巯基聚乙二醇5000修饰的金溶胶的稳定性: 从DLVO稳定到空间稳定

研究了α-甲氧基-ω-巯基聚乙二醇(mPEG-SH, 5000 MW)修饰的金溶胶的稳定性, 初步探讨了其稳定机制. 将线性mPEG-SH通过巯基化学吸附于金溶胶表面, 可形成高分子层包被的金溶胶. 研究结果表明, PEG修饰的金溶胶可以在pH＝1～13.5或盐浓度高达1.20 mol/L的较苛性条件下保持稳定. 这是由于金溶胶表面吸附的高分子保护层为溶胶提供了新的空间稳定, 取代了溶胶原来的DLVO稳定(实质是电荷稳定). 因而, PEG保护的金溶胶在很大程度上克服了DLVO稳定的溶胶对环境敏感、易聚沉的缺点, 能在复杂的条件(如生理条件)下应用. 鉴于PEG的水溶性、无毒性和生物亲和性, 这种具有较高稳定能力的金纳米粒子/PEG复合体结合了金纳米粒子和PEG的优异性能, 可作为生物纳米探针用于复杂条件下的生物分析.

Stability of Thiolated PEG 5000-Coated Gold Colloids: from DLVO Stability to Steric Stability

The stability of α-methoxy-ω-mercapto-poly(ethylene glycol) (mPEG-SH, MW 5000) modified gold colloids was investigated, and the corresponding stability mechanism was preliminarily interpreted. Linear mPEG-SH molecules were chemically bonded to gold particle surfaces via the end group, SH, forming polymer brush-coated gold colloids. Experimental results indicate that the PEG-modified gold colloids can resist aggregation under rigorous conditions of pH＝1～13.5 or salt concentration as high as 1.20 mol/L. It is because that the adsorbed PEG layer provides steric stabilization for the gold colloids instead of their original DLVO stabilization (viz. charge stabilization). Therefore, the PEG layer-coated gold colloids largely overcome the problems associated with DLVO-stabilized colloids, such as susceptivity to environment conditions and easiness in aggregation, and can survive in complex conditions (e.g. physiological conditions). Because of the water soluble, nontoxic, and biocompatible properties of PEG, the gold nanoparticle/PEG conjugates with high stability possess the excellent properties of both gold nanoparticles and PEG and can serve as bio-nanoprobes for bio-analysis.