Immunoglobulin G Recognizing Polymer Membrane with Protein A-bearing Staphylococcus aureus Cells

Protein A, a cell wall polypeptide (MW=42000) elaborated by many strains of Staphylococcus aureus, binds the Fc portion of certain types of immunoglobulin G (IgG). Protein A-bearing St. aureus cells completely retain the binding properties of protein A. Because of the convenient handling of bacteria, staphylococci-bearing protein A was covalently attached to a polymer membrane. The present study demonstrated that the Staphyrococcus aureus cell-bound polymer membrane is capable of recognizing specifically IgG. The membrane was then coupled with a Clark-type oxygen electrode to construct the biosensing system for IgG molecules in a solution. Catalase-labeled IgG was put in competition with IgG to be determined against the polymer membrane-bound staphylococci. The catalaselabeled IgG complexed on the membrane was assayed for enzyme activity to decompose H2O2to O2 with the oxygen electrode. IgG was determined in the concentration ranging from lx 10-7 to 1 x10-5 g·ml-1. The Staphylococcus aureus-bound membrane seems feasible in recognizing and sensing a trace amount of IgG in a solution.