Self-assembly of super-hydrophobic PMMA microspheres on silicon wafer as MALDI-MS chip for rapid quantification of peptides

Rapid quantification of peptides by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a challenge. Herein, we prepared a super-hydrophobic poly(methyl methacrylate) (PMMA) structured chip for quantifying peptides without internal standard by improving the detection reproducibility and sensitivity. The chip was formed by PMMA microspheres through a self-assembly method. As a good adsorbent of peptides, PMMA microspheres make peptides distributed uniformly on the chip, resulting in the elimination of the coffee ring effect and the homogeneous co-crystallization of peptides/matrix. The relative standard deviations (∼ 10 %) and coefficients of determination (∼ 0.99) are satisfactory when detecting 3 standard peptides, which show that the chip is applicable for rapid quantification of peptides. The limit of detection is improved by 1000-fold on this chip compared with conventional steel target because of the enrichment of the super-hydrophobicity. It can be concluded that the detection reproducibility and sensitivity are significantly improved by the super-hydrophobic structured-PMMA chip. The applicability of the chip for practical samples is demonstrated by quantifying bacitracin A in milk extract and bradykinin1-7 in serum with good linearities. The structured-PMMA chips exhibit competitive advantages for quantitative analysis of peptides, which have a great potential for proteomic research.