A comparative study between the adsorption and covalent binding of human immunoglobulin and lysozyme on surface-modified poly(tert-butyl methacrylate)

Abstract

The adsorption and covalent immobilization of human immunoglobulin (HIgG) and lysozyme (LYZ) on surface-modified poly(tert-butyl methacrylate) PtBMA films have been evaluated using x-ray photoelectron spectroscopy (XPS), ellipsometry and atomic force microscopy (AFM). Surface modification of PtBMA (UV irradiation) afforded surfaces suitable for both the physical and covalent attachment of proteins. The XPS and ellipsometry results showed good correlation in terms of variable-dense/thickness protein layer formation between physisorbed and covalently bound proteins. The amount of physisorbed HIgG ranged from 23.0 ± 1.6 ng mm2 on PtBMA, with corresponding film thicknesses 17.0 ± 1.2 nm. Covalent immobilization mediated through 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysulfosuccinimide (sulfo-NHS) coupling chemistry, afforded 5.6–8 ng mm2 of HIgG with a corresponding thickness of 5.9 ± 0.6 nm on PtBMA. The attachment of LYZ to modified PtBMA surface was similarly translated, where adsorption yielded up to 15 ng mm2, while covalent immobilization afforded typically 7–8 ng mm2. The thickness of the adsorbed LYZ protein layer was 11.0 ± 3.2 nm (PtBMA), suggesting the greater portion of protein adsorbs on surface-modified PtBMA.