Kumar Arun, Aravamudhan Shyam, Gordic Milorad, Bhansali Shekhar, Mohapatra Shyam S
Department of Internal Medicine, Division of Allergy and Clinical Immunology, College of Medicine, University of South Florida, Tampa, FL 33612, USA.
Biosens Bioelectron. 2007 Apr 15;22(9-10):2138-44. doi: 10.1016/j.bios.2006.09.035. Epub 2006 Nov 9.
Cortisol is a member of the glucocorticoid hormone family and a key metabolic regulator. Increased intracellular cortisol levels have been implicated in type 2 diabetes, obesity, and metabolic syndrome. Cortisol is an important bio-marker of stress and its detection is also important in sports medicine. However, rapid methods for sensitive detection of cortisol are limited. Functionalized gold nanowires were used to enhance the sensitivity and selectivity of cortisol detection. Gold nanowires are used to improve the electron transfer between the electrodes. Moreover, the large surface to volume ratio, small diffusion time and high electrical conductivity and their aligned nature will enhance the sensitivity and detection limit of the biosensor several fold. The biosensor was fabricated using, aligned gold (Au) nanowires to behave as the working electrode, platinum deposited on a silicon chip to function as the counter electrode, and silver/silver chloride as reference electrode. The gold nanowires were coupled with cortisol antibodies using covalent linkage chemistry and a fixed amount of 3alpha-hydroxysteroid dehydrogenase was introduced into the reaction cell during each measurement to convert (reduce) ketosteroid into hydroxyl steroid. Furthermore, the micro-fluidic, micro-fluid part of the sensor was fabricated using micro-electro-mechanical system (MEMS) technology to have better control on liquid flow over Au nanowires to minimize the signal to noise ratio. The biosensor was characterized using SEM, AFM and FTIR technique. The response curve of the biosensor was found to be linear in the range of 10-80 microM of cortisol. Moreover, the presence of hydrocortisone is sensitively detected in the range of 5-30 microM. It is concluded that the functionalized gold nanowires with micro-fluidic device using enzyme fragment complementation technology can provide an easy and sensitive assay for cortisol detection in serum and other biological fluids.
皮质醇是糖皮质激素家族的一员，也是关键的代谢调节因子。细胞内皮质醇水平升高与2型糖尿病、肥胖症和代谢综合征有关。皮质醇是应激的重要生物标志物，其检测在运动医学中也很重要。然而，用于灵敏检测皮质醇的快速方法有限。功能化金纳米线被用于提高皮质醇检测的灵敏度和选择性。金纳米线用于改善电极之间的电子转移。此外，大的表面积与体积比、短的扩散时间、高的电导率以及它们的排列性质将使生物传感器的灵敏度和检测限提高几倍。该生物传感器的制作方法是，使用排列好的金（Au）纳米线作为工作电极，沉积在硅芯片上的铂作为对电极，银/氯化银作为参比电极。金纳米线通过共价连接化学与皮质醇抗体偶联，并且在每次测量时向反应池中引入固定量的3α-羟基类固醇脱氢酶，以将酮类固醇转化（还原）为羟基类固醇。此外，传感器的微流体部分采用微机电系统（MEMS）技术制作，以便更好地控制液体在金纳米线上的流动，从而将信噪比降至最低。该生物传感器采用扫描电子显微镜（SEM）、原子力显微镜（AFM）和傅里叶变换红外光谱（FTIR）技术进行表征。发现该生物传感器的响应曲线在皮质醇浓度为10 - 80微摩尔范围内呈线性。此外，氢化可的松在5 - 30微摩尔范围内能够被灵敏检测。结论是，采用酶片段互补技术的功能化金纳米线与微流体装置可为血清和其他生物流体中皮质醇的检测提供一种简便且灵敏的检测方法。
