Pressure-Based Bioassay Perceived by a Flexible Pressure Sensor with Synergistic Enhancement of the Photothermal Effect

An effective signal amplification strategy based on temperature-amplification synergistic pressure was designed for the sensitive detection of carcinoembryonic antigen (CEA) by using a noncontact point-of-care testing (POCT) aptasensor with a flexible pressure sensor based on a poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS)-modified sponge (PEDOT:PSS-sponge). In the biological recognition system, target analyte triggered the release of platinum nanoparticle-labeled complementary DNA (Pt–cDNA) from CEA aptamer-conjugated magnetic beads. On the basis of the unique characteristics of platinum nanoparticles (e.g., catalytic ability for H₂O₂ decomposition, peroxidase-like catalytic activity, and photothermal characteristics), the platinum nanoparticles (PtNPs) could not only catalyze hydrogen peroxide (H₂O₂) to produce a large amount of oxygen (O₂) but could also assist the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to a photothermal agent ox-TMB with the increasing temperature. Under 808 nm near-infrared (NIR) laser irradiation, an increase in the pressure and temperature occurred simultaneously in the closed detection cell. Meanwhile, the increasing temperature could be helpful for further increasing the pressure. The flexible pressure sensor was compressed in a closed system to cause a decrease in contact resistance, thereby establishing a correlation between the concentration and the resistance-readable analysis. Under optimum conditions, the dynamic detection range of this detection strategy for target CEA was between 0.2 and 80 ng mL^–1, and the limit of detection (LOD) was 0.15 ng mL^–1. Overall, the signal amplification strategy of temperature coordination provides possibilities for the future development of sensitive and portable POCT protocols.