Dual fluorophores embedded into zeolitic imidazolate framework-8 for ratiometric fluorescence monitoring of pH and histamine in seafood samples and bioimaging

Talanta. 2025 Jun 16:296:128476. doi: 10.1016/j.talanta.2025.128476. Online ahead of print.

Abstract

The accurate and dynamic monitoring of pH and histamine is essential for the assessment of the freshness of seafood and the diagnosis of early diseases. A ratiometric fluorescence nanoprobe GQDs/AuNCs@ZIF-8 is constructed via embedding gold nanoclusters (AuNCs) and adsorbing graphene quantum dots (GQDs) on zeolitic imidazolate framework-8 (ZIF-8) for detecting pH and histamine. Given the enrichment characteristics of ZIF-8, intramolecular movements of embedded AuNCs are limited and yield aggregation-induced emission, increasing the fluorescence by 5-fold compared to AuNCs. The GQDs/AuNCs@ZIF-8 nanoprobe exhibits a dual-emissive response from pH 9.5 to pH 4.5 by attracting pH-responsive GQDs with electrostatic effects. This results in a decreased emission at 580 nm due to the released AuNCs from acid-degraded ZIF-8 and an increased emission at 460 nm attributed to protonated GQDs. This can provide insight into the precise differentiation of cancerous cells from healthy cells. Moreover, alkaline histamine produced by food spoilage ulteriorly increases pH, the nanoprobe therefore realizes histamine determination from 20 to 240 μM with a detection limit of 7.49 μM. Interestingly, a smartphone-integrated histamine-responsive sensor exhibits a linearity of 20-220 μM through changed colors under UV lamps, achieving visual evaluation of seafood freshness. The GQDs/AuNCs@ZIF-8 nanoprobe establishes connections between cancer identification and seafood analysis, thereby offering guidance for the development of dual-emissive sensors to measure multiple-markers in diverse applications.

Keywords: Food freshness; Ratiometric fluorescence; Smartphone-integrated sensor; Zeolitic imidazolate framework-8; pH bioimaging.