Peptide nucleic acid biosensors: Structure–interface interactions, electrochemical signal strategies, and diagnostic applications

Abstract

Peptide nucleic acid (PNA) is a synthetic analog of DNA, uniquely characterized by a charge-neutral peptide backbone that imparts resistance to enzymatic degradation and enhances hybridization specificity. These intrinsic properties make PNA-based biosensors attractive alternatives to DNA-based systems, especially for use in complex biological and environmental matrices. This review systematically examines the electrochemical performance of PNA biosensors, with a focus on probe–electrode interactions that are governed by the absence of electrostatic repulsion. Particular focus is given to how charge neutrality influences probe orientation, hybridization efficiency, and accessibility of the redox mediator within the electroactive region defined by the Debye length and electron transfer distance. We analyze over 70 published PNA biosensor systems by comparing detection methods, electrode materials, and probe immobilization strategies. Reported limits of detection range from the attomolar to nanomolar level, with gold and carbon-based electrodes exhibiting consistently high sensitivity. The review also highlights recent advances in signal amplification, material optimization, and surface chemistry. Despite these achievements, challenges remain in scalable synthesis, stable probe immobilization, and multiplexing capabilities. Future development is expected to benefit from the integration of nanostructured electrodes, microfluidic platforms, and AI-assisted probe design. These innovations are expected to enhance sensitivity, specificity, and field deployability, thereby reinforcing the position of PNA biosensors as a next-generation solution for nucleic acid diagnostics.