Proteins modification of poly(dimethylsiloxane) microfluidic channels for the enhanced microchip electrophoresis

This report described proteins modification of poly(dimethylsiloxane) (PDMS) microfluidic chip based on layer-by-layer (LBL) assembly technique for enhancing separation efficiency. Two kinds of protein-coated films were prepared. One was obtained by successively immobilizing the cationic polyelectrolyte (chitosan, Chit), gold nanoparticles (GNPs), and protein (albumin, Albu) to the PDMS microfluidic channels surface. The other was achieved by sequentially coating lysozyme (Lys) and Albu. Neurotransmitters (dopamine, DA; epinephrine, EP) and environmental pollutants (p-phenylenediamine, p-PDA; 4-aminophenol, 4-AP; hydroquinone, HQ) as two groups of separation models were studied to evaluate the effect of the functional PDMS microfluidic chips. The results clearly showed these analytes were efficiently separated within 140 s in a 3.7 cm long separation channel and successfully detected with in-channel amperometric detection mode. Experimental parameters in two protocols were optimized in detail. The detection limits of DA, EP, p-PDA, 4-AP, and HQ were 2.0, 4.7, 8.1, 12.3, and 14.8 microM (S/N=3) on the Chit-GNPs-Albu coated PDMS/PDMS microchip, and 1.2, 2.7, 7.2, 9.8, and 12.2 microM (S/N=3) on the Lys-Albu coated one, respectively. In addition, through modification, the more homogenous channel surface displayed higher reproducibility and better stability.