Bioseparation Engineering Group, Department of Mechanical Engineering, Technical University of Munich, Boltzmannstraße 15, Garching, 85748, Germany.
Faraday Discuss. 2017 Oct 26;204:233-250. doi: 10.1039/c7fd00105c.
Magnetic metal oxide nanoparticles demonstrate great applicability in several fields such as biotechnology, medicine and catalysis. A stable, magnetic and low-cost material, nanoscale magnetite, is an interesting adsorbent for protein purification. Downstream processing can account for up to 80% of the total production costs in biotechnological production. As such, the development of new innovative separation methods can be regarded as highly profitable. While short peptide sequences can be used as specific affinity tags for functionalised adsorber surfaces, they need expensive affinity ligands on the particle surface for adsorption. In order to identify peptide tags for several non-functionalised inorganic surfaces, different binding conditions to iron oxide nanoparticles are evaluated. Therefore, magnetite nanoparticles in a range of 5-20 nm were synthesised with a co-precipitation method. Zeta potential measurements indicated an amphiphilic surface with an isoelectric point in the neutral pH region. Glutamic acid-based homo-peptides were used as affinity peptides for the magnetite nanoparticles. We demonstrate a dependence of the binding affinity of the peptides on pH and buffer ions in two different experimental set-ups. The nature of surface coordination for glutamic acid-based peptides can be demonstrated with different spectroscopic approaches such as infrared spectroscopy (IR), Raman spectroscopy and circular dichroism spectroscopy (CD). We want to emphasise the importance of physicochemical properties such as surface energy, polarity, morphology and charge. These parameters, which are dependent on the environmental conditions, play a crucial role in peptide interactions with iron oxide surfaces. The understanding of the adsorption of simple biomolecules on nanoscale metal oxide surfaces also represents the key to the even more complex interactions of proteins at the bio-nano interface. From the identification of interaction patterns and an understanding of the adsorption of these peptides, the up-scaling to tagged model proteins facilitates the possibility of an industrial magnetic separation process and might therefore reduce time and costs in purification processes.
磁性金属氧化物纳米粒子在生物技术、医学和催化等领域具有广泛的应用。纳米级磁铁矿是一种稳定、磁性且低成本的材料，是蛋白质纯化的一种有趣的吸附剂。下游处理过程可占生物技术生产总成本的 80%。因此，开发新的创新分离方法可以被视为非常有利可图的。虽然短肽序列可以用作功能化吸附剂表面的特定亲和标签，但它们需要在颗粒表面使用昂贵的亲和配体进行吸附。为了鉴定几种非功能化无机表面的肽标签，评估了不同的结合条件到氧化铁纳米粒子上。因此，采用共沉淀法合成了一系列 5-20nm 的磁铁矿纳米粒子。Zeta 电位测量表明其表面具有两性，等电点在中性 pH 区域。基于谷氨酸的同肽被用作磁铁矿纳米粒子的亲和肽。我们在两种不同的实验设置中证明了肽的结合亲和力对 pH 和缓冲离子的依赖性。基于不同的光谱方法，如红外光谱（IR）、拉曼光谱和圆二色光谱（CD），可以证明基于谷氨酸的肽的表面配位性质。我们想强调表面能量、极性、形态和电荷等物理化学性质的重要性。这些参数取决于环境条件，在肽与氧化铁表面的相互作用中起着至关重要的作用。了解简单生物分子在纳米级金属氧化物表面的吸附也代表了蛋白质在生物-纳米界面上更复杂相互作用的关键。从识别相互作用模式和理解这些肽的吸附，将其扩展到标记的模型蛋白上，为工业磁性分离过程提供了可能性，并可能因此减少纯化过程中的时间和成本。
