Physical Chemistry I, ‡Research Center of Micro and Nanochemistry and Engineering (Cμ), and §Institute of Materials Engineering, University of Siegen , 57076 Siegen, Germany.
Langmuir. 2017 Jan 24;33(3):802-813. doi: 10.1021/acs.langmuir.6b04177. Epub 2017 Jan 9.
The adsorption of bovine serum albumin (BSA) on micro- and nanocrystalline diamond/β-SiC composite films synthesized using the hot filament chemical vapor deposition (HFCVD) technique has been investigated by confocal fluorescence lifetime imaging microscopy. BSA labeled with fluorescein isothiocyanate (FITC) was employed as a probe. The BSA conjugate was found to preferentially adsorb on both O-/OH-terminated microcrystalline and nanocrystalline diamond compared to the OH-terminated β-SiC, resulting in an increasing amount of BSA adsorbed to the gradient surfaces with an increasing diamond/β-SiC ratio. The different strength of adsorption (>30 times for diamond with a grain size of 570 nm) coincides with different surface energy parameters and differing conformational changes upon adsorption. Fluorescence data of the adsorbed BSA on the gradient film with different diamond coverage show a four-exponential decay with decay times of 3.71, 2.54, 0.66, and 0.13 ns for a grain size of 570 nm. The different decay times are attributed to the fluorescence of thiourea fluorescein residuals of linked FITC distributed in BSA with different dye-dye and dye-surface distances. The longest decay time was found to correlate linearly with the diamond grain size. The fluorescence of BSA undergoes external dynamic fluorescence quenching on the diamond surface by H- and/or sp-defects and/or by amorphous carbon or graphite phases. An acceleration of the internal fluorescence concentration quenching in BSA because of structural changes of albumin due to adsorption, is concluded to be a secondary contributor. These results suggest that the micro- and nanocrystalline diamond/β-SiC composite gradient films can be utilized to spatially control protein adsorption and diamond crystallite size, which facilitates systematic studies at these interesting (bio)interfaces.
采用热丝化学气相沉积（HFCVD）技术合成的微/纳晶金刚石/β-SiC 复合薄膜对牛血清白蛋白（BSA）的吸附作用，利用共聚焦荧光寿命成像显微镜进行了研究。使用异硫氰酸荧光素（FITC）标记的 BSA 作为探针。结果发现，与 OH 终止的β-SiC 相比，BSA 缀合物优先吸附在 O-/OH 终止的微晶和纳晶金刚石上，导致随着金刚石/β-SiC 比例的增加，更多的 BSA 被吸附在梯度表面上。不同的吸附强度（对于粒径为 570nm 的金刚石，吸附强度超过 30 倍）与不同的表面能参数和吸附时的构象变化相一致。不同金刚石覆盖率的梯度膜上吸附 BSA 的荧光数据显示，粒径为 570nm 的金刚石具有四个指数衰减，衰减时间分别为 3.71、2.54、0.66 和 0.13ns。不同的衰减时间归因于与不同的染料-染料和染料-表面距离相连的 FITC 连接的硫脲荧光素残基在 BSA 中的荧光。发现最长的衰减时间与金刚石粒径呈线性相关。BSA 的荧光在金刚石表面通过 H 和/或 sp 缺陷以及无定形碳或石墨相发生外部动态荧光猝灭。由于吸附导致白蛋白结构发生变化，BSA 内部荧光浓度猝灭的加速被认为是次要贡献。这些结果表明，微/纳晶金刚石/β-SiC 复合梯度膜可用于空间控制蛋白质吸附和金刚石晶粒尺寸，这有利于在这些有趣的（生物）界面进行系统研究。
