Single-coil, multisample, proton relaxation method for magnetic relaxation switch assays.

Nanoparticle based magnetic relaxation switch (MRSw) biosensors offer the opportunity to develop magnetic resonance based in vitro diagnostics. Critical attributes for point of care in vitro diagnostic products include simple instrumentation and ease of use. To this end, high-resolution biexponential analysis was used to permit measurement and assignment of two samples with a single radio frequency detection coil. This approach was used to calibrate and expand the dynamic range of MRSw biosensors in a single step. The potential for easy-to-use MRSw-based diagnostics was demonstrated by combining the method for single-step measurement of two samples with a disposable, plastic cartridge and dried MRSw reagents to obtain a calibrated reading after only two steps: mix and read. Taken together, our results suggest the feasibility of developing magnetic resonance based in vitro diagnostics that offer extreme ease of use and simple instrumentation.