Developing a novel biosensor for detection of neurochemicals in blood

中枢神经系统中神经通讯的中心方面是涉及氨基酸及其衍生物的化学信号。谷氨酸、天冬氨酸及其衍生物N-乙酰天冬氨酸(NAA)在神经元和神经胶质细胞中含量较高。谷氨酸和NAA在健康人脑的质子磁共振波谱(MRS)扫描中产生最大的峰，在神经病理和精神障碍中，它们的水平降低。研究表明，在与年龄相关的神经退行性疾病中，这些氨基酸的水平在大脑中急剧下降，因为它们泄漏到细胞外空间和血液中。因此，这些化合物可以作为神经元健康的生物标记物，因为它们提供了对缺血损伤或脑损伤程度的洞察。L-天冬氨酸氧化酶(LAO)是已知的代谢L-天冬氨酸的酶。老挝将L-天冬氨酸氧化成亚氨基天冬氨酸，同时产生过氧化氢。由于底物的特异性，它可以与其他酶结合使用，以区分血液中是否存在大脑特有的氨基酸。纯化的酶可以固定在微电极的表面，在那里过氧化氢的存在会导致可以测量的电流的变化。该项目的目标是将这些酶集成到一个微电极生物传感器中，该传感器可以在体外检测和测量神经活性化学物质的水平。到目前为止，测量只能通过质子磁共振波谱或微渗析和高压液相色谱(HPLC)进行；这些技术既昂贵又耗时，而且由于其丰富，经常产生因存在一种或另一种氨基酸而受到污染的信号。一种能够提供快速测量并直接给出代谢变化指示的电化学生物传感器可能成为监测不同疾病条件下氨基酸水平的一种新的诊断工具。

The central aspect of neural communication in the central nervous system is chemical signalling involving amino acids and their derivatives. Amino acids glutamate and aspartate and the derivative N-acetyl aspartate (NAA), are present in high concentrations in the neurons and glial cells. Glutamate and NAA produce the largest peak in a proton magnetic resonance spectroscopy (MRS) scan of a healthy human brain, and their levels are reduced in neuropathologies and psychotic disorders. It has been shown that in age-related neurodegenerative diseases, levels of these amino acids drop dramatically in the brain as they leak into the extra cellular space and into the bloodstream. These compounds can therefore be employed as biomarkers for neuronal health, as they provide insight into the extent of ischaemic damage or brain injury. L-Asparte Oxidase (LAO) is the enzyme known to metabolise L-aspartate. LAO oxidises L-aspartate to iminoasparate, simultaneously producing H2O2. Because of substrate specificity, it can be used in conjunction with other enzymes in discriminating the presence of brain specific amino acids in the blood. Purified enzyme can be immobilised on the surface of the microelectrode, where the presence of H2O2 induces changes in the current which can be measured. The goal of the project is to integrate these enzymes into a microelectrode biosensor, that can detect and measure levels of neuroactive chemicals in vitro. To date measurements are made only through proton MRS, or microdialysis and High-Pressure Liquid Chromatography (HPLC); techniques which are both expensive and time consuming, and often produce signals that are contaminated by the presence of one or other amino acid because of their abundance. An electrochemical biosensor that can provide rapid measurement and directly give an indication of metabolic changes would potentially serve as a novel diagnostic tool for monitoring levels of amino acids in different disease conditions.