Chemiluminescence Sensor Based on Composite Functional Nucleic Acid for Detection of Ochratoxin A in Wine

A peroxyoxalate chemiluminescence recovery system based on the interaction of N-doped graphene oxide nanosheets and an oligopeptide for ultra-sensitive and selective copper(II) ion detection

In this paper, a peroxyoxalate chemiluminescence (CL) recovery system based on the interaction of N-doped graphene oxide nanosheets (N-GONs) and an oligopeptide for copper(II) ion detection has been reported. N-GONs as an excellent CL enhancer are prepared by the hydrothermal method using citric acid and ammonia, and the morphology and structure are characterized in detail by TEM, XPS, FT-IR and UV/vis, etc. In the bis(2,4,6-trichlorophenyl)oxalate (TCPO) and hydrogen peroxide (TCPO + H₂O₂) CL reaction system, the addition of N-GONs gives a remarkable CL emission, which can be quenched by an oligopeptide composed of ten amino acid residues due to the interaction between the N-GON plane and the oligopeptide strand. While in the presence of copper(II) ion, the quenched CL is recovered gradually along with the addition of copper(II) ion in the system. Based on the above CL reactions, a TCPO + H₂O₂ + N-GONs + oligopeptide CL system is constructed, achieving an ultra-sensitive and selective detection of copper(II) ion in environmental water samples. The detection limit of this method is as low as 0.2 pmol L^-1, which is at least three orders of magnitude lower than other CL methods. The N-GONs and oligopeptide involved in the CL system are environmentally friendly, making it possess potential in the detection of copper(II) ion in environmental water samples.

Design of a Quencher-Free Fluorescent Aptasensor for Ochratoxin A Detection in Red Wine Based on the Guanine-Quenching Ability

This study describes a quencher-free fluorescent aptasensor for ochratoxin A (OTA) detection using the specific quenching ability of guanine for fluorescein (FAM) molecules based on photo-induced electron transfer (PIET). In this strategy, OTA is detected by monitoring the fluorescence change induced by the conformational change of the aptamer after target binding. A new shorter OTA aptamer compromising three guanine bases at the 5' end was used in this study. This new aptamer, named G3-OTAapt1-FAM (F1), was labeled with FAM on the 3' end as a fluorophore. In order to increase the binding affinity of the aptamer and OTA, G3-OTAapt2-FAM (F2) was designed; this added a pair of complementary bases at the end compared with F1. To prevent the strong self-quenching of F2, a complementary chain, A13, was added. Although the F1 aptasensor was simpler to implement, the sensitivity of the F2 aptasensor with A13 was better than that of F1. The proposed F1 and F2 sensors can detect OTA with a concentration as low as 0.69 nmol/L and 0.36 nmol/L, respectively.