Noninvasive electrochemical biosensor for rapid detection of Helicobacter pylori in patient saliva

The carcinogenic bacterium Helicobacter pylori infect over half the global population, with a higher prevalence in low-income countries. It is linked to diseases such as chronic gastritis, peptic ulcers, and gastric cancer, a leading cause of cancer-related deaths worldwide. The gold standard diagnostic method involves histopathological evaluation of gastric biopsy tissue via upper gastrointestinal endoscopy—an invasive, complex, and time-intensive procedure requiring specialized professionals. This study presents a noninvasive alternative: an impedimetric electrochemical biosensor for H. pylori antigen detection in saliva. The biosensor was developed using a screen-printed carbon electrode modified with polypyrrole nanotubes and carboxylated multi-walled carbon nanotubes. Monoclonal antibodies targeting CagA, a cytotoxic effector protein of H. pylori , were immobilized on carbon nanotubes using EDC/NHS chemistry. The platform was characterized via scanning electron microscopy and electrochemical techniques. Electrochemical impedance spectroscopy (EIS) was employed for analyte detection, with an analytical curve constructed in phosphate-buffered saline (PBS) spiked with CagA protein. The biosensor demonstrated a linear detection range of 0.5 pg mL⁻¹ to 3.3 ng mL⁻¹ and a detection limit of 109.9 fg mL⁻¹. Validation with patient saliva samples, confirmed by histopathology and rapid urease testing, yielded 97% accuracy, 80% sensitivity, and 100% specificity. Results were obtained within 15 minutes. This EIS-based biosensor offers a sensitive, innovative, and noninvasive platform for early H. pylori diagnosis, which is essential for preventing severe diseases such as gastric cancer. • Addresses a global health challenge by providing a minimally invasive and accessible diagnostic tool for early detection of H. pylori . • Employs a novel strategy to target CagA, an H. pylori biomarker strongly associated with disease severity, in patient saliva. • Utilizes the redox activity of polypyrrole nanotubes to eliminate the need for added redox probes, simplifying sample preparation. • EIS measurements are conducted at open-circuit potential to minimize surface destruction and improve measurement reliability. • Achieved a detection limit of 109.9 fg/mL, the lowest reported for H. pylori biomarkers using electrochemical biosensors. • Biosensor validated with real patient saliva samples, demonstrating 97% accuracy, 80% sensitivity, and 100% specificity. • Rapid results obtained within 15 minutes, enabling point-of-care applications in clinical and resource-limited settings.