Using conformational changes in polyelectrolytes as a transduction component signals in bioelectronics
The need for biocompatible scaffolds that can be integrated into the body to support therapeutic applications requires a number of factors to work in concert. Material must be biocompatible and preferably biodegradable on time scales commensurate with the application (i.e. the time during which they are required), it must mechanically adapt to surrounding tissue (i.e, have an appropriate elastic modulus), and there must be the ability to chemically attach organic electronic components that relay information.If this can be achieved, then simple and fast in vitro and in vivo detection of disease warning signs has clear long-term benefits. This project is to link transistor technologies with stimuli-responsive polyelectrolyte materials which signal the presence of factors (molecules or cells) associated with risks to health. The challenge for in vivo measurements is to identify the relevant event but avoiding problems due to the measurement itself. Electrolyte-gated organic field-effect transistors (EGOFETs) are ideal here because of their environmental versatility and their potential for chemical functionality. A typical challenge may be the detection of a response to pH changes associated with inflammation. To achieve this, polyelectrolytes may be used as part of the gate of a transistor. This polymer undergoes a conformational transition due to changes in local pH, changing the capacitance of the transistor dielectric. If the polymer is a grafted polyelectrolyte gel, then this signal will be indicated by a change in thickness. Similarly, the response of transistors to the presence of different types of cells may allow early detection of serious conditions. Experiments triggering conformational changes in polyelectrolytes are an important means of detecting these cells, although controlling their behaviour in media with high ionic strength is not trivial. Here, ions shield the effect of charges, limiting the effect of pH which controls polyelectrolyte conformational transitions, and so requires particularly sensitive materials. The project is multidisciplinary and covers aspects of physics, chemistry, and biology.
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