Nature-inspired fungal fusarinine C-powered dual-mode fluorometric/colorimetric biosensing of fecal Helicobacter pylori with high-reliability

Abstract

Conventional diagnostic approaches for Helicobacter pylori lack sufficient sensitivity, accuracy, and flexibility, especially for low-density H. pylori infection. To overcome this limitation, we developed a highly reliable fluorometric/colorimetric dual-mode biosensing technique to detect minute quantities of H. pylori in human stool samples. Inspired by natural porphyrins, we discovered that the water-soluble fungal siderophore fusarinine C (FsC) emitted intense green fluorescence owing to intramolecular through-bond and intermolecular through-space conjugation, and turned reddish upon coordination with Fe3+. With FsC as an intrinsic fluorometric/colorimetric probe, a dual-mode biosensor was developed. It included an enrichment module of truncated H. pylori-specific-aptamer-modified superparamagnetic nanoparticles to capture H. pylori from samples, and a transduction module of alginate conjugated with FsC[Fe3+] and an optimized amount of FsC without Fe3+ to amplify the captured H. pylori to fluorescent and/or color signals. Remarkably, significantly increased sensitivity was achieved for this biosensor, with an actual limit of detection of 5 CFU/mL and single-cell-level detection resolution, as validated using laser-tweezer-sorted single H. pylori cells. Moreover, highly reliable dual-mode detection of low-density H. pylori (between 5 and 10 CFU/mL) was demonstrated. Using the colorimetric mode, a smartphone-biosensor platform for sensitive point-of-care testing of fecal H. pylori within 20 min was demonstrated, outperforming the clinical fecal antigen test strips; meanwhile, the fluorometric mode of the biosensor, owing to its greater sensitivity, can verify the colorimetric detection of minute H. pylori. This study first showcased a FsC-powered dual-mode biosensor for ultra-sensitive and accurate point-of-care detection of H. pylori with high reliability.