Scenario-driven fluorescent probes for formaldehyde: From food safety testing to biomedical imaging.

Formaldehyde is ubiquitous in food-processing environments and in living systems, which causes irritation and potential toxicity, threatening human health and disturbing cellular homeostasis with excess exposure. Conventional analytical approaches, including chromatography, mass spectrometry and electrochemical assays, can offer high accuracy, yet they are often limited by strong instrument dependence, laborious sample pretreatment, and insufficient capability for rapid on-site screening and in situ analysis in complex matrices. Fluorescent probes have therefore emerged as promising alternatives because of their high sensitivity, fast response, visual readout, compatibility with bioimaging, and feasibility for portable integration. Nevertheless, major bottlenecks remain, including selectivity and anti-interference performance in real samples, response kinetics and operational stability, quantitative reliability, and biocompatibility. From an application-oriented perspective, recent fluorescent probes for formaldehyde are systematically summarized here, with an emphasis on their recognition reaction pathways and signal-output modes. Design principles and construction strategies are compared, and representative performances in food safety screening and bioanalytical imaging are critically discussed. These insights might provide a potential guidepost for rational probe engineering and multimodal integration, accelerating the development of robust, quantitative and field-deployable platforms for formaldehyde sensing. From an application-oriented perspective, this review systematically summarizes recently developed fluorescent probes for formaldehyde, with an emphasis on their recognition reaction pathways and signal-output modes.