Kinetically Tuned Single-Walled Carbon Nanotube Corona for Selective Detection of Circulating Tumor DNA Point Mutations

Point mutations in circulating tumor DNA (ctDNA) represent critical biomarkers for minimally invasive cancer management. However, their detection remains challenging because single-base mismatches impose only a modest energetic penalty within long ctDNA fragments and ensemble signal averaging in conventional transducer configurations obscures such subtle differences. Here, we present a kinetically tuned single-walled carbon nanotube nanosensor that selectively resolves the single-nucleotide KRAS G12D mutation against wild-type backgrounds through near-infrared (nIR) fluorescence modulation. The DNA corona was rationally engineered by computational anchoring-domain selection to maximize nanotube affinity and transduction gain, followed by capture-domain length tuning to suppress wild-type hybridization while preserving mutant complementarity. Stronger anchoring yielded amplified and reproducible spectral shifts, and systematic probe truncation revealed that the site of shortening governs the balance between mutant affinity and wild-type exclusion. By fitting single-analyte and cotitration assays to a competitive binding model, we extracted quantitative kinetic parameters, and these kinetic binding models rationalize the observed selectivity trends in terms of mismatch-dependent hybridization thermodynamics, thereby defining generalizable design rules for point mutation-selective DNA/single-walled carbon nanotube (SWCNT) sensors. Guided by this framework, the optimized construct achieved a limit of detection (LOD) of 151.6 nM in serum spiked with wild-type DNA, demonstrating robustness in complex biofluids. This kinetic-model-driven nanosensor strategy introduces a principled route for precise point mutation detection directly in liquid biopsy samples, providing a disruptive alternative to sequencing-based assays for portable, real-time cancer monitoring.