Using an oxidized porous silicon interferometer for determination of relative protein binding affinity through non-covalent capture probe immobilization

An oxidized porous Si interferometer was used to measure binding of immunoglobulin G (IgG) to an immobilized protein A capture probe. Protein A was non‐covalently immobilized on a thermally oxidized porous Si (PSiO2) sample and exposed to IgG originating from different species. The resulting order of IgG affinity toward the protein A‐coated surface (human > rabbit ≫ sheep IgG) agrees with previous inhibition studies for protein A/IgG binding. No signal change was observed when a protein A coated sample was exposed to bovine serum albumin (BSA), demonstrating that the adsorbed sensing layer sufficiently coats the PSiO2 surface to prevent non‐specific binding. This strategy is excellent for qualitative measurements of protein binding affinity because it is label‐free, requires minimal sample preparation, and can be implemented using an inexpensive CCD‐based spectrometer coupled to a tungsten lamp. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)