LASER & PHOTONICS REVIEWS R

Abstract Tissue optical clearing technique provides a prospec-tive solution for the application of advanced optical methods in life sciences. This paper gives a review of recent developments in tissue optical clearing techniques. The physical, molecular and physiological mechanisms of tissue optical clearing are overviewed and discussed. Various methods for enhancing pen-etration of optical-clearing agents into tissue, such as physical methods, chemical-penetration enhancers and combination of physical and chemical methods are introduced. Combining the tissue optical clearing technique with advanced microscopy im-age or labeling technique, applications for 3D microstructure of whole tissues such as brain and central nervous system with unprecedented resolution are demonstrated. Moreover, the dif-ference in diffusion and/or clearing ability of selected agents in healthy versus pathological tissues can provide a highly sensi-tive indicator of the tissue health/pathology condition. Finally, recent advances in optical clearing of soft or hard tissue for in vivo imaging and phototherapy are introduced. Recent progress in tissue optical clearing Dan Zhu1,2,∗, Kirill V. Larin3,4, Qingming Luo1,2, and Valery V. Tuchin4,5,6,∗ 1