Digital microfluidic sample preparation for biological mass spectrometry
Stokes, Adam A.
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The use of mass spectrometry in the biosciences has undergone huge growth in re- cent years due to sustained effort in the development of new ionisation techniques, more powerful mass analysers and better bioinformatic tools. These developments mean that it is now possible to introduce complex crude biological-mixtures into a mass spectrometric platform and to obtain detailed information about the sample. The front-end sample handling techniques used for sample preparation have, for the most part, not changed despite the recent advances in hyphenation of liquid- chromatography and mass spectrometry required to tackle the issue of increased sample complexity. In this thesis the possibility of using Digital Microfluidics (DMF) for front-end sample preparation prior to mass-spectrometric analysis of protein samples has been investigated. DMF is a micro-electromechanical system (MEMS) technology used for manipulation of sub-microlitre droplets. The movement of discrete droplets of liquid is exploited using the Coulombic forces arising due to free charge polarisation. Droplets can be split, joined, dispensed and moved over a sub-surface electrode array. In this thesis a range of DMF devices have been designed, manufactured and coupled with mass spectrometric platforms for protein analysis. A variety of techniques for mass spectrometry- based analysis of biological samples from the fluidic chips have been investigated. A robotic system has been developed to automate sample introduction, manipulation and removal. Finally the application of on-chip sample purification and enzymatic digestion have been demonstrated, providing proof of concept for digital microfluidic sample preparation in mass spectrometry-based proteomics.