Oxford biosensor blends best of both worlds

An interdepartmental team of Oxford University scientists has developed a new type of biosensor which marries an electrochemical enzyme selective analytical technique with semiconductor and materials processing technology.

Colleagues from the Departments of Engineering and Inorganic Chemistry have been working on an electrochemical sensor based on an array of microelectrodes, each having a size of 1 to 10 micro m2. These small electrodes have a small charging capacitance, a rapid response time and a simple and easily interpreted current-voltage behaviour.

The team’s early devices were based on a gold-silicon wafer technology and used conventional photolithography and semiconductor device-processing techniques to make the arrays. These gold microelectrodes can be `functionalized’ with a variety of enzymes which are held in place via `linker’ molecules.

Following investigation into less expensive technologies, Carbon is now emerging as the favoured material. Electrodes are being made using a variety of methods: from the use of screen-printable inks to sputtered graphite layers. Recently, the group patented a technology based on making a glassy carbon electrode from a spin-coated sugar or polymer solution. This carbon layer is overcoated with an insulating glassy layer of silica in which `holes’ are defined using tiny polymer spheres. This material lends itself to the preparation of microelectrodes on a variety of shaped surfaces.

Using this technology it could be possible to make sensors which detect a wide range of compounds in medical applications. The team hopes to develop the technology to the point where the basic microelectrode device can be functionalized with whatever enzyme is required for specific applications.

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