Assembly of poly(dopamine)/poly(acrylamide) mixed coatings by a single-step surface modification strategy and its application to the separation of proteins using capillary electrophoresis.

In this work, a facile approach was developed to modify a fused-silica capillary inner surface based on poly(dopamine) and poly(acrylamide) mixed coatings for protein separation by capillary electrophoresis. The surface morphology, thickness, and chemical components of poly(dopamine)/poly(acrylamide) mixed coatings on glass slides and silicon wafers were studied by atom force microscopy, ellipsometry, and X-ray photoelectron spectroscopy, respectively. The hydrophilicity and stability of the mixed coatings on glass slides were investigated by static water contact angle measurements. A comparative study of electroosmotic flow showed that the poly(dopamine)/poly(acrylamide) mixed coatings could provide effective suppression of electroosmotic flow. Meanwhile, the fast and efficient separations of the mixture of four alkaline proteins, the mixture of acidic, basic, and neutral proteins and egg white proteins were obtained by capillary electrophoresis. Furthermore, the consecutive protein separation runs and low RSDs of migration time demonstrated that these poly(dopamine)/poly(acrylamide) mixed coatings were capable of minimizing protein adsorption during the protein separation by using capillary electrophoresis.