Ultrasensitive and selective recognition of peptide hormone using close-packed arrays of hPTHR-conjugated polymer nanoparticles.

Recognition of diverse hormones in the human body is a highly significant challenge because numerous diseases can be affected by hormonal imbalances. However, the methodologies reported to date for detecting hormones have exhibited limited performance. Therefore, development of innovative methods is still a major concern in hormone-sensing applications. In this study, we report an immobilization-based approach to facilitate formation of close-packed arrays of carboxylated polypyrrole nanoparticles (CPPyNPs) and their integration with human parathyroid hormone receptor (hPTHR), which is a B-class family of G-protein-coupled receptors (GPCRs). Our devices enabled use of an electrically controllable liquid-ion-gated field-effect transistor by using the surrounding phosphate-buffered saline solution (pH 7.4) as electrolyte solution. Field-induced signals from the peptide hormone sensors were observed and provided highly sensitive and selective recognition of target molecules at unprecedentedly low concentrations (ca. 48 fM). This hormone sensor also showed long-term stability and excellent selectivity in fetal bovine serum. Importantly, the hormone receptor attached on the surface of CPPyNPs enabled GPCR functional studies; synergistic effects corresponding to increased hPTH peptide length were monitored. These results demonstrate that close-packed CPPyNP arrays are a promising approach for high-performance biosensing devices.