Nanotechnology-enabled aptamer/G-quadruplex DNAzyme biosensors for food contaminant detection: nanoscale engineering, signal amplification strategies, and analytical applications.

Despite several advances in biosensor technology, reliable quantification in complex matrices remains challenging due to limitations in signal amplification, selectivity, and operational stability. The development of nanotechnology has played an important role in improving the performance of biosensors. Considerable attention has been paid to the integration of various nanomaterials and bioreceptors in the structure of sensing devices. DNA-based biosensors have provided promising alternatives to protein-based systems due to excellent chemical stability, ease of modification, and selectivity. Aptamers have served as highly specific biological elements, and G-quadruplex DNAzymes have enabled enzyme-mimicking catalytic signal amplification through the formation of G-quadruplexes. The integration of aptamers and G-quadruplex DNAzyme has been widely used to couple target recognition and a signal amplification strategy for selective detection of target analytes in complex matrices. However, critical challenges, such as limited catalytic activity, structural interaction between these two DNA-based components, and instability in complex matrices, still remain. Primarily, in the current review, we attempted to evaluate the design principles of aptamers and G-quadruplex DNAzyme, with a particular focus on structural mechanisms, signal amplification strategies, and their applications in the detection of four important classes of food contaminants, including mycotoxins, antibiotics, pathogenic bacteria, and heavy metals. In addition, we focused on future perspectives in the biosensing field for improving analytical performance and enabling next-generation approaches. Furthermore, the advantages and disadvantages of the developed platforms are also discussed.