Patterned cellulose membrane for surface plasmon resonance measurement

We developed a patterned cellulose membrane for surface plasmon resonance (SPR) measurement that works as a capillary force inducing material to provide liquid flow and as a support for antibody immobilization. The patterned cellulose membrane was directly prepared on a gold film/glass substrate by using an approach based on the phase separation method. We optimized the preparation conditions to produce a cellulose membrane that was sufficiently porous and robust to use for the measurement of protein binding from an aqueous solution. A ready-to-use measurement chip was prepared by attaching a plastic body with inlet holes to a substrate on which the patterned cellulose membrane had been modified with antibody followed by blocking reagent. We realized sample flow and antigen detection using this measurement chip mounted on SPR instrument with a simple procedure, which consisted of injecting a raw sample solution into the inlet hole using a mechanical pipette. We selected human IgG as a model antigen that was certain not to be present in non-homogeneous milk, a model raw sample, to investigate the detection performance. The measurement chip successively detected 1.0 and 0.5 μg mL−1 IgG in the raw sample, which included many kinds of foreign substances without any sample pre-treatment. The whole immunoassay can be completed within 15 min, which is an acceptable period for an on-site test designed for agricultural and medical applications.