Bridging interactions of proteins with silica nanoparticles: The influence of pH, ionic strength and protein concentration
Bridging interactions of proteins with silica nanoparticles: The influence of pH, ionic strength and protein concentration
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DOI：
10.1039/c3sm52401a
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发表时间：
2014-01-01
期刊：
影响因子：
3.4
通讯作者：
Findenegg, Gerhard H.
中科院分区：
文献类型：
--
作者：
Bharti, Bhuvnesh;Meissner, Jens;Findenegg, Gerhard H.
电荷驱动的纳米粒子的大分子桥是一个很有前途的工程功能结构的路线，但使用传统的聚电解质时，涉及的强静电相互作用赋予不可逆的络合和不明确的结构。最近，人们发现，二氧化硅纳米粒子与小球状蛋白质的静电相互作用导致聚集体结构，可以通过pH值控制。在这里，我们研究了pH值和电解质浓度的组合影响的二氧化硅纳米粒子与溶菌酶在稀水性分散体的桥接聚集。我们发现，蛋白质结合的二氧化硅颗粒是由pH值的离子强度无关。通过小角X射线散射（SAXS）研究了由二氧化硅颗粒与蛋白质形成的异质聚集体结构，并基于短程方阱吸引对势（接近粘硬球极限）分析了结构因子数据。结果发现，电解质浓度有很强的影响，在pH 5附近的粘性，其中弱电荷的二氧化硅颗粒被桥接的强电荷的蛋白质。在蛋白质的等电点（pI - 10.7）附近发现电解质的更强的影响，并且归因于高度带电的二氧化硅颗粒之间的排斥和桥接蛋白质分子之间的疏水相互作用的屏蔽。
Charge-driven bridging of nanoparticles by macromolecules represents a promising route for engineering functional structures, but the strong electrostatic interactions involved when using conventional polyelectrolytes impart irreversible complexation and ill-defined structures. Recently it was found that the electrostatic interaction of silica nanoparticles with small globular proteins leads to aggregate structures that can be controlled by pH. Here we study the combined influence of pH and electrolyte concentration on the bridging aggregation of silica nanoparticles with lysozyme in dilute aqueous dispersions. We find that protein binding to the silica particles is determined by pH irrespective of the ionic strength. The hetero-aggregate structures formed by the silica particles with the protein were studied by small-angle X-ray scattering (SAXS) and the structure factor data were analyzed on the basis of a short-range square-well attractive pair potential (close to the sticky-hard-sphere limit). It is found that the electrolyte concentration has a strong influence on the stickiness near pH 5, where the weakly charged silica particles are bridged by the strongly charged protein. An even stronger influence of the electrolyte is found in the vicinity of the isoelectric point of the protein (pI - 10.7) and is attributed to shielding of the repulsion between the highly charged silica particles and hydrophobic interactions between the bridging protein molecules.