In a recent post, I compiled a list of commercially available label-free biosensors. The list is fairly impressive with twenty five companies offering label-free sensing based on variety of transduction platform including optical, thermal, mass and electrical. Based on the list, one could assume that market is mature and the space for new sensors will be limited but the furious pace of research in label free sensors presents a completely opposite picture. The question then arises: what is driving the research into new label-free biosensing platforms? My opinion, as someone who has worked in this field for very long time is as follows.
Reason number one: Money, money, money. Bio-sensors in general continue to attract significant funding because of their wide ranging applications in fundamental biological research, clinical diagnostics, environmental monitoring, food testing, and biodefense. The biodefense is one of the key driver for biosensor research especially after 9/11 attack and the anthrax incidents of 2001. Federal funding for Biodefense for Year 2001 was $294 million dollars that jumped to $ 3.1 billion dollar in 2002 and has remained between 5-7 billion dollars since then. A portable biosensor for detection of biological agents will be the key requirements for strengthening the defenses against biological attack at local, state and national level. Clinical diagnostics is another key driver for biosensor research with glucose sensor alone responsible for multibillion dollar market.
Reason number two: Miniaturization and multiplexing and maybe sensitivity. Label-free (bio) sensors are attractive because of single step detection without the need for secondary or tertiary binding event for detection as is required for traditional biosensors and ELISA type of assays. Other attributes (currently available or desired) include, quantitative and sensitive measurement, possibly lower cost as there is no need for reporter labeled detection reagents, single step detection hence simple to use (at least theoretically) and possibly portable. But as of today, commercial label-free biosensors are big laboratory instrumentation, expensive, and difficult to operate. This brings me to my third reason.
Reason number three: Nanotechnology has brought a quantum shift in biosensor research (at least on research scale). Label-free biosensors today are using metal nanoparticles/nano structures, carbon nanotubes, micro/nano electro-mechanical systems (MEMS/NEMS,) nano/micron sized photonic crystals, and lithographically designed micro/nanoscale waveguides for transducing biomolecular binding into optical/electrical/thermal signal. These devices are small, can possible be mass produced at low enough cost and more importantly several of these sensors can be used in parallel for multiplexing. The sensitivity of these sensors are routinely being reported in pM, fM and event attomolar concentration.
I have made a list of key technologies in label-free biosensing that are being actively explored as is evident by several publications in last few years. In addition to brief description of the technology I have included the link to key research laboratories or publications. Publication lists have been picked from Google Scholar Search. These links are by no means only source for research and I will be happy to include more as I gather/get more information. The list is not intended be all inclusive and I expect it to grow over time so come back for updates.