Ultra-sensitive selective detection of HopQ protein as a biomarker for Helicobacter pylori bacteria by an electrochemical voltammetric sensor

Background Helicobacter pylori (H. pylori) is a highly contagious pathogenic bacterium that can cause gastrointestinal ulcers and may gradually lead to gastric cancer. H. pylori expresses the outer membrane HopQ protein at the earliest stages of infection. Therefore, HopQ is a highly reliable candidate as a biomarker for H. pylori detection in saliva samples. Materials and Methods: An H. pylori immunosensor is developed based on detecting HopQ as a biomarker in saliva by a screen-printed carbon electrode (SPCE) modified with MWCNT-COOH decorated with gold nanoparticles (AuNP). The HopQ antibodies are grafted on the SPCE/MWCNT/AuNP surface using EDC/S-NHS chemistry. The sensor performance is investigated by various methods and H. pylori detection performance in spiked saliva samples is evaluated by square wave voltammetry. Results: The sensor is suitable for HopQ detection with high sensitivity and excellent linearity in the 10 pg/mL - 100 ng/mL range and with a 10 pg/ml limit of detection. The sensor was tested in saliva at 10 ng/mL and returned an 107.6% recovery. The dissociation constant Kd for HopQ/HopQ antibody interaction, estimated from Hill's model, is calculated with a value of an order of 4.605 × 10−10 mg/mL. Conclusions: Due to the strategical choice of biomarker, the utilization of nanocomposite material to enhance the SPCE electrical performance, the intrinsic selectivity of the antibody-antigen interaction, and effective immobilization, the fabricated platform shows high selectivity, good stability, reproducibility, and cost-effectiveness for early H. pylori detection. Additionally, we provide insight into possible future aspects the researchers are recommended to focus on.