Objectives We have developed a novel Point-of-Care (PoC) system, Velox, comprising an assay-specific cartridge and instrument with a turnaround time of 25 min. The system has been developed for Chlamydia trachomatis and Chlamydia/Gonorrhoea. We have now developed a Trichomonas vaginalis (TV) test suitable for integration onto the cartridge. The assay utilises a novel electrochemical detection method to demonstrate low copy number amplification and detection of TV in <25 min.
Methods The method employs prototype PCR cartridges in conjunction with an ultra-rapid thermocycler. All reagents necessary to perform the extraction, amplification and detection are deposited into the cards and air dried at the point of manufacture. A sample is added to the card and DNA extracted from the sample. The resulting eluate reconstitutes dried PCR reagents and PCR is performed using rapid thermocycling. Amplified target is detected using electrochemically-labelled TV target-specific probes and a double-stranded DNA-specific exonuclease to release the electrochemical label. Released label is read by applying a voltage to a screen printed carbon electrode and at a known oxidation potential the label is oxidised producing a measurable current.
Results Analytical sensitivity of the TV assay was evaluated by testing dilutions of the organism in the presence of Internal Control (IC) DNA. The results show a TV limit of detection of 50 copies when co-extracted, amplified in duplex and detected electrochemically with the IC DNA. Tests on the reagents dried into the device showed stability for 18 months when stored at ambient temperature (20–25°C).
Conclusions The results show that in conjunction with the instrument, the TV assay could be used to perform ultra-rapid PCR with no user intervention after sample addition. This allows minimally-trained staff to carry out the assay in <25 min, meeting the needs of a PoC device.
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