Isothermal amplification using modified primers for rapid electrochemical analysis of coeliac disease associated DQB1*02 HLA allele

DNA biosensors are attractive tools for genetic analysis as there is an increasing need for rapid and low-cost DNA analysis, primarily driven by applications in personalized pharmacogenomics, clinical diagnostics, rapid pathogen detection, food traceability and forensics. A rapid electrochemical genosensor detection methodology exploiting a combination of modified primers for solution-phase isothermal amplification, followed by rapid detection via hybridization on gold electrodes is reported. Modified reverse primers, exploiting a C18 spacer between the primer-binding site and an engineered single stranded tail, are used in a recombinase polymerase amplification reaction to produce an amplicon with a central duplex flanked by two single stranded tails. These tails are designed to be complementary to a gold electrode tethered capture oligo probe as well as a horseradish peroxidase labelled reporter oligo probe. The time required for hybridization of the isothermally generated amplicons with each of the immobilized and reporter probes was optimised to be 2 min, in both cases. The effect of amplification time and the limit of detection were evaluated using these hybridization times for both single stranded and double stranded DNA templates. The best detection limit of 70 fM for a ssDNA template was achieved using 45 min amplification, whilst for a dsDNA template, just 30 min amplification resulted in a slightly lower detection limit of 14 fM, whilst both 20 and 45 min amplification times were observed to provide detection limits of 71 and 72 fM, respectively, but 30 and 45 min amplification resulted in a much higher signal and sensitivity. The genosensor was applied to genomic DNA and real patient and control blood samples for detection of the coeliac disease associated DQB1*02 HLA allele, as a model system, demonstrating the possibility to carry out molecular diagnostics, combining amplification and detection in a rapid and facile manner.