Baio J E, Weidner T, Interlandi G, Mendoza-Barrera C, Canavan H E, Michel R, Castner D G
National ESCA and Surface Analysis Center for Biomedical Problems, Department of Chemical, University of Washington, Seattle, WA 98195.
J Vac Sci Technol B Nanotechnol Microelectron. 2011 Jul;29(4):4D113. doi: 10.1116/1.3613919.
In this study the binding and assembly of bovine serum albumin (BSA) onto three different calcium phosphate phases (hydroxyapatite, dibasic calcium phosphate dihydrate, and β-tricalcium phosphate) was investigated using a combination of X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). XPS was used to record adsorption isotherms and to quantify the amount of BSA adsorbed onto the different CaP surfaces. On all three surfaces a monolayer of adsorbed BSA was formed. ToF-SIMS was then used to investigate how the structure of BSA changes upon surface binding. ToF-SIMS data from BSA films on the three CaP surfaces showed intensity differences of secondary ions originating from both hydrophobic and hydrophilic amino acids. For a more quantitative examination of structural changes, we developed a ratio comparing the sum of intensities of secondary ions from hydrophobic and hydrophilic residues. A small, but statistically significant, increase in the value of this ratio (7%) was observed between a BSA film on hydroxyapatite versus dibasic calcium phosphate dihydrate. From this ratio we can make some initial hypotheses about what specific changes in BSA structure relate to these differences observed in the ToF-SIMS data.
在本研究中，使用X射线光电子能谱（XPS）和飞行时间二次离子质谱（ToF-SIMS）相结合的方法，研究了牛血清白蛋白（BSA）在三种不同磷酸钙相（羟基磷灰石、二水磷酸氢钙和β-磷酸三钙）上的结合和组装情况。XPS用于记录吸附等温线并量化吸附在不同磷酸钙表面的BSA量。在所有三个表面上均形成了单层吸附的BSA。然后使用ToF-SIMS研究BSA在表面结合后其结构如何变化。来自三种磷酸钙表面上BSA薄膜的ToF-SIMS数据显示，源自疏水和亲水氨基酸的二次离子强度存在差异。为了更定量地研究结构变化，我们开发了一个比率，用于比较来自疏水和亲水残基的二次离子强度总和。在羟基磷灰石上的BSA薄膜与二水磷酸氢钙上的BSA薄膜之间，观察到该比率的值有小幅但具有统计学意义的增加（7%）。根据这个比率，我们可以对BSA结构的哪些具体变化与ToF-SIMS数据中观察到的这些差异相关，做出一些初步假设。
