A multifunctional probe for optical and electrochemical detection of hydrogen sulfide and real-time selective fungal imaging

This study reports the synthesis of 2-hydroxy-N-(6-nitro-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)benzamide (SNN), designed for the selective detection of hydrogen sulfide (H2S) and real-time imaging of Candida albicans. The probe was synthesized via imidation of 4-nitronaphthalic anhydride with salicyl hydrazide, leveraging the environmentally responsive fluorescence properties of naphthalimide derivatives. SNN demonstrated dual-mode functionality, enabling both optical and electrochemical sensing of H2S across a range of pH conditions, thereby providing insights into sulfur chemistry. Remarkably, SNN allowed direct wet-mount imaging of C. albicans without the need for prolonged incubation, producing high-contrast fluorescence with minimal background noise via endogenous H2S activation. It showed selective nuclear localization in C. albicans but did not facilitate fluorescence imaging in Aspergillus niger. Additionally, SNN was used for effective visualization of other fungi associated with bread spoilage, highlighting its promise as a versatile tool for fungal diagnostics and food safety applications. Moreover, the H2S-specific imaging was validated through incubation studies using 2-(aminooxy)acetic acid hydrochloride, a selective inhibitor of the cystathionine beta-synthase enzyme involved in the production of H2S and the metabolism of homocysteine.