Photopolymerized sol-gel monoliths for separations of glycosylated proteins and peptides in microfluidic chips

Photopolymerized silica sol-gel monoliths, functionalized with boronic acid ligands, have been developed for protein and peptide separations in polydimethylsiloxane microfluidic devices. Pore size characterization of the monoliths was carried out with SEM, image analysis, and differential scanning calorimetry to evaluate both the micron-sized macropores and the nanometer-sized mesopores. Monoliths were functionalized with boronic acid using three different immobilization techniques. Batch experiments were conducted to determine the capacity of the monoliths and selectivity toward cis-diol-containing compounds. Conalbumin was used as a model glycoprotein, and a tryptic digest of the glycoprotein horseradish peroxidase was used as a peptide mixture to demonstrate proof-of-concept extraction of glycoproteins and glycopeptides by the monoliths formulated in polydimethylsiloxane microfluidic chips. For proteins, fluorescence detection was used, whereas the peptide separations employed off-line analysis using MALDI-MS.