Detection of oxytocin, atrial natriuretic peptide, and brain natriuretic peptide using novel imprinted polymers produced with amphiphilic monomers.

The cystine-bridged cyclic peptide hormones (CBCPHs) represent signature structural feature as well as unique biological activity. In this study, three CBCPHs have been identified and characterized, namely, oxytocin, atrial natriuretic peptides (ANPs), and brain natriuretic peptides (BNPs). Because research has shown that ANPs and BNPs are powerful diagnostic biomarkers for heart disease, a highly laudable endeavor would be to develop a novel sensor for detecting ANP or BNP levels. Therefore, an amphiphilic monomer Acr-His-NHNH-Fmoc was synthesized to form molecularly imprinted polymers (MIPs) for targeted CBCPH detection. First, oxytocin, a cardiovascular hormone and a CBCPH, was used as a template to fabricate MIPs on quartz crystal microbalance (QCM) chips. On the other hand, fabricated selected ANP segment or BNP segment as an epitope is able to construct epitope-mediated MIPs (EMIPs) for ANP or BNP. The developed oxytocin or ANP sensor reached a detection limitation of 0.1nM with the dissociation constants being 30pM for oxytocin and 20pM for ANP. Moreover, BNP sensor achieved a detection limitation of 2.89pM with an even lower Kd value as 2pM. Compared with the performance of EMIPs, the imprinted films showed high affinity and selectivity in special binding to CBCPHs. The developed MIPs-QCM biosensors thus provide an improved sensing platform using an amphiphilic monomer and may be useful for applications toward cyclotides, cystine knot motifs, or insulin-like peptides.