A novel controlled release system-based homogeneous immunoassay protocol for SCCA using magnetic mesoporous Fe3O4 as a nanocontainer and aminated polystyrene microspheres as a molecular gate

A novel controlled release system-based homogeneous immunoassay protocol (CRSHIP) was developed for the detection of squamous cell carcinoma antigen (SCCA). The positively charged aminated polystyrene microsphere (APSM) used as molecular gate was capped on the pores of the negatively charged antibody-conjugated magnetic mesoporous Fe3O4 (Ab-Fe3O4) by electrostatic interaction to achieve encapsulation of toluidine blue (TB). With the addition of SCCA, APSM was replaced from Ab-Fe3O4 due to the specific binding of antibody to antigen, and then the trapped TB was released from the pores. The released TB could be detected by square wave voltammetry and the signal could be correlated with the amount of SCCA. The developed CRSHIP displayed a high current response, a relatively wide linear range (from 0.001 to 4.0 ng/mL) and a low detection limit (0.33 pg/mL) for the detection of SCCA. The method showed high selectivity and good reproducibility. In addition, the CRSHIP provided a simple, fast and sensitive approach for the detection of SCCA in serum sample.