Nanodiagnostics: application of nanotechnology in molecular diagnostics.

Nanotechnology extends the limits of molecular diagnostics to the nanoscale. Nanotechnology-on-a-chip is one more dimension of microfluidic/lab-on-a-chip technology. Biological tests measuring the presence or activity of selected substances become quicker, more sensitive and more flexible when certain nanoscale particles are put to work as tags or labels. Magnetic nanoparticles, bound to a suitable antibody, are used to label specific molecules, structures or microorganisms. Magnetic immunoassay techniques have been developed in which the magnetic field generated by the magnetically labeled targets is detected directly with a sensitive magnetometer. Gold nanoparticles tagged with short segments of DNA can be used for detection of genetic sequence in a sample. Multicolor optical coding for biological assays has been achieved by embedding different-sized quantum dots into polymeric microbeads. Nanopore technology for analysis of nucleic acids converts strings of nucleotides directly into electronic signatures. DNA nanomachines can function as biomolecular detectors for homogeneous assays. Nanobarcodes, submicrometer metallic barcodes with striping patterns prepared by sequential electrochemical depositon of metal, show differential reflectivity of adjacent stripes enabling identification of the striping patterns by conventional light microscopy. All this has applications in population diagnostics and in point-of-care hand-held devices.