Adsorption and desorption of F(ab′) 2Anti-hIgG on plasma-polymerized allylamine thin film: The application of the film to immunoassay

Abstract

The plasma-polymerization technique can easily modify the characteristics of the surface of materials. Here, allylamine thin film was formed on a flat glass plate (referred to as ALAM(GLA)) by plasma-polymerization. Adsorption of F(ab′) 2anti-human IgG (hIgG) onto ALAM(GLA) and desorption of the protein from ALAM(GLA) were investigated. ALAM(GLA) was used as a solid phase in two-site immunoradiometric assay (IRMA) of human serum IgG. The following results were obtained: (i) The adsorption of F(ab′) 2anti-hIgG onto ALAM(GLA) or GLA was a Langmuir type. The binding constant ( a) and the saturation concentration ( b) for the protein onto ALAM(GLA) were 5.6 × 10 5 l mol −1 and 264.2 nmol m −2, respectively. For GLA, a and b were 3.5 × 10 5 l mol −1 and 26.1 nmol m −2, respectively. The saturated level of ALAM(GLA) was about 10 times larger than that of GLA. (ii) The within-lot coefficient of variation (CV) of the adsorption of F(ab′) 2anti-hIgG onto ALAM(GLa) was 1.1–3.7% ( n = 8) and the between-lot CV was 3.5% ( n = 3). (iii) The adsorption of F(ab′) 2anti-hIgG was independent of the power of glow-discharge in plasma-polymerization. (iv) The surface of ALAM(GLA) was as flat and smooth as that of GLA. (v) The desorption of and the exchange of F(ab′) 2anti-hIgG adsorbed onto ALAM(GLA) was small. (vi) The ALAM film was transparent for visible light from 400 to 800 nm. (vii) The values of IgG in human sera measured by the two-site IRMA using ALAM(GLA) as a solid phase were compared with those obtained with laser nephelometry (LNM); the correlation coefficient was 0.929 ( P < 0.01) and the equation for the line of regression was Y = 0.801 X + 1.35.