Homocysteine fluorescent probes: Sensing mechanisms and biological applications

Homocysteine, cysteine, and glutathione are small molecules containing thiols that have important functions in several physiological and pathological processes in living beings. Homocysteine specifically, is a biological thiol linked with various kinds of diseases and conditions, including cancer, atherothrombosis, Alzheimer's disease, osteoporosis, mental disorders, etc. Consequently, real-time detection of Homocysteine holds significant value in preserving normal physiological conditions and monitoring the advancement of specific diseases. Therefore, advancing the development of fluorescent probes and elucidating their sensing mechanisms for homocysteine is paramount. This review highlights recent developments in fluorescent probes designed for detecting Homocysteine and explores their sensing mechanisms based on recent literature. This review discusses the development and application of homocysteine-specific probes in biomedical imaging. Additionally, our focus extends to the design strategies employed in creating fluorescent probe compounds and their derivatives, encompassing compounds such as coumarin, nitrobenzofurazan, cyanine, pyronin, BODIPY, and metal complexes. We also delve into the sensing mechanisms involved in the reaction of homocysteine, including the Michael addition reaction, Aromatic substitution rearrangement, Nucleophilic substitution rearrangement, cyclization reactions, metal complexes, and other reaction mechanisms. Discussions in all sections revolved around specific sensing mechanisms tailored for homocysteine, focusing on emission, color changes, detection limits, and their practical applications.