Design and fabrication of a portable potentiostat for DNA-based electrochemical detection of Coniella granati in pomegranate (Punica granatum) fruit

Coniella granati is a fungal pathogen associated with postharvest fruit rot in a wide variety of hosts, including pomegranate fruit. The current method for detecting Coniella granati is based on nested-polymerase chain reaction (nested-PCR), which takes several hours using laborious wet chemistry. Therefore, a fast and portable device for early field-based detection of Coniella granati is needed. The purpose of this research was to fabricate a biosensor device for the early detection of the Coniella granati pathogen in pomegranate fruit. The fabricated potentiostat device was shown to be adaptable and capable of performing double-stranded DNA (ds-DNA) electrochemical detection of the pathogen. A cyclic voltammetry electrochemical measurement was done using 50 µL of 2.8 mg mL^‑1 biotinylated-DNA sample of Coniella granati immobilized onto a streptavidin screen-printed electrode sensing surface. A specificity test was carried out using unrelated Candidatus Phytoplasma asteris DNA as control. Compared to the current PCR-based detection method, the fabricated potentiostat device accurately detected the presence of the Coniella granati pathogen in less than 10 min. However, when considering the amplification of pathogenic DNA using recombinase polymerase amplification (RPA), the detection time was estimated to be an hour.