[Resonance scattering spectral study of IgA immune complex particles and its analytical application]

Based on the resonance scattering (RS) effect of immune complex particles, a new resonance scattering spectral method for the determination of trace IgA in the human blood serum was developed. It was based on that goat anti-human IgA was combined with the antigen of IgA. It is known that antibody has C-terminal and N-terminal and the N-terminal is binding site of antigen, and it could combine antigen. Because the stereo structure anastomoses and the charge are opposite between goat anti-human IgA and IgA, they could attract and combine each other. The attraction and combination have high idiosyncrasy and they are done by Val der Waals force, hydrophobic force, Coulomb attracting force and hydrogen bond binding force, and aggregate to form immune complex particles that exhibit three resonance scattering peaks at 340, 390, 420, 450, 470 and 520 nm respectively, in the pH 6.2 Na2 HPO4-citrate buffer solutions and in the presence of polyethylene glycol (PEG) 4000. The laser scattering results indicate that the average diameter of the immune complex particles is about 1 100 nm. The influences of pH, PEG type and its concentration, goat anti-human immunoglobulin A concentration, incubation temperature and incubation time, foreign substance such as glucose, human serum albumin (HSA), urea and L-tyrosine were examined in details. Under the chosen conditions of pH 6.2 Na2 HPO4-citrate buffer solutions-60 mg x mL(-1) polyethylene glycol(PEG) 4000-0.35 mL anti-human immunoglobulin, the resonance scattering intensity at 340 nm deltaI340 nm and the resonance scattering intensity at 470 nm deltaI470 nm all are both proportional to the concentration of IgA in the range of 0.133-4.67 microg x mL(-1). Its regress equation was deltaI340 nm 18.61 C(IgA) 3.19, deltaI470 nm = 18.57C(IgA+) 6.51, with a detection limit of 0.068 and 0.072 microg x mL(-1), respectively. The assay has been applied to the analysis of IgA in human serum, which was also determined by the immunoturbidimetric method, with satisfactory results. The slope, intercept and correlation coefficient of the linear regress analysis were 1.064, -0.213 and 0.929 9, respectively.