Recent Developments in Biosensors

Novel ideas in engineering nanomaterials and thin films technology are under development in near patient testing applications, for example, using quantum dots (Goldman et al 2002, Pathak et al 2007); nanowire based field detector (Wang et al 2005); layer of silica coated nano-magnet with higher biocatalystic sensitivity, and encapsulation of radioisotopes in CNTs and nano-carbon onions, as examples of synthesis of materials (magnetic, radionuclide) for medical diagnosis (Tsang, Oxford 2009).

Fig 14 – To scale model of a SWNT tip that has been modified with biotin and is interacting with streptavidin.(Woolley et al 2000)

Security applications exploit spectral characteristics and imaging in terahertz domain, which is capable to travel through materials that block light (Tonouchi 2007, Baker 2007). Terahertz sensing technique combined with surface plasmon polaritons with unique imaging results of superfocus pulsed terahertz radiation is developed to visualize below surface of objects (Johnston M 2007, Davies 2008). THz spectroscopy measures changes of both amplitude and phase not only intensity of transient electric field thus, provides simultaneous information on the absorption coefficient and index of refraction (Schmuttenmaer 2004). Photonics are key players for development of THz devices such as quantum cascade laser QCL or THz single photon detector.

In multiplexed arrayed formats different antibodies can be functionalized in single wall nanotubes SWNTs for protein detection. SWNTs display sharp scattering peaks when functionalized as coloured biomarkers for Raman labels due to strong sensitivity of SERS substrates. Super conducting Quantum Interference Device SQUID measurements for detection of prostate-specific antigen PSA is targeted using Magnetic Nanoparticles MNPs functionalized by biotin/streptavidin in a mono-dispersed stable solution able to track binding events in real time. Frequency and time domain characterization of changes in MNPs improved sensitivity to smaller sample volume down to 2 μl, and to as few as 100 million MNPs (Oisjoen et al 2010, Eberbeck et al 2008).

Following increasing R&D in biosensors to create precision techniques many technology transfer spin outs are emerged from universities to commercialize novel diagnostic devices. Comprehensive records of UK spin out companies are available by KTN (Knowledge Transfer Network), which includes Oxford Medical Diagnostics; Oxford Nanolabs; Oxford Catalysts; Oxford Advanced Surfaces and OxTox to name a few. Commercialized instruments are also launched in the United States and Europe for example, GWC technologies (Madioson USA) IBIS Technologies B V (Hengelo, The Netherlands), Genoptics Bio Interactions (Orsay France), GE Healthcare (Uppsala, Sweden). Nonetheless, Newman recent review of the industry points out that biosensors are still far from common use, with glucose biosensors mostly disposable test strips accounting for 85% of the world market, which is estimated at around 5 billion dlrs per annum. Abbott laboratories, Bayer diagnostics, LifeScan, and Roche diagnostics are among active players (Newman et al 2004, Davis et al 2004)).



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