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 (similar to 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.