| Description |
The absorption of three types of hemoglobin (Hb): deoxyHb, OxyHb, and MetHb, were determined on glass and polymer surfaces: (1) clean glass, (2) n-pentyl triethoxy silane (NPS)-treated glass, (3) polystyrene (PS), (4) polyetherurethane (PU), and (5) polydimethyl siloxane (PDMSO). The absorbed amounts range from 0.1 to 0.6 µg/cm2 for OxyHb and from 0.3 to 038 µg/cm2 for DeoxyHb. DeoxyHb absorbs more onto all of these surfaces than OxyHb. Except for PDMSO, the more the hydrophobic the surface, the more absorption of both Deoxy and OxyHb forms. All three type of Hb did not absorb on PDMSO surfaces as determined by X-ray photoelectron spectroscopy (XPS). Radiolabelling studies confirmed this using commercial PDMSO film. However, spin cast or dip coated PDMSO surfaces did show absorption, i.e., 035 ± 0.1 µg/cm2, which may indicate that the Hb probably distributed around the edge of the spin cast or dip coated PDMSO surface. The quantitation and pattern of Hb coverage on the clean glass were measured by XPS. The N/Si ratio was obtained using the variable angle technique followed by ratio counting using the same glass coverslip. The results suggest a possible 50% patchy coverage with 40?A average thickness, assuming a 40?A mean free path. These results suggest that OxyHb and DeoxyHb interact differently with surfaces. The DeoxyHb surface is more hydrophobic than OxyHb surface. Yet, the net charge on the surface of DeoxyHb and OxyHb in probably similar at pH 7.4. It is likely that the surface hydrophobicity of Hb plays the major role for Hb absorption onto surfaces. The binding sites for Hb absorption were proposed as the clefts between a1, B2 and between A2, B1. |
