Fluorophore-labeled molecule recognition peptide: Static quenching in metal-organic frameworks for ultrasensitive ratiometric fluorescence biosensing of ochratoxin a in grain products

Ochratoxin A (OTA) is a notable mycotoxin prevalent in grain products. In this paper, we computationally designed a high-affinity molecular recognition peptide (MRP, KQRLKCASLQKFGERAF) targeted at OTA according to structural analysis and molecular dynamics with a dissociation constant (K_d) of 12.18 ± 6.59 nM. A novel fluorescent probe, RhB-MRP (MRP-lysine-rhodamine B), was synthesized to convert the binding of MRP and OTA into optical signals. Based on RhB-MRP, we constructed a ratiometric fluorescence biosensor utilizing the classic blue fluorescent MOFs (NH₂-MIL-88(Fe)). The fluorescence of NH₂-MIL-88(Fe) was strongly quenched by RhB-MRP, which formed a ground state complex leading to static quenching. The developed biosensor exhibited exceptional sensitivity with detection limit of 0.32 pg mL⁻¹ and rapid response time (11 min). A good recovery rate of 87.3–114.1 % was achieved in grain products. Although there are currently few MRPs that can specifically recognize small molecules, this highly sensitive and selective biosensor demonstrates the great potential of MRPs for detecting other molecules.