A Rapid and Ultra-sensitive Biosensing Platform based on Tunable Dielectrophoresis for Robust POC Applications

With the ongoing pandemic, there have been increasing concerns recently regarding major public health issues such as abuse of organophosphorus compounds, pathogenic bacterial infections, and biosecurity in agricultural production. Biosensors have long been considered a kernel technology for next-generation diagnostic solutions to improve food safety and public health. Significant amounts of effort have been devoted to inventing novel sensing mechanisms, modifying their designs, improving their performance, and extending their application scopes. However, the reliability and selectivity of most biosensors still have much to be desired, which holds back the development and commercialization of biosensors, especially for on-site and point-of-care (POC) usages. Herein, we introduce an innovative two-phase sensing strategy based on tunable AC electrokinetics and capacitive sensing. By dividing the detection process into a sensitivity-priority step and a selectivity-priority step, the specificity and sensitivity of a biosensor can be significantly improved. A capacitive POC aptasensor is fabricated for the implementation of the 2-phase detection and a quasi-single-cell level detection of limit together with an excellent selectivity is achieved simultaneously. The sensor is capable of handling real-world clinic samples without sophisticated pretreatment. Just after a simple one-step dilution, the developed sensor can detect bacteria no less than 2~3 bacteria/10 µL in raw milk samples within 100 s. Alongside whole bacteria detection, the biosensor can also detect endotoxin, the lipopolysaccharide, in bovine serum samples, with a limit of detection of 10 pg/mL. The biosensor is low-cost and easy to use. This work not only demonstrates a biosensor with significant advantages in sensitivity, selectivity and assay time but also opens up a new horizon for further research of all affinity-based biosensors.