Authors: S. Klitgaard, T. Rasmussen, M.T. Neves Petersen and S.B. Petersen
Affilation: Aalborg University, Denmark
Pages: 410 - 411
Keywords: biosensor, plasmon-enhanced fluorescence, lactate oxidase, picosecond detection
Quick and precise detection of blood metabolites is a key parameter in monitoring and treating critically sick patients. Each analysis requires a certain amount of blood, and especially for babies in neonatal care repeated sampling can be life threatening. Therefore it is crucial to minimize the required amount of blood for analysis, which demands highly sensitive detectors. Optical detectors based on fluorescence possess high intrinsic sensitivity which by plasmonic signal enhancement can be increased even further. Blood lactate is a clinically valuable diagnostic indicator and there is considerable medical interest in measurements of blood lactate. Elevated concentrations of blood lactate are indicators of a considerable number of medical conditions. As examples, serum lactate levels are predictive of survival in children after open heart surgery and mortality in ventilated infants and may be preferable to pH for evaluating fetal intraparteum asphyxia. In adults elevated blood lactate can predict multiple organ failure and death in patients with septic shock and the function known to accompany decreased tissue oxygenation, hypovolemic, left ventricular failure, and drug toxicity. In the present work we report the possibility of monitoring lactate oxidase activity by spectral changes due to the presence or absence as well as different oxidation states in the flavinmononucleotide (FMN) cofactor. The investigation encompass emission properties including lifetimes and spectral resolution of the free-space - as well as plasmon-enhanced emission performed with a streak camera with picosecond resolution. Studies of the exited state absorption using the pump-probe will also be reported. The improved understanding of the kinetics of the excited state is essential for establishing a comprehensive spectroscopic knowledge about the function of lactate oxidase, which is essential for optimising biosensor applications.