Single molecule detection of tuberculosis nucleic acid using dark field Tethered Particle Motion

Current methods for tuberculosis nucleic acid detection require amplification and labeling before detection is possible. We propose here a method for direct detection using Tethered Particle Motion: gold nanoparticles are tethered to a glass substrate by single-stranded DNA molecules consisting of the complementary sequence to the target. Detection takes place by observing a change in the motion of the nanoparticles. The particles are imaged by a dark field microscope and captured on an EMCCD camera. Single particle tracking is carried out through maximum likelihood estimation of the Poisson noise limited Gaussian image profile using a parallelized algorithm on a GPU. The method is characterized by biophysical modeling and the ability to detect nucleic acids is shown. This single molecule method is suitable for multiplexing and could form the basis of an exquisitely sensitive method of detecting the presence of nucleic acids derived from human pathogens directly from patient material.