Diamond devices for bioelectronic applications - invited resubmission

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The interfacing between modern microelectronic device sensors and living organisms is a growing field, in which the electronic signals produced are used to provide information concerning the chemical and electrical processes occurring in the organisms concerned. Applications arise in the fields of biology and medicine, and in industries such as the biotechnology and food industries. An interesting field at present is neuron interfacing. Neurons are cells of the nervous system - the human brain has around 100 billion neurons - which carry messages through an electrochemical process. The behaviour of neurons can be followed by detecting electrical signals arising when a neuron sends a signal, or by chemical detection of neurotransmitters, which are specific chemicals that transmit information between one neuron and the next. Neuron interfacing requires intimate contact between the biological media and electronic or electrochemical devices, which typically might be silicon-based electronic devices or graphitic carbon/metal electrodes or electrode arrays. Progress in the research has been limited, either because the monitoring devices do not possess sufficient sensitivity, are hostile to the cultured cells, or undergo chemical change and significant degradation in the biological media. It is also the case that the traditional devices tend to carry out one function only, such as measurement of action potential. Ideally the devices should be able to stimulate the cells and control the chemical environment on the nanoscale at the device-culture interface, whilst monitoring the release of neurotransmitters and action potentials. Recently synthetic diamond, formed by the low pressure reactions of hydrocarbons and hydrogen in an energised plasma state at a solid surface, has become available at an economic price, with properties similar or surpassing those of natural diamond. The material can be prepared in an electrically insulating, semi-conducting or metallic state, depending on the exact growth conditions employed, and is ideally suited for electronic and electrochemical applications in harsh environments, in part because of the very high chemical stability of diamond. The properties of this new material make it ideal for exploitation in the field of neuron interfacing, and it should be possible to formulate multifunctional devices, which exploit both the electronic and electrochemical properties of diamond, and which yield more reliable and sensitive signals than the present devices.Although the biocompatibility of thin film diamond has been identified previously attempts to exploit it have mainly been concerned with passive applications, such as a wear- or chemically- resistant barriers. Here we will explore the potential of using diamond to fabricate active multifunctional sensors for neuronal applications. The project will involve growing the special forms of thin film diamond needed for the project, making FET and electrochemical sensors from it, culturing neuronal cells at the interface between the diamond and the biological media, and testing these biolectronic devices in the measurement of action potential and neurotransmitter release.To do this, we have assembled a multidisciplinary team comprising expertise in diamond electronic engineering, diamond electrochemistry and neuronal cell biology. If promising results are obtained, the project will pave the way for developing applications which could clearly have a huge impact in biomedical technology.