Road to in vivo cholesterol analysis in human diagnostics.

摘要

Nose probe electrodes were fabricated to be used for in vivo cholesterol analysis of epithelial membrane for tracking progression and treatment of cystic fibrosis (CF). Cholesterol oxidase, which can catalyze the oxidation of cholesterol, was covalently linked to an 11-mercaptoundecanoic acid submonolayer on the Pt electrode surface. Background subtraction charge measurement scheme was used in this work. Hydrogen peroxide generated from the oxidation of cholesterol was accumulated during the hold time, and then double potential pulse experiments were conducted on the modified electrodes. The difference of analog charge from first step and second step is an estimate of the accumulated hydrogen peroxide. The modified electrode showed a response at living tissue that was larger than a bare Pt electrode, indicating detection of cholesterol using the nose probe electrode geometry.;Cholesterol oxidase was immobilized on the glass insulating region of the nose probe electrode, instead of the Pt region, as a possible means of increasing signal. The surface area of the glass insulating surface (the tip) is larger and can thus accommodate more immobilized enzyme. The hydrogen peroxide generated from oxidation of cholesterol is detected by the disk Pt electrode. Such electrodes with enzyme only immobilized on the glass region showed increased signal with increasing concentration of cholesterol solution.;A differential amperometric analysis system was designed to analyze cholesterol where the signal is referenced to the solution baseline in real time. The instrument and method are demonstrated for detection of cholesterol in small liquid volumes. The system contains two working electrodes where one electrode is sensitive to cholesterol and the other is not. The difference current between the two electrodes provides a signal for cholesterol detection. Cholesterol solutions of different concentration were analyzed and the response shows saturation behavior, which is consistent with the Michalis-Menten mechanism. With this system, only 100 microL solution was needed for the analysis of cholesterol. The system was also used to detect cholesterol at the airways surface of mouse trachea tissue and the current response was 21+/-2.6 pA.