Toworfe G K, Bhattacharyya S, Composto R J, Adams C S, Shapiro I M, Ducheyne P
Center for Bioactive Materials and Tissue Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
J Tissue Eng Regen Med. 2009 Jan;3(1):26-36. doi: 10.1002/term.131.
Bioactive glass (BG) can directly bond to living bone without fibrous tissue encapsulation. Key mechanistic steps of BG's activity are attributed to calcium phosphate formation, surface hydroxylation and fibronectin (FN) adsorption. In the present study, self-assembled monolayers (SAMs) of alkanesilanes with different surface chemistry (OH, NH(2) and COOH) were used as a model system to mimic BG's surface activity. Calcium phosphate (Ca-P) was formed on SAMs by immersion in a solution that simulates the electrolyte content of physiological fluids. FN adsorption kinetics and monolayer coverage was determined on SAMs with or without Ca-P coating. The surface roughness was also examined on these substrates before and after FN adsorption. The effects of FN-adsorbed, Ca-P-coated SAMs on the function of MC3T3-E1 were evaluated by cell growth, expression of alkaline phosphatase activity and actin cytoskeleton formation. We demonstrate that, although the FN monolayer coverage and the root mean square (rms) roughness are similar on --OH and --COOH terminated SAMs with or without Ca-P coating, higher levels of ALP activity, more actin cytoskeleton formation and more cell growth are obtained on --OH- and --COOH-terminated SAMs with Ca-P coating. In addition, although the FN monolayer coverage is higher on Ca-P-coated --NH(2)-terminated SAMs and SiO(x) surfaces, higher levels of ALP activity and more cell growth are obtained on Ca-P-coated --OH- and --COOH-terminated SAMs. Thus, with the same Ca-P coatings, different surface functional groups have different effects on the function of osteoblastic cells. These findings represent new insights into the mechanism of bioactivity of BG and thereby may lead to designing superior constructs for bone grafting.
生物活性玻璃（BG）可直接与活骨结合，无需纤维组织包裹。BG活性的关键机制步骤归因于磷酸钙形成、表面羟基化和纤连蛋白（FN）吸附。在本研究中，具有不同表面化学性质（OH、NH₂和COOH）的烷硅烷自组装单分子层（SAMs）被用作模拟BG表面活性的模型系统。通过浸入模拟生理流体电解质含量的溶液中，在SAMs上形成磷酸钙（Ca-P）。测定了有无Ca-P涂层的SAMs上FN的吸附动力学和单分子层覆盖率。还检测了这些底物在FN吸附前后的表面粗糙度。通过细胞生长、碱性磷酸酶活性表达和肌动蛋白细胞骨架形成，评估了FN吸附、Ca-P涂层的SAMs对MC3T3-E1功能的影响。我们证明，尽管在有无Ca-P涂层的-OH和-COOH封端的SAMs上，FN单分子层覆盖率和均方根（rms）粗糙度相似，但在有Ca-P涂层的-OH和-COOH封端的SAMs上，可获得更高水平的碱性磷酸酶活性、更多的肌动蛋白细胞骨架形成和更多的细胞生长。此外，尽管在Ca-P涂层的-NH₂封端的SAMs和SiO(x)表面上FN单分子层覆盖率更高，但在Ca-P涂层的-OH和-COOH封端的SAMs上可获得更高水平的碱性磷酸酶活性和更多的细胞生长。因此，在相同的Ca-P涂层下，不同的表面官能团对成骨细胞功能有不同的影响。这些发现代表了对BG生物活性机制的新见解，从而可能有助于设计出更优质的骨移植构建体。
