Lysozyme placed on the SiO2 surfaces that have previously been derivatized with C-18 coating will capture both Escherichia coli and Listeria monocytogenes cells front PBS buffer at pH 7.2. This phenomenon is of significance for the design and fabrication of protein biochips that are designed to capture bacteria from buffer or water so that these can be further interrogated with respect to possible pathogenicity. Fluorescent microscopy shows that two types of bacteria (gram-negative E. coli and gram-positive Listeria spp.) will be adsorbed by lysozyme placed on the surface of the biochip but that strong adsorption of the bacteria is reduced but not eliminated when Tween 20 is present (at 0.5%) in the PBS buffer in which the cells are suspended. In comparison, Tween 20 and Bovine Serum Albumin (BSA) almost completely block adsorption of these bacteria on C-18 coated surfaces. The combination of a lysozyme surface with Tween 20 gives a greater degree of adsorption of L. monocytogenes than E. coli, and hence suggests selectivity for the more hydrophobic E. coli may be reduced by the Tween 20. This paper presents protocols for preparing protein-coated, SiO2 surfaces and the effect of buffer containing Tween 20 on adsorption of bacteria by SiO2 surfaces coated with C-18 to which BSA, lysozyme or C11E9 antibody is immobilized at pH 7.2 and ambient temperature. (C) 2003 Elsevier Inc. All rights reserved.