Engineering Nanostructured Porous SiO2 Surfaces for Bacteria Detection via “Direct Cell Capture”

摘要

An optical label-free biosensing platform fornbacteria detection (Escherichia coli K12 as a model system)nbased on nanostructured oxidized porous silicon (PSiO2) isnintroduced. The biosensor is designed to directly capture thentarget bacteria cells on its surface with no prior sample processingn(such as cell lysis). The optical reflectivity spectrum of thenPSiO2 nanostructure displays Fabryu0001Pu0001erot fringes characteristicnof thin-film interference, enabling direct, real-time observationnof bacteria attachment within minutes. The PSiO2 opticalnnanostructure is synthesized and used as the optical transducernelement. The porous surface is conjugated with specific monoclonal antibodies (immunoglobulin G's) to provide the activencomponent of the biosensor. The immobilization of the antibodies onto the biosensor system is confirmed by attenuated totalnreflectance Fourier transform infrared spectroscopy, fluorescent labeling experiments, and refractive interferometric Fourierntransform spectroscopy. We show that the immobilized antibodies maintain their immunoactivity and specificity when attached tonthe sensor surface. Exposure of these nanostructures to the target bacteria results in “direct cell capture” onto the biosensor surface.nThese specific binding events induce predictable changes in the thin-film optical interference spectrum of the biosensor. Ournpreliminary studies demonstrate the applicability of these biosensors for the detection of low bacterial concentrations. The currentndetection limit of E. coli K12 bacteria is 104 cells/mL within several minutes.