Antibody-free biomarker determination: exploring molecularly imprinted polymers for pro-gastrin releasing peptide

Biomarker mass spectrometry assays are in high demand, and analysis of pro-gastrin releasing peptide (ProGRP) as a small cell lung cancer marker has been recently investigated by mass spectrometry after immunoextraction. In this article, we introduce an assay based on molecularly imprinted polymers (MIPs) targeting the proteotypic peptide of ProGRP as a possible alternative to current immuno-based assay. The MIPs were prepared by surface-initiated reversible addition-fragmentation chain transfer polymerization and were introduced as sorbents for the cleanup and enrichment of a ProGRP signature peptide from tryptically treated serum samples. The use of an appropriate solid-phase extraction protocol allowed specific extraction of the target peptide while depleting other peptides that arose from the sample digestion, hence resulting in reduced background. The selective extraction of a ProGRP signature peptide, after digestion of serum samples, translates into a time- and cost-effective method suited for bottom-up analysis wherever targeted peptide extraction from complex matrices is required.