UC San Diego

We are developing a rapid, point-of-care (POC) test for detection of Candidemia using giant magnetoresistive (GMR) biosensors. Candidemia is a fungal infection caused by the overgrowth of a yeast called Candida albicans. It is the 4th leading cause of bloodstream infections in hospitalized patients in the U.S. and severely affects immunocompromised individuals. Candidemia can be fatal if not treated rapidly and is often only detected post-mortem. The current gold standard for its detection is a blood culture, which typically takes 3-5 days, wasting precious treatment time. Therefore rapid, unambiguous diagnosis is required to improve prognosis. This technology aims to detect a unique enzyme that is secreted by C. albicans during infection. This enzyme, Sap6, is a protease that can degrade a synthetic peptide. The POC test works by immobilizing magnetic nanoparticles onto the GMR biosensor via the peptide. Once peptide cleavage by Sap6 occurs, the magnetic nanoparticle is released away from the sensor surface. This change in the magnetic field of the GMR sensors is detected in real-time. We have demonstrated this proof-of-concept in a 96-well plate format using a fluorescent sensor. This assay immobilizes approximately 1.8 g of peptide per well which can then be released by 13.34 g of protease in 10 minutes at room temperature. We have translated the assay to the GMR biosensors and detected up to 60% reduction in signal within 60 minutes. We hope to optimize this technology by reducing the detection time and expand it further to test other diseases like cystic fibrosis.