Graphene foam biosensors for molecular diagnostics of antimicrobial resistance and emerging pathogen threats

Pandemic preparedness for the surge of antimicrobial resistance (AMR) and newly emerging pathogens creates an urgent need for rapid diagnostic tools which can be mass manufactured and ideally used at the point of care. Rapid adaptation to new diagnostic targets is therefore a key requirement. To meet this need, we developed a sensitive electrochemical biosensor based on disposable graphene foam (GF) electrodes functionalised with peptide nucleic acid (PNA) probes, along with a rapid and generic functionalisation strategy. Pyrene-modified PNA probes were co-immobilised with pyrene-butanol on GF through π-π stacking, avoiding on-surface chemical reactions while preserving the electronic properties and high surface area of GF. The optimised biosensor enabled amplification- and label-free detection of the colistin resistance gene (mcr-1), with a limit of detection of 80 nM for synthetic ssDNA and 7.4 pM for bacterial plasmids. A key innovation is a heat-assisted protocol that accelerates biosensor functionalisation by over 300-fold (from 12 h to 2 min) without compromising performance. The biosensor discriminated the complementary mcr-1 target from a size-matched non-complementary sequence, producing a 7.29-fold signal increase for the target compared to 2.06-fold for the non-target at 2000 nM. Swapping the PNA probe enabled specific detection of the bla_NDM gene, demonstrating that the platform can be readily retargeted. This work establishes a reproducible biosensing platform with consistent performance across independently fabricated sensors (CV < 10%), providing a significant advance towards scalable manufacturing of decentralised diagnostics for AMR and other pandemic threats.