A biosensor is a small, analytical device that can facilitate the rapid and specific detection of an analyte. The best known example of a biosensor is the glucose sensor, which is used by diabetics for monitoring blood glucose levels. Biosensors offer several major advantages over traditional lab-based analytical techniques; they are much faster, much cheaper and can be used on-site (e.g. at a patient’s bedside) without the need for highly skilled users.
Biosensors essentially comprise of two key parts: (1) a biorecognition element (e.g. enzyme, antibody, aptamer) to facilitate highly specific analyte detection, and (2) a transducer element which converts analyte binding into a measurable signal. Such signals include an electrochemical, optical or piezoelectric readout.
In the Millner lab, our focus is upon electrochemical biosensors, as these present inherent advantages such as low cost, ease of miniaturisation and mass manufacture. Electrochemical biosensors include amperometric, potentiometric and impedimetric systems.
We have developed biosensors against a range of diverse analytes, including:
A particular focus of the group is upon impedimetric biosensors , which couple directly analyte binding to an electrochemical readout without the need for redox activity. Therefore, impedimetric sensors can allow for the reagentless detection of a very wide range of analytes.
Current biosensor projects in the lab involve the detection of large analytes such as whole bacteria and sperm, biosensor regeneration to allow the multiple re-use of systems, the development of conformation-specific amyloid biosensors, testing novel bioreceptors such as non-antibody binding proteins, optimising electrodes, building better flow cells to house biosensors.... We are particularly interested in characterising and optimising the nanoscale surface of biosensors using techniques such as SEM and AFM.
Nanoparticles for medical applications
We are interested in the medical application of nanoparticles. These small (nm) sized particles can be functionalised to carry useful biomolecules such as antibodies and fluorescent dyes. As such, fluorescent nanoparticles carrying antibodies against cancer cell-specific antigens can be employed as an intra-operative method of cancer imaging. Such a system is currently being developed for use in colo-rectal cancer surgery and for cancer imaging in general. The use of fluorescent nanoparticles will allow the surgeon to locate and remove much more specifically the cancerous section of bowel, which is a current challenge.
Nanomaterials offer a very high surface area for the attachment or entrapment of useful molecules. Nanoparticles containing entrapped enzymes are highly useful in biocatalysis and other industrial applications. In our group, biosilicate nanoparticles have been produced which can entrap and/or stabilise commercially interesting enzymes (EC Project SANTS - www.sants-nanosilicates.com). We are also interested in developing nanoparticles with tunable properties, such as size, functionalisation and aggregation properties, along with magnetic nanoparticles.
Figure: Biosilicate nanoparticles.
We also research other nanomaterials, such as electrospun nanofibres and metal oxide nanorods, which also offer a large surface area. Nanofibres loaded with photosensitisers are currently being investigated for their ability to kill bacteria, with the aim of providing a cheap and efficient method of water clean-up that could be used in the developing world.