Bio-Interface & Environmental Engineering Lab, Department of Biosciences and Bioengineering , Indian Institute of Technology Guwahati , Guwahati , Assam 781039 , India.
Langmuir. 2018 Jul 17;34(28):8178-8194. doi: 10.1021/acs.langmuir.8b01110. Epub 2018 Jul 6.
Physicochemical interactions of proteins with surfaces mediate the interactions between the implant and the biological system. Surface chemistry of the implant is crucial as it regulates the events at the interface. The objective of this study was to explore the performance of modified surfaces for such interactions relevant to various biomedical applications. Because of a wide range of surface wettability, we aimed to study protein behavior (i.e., conformational changes and their packing) during competitive protein adsorption. Three serum proteins (bovine serum albumin, BSA; fibrinogen, FB; and immunoglobulin G, IgG) were tested for their conformational changes and orientation upon adsorption on hydrophilic (COOH and amine), moderately hydrophobic (mixed and hybrid), and hydrophobic (octyl) surfaces generated via silanization. Modified surfaces were characterized using Fourier-transform infrared spectroscopy, contact angle, and atomic force microscopy (AFM) techniques. Adsorbed masses of proteins from single and binary protein solutions on different surfaces were quantified along with their secondary structure analyses. Maximum adsorbed protein masses were found to be on negatively charged and hydrophobic (octyl) surfaces because of ionic and hydrophobic interactions between protein molecules and surfaces, respectively. Side-on and end-on orientations of adsorbed protein molecules were analyzed using theoretical and AFM analyses. We observed compact and elongated forms of BSA molecules on hydrophilic and hydrophobic surfaces, respectively. We further found a linear increase in the α-helix content of BSA and β-sheet contents of FB and IgG proteins with the increasing side-on (%)-oriented protein molecules on the surfaces. This indicates that side-on orientations of adsorbed FB and IgG lead to the formation of β-sheets. Sodium dodecyl sulfate polyacrylamide gel electrophoresis was employed to quantify the protein types and their ratio in competitively adsorbed proteins on different surfaces. A theoretical analysis was also used to determine the % secondary structures of competitively adsorbed proteins from BSA/FB and BSA/IgG solutions, which very well agreed with experimental results. The competitive protein adsorption from both BSA/FB and BSA/IgG solutions was found to be entropy-driven, as revealed by thermodynamic studies performed using isothermal titration calorimetry.
蛋白质与表面的物理化学相互作用介导了植入物与生物系统之间的相互作用。植入物的表面化学性质至关重要，因为它调节界面上的事件。本研究的目的是探索与各种生物医学应用相关的改性表面的性能。由于具有广泛的表面润湿性，我们旨在研究蛋白质在竞争蛋白质吸附过程中的行为（即构象变化及其组装）。三种血清蛋白（牛血清白蛋白、BSA；纤维蛋白原、FB；和免疫球蛋白 G、IgG）被测试了它们在亲水（COOH 和胺基）、中等疏水性（混合和混合）和疏水性（辛基）表面上的构象变化和取向，这些表面是通过硅烷化生成的。改性表面的特征使用傅里叶变换红外光谱、接触角和原子力显微镜（AFM）技术进行了研究。通过单蛋白和双蛋白溶液在不同表面上的吸附，定量了吸附的蛋白质质量，并对其二级结构进行了分析。由于蛋白质分子与表面之间的离子和疏水相互作用，最大吸附蛋白质质量被发现存在于带负电荷和疏水性（辛基）表面上。使用理论和 AFM 分析，分析了吸附蛋白质分子的侧视和端视取向。我们观察到，BSA 分子在亲水和疏水性表面上分别呈现紧凑和拉长的形式。我们还发现，随着表面上侧视取向（%）蛋白质分子数量的增加，BSA 的α-螺旋含量和 FB 和 IgG 蛋白质的β-折叠含量呈线性增加。这表明，吸附 FB 和 IgG 的侧视取向导致β-折叠的形成。十二烷基硫酸钠聚丙烯酰胺凝胶电泳用于定量不同表面上竞争吸附蛋白质的蛋白质类型及其比例。还使用理论分析来确定来自 BSA/FB 和 BSA/IgG 溶液中竞争吸附蛋白质的%二级结构，这与实验结果非常吻合。通过等温滴定微量热法进行的热力学研究表明，来自 BSA/FB 和 BSA/IgG 溶液的竞争蛋白质吸附是熵驱动的。
