Modifying the adsorption behavior of polyamidoamine dendrimers at silica surfaces investigated by total internal reflection fluorescence correlation spectroscopy
Modifying the adsorption behavior of polyamidoamine dendrimers at silica surfaces investigated by total internal reflection fluorescence correlation spectroscopy
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DOI：
10.1021/ac035100c
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发表时间：
2004-02-15
影响因子：
7.4
通讯作者：
Harris, JM
中科院分区：
文献类型：
--
作者：
McCain, KS;Schluesche, P;Harris, JM
聚酰胺-胺（PAMAM）树枝状聚合物进行了修改和测试，用作溶液相扩散探针在二氧化硅纳米结构。为了使树枝状聚合物作为溶液相探针的成功应用，必须理解和控制它们与二氧化硅表面的相互作用，使得探针的运动不受吸附的影响。采用全内反射荧光相关光谱（TIR-FCS）研究了PAMAM树枝状大分子在SiO2表面的吸附/脱附动力学及其在溶液中的扩散行为。第3、5和7代的树枝状聚合物用羧基罗丹明6 G染料标记。由于PAMAM树枝状聚合物在溶液中带正电荷（具有伯胺作为端基），观察到这些分子对带负电荷的二氧化硅表面的显著吸附。吸附/解吸速率和吸附平衡常数通过拟合的自相关函数的动力学模型来确定。随着树枝状大分子代数的增加，脱附速率降低，吸附平衡常数增加。为了减少这些探针对二氧化硅表面的吸附，使标记的树枝状聚合物与琥珀酸酐反应，将伯胺端基转化为带负电荷的羧酸基团。这些羧基化的树枝状聚合物没有可检测地吸附到二氧化硅从水溶液中。TIR-FCS被用来确定他们的自由溶液的扩散常数附近的二氧化硅表面，相应的流体动力学半径比较有利的强迫瑞利散射测量报告的值。
Polyamidoamine (PAMAM) dendrimers were modified and tested for use as solution-phase diffusion probes in silica nanostructures. In order for the successful application of dendrimers as solution-phase probes, their interactions with silica surfaces must be understood and controlled, so that the motion of the probe is not influenced by adsorption. Adsorption/desorption kinetics of PAMAM dendrimers and their diffusion in solution near silica surfaces were investigated with total internal reflection fluorescence correlation spectroscopy (TIR-FCS). Dendrimers of generations 3, 5, and 7 were dye-labeled with carboxyrhodamine 6G. Because PAMAM dendrimers are positively charged in solution (having primary amines as end groups), significant adsorption of these molecules to the negatively charged silica surface was observed. Adsorption/desorption rates and the equilibrium constant for adsorption were determined by fitting the autocorrelation functions to a kinetic model. The desorption rate decreases and the absorption equilibrium constant increases with higher dendrimer generation. To reduce the adsorption of these probes to silica surfaces, the labeled dendrimers were reacted with succinic anhydride, converting the primary amine end groups to negatively charged carboxylic acid groups. These carboxylated dendrimers did not detectably adsorb to silica from aqueous solution. TIR-FCS was used to determine their free-solution diffusion constants near silica surfaces, and the corresponding hydrodynamic radii compare favorably with values reported from forced Rayleigh scattering measurements.