Abstract
Supplemental Material
Binding of pure IgG to porous silicon wafers was monitored by atomic force microscopy (Supplemental Figure 1). Continuous porous layers were formed on silicon wafers by electrochemical etch using the same parameters described for silicon microparticles. The wafers were oxidized using piranha solution and treated with 0.5% APTES for 2 hours. IgG was introduced at 0.4 mg/mL for 60 minutes at 4°C, followed by washing in PBS. The surface of the wafer was evaluated using a Veeco Nanoscope III (Digital Instruments) in tapping mode in air using TESP (NanoWorld, Switzerland) cantilevers (fo = 320 kHz, k = 42 N/m). Abundant IgG was bound to both the anionic, oxidized surface and the cationic, APTES-modified surface.
AFM height profiles for IgG-bound silicon wafers are presented in Supplemental Figure 2. Height profiles for lines indicated in the height images show higher amplitude for IgG-bound, APTES-modified wafers, compared to oxidized wafers. As an example, the horizontal distance between the rise and fall of individual peaks is shown to be 18.32 and 44.49 nm for oxidized and APTES-treated silicon wafers, respectively, supporting different presentations of IgG on the silicon surface.
Porous silicon wafers were oxidized and then incubated with either IgG (0.4 mg/mL) or APTES (2%, 2 hours) followed by IgG. Atomic force micrographs show the three-dimensional structure of treated wafers.
AFM height profiles of the surface of oxidized or APTES-modified porous silicon wafers following treatment with 0.4 mL/mL IgG.
Unlabeled IgG binding to microparticles alters zeta potential and enhances binding by a phycoerythrin (PE)-labeled secondary antibody. A, Alteration of microparticle zeta potential following incubation with 2 concentrations of unlabeled IgG. B, Microparticle binding by phycoerythrin-labeled secondary IgG before and after exposure to unlabeled IgG.
MS Acquisition
