ABSTRACT
Kirill V. Larin University of Houston, Houston, TX 77204, USA, Institute of Optics and Biophotonics, Saratov State University, Saratov, 410012, Russia
Mohamad G. Ghosn University of Houston, Houston, TX 77204, USA Valery V. Tuchin Institute of Optics and Biophotonics, Saratov State University, Saratov, 410012, Russia, Institute of Precise Mechanics and Control of RAS, Saratov 410028, Russia
17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 17.2 Principles of OCT Functional Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447 17.3 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450 17.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452 17.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 460 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461
Noninvasive imaging, monitoring, and assessment of molecular transport in epithelial tissues are extremely important for many biomedical applications. For example, successful management of many devastating diseases (e.g., cancer, diabetic retinopathy, glaucoma, and different cardiovascular disorders) requires long-term treatment with drugs. In contrast to the traditional oral route, topical or local drug delivery through epithelial tissues (e.g., skin or cornea and sclera of the eye) is currently accepted as a preferred route for drug administration because the hepatic first pass effect of orally administered drugs and problems of the acidic environment and pulsed absorption in the stomach can be avoided and complications and side effects can be reduced. However, topical delivery of therapeutic agents to target tissues in effective concentrations remains a significant challenge due to low permeability of epithelial tissues and drug washout. Significant research effort is now devoted to the development of therapeutically effective topical formulations such as drug delivery systems (patches), gels, creams, ointments, lotions, as well as application of various diffusion enhancers. Successful developments of these formulations require advanced understanding of the kinetics of drug distribution in epithelial tissues for better manipulation and optimization of therapeutic processes and outcomes. This chapter describes recent progress made on the development of a noninvasive biosensor, based on optical coherence tomography (OCT) technique, for assessment of molecular and drug diffusion in epithelial tissues. High in-depth and transverse resolution (up to a few m) and high dynamic range (up to 120 dB) of the OCT allows sensitive and accurate real-time monitoring of the diffusion processes due to precise depth-resolved measurements of tissue optical properties at different layers.
