Entropy-driven DNA nanomachine with magnetic assistance manipulating the aggregation of Au nanoparticles for label-free photothermal Aptasensing

Photothermal sensing has attracted increasing attention as a fast and portable detection method. However, photothermal sensors with excellent comprehensive performance still face challenges. Herein, a unique photothermal biosensor for bisphenol A as a model target is successfully constructed based on aptamer recognition coupled with the programmable entropy-driven DNA nanomachine cascaded strand displacement manipulating the aggregation of gold nanoparticles. In this protocol, the exposed bases of two DNA probes released from the DNA amplification network can anchor gold nanoparticles by van der Waals attraction. This allows gold nanoparticles to resist aggregation induced by a certain concentration of sodium chloride. Based on this exclusive mechanism, target-induced visual detection can be achieved by reading temperature changes. The two probes that are fully utilized to improve the atomic economy of the reaction and enhance the detection sensitivity. Also, label-free gold nanoparticles save time in the fabrication of the photothermal sensor. Moreover, visualized photothermal sensors with multi-color gradients enable self-verification of detection results, increasing sensor reliability. In particular, the splitting mode of magnetic-assisted extraction gives the designed photothermal sensor excellent specificity, which can meet the needs of real sample detection with high background noise. Additionally, this programmable and robust photothermal sensor has advantages of portability, replicability, rapid response, and simple operation.