UC Riverside

Citrus greening disease, also known as Huanglongbing (HLB), is posing a worldwide threat to the multi-billion dollars citrus industry. Currently, there are no cures for infected plants while containment of the spread of disease is heavily dependent on early detection of infected hosts for quarantine. The pathogen responsible for causing the disease is the bacteria Candidatus Liberibacter asiaticus (CLas). Thus, it is imperative that disease management strategies address current demands for accurate, timely, and robust disease detection and diagnosis minimize the spread of disease. By adopting a novel detection strategy targeting a recently discovered secreted protein biomarker, SDE1, which is unique to CLas, we hope to overcome the challenges faced by current detection methods, such as nucleic acid-based and symptom-based which have been found prone to false negatives and mis-diagnoses, respectively. To do this, we have worked to procure and characterize the antibodies specific for the novel HLB biomarker. In the process of characterizing the anti-SDE1 antibodies, we have also developed a specific and sensitive enzyme-linked immunosorbent assay (ELISA) for high-throughput and point-of-laboratory analysis of citrus plant samples. With the final goal of using the anti-SDE1 antibodies to develop sensitive, facile, and specific HLB detection method, we have integrated these antibodies into nanoscale electrical biosensor platforms. Using the novel semiconducting carbon nanomaterials, reduced graphene oxide (RGO) and single-walled carbon nanotubes (SWNTs), as the electrical transducer element for our biosensors, we have developed chemiresistive biosensors that demonstrate specificity and sensitivity to the SDE1 biomarker in simple phosphate buffer and in plant extracts.