Self-Assembled Monolayer Epitope Bridges for Molecular Imprinting and Cancer Biomarker Sensing

Abstract

The research in biomedicine, cell signaling, diagnostics, and biocatalysis rely on selective protein binders that specifically capture a protein in a complex medium for either preparative or analytical use. These molecules are generally of biological origin and exposed to instability, denaturation, high cost, and inherently low binding capability. Imprinted polymers, serving as the artificial protein binders, demonstrate good potential to overcome these drawbacks. In this study, a novel epitope imprinting strategy is reported by employing double-cysteine-modified peptides as the templates and adsorbing the templates on a gold surface by means of forming self-assembled monolayer bridges, followed by electropolymerization to create a polymer network. The imprinted surface was initially designed to demonstrate specific affinity toward a short peptide (i.e., the epitope) or a target protein (i.e., neuron specific enolase) in buffer. This surface was subsequently used to measure the cancer biomarker in human serum that allows detecting 12 times lower concentration than threshold level of the biomarker. The molecular receptors exhibited a K_d < 65 pM for their respective target protein and low cross-reactivity with four nonspecific molecules. As compared to current strategies for the epitope imprinting, for example, through traditional, vertically adsorbed, or histidine-modified peptides, such a molecularly tunable system based on a surface-imprinting process may provide more efficient sensing systems with desirable affinity, sensitivity, and specificity in diagnostics applications.