Design of Hyperporous Molecularly Imprinted Thin Films for Ultrasensitive Antibody-Free QCM Detection of a Small-Cell...

A hyperporous polymer-based quartz crystal microbalance (QCM) chemosensor was developed for the selective determination of the signature peptide ELPLYR, a clinically significant biomarker for the prognosis of small-cell lung cancer. The sensor consists of an ELPLYR-imprinted poly(3,4-ethylenedioxythiophene) (PEDOT) recognition film electrosynthesized on gold-sputtered quartz (Au/quartz) transducers. Synthetic receptor-like cavities for ELPLYR were embedded within the PEDOT matrix using molecular imprinting. Hierarchical hyperporous networks of imprinted (MIP) and reference (REF) polymer films were fabricated using self-assembled, crystal-lattice-like sacrificial templates of amine-modified latex beads (LB-NH2). Imprinting of ELPLYR was achieved via electropolymerization of 3,4-ethylenedioxythiophene (EDOT) and functionalized monomers (EDOT-OH and EDOT-NH2) on the ELPLYR-modified, LB-NH2-coated Au/quartz surface. 1H NMR spectroscopy, molecular dynamics, and docking simulations confirmed strong hydrogen-bonding interactions between ELPLYR and the functional monomers in the prepolymerization solution. Selective extraction of the LB-NH2 beads and the ELPLYR template yielded a hyperporous network with surface-confined imprinted cavities. Microscopic (SEM and profilometry), electrochemical (CV and EIS), and spectroscopic (XPS and RAIRS) characterization revealed a uniformly grown, permeable, and long-range ordered PEDOT film (approx. 0.3 μm thick) with interconnected cavities maintained over millimeter scales. QCM measurements under flow injection analysis (FIA) conditions demonstrated the highly selective binding of ELPLYR to the hyperporous structure (MIP-Np-S + B). The sensitivity was found to be 166.51 ± 22.35 Hz/mM (R2 = 0.998), which is more than 5-fold higher than that of the nonimprinted analogue (REF-Np, 33.06 ± 1.47 Hz/mM, R2 = 0.997). The sensor exhibited excellent cross-reactivity, selectively detecting ELPLYR over structural interferents such as Z-ELPLYR (73.30 ± 3.91 Hz/mM) and a constituent amino acid cocktail (11.37 ± 2.23 Hz/mM). Furthermore, the sensor successfully recognized ELPLYR in artificial cerebrospinal fluid. Under optimized FIA conditions, the linear dynamic range extended from 39 ng/mL to 450 μg/mL (R2 = 0.998), with a limit of quantitation of 78 ng/mL (S/N = 5). Finally, the platform detected the signature peptide in blood and digested serum samples (100 ng/mL) collected via quantitative dried blood spot cards, demonstrating its potential for on-site sampling and clinical diagnostics. This work highlights the critical role of hierarchical nanostructures in enhancing chemosensor performance and the feasibility of peptide detection in complex biological fluids.