摘要
The growth of gold nanobipyramids (AuNBPs) provides a superior colorimetric quantification method for point-of-care testing due to their superior growth uniformity, high-resolution multicolor response, and excellent seed storage stability. However, conventional growth methods face significant limitations in sensing applications due to their reliance on a single reductant and stringent acidic conditions. This study systematically investigated the reductant mechanism in AuNBP growth, revealing that the pH-regulated redox potential is crucial for achieving anisotropic AuNBP growth. By employing nine different reductants, the growth pH was expanded from 1.5 to 8.5. Notably, dihydroxybenzene-mediated systems exhibited a slender morphology, reduced reductant consumption, enhanced stability, and comparable analytical performance compared to the conventional growth system. Among these systems, the hydroquinone (HQ)-mediated system was integrated with horseradish peroxidase (HRP)-catalyzed reactions in a pH-compatible manner. By incorporating this integrated system into a commercial HRP immunoassay, a novel multicolor immunosensor was developed for thyroglobulin (Tg) detection. This immunosensor exhibited a distinct nine-color gradient across a ten-fold Tg concentration range (0.1-1.3 ng/mL), achieving a visual detection limit of 0.1 ng/mL and an instrumental detection limit of 29 pg/mL. It accurately detected Tg in human serum with good recoveries of 94.1%-104.8% and signal stability for six hours. The results correlated well with the commercial immunoassay while offering superior visual readout for point-of-care settings. These findings validate the applicability of the HQ-mediated system in converting conventional single-color HRP immunoassays to multicolor immunosensors. Furthermore, expanding reductant selection and pH adaptability in AuNBP growth offers more possibilities for developing versatile pH-flexible multicolor sensors.
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