DiagNano's core technology, nanoparticle surface coatings , was developed from research by Brad Kairdolf and Dr. Shuming Nie at Georgia Tech and Emory University. The surface coating technology allows quantum dots and other metal nanoparticles to be used in a number of biological applications, including In Vitro Diagnostics.
Nanotechnology Introduction
Nanotechnology is a very multidisciplinary field, with major contributions from the areas of chemistry, materials science and engineering. It is the field of technology that deals with the study or control of matter with at least one dimension below 100 nanometers (1 nm is one billionth, or 10-9, of a meter). To put this size in perspective, the length between two carbon atoms bound together is about 0.15 nm and the width of double stranded DNA is about 2 nm (right).
Nanotechnology has many potential applications, ranging from new materials with superior mechanical properties to improved medical diagnostics and therapeutics. For instance, quantum dot nanoparticles can be synthesized for use as fluorescent imaging probes in biomedical applications. By simply changing the size of the particles, we can alter the optical signal produced, allowing for multiple signals to be measured simultaneously.
Quantum Dots
At the macroscale, most material properties are not dependent on size. For instance, bulk semiconductors have a defined band gap that is dependent on the material itself, irrespective of the size. Cutting that semiconductor in half yields two smaller semiconductors, each with the band gap of the larger. Further cutting of the material to yield smaller and smaller pieces, again, has no effect on the band gap of the semiconductor. However, as the pieces of semiconductor become "nano-sized" particles, the band gap of the material begins to increase. Further shrinking of the semiconductor nanoparticles further alters the band gap of the material. The ability to tune this and other properties by controlling the particle size allows the nanotechnologist to design extremely small devices with unique properties and capabilities.
Quantum Dots are nanoparticles made of semiconductor materials, such as Cadmium Selenide (CdSe), that are small enough to be "quantum confined". In this size range, we are able to design particles that fluoresce from the UV region out to the infrared simply by changing the size of the particles. For cell and tissue staining, the most useful quantum dot material is CdSe, as it is capable of producing fluorescence in most of the visible light range.
Applying DiagNano's proprietary "non-stick" coating and surface treatment to these particles, we are able to provide bright nanoparticles in a number of colors for targeted biomolecule staining and quantification in complex samples without the risk of nonspecific binding.
Molecular Imaging
With standard light microscopy, there is a size limit to which light can focus which is approximately half the wavelength of the light used. For visible light (wavelength between 400 and 700 nm), this corresponds to a size of approximately 250 nm. This limitation (refered to as "diffraction-limited") presents a problem for imaging biological molecules such as proteins and DNA which are considerably smaller than the diffraction limit (proteins are on the order of 1-10 nm in diameter). Even larger objects of biological interest, such as viruses (20-500 nm), can be below the size limit. Because of this problem, a number of techniques have been developed to overcome the diffraction limitation. One way to image these molecules is to use fluorescent tags targeted to the molecules of interest.
Using the principles discussed above, we can design optically active quantum dot nanoparticles capable of imaging at the molecular level.