Fabrication of a high-performance photoelectrochemical aptamer sensor based on Er-MOF nanoballs functionalized with ionic liquid and gold nanoparticles for aflatoxin B1 detection

One of the most dangerous mycotoxins is Aflatoxin B1 (AFB1) that is commonly found in food. Thus, AFB1 has been considered as a serious food safety concern. Herein, using Er-MOF nanoballs assembled with gold nanoparticles (AuNPs) as photoactive elements, a photoelectrochemical aptasensor with high analytical performance was developed for sensing AFB1. Er-MOFs nanoballs were prepared by using ionic liquid as a ligand and Er3+ as a metal center through a solvothermal method. Chloroauric acid was reduced in-situ onto Er-MOF nanoballs to form [email protected] nanocomposites. AuNPs can effectively enhance the photocurrent of Er-MOF nanoballs attributed to their excellent conductivity and local surface plasma resonance effect. In addition, they can provide active sites for immobilizing more biorecognition elements that can further enhance the sensing performance. Through self-assembling reaction, thiol-functionalized hairpin DNA (hDNA) was immobilized onto an [email protected] interface to construct a photoelectrochemical biosensing platform. As the AFB1 aptamers labeled with gold nanoparticles (AuNPs-Apt) were selectively recognized, the photocurrent response can be further amplified. Due to the high affinity of AFB1 and its aptamer (Apt), when Apt is reacted with AFB1, it causes AuNPs-Apt detaching from the PEC aptasensing interface, and thus a reduced photocurrent response is generated. Under optimized conditions, the changes of photocurrent before and after recognition of AFB1 exhibits a linear response from 0.005 to 10.0 ng mL−1. In addition, the limit of detection obtained was 19.6 fg mL−1. This PEC aptasensor provides relatively high selectivity, reproducibility and accuracy in the determination of AFB1 in real corn samples.