Self-assembled programmable DNA nanoflower for in situ synthesis of gold nanoclusters and integration with Mn-MOF to sensitively detect AFB1

Abstract

Aflatoxin B1 (AFB1) is a potent carcinogenic mycotoxin that is susceptible to contamination of agricultural products and can cause chronic effects on humans. Thus, the establishment of highly sensitive and efficient AFB1 detection method is crucial to ensure food safety and human health. Here, we developed programmable DNA nanoflowers (DNF) with dual functionality for in situ synthesis of gold nanoclusters (AuNCs) and DNA recognition. The AuNCs synthesized using DNF as template (DNF@AuNCs) possessed good fluorescence properties and stability, and were applied as stable signal probes for constructing sensitive aptasensor. DNF completed the transition from bud to blooming flower, shifting its morphology from 3D to 2D structure during the in-situ synthesis of AuNCs, leading to the exposure of more template sequences. The designed hairpins DNA were subsequently used for local catalytic hairpin assembly (LCHA) on the surface of Mn-MOF. A substantial number of amplified products H2-H3 was obtained by conformational conversion, which was complementary to the sequence of DNF. Upon hybridization of H2-H3 with DNF@AuNCs, the fluorescence of AuNCs is quenched by adjacent guanine-rich (G-rich) base at the 3′ end of H3. The switch of LCHA is controlled by the conformational change of H1 which contains the AFB1 aptamer sequence, thus enabling precise detection of AFB1. The DNF@AuNCs and Mn-MOF-based fluorescence aptasensor achieved a detection limit of 7 pg/mL for AFB1, with a detection range of 0.01–200 ng/mL. The aptasensor also exhibits high selectivity, reproducibility, and stability, making it prospective for food safety monitoring.