Fiber optic-SPR platform for fast and sensitive infliximab detection in serum of inflammatory bowel disease patients

Infliximab (IFX) is a therapeutic monoclonal antibody used for treating patients with inflammatory bowel disease (IBD). In order to improve therapeutic outcomes it is recommended to monitor IFX trough concentrations. Although ELISA is currently widely used for this purpose, this method is not suitable for single patient testing. In this paper we describe the development of a fast bioassay for determining IFX concentration in serum using an in-house developed fiber-optic surface plasmon resonance (FO-SPR) biosensor. Studies were first conducted to optimize covalent immobilization of the IFX-specific antibody on the sensor surface as well as to select an optimal blocking buffer for restraining the non-specific binding. In order to reach clinically relevant sensitivity for detecting IFX in patients' serum, the SPR signal was amplified by employing gold nanoparticles functionalized with another set of IFX specific antibodies. Using the optimized sandwich bioassay, calibration curves were made with series of IFX concentrations spiked in buffer and 100-fold diluted serum, reaching the limit of detection of 0.3 and 2.2ng/ml, respectively. The established bioassay was finally validated using five IFX treated IBD patients samples. Results from the FO-SPR platform were compared with an in-house developed, clinically validated ELISA resulting in excellent Pearson and intraclass correlation coefficient of 0.998 and 0.983, respectively. Furthermore, the assay time of the FO-SPR platform was significantly reduced compared to ELISA, demonstrating the potential of this platform to be used as a point-of-care diagnostic tool for improving therapeutic outcomes of IBD patients.