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.