Chimeric Peptide-Based Biomolecular Constructs for Versatile Nucleic Acid Biosensing

Nucleic acid biomarkers hold great potential as key indicators for the diagnosis and monitoring of diseases. Herein we design and implement bifunctional chimeric biomolecules composed of a solid-binding peptide (SBP) domain that specifically adsorbs onto solid sensor surfaces and a peptide nucleic acid (PNA) moiety that facilitates anchoring of antisense oligonucleotide (ASO) probes for the detection of nucleic acid targets. A gold-binding peptide, AuBP1, previously selected by directed evolution to specifically bind to gold, served as the basis for immobilizing nucleic acid probes onto gold substrates. Using surface plasmon resonance (SPR) spectroscopy and quartz crystal microbalance (QCM) analyses, we demonstrate the sequential biomolecular assembly of the heterofunctional solid-binding peptide–antisense oligomer (SBP-ASO) construct onto a sensor surface and the subsequent detection of DNA in an aqueous environment. The effect of steric hindrance on optimal probe assembly is observed, establishing that less packing density results in greater target capture efficacy. In addition, an adsorbed layer of chimeric solid-binding peptide–peptide nucleic acid (SBP-PNA) undergoes viscoelastic changes at the solid–liquid interface upon probe immobilization and DNA target capture, whereby the rigid biofunctional layer becomes more flexible. The dual nature of the chimeric construct is highly amenable to a variety of platforms allowing for both specific recognition and probe immobilization on the sensor surface, while the modular design of the solid-binding peptide–antisense oligonucleotide provides facile functionalization of a wide diversity of solid substrates.