy are covered in the subsequent sections. In the conclusion section, perspectives on future directions for the development of novel optical contrast agents are briefly discussed.