Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069, Dresden, Germany.
Soft Matter. 2017 Feb 7;13(5):1074-1084. doi: 10.1039/c6sm02380k. Epub 2017 Jan 17.
Control and tuning of surface properties is indispensable for the programmed and rational design of materials. Particularly, polymeric brush-modified colloids can be used as carrier materials for enzyme immobilization. Although it is of prime importance to control the brush architecture, there is still a lack of systematic investigations concerning the impact of grafting density on the properties of the designed interface, as well as on the immobilization of biomolecules. In this work, we investigate the surface properties of polymer brushes with different grafting densities prepared using a "grafting from" approach on flat and on colloidal particle substrates by varying the density of initiator groups. In this way, we control and tune interfacial properties of the carrier material such as swelling, charge, adhesion as well as adsorption of laccase from Trametes versicolor on the grafted polyelectrolyte layer. We show that there is no direct transferability of the results received from planar to curved substrates regarding the swelling behavior in dependence on the grafting density. The maximum of swelling degree of PDMAEMA layers is achieved at 0.34 nm and at 0.1 nm grafting density for planar and curved particle substrates, respectively. The adhesion properties of the polymeric layer on both substrates are also strongly influenced by the grafting density, i.e. a decrease of the grafting density causes a transition from the adhesive to non-adhesive state. As proven by the cryo-TEM and AFM force distance measurements, an immobilization of laccase from Trametes versicolor causes a decrease of the polymer swelling and therefore leads to the changes in the surface morphology, charge and adhesion performance of final polymer-enzyme layer. Moreover, the higher effectiveness and activity of laccase were observed for the intermediate grafting densities which seem to be preferable over the maximum brush densities.
控制和调节表面性质对于材料的程序化和理性设计是不可或缺的。特别是，聚合物刷修饰胶体可用作酶固定化的载体材料。尽管控制刷结构至关重要，但对于接枝密度对设计界面性质以及生物分子固定化的影响，仍缺乏系统的研究。在这项工作中，我们通过改变引发剂基团的密度，在平面和胶体颗粒基底上使用“从接枝”方法制备了不同接枝密度的聚合物刷，研究了其表面性质。通过这种方式，我们控制和调节了载体材料的界面性质，如溶胀、电荷、附着以及接枝聚电解质层对来自变色栓菌的漆酶的吸附。我们表明，在平面和弯曲基底上，关于溶胀行为与接枝密度的关系，没有直接的可转移性。在平面和弯曲的颗粒基底上，PDMAEMA 层的最大溶胀度分别在 0.34nm 和 0.1nm 接枝密度时达到最大值。聚合物层在两种基底上的附着性质也受到接枝密度的强烈影响，即接枝密度的降低会导致从附着状态到非附着状态的转变。正如低温透射电子显微镜和原子力显微镜力距离测量所证明的那样，来自变色栓菌的漆酶的固定化会导致聚合物溶胀的降低，从而导致最终聚合物-酶层的表面形貌、电荷和附着性能的变化。此外，在中等接枝密度下观察到漆酶的更高效率和活性，这似乎比最大刷密度更可取。
