Nucleic Acid Aptamer-Based and Oligonucleotide Hybridization Biosensors for the Detection of Helicobacter pylori: Recent Advances, Transduction Mechanisms and Point-of-Care Perspectives

Helicobacter pylori infects about half of the world's population and is classified as a group 1 carcinogen, yet routine diagnosis still depends on methods that are invasive, instrument-heavy or insensitive at low bacterial burden. Nucleic-acid aptamers—short single-stranded DNA or RNA oligonucleotides isolated by SELEX—are chemically synthesised, thermally robust and programmable recognition elements for H. pylori biosensors, whereas sequence-complementary oligonucleotide probes detect bacterial genomic and ribosomal nucleic acids (genosensors). This review synthesises the 2019–2026 literature on both classes and keeps them explicitly separate. We examine whole-bacterium and recombinant-protein SELEX together with post-SELEX truncation and spacer engineering; the validated target spectrum, from whole cells and surface antigens to CagA, Hsp60, BabA and HpaA; electrochemical, optical, mass-sensitive and microfluidic transduction; and nucleic-acid circuitry, nanozyme and nanomaterial amplification. Six comparative tables summarise targets, platform performance, nanomaterial roles, amplification schemes, point-of-care formats and remaining barriers. Reported limits of detection reach 1 CFU mL⁻¹ for whole cells, 0.017 ng mL⁻¹ to 0.429 nM for proteins and 0.32 fM to 0.098 µM for nucleic acids, with preliminary clinical agreement against the ¹³C-urea breath test and PCR. Interface stability, standardisation, multiplexing, extension of protein-SELEX to VacA and urease, and multi-centre validation remain the main obstacles to routine deployment.