Polydopamine-graft-PEG antifouling coating for quantitative analysis of foodproteins by CE

Abstract

In this paper, firstly the surface plasma resonance (SPR) was used to evaluate the antifouling property of polydopamine-graft-poly(ethylene glycol) (PEG) copolymer coating, and then the quantitative analysis of food proteins (such as hen eggs and milk powder) was investigated by capillary electrophoresis (CE) method using polydopamine-graft-PEG copolymer coated capillary. The great separations of lysozyme, conalbumin and ovalbumin from hen egg white could be achieved in phosphate–citrate buffer (pH 3.20) with an applied voltage of +20 kV in polydopamine-graft-PEG copolymer coated capillary. The range of protein recovery percentage of the three kinds of egg white proteins was 96.67% to 101.02%. According to the quantitative analysis results, the protein content of lysozyme, conalbumin and ovalbumin in hen egg white was 13.268 mg mL⁻¹, 28.360 mg mL⁻¹ and 157.418 mg mL⁻¹, respectively. Whey proteins (β-lactoglobulin A, β-lactoglobulin B and α-lactalbumin) in nonfat milk powder could be separated completely with an applied voltage of −20 kV in sodium tetraborate buffer (pH 8.5). The protein recovery of β-lactoglobulin A, β-lactoglobulin B and α-lactalbumin was in the range of 86.40–94.38%. Finally, the quantitative protein content of β-lactoglobulin A, β-lactoglobulin B and α-lactalbumin in nonfat milk powder was 1.418 mg mL⁻¹, 0.129 mg mL⁻¹, and 0.073 mg mL⁻¹, respectively. Also the egg white proteins could be separated consecutively 25 times without a noticeable loss in separation efficiency using polydopamine-graft-PEG copolymer coated capillary in one day.