Activity-based NIR fluorescent probes based on the versatile hemicyanine scaffold: design strategy, biomedical applications, and outlook

Abstract

In this review, we summarize the recent progress of activity-based NIR fluorescent probes based on the versatile hemicyanine scaffold for detection, bioimaging, and diagnosis and therapy of diseases.

Distinguishing cancer cells from normal cells with an organelle-targeted fluorescent marker

“…[26][27][28] Therefore, hemicyanine dyes have been widely used in the field of fluorescence imaging due to their excellent photophysical properties. 29 Hemicyanine dyes with an oxazolo [4,5-b]pyridine unit as the basic skeleton have the characteristics of excellent photostability, good biocompatibility, and long retention time in organelles. 30,31 The nitrogen atom on the pyridine ring of the oxazolo [4,5-b]pyridine unit was preferentially alkylated, 32 which redshifted the fluorescence emission wavelength of the structure.…”

Single-molecule photosensitizers for NIR-II fluorescence and photoacoustic imaging guided precise anticancer phototherapy

“…[5][6] PTT is oxygen-independent and induces light-to-heat conversion to cause tumor cells death through non-radiative internal conversion (IC) to the ground state (S 0 ). [7][8] However, the unavoidable oxygen consumption behavior for PDT and the suboptimal photothermal conversion efficiency for PTT make it impossible to effectively kill cancer cells via single phototherapy mode. 3,[9][10] Thus, developing combined PDT and PTT in a single molecule PS (sm-PS) can not only maximize the photon utilization, realizing 1 + 1 > 2 effect, [11][12] but also overcome the complex tumor microenvironment and enhance the curative effect to tumor.…”

Novel Lysosome-Targeting Fluorescence Off-On Photosensitizer for Near-Infrared Hypoxia Imaging and Photodynamic Therapy In Vitro and In Vivo

“…Additionally, PSs generally possess certain fluorescence-emitting abilities and can facilitate antitumor effects and image-guided therapy during PDT [ 4 , 5 ]. However, the fluorescence of PS is “always-on”, resulting in low signal-to-noise ratios and poor imaging qualities [ 6 , 7 , 8 ]. Moreover, PS-generated ROS exhibit a short life (0.03–0.18 ms) and limited distance of action (0.01–0.02 μm) [ 9 , 10 , 11 ].…”