Laboratory for Polymer Analysis, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojapurra, Trivandrum, India.
Biosens Bioelectron. 2011 Sep 15;27(1):197-200. doi: 10.1016/j.bios.2011.06.015. Epub 2011 Jun 21.
Functionalized colloidal gold is widely used for qualitative and quantitative detection of specific analytes. We report here a novel modification of gold nanoparticles by digitonin, a glycoside used for precipitating membrane cholesterol. The specific molecular recognition of cholesterol by digitonin gold nanoparticles (DGNP), make it an attractive alternative to the existing enzymatic methods for cholesterol sensing. To enable cholesterol binding, we modified mercapto modified GNPs with digitonin, by a simple esterification reaction. The blue shift in the plasmon absorption spectra of DGNP with different cholesterol concentrations accompanied by a decrease in the absorbance is the principle applied here for the estimation. The observed size reduction followed by cholesterol binding is reasoned due to the enhanced hydophobicity of the surface which in turn expels the water layers associated with the particles prior to cholesterol binding. The method exhibited linearity between concentration of cholesterol and the corresponding absorbance of the plasmon peak, in the range of 160-600 ng/mL with a detection limit of 100±9 ng/mL. Other steroids did not show any binding affinity towards DGNP. The method depicted here has potential for development as an enzyme free sensor for cholesterol although many factors need to be addressed to transform it for assaying samples like blood.
功能化胶体金被广泛用于特定分析物的定性和定量检测。我们在此报告一种通过胆甾醇苷（用于沉淀膜胆固醇的糖苷）修饰金纳米粒子的新方法。胆甾醇苷金纳米粒子（DGNP）对胆固醇的特异性分子识别，使它成为现有胆固醇传感酶法的一种有吸引力的替代方法。为了实现胆固醇结合，我们通过简单的酯化反应将巯基修饰的 GNPs 与胆甾醇苷修饰。随着胆固醇浓度的增加，DGNP 的等离子体吸收光谱发生蓝移，同时吸收强度降低，这是此处应用的估计原理。观察到的结合胆固醇后粒径减小，原因是表面疏水性增强，从而在胆固醇结合之前排斥与颗粒相关的水层。该方法在 160-600ng/ml 的浓度范围内，与等离子体峰的相应吸收值呈线性关系，检测限为 100±9ng/ml。其他甾体类化合物对 DGNP 没有任何结合亲和力。虽然需要解决许多因素才能将其转化为用于检测血液等样本的方法，但此处所示的方法具有作为无酶传感器检测胆固醇的潜力。
