Nanoscience in Diagnostics: A Short Review‪.‬

INTRODUCTION Nanoscience is the study of phenomena and manipulation of materials at atomic, molecular and macromolecular scales, where properties differ significantly from those at a larger scale; and nanotechnology is the design, characterization, production and application of structures, devices and systems by controlling shape and size at the nanometre scale. (1) The prefix 'nano' is derived from the Greek word for dwarf. One nanometre (nm) is equal to one-billionth of a metre. A human hair is approximately 80,000nm wide, and a red blood cell approximately 7000nm wide. Nanobiotechnology is another chief field of investigation. The thrust is to combine nanoscale engineering with biology to manipulate living systems directly or build biologically inspired materials and devices at the molecular level. The origin of nanoscience and nanotechnologies is often attributed to a concept advanced by Nobel Laureate Richard P. Feynman, who in a 1959 lecture at the California Institute of Technology, stated "There is plenty of room at the bottom. Many of the cells are very tiny, but they are active: they manufacture substance; they walk around; they wiggle: and they do all kinds of marvelous things all on a very small scale. Also they store information. Consider the possibility that we too can make things very small which does what we want when we want-and that we can manufacture an object that maneuvers at that level." (2 3) The term 'nanotechnology' was not used until 1974, when Norio Taniguchi, a researcher at the University of Tokyo, Japan used it to refer to the ability to engineer materials precisely at the nanometre level. (4) The primary driving force for miniaturisation at that time came from the electronics industry, which aimed to develop tools to create smaller (and therefore faster and more complex) electronic devices on silicon chips. Because of the small dimensions, most of the applications of nanobiotechnology in molecular diagnostics fall under the broad category of biochips/microarrays but are more correctly termed nanochips and nanoarrays. Microarray/biochip methods employing the detection of specific biomolecular interactions are now an indispensable tool for molecular diagnostics, but there are some limitations. DNA microarrays and ELISA rely on the labeling of samples with a fluorescent or radioactive tag--a highly sensitive procedure that is time consuming and expensive. The chemical modification and global amplification of the nucleic acid samples are achieved by PCR which can introduce artefacts caused by the preferential amplification of certain sequences. Alternative label-free methods include surface plasmon resonance and quartz crystal microbalance. Nanotechnologies also provide label-free detection. Nanotechnology is thus being applied to overcome some of the limitations of biochip technology. (5)