Biomolecular engineers develop chip to monitor living cells in real time.

Japanese researchers have developed an electrochemical sensor chip capable of measuring enzymatic activity in real time.

Conventional methods for monitoring enzyme activity generally involve removing samples from the system under investigation and then treating them to prepare them for analysis. This has disadvantages, including the need for sufficient material for repeated sampling, the time-consuming process of sample removal and treatment, and the possibility that the treatment steps might perturb the natural cell growth. Electrochemical detection should avoid such problems because it can be carried out in situ.

Tomokazu Matsue, from Tohoku University, believes that 'the combination of electrochemistry with techniques on Bio-microelectromechanical systems (Bio-MEMS) will drastically improve the protocols routinely adopted by molecular biologists or genetic engineers'.

Motivated by this belief, Matsue and his colleagues have exploited the strengths of electrochemical detection techniques to prepare a sensor chip which contains a micropore (for the reaction) and a microelectrode (for detection) on the same glass substrate.

The researchers demonstrate that their chip can be used to detect the expression of ß-galactidose in E. coli cells in real time and show that the results match those obtained using a conventional colorimetric assay.

The colorimetric method requires about 10 ⁸E. coli cells and a multi-step procedure whereas Matsue's approach requires only about 1000 cells and is monitored in real time.

The hope is that the new chip could allow researchers to investigate systems for which too few cells are available to use conventional techniques, and situations in which real time measurements are essential.

'This is an exciting development which holds great promise for the fabrication of sensors for screening DNA cloning systems,' comments Phil Bartlett, head of electrochemistry research at Southampton University, 'as well as for the development of microbial arrays engineered for drug screening or environmental monitoring.'

Caroline Evans