An activatable photoacoustic probe for precise hydrazine detection in biological and environmental systems

Abstract

Hydrazine (N₂H₄) is a widely used raw material in pesticide manufacturing. Its high water solubility raises concerns because it can contaminate water sources and enter living organisms, leading to significant health issues. Current methods for detecting N2H4 face challenges such as complex procedures, poor biocompatibility, shallow penetration depth, inadequate temporal and spatial resolution. Photoacoustic (PA) imaging is an innovative biomedical imaging technique that detects sound waves rather than photons following light stimulation, enabling non-invasive visualization of biological processes within deep tissues at high spatial resolution. Here, we present an activatable PA probe (SH-ONS) for sensitive and selective detection of N₂H₄. This thoughtfully engineered probe incorporates a sulfur-substituted hemicyanine dye (SH-OH) as the PA reporter and features a 4-nitrobenzenesulphonate group as the recognition element. The designed probe SH-ONS achieves a low detection limit of 0.15 μM, a high PA signal-to-background ratio of 10.8-fold, and excellent selectivity in vitro. The probe was successfully applied to visualize exogenous N₂H₄ in living mice and to detect N₂H₄ in real environmental water samples, in both cases showing dose-dependent PA responses. This work demonstrates that SH-ONS is a robust and versatile tool for monitoring N₂H₄ across biological and environmental contexts.

HIGHLIGHTS • An activatable photoacoustic probe (SH-ONS) for N2H4 detection was developed. • SH-ONS achieved a 0.15 μM detection limit and a 10.8-fold activation fold. • SH-ONS achieved precise N2H4 detection in biological and environmental systems.