A MORE CONVENIENT ROUTE TO ANTIBODY IMMOBILIZATION ON GLASS SURFACES
Authors:Christopher Borcuk, Kyle Cole, Sean Nguyen
Mentor:Ertan Salik, Associate Professor of Physics, Cal Poly Pomona
Unlabeled optical biosensors can give rapid response when binding occurs between the specific recognition molecules (e.g. antibodies) and the target proteins. Many optical biosensors use glass surfaces, and an important part of sensor preparation is the covalent immobilization of antibodies on the surface. This step is usually a lengthy process, and requires numerous reagents. In our experiments with tapered fiber optic biosensors, we first adopted a protocol  that took at least 8 hours to complete, required harsh acids and bases, elevated temperatures, and the immobilization efficiency was sensitive to solution pH values in multiple steps. We modified these steps and used alternate reagents, which reduced the time required for the entire protocol to less than 4 hours. In the new protocol, first the sensor is bound with hydroxyl groups using plasma treatment. These hydroxyl groups allow (3-Aminopropyl)triethoxysilane (APTES) to bind, which in turn allows for the adherence of the crosslinker, bis(sulfosuccinimidyl)suberate (BS3). Finally the antibodies, in our case Immunoglobulin G (IgG), may attach to the crosslinker and coat the sensor. The alternate protocol we tested does not require any harsh acid/base treatment but rather a quick treatment with a high frequency generator. Nor does it require elevated temperatures, or special equipment, such as a precise pH meter, due to us using a pure ethanol solvent during the APTES step, rather than the carefully monitored acidic/heated water solvent we used previously. In our multiple tests using tapered fiber optic biosensors, we measured stronger response as compared to our results with the previous protocol.