Dr Danny O'Hare
Tel: +44 (0)20 7594 5173
d.ohare@imperial.ac.uk

Research Intro

Biosensor Research Group

The measurement of chemical concentration in living systems represents a formidable technical challenge: many different length scales (from sub- micron to millimetre) are of relevance and ideally one should see data in real time, ideally with sub millisecond resolution to observe the effects of pharmacological and physiological intervention.

Energy utilisation and the signalling molecules that control these are central to understanding living systems. The spatial and temporal variation of metabolites and signalling molecules are therefore essential for improved understanding of fundamental biology and identification of new therapeutic targets.

We build and design microengineered sensors and sensor arrays for the measurement of metabolism (including dissolved oxygen, pH, glucose, lactate, ATP), signalling molecules (nitric oxide, monoamine neurotransmitters, cytokines, hormones) and apply these to a wide range of biomedical and clinical research problems including: angiogenesis and neurotransmission. Group activities include microfabrication, sensor and system characterisation and signal processing as well as researching biocompatibility, molecular recognition and the fundamental physical chemistry that will inform the design of the next generation of sensors.

Research Topics and Selected Papers

Angiogenin Induces Nitric Oxide Synthesis in Endothelial Cells through PI-3 and Akt Kinases

Angiogenesis is the growth of new blood vessels and is a crucial stage in tumour growth. We have shown for the first time that nitric oxide is released in the first few minutes of endothelial cells being exposed to angiogenin, an angiogenic peptide. We have used our novel microsensor array to identify the intracellular pathways that are responsible for NOS activation and show key roles for PI3 kinase and nuclear translocation of angiogenin. This work is part of an ongoing collaboration with Prof Soo-Ik Chang, Chungbuk National University, Republic of Korea.

Simultaneous Detection of pH Changes and Histamine Release from Oxyntic Glands in Isolated Stomach

Acid release by the stomach is governed by complex interactions of several cell types. Here we simultaneously apply microelectrode sensors for pH (based on iridium oxide) and for histamine (using boron-doped diamond) to isolated perfused stomach tissue to identify the relative importance of the different signalling pathways and the effect of different pharmacological interventions.

Microelectrode investigation of neuroneal ageing from a single identified neurone

Normal ageing is associated with losses of neuronal plasticity and cognitive impairment ("senior moments"). Here we use the intact CNS of Lymnea stagnalis, the water snail, to investigate changes in neurotransmitter dynamics associated with ageing. We measure serotonin release from individual vesicles and nitric oxide both from identified single neurones using microfabricated carbon-fibre electrochemical sensors. The local concentration profiles of both neurotransmitters change with age to increase signal intensity. For serotonin, this is achieved by decreasing re-uptake. For NO, changes in nitric oxide synthases seem to be responsible. The changes in transmitter dynamics appears to be an adaptive response to losses of post-synaptic sensitivity.

Development of inlaid electrodes for whole column electrochemical detection in HPLC

Microfabrication and miniaturisation of analytical instrumentation offers advantages of low cost, increased throughput and holds out the possibility of point-of-care use. Liquid chromatography is a workhorse technique in the analytical lab but has hitherto proven difficult to miniaturise due to enormous back pressures. Here we report a PET/TPE plastic hplc chip and demonstrate its application to the separation of neurotransmitters and their metabolites. Separations are normally optimised using end-column detectors. Here we develop a wholly novel approach of using an array of microelectrochemical sensors inside the column to follow the separation in real time. New microfabrication techniques enabling this development are described. Whole column detection allows optimisation for more than one analyte and facilitates method development. This work was undertaken in collaboration with Prof Jingoo Park, Hanyang University, Republic of Korea.

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