Rapid Newcastle Disease Virus Detection Based on Loop-Mediated Isothermal Amplification and Optomagnetic Readout

Rapid and sensitive diagnostic methods based on isothermal amplification are ideal substitutes for PCR in out-of-lab settings. However, there are bottlenecks in terms of establishing low-cost and user-friendly readout methods for isothermal amplification schemes. Combining the high amplification efficiency of loop-mediated isothermal amplification (LAMP) with an optomagnetic nanoparticle-based readout system, we demonstrate ultrasensitive and rapid detection of Newcastle disease virus RNA. Biotinylated amplicons of LAMP and reverse transcription LAMP (RT-LAMP) bind to streptavidin-coated magnetic nanoparticles (MNPs) resulting in a dramatical increase in the hydrodynamic size of the MNPs. This increase was measured by an optomagnetic readout system and provided quantitative information on the amount of LAMP target sequence. Our assay resulted in a limit of detection of 10 aM of target sequence with a total assay time of 30 min. The assay has also been tested on clinical samples (vaccine and tissue specimens) with a performance comparable to real-time RT-PCR. By changing the LAMP primers, this strategy can serve as a general method for the detection of other DNA/RNA targets with high specificity and sensitivity.