Dual-Mode Microcantilever Sensor with Surface-Attached Nanofiber Membrane for Rapid and Highly Sensitive Detection of Ractopamine.

In light of the escalating demand for highly sensitive and reliable detection methods for ractopamine (RAC) residues in food safety, this study introduces an innovative dual-mode immunosensor. This sensor is constructed from a PZT microcantilever integrated with CTFx@FTP composite nanoparticles and a PANI@rGO-COOH nanofiber membrane. It is capable of simultaneously generating electrical signals and cantilever vibration-amplitude signals, thus facilitating quantitative detection of RAC. B-site Fe incorporation was employed to regulate mixed-valence states and oxygen-vacancy-related defects in CaTi1-xFexO3-σ, while FeTCPP-mediated π-d electronic coupling and the π-conjugated PANI@rGO-COOH network were integrated to construct a composite sensing interface that facilitates charge transfer and electromechanical transduction, enabling specific immunorecognition events to be converted into measurable dual-mode signals. At an Fe doping level of x = 0.20, the sensor demonstrates optimal interfacial transport characteristics, achieving a remarkably low limit of detection of 0.17 ng mL-1, alongside a wide detection range of 0.17 to 50 ng mL-1, and good linearity. The dual-mode signals exhibit good selectivity, storage stability, reproducibility, and repeatability. In spiked pig and bovine serum samples, recovery rates of 97-104% and consistency with ELISA results confirmed the applicability of the proposed sensor in complex biological matrices. The defect-engineering and interface-coupling-based electromechanical synergistic amplification strategy proposed in this study offers a promising pathway for the development of dual-mode electrical and mechanical immunosensors for small molecules. This approach holds significant potential in food safety monitoring.