基于生物素-亲和素相互作用的胶体晶体阵列的构筑与特性

将胶体晶体阵列(crystalline colloidal arrays,CCA)的Bragg衍射特性与水凝胶的刺激响应性功能结合起来,可制成一种有效的对特定分子具有识别和响应能力的传感材料.采用无皂乳液聚合制备的单分散聚(苯乙烯-4-苯乙烯磺酸钠)纳米颗粒,通过表面电荷的静电斥力可自组装形成CCA,经光聚合固定在水凝胶网络内形成聚合胶体晶阵(polymerized CCA).在水凝胶网络中用共价结合引入生物素分子,通过强的亲和相互作用可与蛋白质亲和素生成生物素-亲和素复合物,在水凝胶网络中形成交联点,引起水凝胶体积相变,进而导致CCA晶面间距发生改变,从而引发Bragg衍射波长发生相应的移动.

PREPARATION AND CHARACTERISTICS OF POLYMERIZED CRYSTALLINE COLLOIDAL ARRAYS BASED ON INTERACTIONS BETWEEN BIOTIN AND AVIDIN

Monodisperse,highly charged polystyrene colloidal particles with an average diameter of 170 nm were prepared by emulsifier-free emulsion polymerization.These particles spontaneously self-assemble into crystalline colloidal arrays(CCAs)in low ionic strength aqueous solutions due to long-range electrostatic repulsions among the particles.These CCAs diffract light,meeting the Bragg condition in the ultraviolet,visible and near-infrared spectral regions.CCAs were embedded into a polyacrylamide hydrogel to form polymerized crystalline colloidal arrays(PCCA)by adding acrylamide,N,N-methylenebisacrylamide and 2,2-diethoxyacetophene into the liquid CCAs,and then photopolymerizing the mixture of monomers to make a thin PCCA film.Modified PCCAs containing —NH_2 groups were prepared via Mannich reaction with ethylenediamine.Hydrogel modified with ethyleneamide underwent a volume phase transition in response to the change in ionic strength of the solution.The biotinylation of the PCCA was achieved by chemical conjugation of the polymer gel with biotin after appropriate chemical modification of the gel.The interaction of the biotinylated PCCA with avidin led to a shrinkage in volume of the system caused by increased cross-linking in the hydrogels due to the binding between biotin and avidin.This volume change of the hydrogels altered the periodicity of the CCAs,resulting in a blue shift in the diffraction spectra.When excess biotin hydrazide was added,it was able to displace avidin bound to the biotinylated PCCA by the formation of a stronger complex with avidin.The disassociation of avidin from the PCCA led to the re-swelling of the hydrogels,corresponding to an increase in the interparticle distance in the PCCA and thus a red shift in the diffraction spectra.Our results demonstrated the response of a model sensor system made of biotinylated PCCA to the binding of an interacting protein,avidin.This may provide a basis for the sensing of protein molecules by functionalized PCCA systems.