Capture−Release Activity-Based Sensing for Low-Perturbation Formaldehyde Imaging in Spinal Cord Injury

Abstract Formaldehyde (FA) is an endogenous reactive carbonyl metabolite involved in one-carbon metabolism, cellular signaling, and stress-associated pathology. Its measurement by activity-based sensing (ABS), however, can itself alter analyte availability because signal generation typically relies on an analyte-reactive chemical transformation that captures or consumes FA. Here, we report DPM, a capture−release ABS probe designed to reduce this measurement-induced analyte perturbation while providing a ratiometric near-infrared readout. Incorporation of a nucleophilic aliphatic amine and gem-dimethyl preorganization accelerates FA-responsive activation and improves chemical stability. The programmed reaction sequence was verified by chromatographic and spectroscopic analyses, while HMC reporter experiments, DNPH trapping, and [13C]FA isotope tracing demonstrated functional FA release after probe activation. Time-resolved intracellular LC−MS analysis in FA-preloaded cells showed no progressive decrease in the internal-standard-normalized FA signal during probe incubation. DPM further enables in vivo imaging of lesion-associated FA elevation in spinal cord injury (SCI) models and serves as a dynamic chemical reporter for evaluating Taraxerone treatment. This work establishes a kinetically optimized capture−release ABS strategy for FA measurement with reduced analyte perturbation and demonstrates its utility in disease-relevant imaging.