Nucleic Acid Amplicons Detected and Identified by T2 Magnetic Resonance

Abstract

T2 magnetic resonance (T2MR®) is a powerful technique for the detection of minute concentrations of nucleic acids in complex matrices. Magnetic nanoparticles (MPs) with conjugated capture probes change states from dispersed to clustered in the presence of their target nucleic acids, a process that results in a dramatic change in T2MR signal. Unlike optical detection methods, T2MR is agnostic to solution opacity, and detection can be performed in many biological solutions, including blood, urine, and dialysate, without the need for lengthy nucleic acid extraction and purification techniques. High sensitivity is achieved by using large sample volumes for low concentration targets and minimal processing to reduce target loss. Specificity is driven by amplification primer and capture probe design combined with a highly discriminatory detection system. This method has been applied to the rapid detection of Candida spp. causing fungal sepsis, and limits of detection (LoDs) as low as 1 colony-forming units (CFU)/mL have been achieved directly from the blood. Similarly low LoDs have been demonstrated for species causing bacterial sepsis and Lyme disease. Clinical studies utilizing the automated T2Candida Panel® indicated an overall 91.1% sensitivity and 99.4% specificity per assay as compared to blood culture. Results were obtained in 3–5 h directly from patient blood, as opposed to the 2–5 days for results from blood culture. The T2MR method was also shown to detect invasive candidiasis, an infection that often cannot be diagnosed by blood culture.