A point-of-care electrochemical DNA sensor for rapid and sensitive detection of human papillomavirus type 18

We report the development of a paper-based electrochemical DNA biosensor for the rapid and sensitive detection of human papillomavirus type 18 (HPV 18) at the point of care. The sensor integrates a three-electrode system onto a wax-patterned cellulose substrate, with the working electrode modified using a graphene oxide–gold nanoparticle (GO–AuNP) nanocomposite. This nanostructured surface significantly enhances probe immobilization and electron transfer, enabling reliable signal transduction. Single-stranded DNA probes specific to HPV 18 were covalently attached via EDC/NHS chemistry, and target hybridization was detected using differential pulse voltammetry (DPV). The sensor exhibited a linear response from 1 fM to 10 pM, with a detection limit as low as 0.3 fM and a correlation coefficient (R²) of 0.993. Selectivity tests revealed a 70% signal drop for fully complementary sequences, while mismatched and non-complementary strands induced significantly smaller current changes (10–45%). Recovery studies in spiked samples demonstrated accuracy levels between 91.5% and 97.4% across concentrations from 10 fM to 20 pM. The assay was completed within 30 minutes and required only 10 µL of sample. Stability assessments showed signal retention of 88% after four weeks of storage at 4 °C. Unlike fluorescence or colorimetric methods, this sensor eliminates the need for labeling and complex instrumentation, making it especially suitable for resource-limited environments. The synergy of low-cost fabrication, high sensitivity, and portable operation positions this device as a powerful tool for early-stage HPV 18 screening and timely clinical intervention.