Micro- versus nano-sized molecularly imprinted polymers in MALDI-TOF mass spectrometry analysis of peptides

The integration of molecularly imprinted polymers (MIPs) with MALDI-TOF mass spectrometry (MS) combines MIP selectivity with MS sensitivity. Whether the size of the MIP material—micro versus nano—has an effect on the MS analysis was the object of the study. MIPs, targeting respectively the epitope peptide NR11 of cardiac troponin I and the peptide CK13 of human serum transferrin, were synthesized and characterized. The size-related performance of the MIP materials hyphenated with MALDI-TOF-MS analysis was studied by the incubation of the target peptide with the respective micro- or nano-MIP, followed by rinsing to remove non-specific deposition of the MIP to the MALDI target plate, co-crystallization with the organic matrix, and mass analysis. The quality of the MS analysis was assessed comparing the S/N of the mass peaks of the MIP-bound peptide to that of the same quantity of free peptide. Sweet spots and lower S/N (~ 1 order of magnitude) were observed for micro-MIP materials, while in the case of nano-MIP-bound peptide, the S/N was comparable to that of the free peptide, indicating higher compatibility of the nano-MIPs to MALDI-TOF-MS. The nano-MIP/MALDI-TOF-MS permitted the selective determination of the target peptide in real serum samples.