Abstract
Hydrogen sulfide (H(2)S), a well-known endogenous biological molecule, is an acidic, colorless gas notorious for its unpleasant rotten-egg smell. Unveiled as an endogenous signaling molecule, H(2)S demonstrates significant biological functionalities in various physio-pathological processes. Dysregulation of H(2)S expression in biological systems has been implicated in the development of numerous diseases, including cancer. Consequently, precisely sensing H(2)S in cells and organisms becomes crucial for understanding fundamental cellular functions. Fluorescent probes have become a potent tool for monitoring H(2)S biological activities within complex biological systems. While numerous reviews have explored H(2)S sensing and imaging, most have concentrated on exogenous and endogenous detection methods, emphasizing sensing mechanisms and construction. Notably, none have exclusively focused on endogenous H(2)S monitoring without introducing an external stimulator, which is essential for in vivo tracking of H(2)S in various pathologies and oncology. This review aims to fill this gap by summarizing fluorescent probes designed for detecting endogenous H(2)S without the addition of external stimulators, both in vitro and in vivo, from 2014 until 2024. By doing so, we aim to deepen readers' understanding of the biological role of H(2)S and provide them with essential biomedical background knowledge for developing H(2)S probes that can detect endogenous H(2)S without reliance on external stimuli.