Plasma-assisted alignment in the fabrication of microchannel-array-based in-tube solid-phase microextraction microchips packed with TiO2 nanoparticles for phosphopeptide analysis.

Phosphorylated peptides are important for understanding the processes of biological regulation. However, the detection of phosphopeptides remains a challenge because of their low abundance and the suppression by non-phosphopeptides. Here, we report a strategy for the facile and rapid fabrication of TiO2-nanoparticle-packed microchannel-array glass microchips (TMA-microchips) for in-tube solid-phase microextraction (IT-SPME) using a plasma-assisted method for the precise alignment of the microstructure. This proposed strategy was applied to the selective enrichment of phosphopeptides from a protein digestion mixture, demonstrating the high capacity and selectivity of the SPME microchips. An important feature of this array design is that it fully exploits the advantage of nanoparticles for improving extraction capacity and simultaneously provides an effective way to reduce the pressure for driving solutions; thus, it paves the way for future methods that simultaneously take advantage of nanomaterials and microchips.