A biosensor-based digital microfluidic system for neuroanalysis in the intensive care unit

摘要

The primary focus of this thesis is the development of a digital microfluidicudbased system with integrated microelectrode biosensors, designedudfor the analysis of human brain microdialysate in the intensive care unit.udThe main aim is to measure the neurochemical effects of spreading depolarisationsud(SD waves), which have been shown to be detrimental toudthe injured human brain.udA combined electrode was developed containing working electrodes in theudrange of 25 to 125 μM, a reference electrode and an auxiliary electrode,udwithin a needle of outer diameter 300 to 500 μm. Glucose, lactate andudATP biosensors were developed with detection limits of 2 to 10 μM andudresponse times of under 10 seconds.udA digital microfluidic system was designed to segment the dialysate atuda microdialysis probe outlet, thereby eliminating Taylor dispersion andudreducing the time lag between the sample leaving the brain and analysis.udDifferent designs are discussed for the manipulation of droplets for optimaludanalysis, thus creating a microfluidic toolkit. The analysis chamberudwas analysed mathematically, the optimal placement of electrodes foundudand the sensor performance assessed on-chip.udThe on-chip glucose biosensor was used in vivo in a translational pilotudstudy. The biosensor performance was validated against rapid samplingudmicrodialysis with excellent results. The glucose biosensors successfullyudmonitored concentration changes, in response to stimulations, in theudrange of 10 to 400 μM. The data shows that during a SD wave, thereudis a time delay between the increase in potassium and the decrease inudglucose, due to the uncoupling of blood flow and metabolism. For theudfirst time, the microfluidic system was used in the intensive care unit,udmonitoring brain injury patients at the bedside.