Fluorescent Detection of Oral Pathogens by a Solid-Phase Immunoassay on PDMS

We have developed an array of sensors for the oral pathogen Streptococcus mutans (S. mutans) using an enzymelinked linked immunosorbent assay (ELISA) on a polydimethylsiloxane (PDMS) device. The model bacterial analyte, S. mutans, has been implicated in the initiation and progression of dental caries. The PDMS was modified with 3-aminopropyltriethoxysilance (APTS) and glutaraldehyde to covalently crosslink monoclonal anti-S. mutans immunoglobulin G (IgG) to the sensor surface. Successful IgG immobilization was verified by AFM and fluorescence imaging. Colloidal bacteria were captured on the sensor surface and labeled with immuno-active quantum dots (QDs), whose fluorescence was excited by an LED and detected by a CCD. The system was capable of detecting S. mutans concentrations as low as 6 10⁶cells/ml in a 20 μl sample. This work represents a stable foundation for the development of a chair side diagnostic system capable of specific and sensitive detection of pathogens directly from oral fluid.