Label-free CRP detection using optical biosensor with one-step immobilization of antibody on nitrocellulose membrane

To assess the potential of using the MCLW sensor as a label-free optical biosensor system for clinical diagnosis, we evaluated the potential of detecting C-reactive protein (CRP) in a diluted real serum sample by using nitrocellulose as an adlayer. Nitrocellulose was coated on the MCLW sensor chip via spin coating and the CRP antibody was directly immobilized on the sensor surface by hydrophobic physical adsorption. Biosensing using the nitrocellulose surface is highly convenient and does not require any additional treatment for the immobilization of ligand. We optimized the condition for the deposition of nitrocellulose on the MCLW sensor chip with the goal of generating the largest signal difference of the sample against the control signal. In addition, label-free immunosensing of CRP was achieved using the nitrocellulose-coated MCLW sensor in real time. As a result, we were able to quantitatively detect CRP in a human serum within a concentration range of 0.1–10 μg/mL.