Extending the uses of lipid-membrane coated electrodes: Next generation of lipid membrane biosensors and smart implantable cell-electrode devices

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The ability to combine both a functional sensing and signalling membrane-electrode interface system is crucial for developing new technologies that can directly connect the living biosphere with electrical devices. However, there is a considerable distinction between both the chemical and biomechanical properties of live cell membranes versus synthetic electrical prostheses, thus there remain significant challenges that must be overcome in order to establish stable and functionally predictable interactions between these different components. The sparsely tethered bilayer lipid membrane possesses the necessary skeleton onto which novel chemistries can be added in order to succeed in the first iteration of correctly integrating electronic coupling with biological tissue. This dissertation presents an investigation into controlling the ionic and the electronic interface and then detecting ion fluxes arising from nearby biologically active cells at the nanometer scale, by using the detectable electrical signals derived from interfacing of membranes with a gold electrode. In it, the feasibility of implementing tBLMs as either an interface between biological systems and electrical devices or for continual sensing in real-time or for diagnostic purposes is investigated. Commencing is a comprehensive review of variant artificial lipid membrane models and the impedance spectroscopy approach (Chapter 1). A demonstration of the intimate nanoscale contacts of cells with the surface of the electrode is presented in Chapter 2. The aim of this study was to examine the feasibility of applying tBLMs in bio-implantable devices to offer specific transmission of electrical signals to individual target neurons to improve signal fidelity. This was to be achieved by reducing leakage pathways, thereby minimizing electrophoretic ion currents being lost into the surrounding interstitial medium. Chapter 3 describes how, instead of using the lipid membrane-covered electrodes to signal to cells, the electrode might be used to as a nano-biosensor for cell detection. Various approaches to increase sensitivity were explored to enhance this capability. The necessity for detection at the nanometer scale is explored in Chapter 4, recording in real-time the laser-generated heat pulses arising from laser-illuminated gold nanoparticles. Detection of these heat pulses required attachment of the gold nanoparticles to the membrane surface, while non-specific binding of gold nanoparticles failed to elicit a measurable response. Conclusions and perspectives are presented in Chapter 5, sum up of the significant achievements presented in this dissertation, which has focused on extending our understanding of cell membrane interactions and exploring the feasibility of using these across a range of applications.
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