Department of Chemistry, Indian Institute of Technology Kharagpur , West Bengal 721302 India.
J Phys Chem B. 2013 Nov 7;117(44):13767-74. doi: 10.1021/jp406973t. Epub 2013 Oct 24.
Poly(amidoamine) (PAMAM) dendrimers are known to be highly efficient nonviral carriers in gene delivery. Dendrimer-mediated transfection is known to be a function of the dendrimer to DNA charge ratio as well as the size of the dendrimer. In the present study, the binding kinetics of four PAMAM dendrimers (G1, G2, G3, and G4) with calf thymus DNA (CT-DNA) has been studied using stopped-flow fluorescence spectroscopy. The effect of dendrimer-to-DNA charge ratio and dendrimer generation on the binding kinetics was investigated. In most cases, the results of dendrimer-CT-DNA binding can be explained by a two-step reaction mechanism: a rapid electrostatic binding between the dendrimer and DNA, followed by a conformational change of the dendrimer-DNA complex that ultimately leads to DNA condensation. It was observed that the charge ratio on the dendrimer and the DNA phosphate groups, as well as the dendrimer generation (size), has a marked effect on the kinetics of binding between the DNA and the dendrimers. The rate constant (k'1) of the first step was much higher compared to that of the second step (k'2), and both were found to increase with an increase in dendrimer concentration. Among the four generations of dendrimers, G4 exhibited significantly faster binding kinetics compared to the three smaller generation dendrimers.
聚酰胺-胺（PAMAM）树枝状聚合物是众所周知的高效非病毒载体，在基因传递中。树枝状聚合物介导的转染被认为是树枝状聚合物与 DNA 电荷比以及树枝状聚合物的大小的函数。在本研究中，使用停流荧光光谱法研究了四种 PAMAM 树枝状聚合物（G1、G2、G3 和 G4）与小牛胸腺 DNA（CT-DNA）的结合动力学。研究了树枝状聚合物与 DNA 电荷比和树枝状聚合物代对结合动力学的影响。在大多数情况下，树枝状聚合物与 CT-DNA 结合的结果可以用两步反应机制来解释：树枝状聚合物与 DNA 之间的快速静电结合，然后是树枝状聚合物-DNA 复合物的构象变化，最终导致 DNA 凝聚。观察到树枝状聚合物上的电荷比和 DNA 磷酸基团，以及树枝状聚合物的代（大小），对 DNA 与树枝状聚合物之间的结合动力学有显著影响。第一步的速率常数（k'1）远高于第二步的速率常数（k'2），并且都随着树枝状聚合物浓度的增加而增加。在四代树枝状聚合物中，G4 与其他三个较小代的树枝状聚合物相比，表现出更快的结合动力学。
