Effect of polymer ionization on the interaction with DNA in nonviral gene delivery systems
Effect of polymer ionization on the interaction with DNA in nonviral gene delivery systems
复制标题
DOI：
10.1021/bm025736y
复制
发表时间：
2003-05-01
影响因子：
6.2
通讯作者：
Stolnik, S
中科院分区：
文献类型：
--
作者：
Rungsardthong, U;Ehtezazi, T;Stolnik, S
dna -阳离子聚合物络合的优化是非病毒基因传递的关键。虽然DNA与阳离子聚合物相互作用的物理化学表征近年来在非病毒DNA递送领域引起了越来越多的关注，但关于不同多阳离子电荷密度对DNA-阳离子聚合物络合作用影响的文献仍然很少。因此，本研究的目的是系统地评估弱阳离子聚电解质（聚[2（二甲氨基）甲基丙烯酸乙酯]或DMAEMA均聚物）的电离程度对其与DNA形成复合物能力的影响。这是通过改变溶液pH从4.0到8.0，并分析对结合亲和力、热力学性质、配合物大小和形态的影响来实现的。降低溶液pH值导致阳离子聚合物的电离程度更高，因此与DNA的结合亲和力更强，这可以从前者从DNA中取代溴化乙啶的倾向增加和相对较低的单体：核苷酸摩尔比（0.8:1）来判断，以延缓游离DNA的迁移。等温滴定微量热法研究进一步证实，在低pH下比在高pH下发生更强的相互作用。通过将pH从8.0降低到6.6，K-obs从7.8 × 10(5)增加到20.4 × 10(5) M-1。凝胶电泳的加载孔中溴化乙锭的荧光减少，聚合物/DNA比例高时复合物尺寸减小而不发生团聚，以及TEM研究中观察到的离散和密集的球形复合物，都证明了低pH下更有效的缩合。这可能归因于过量阳离子聚合物链的静电稳定作用，这些阳离子聚合物链在聚合物/DNA复合物周围提供了一个排斥壳。理化数据表明，在较低的pH值下，DMAEMA均聚物的电离度增加，其结合亲和力更高，配合物更小、更致密，缩聚效率更高。因此，这些发现强调了电离程度对弱阳离子聚电解质DNA复合体形成的重要性。
The optimization of DNA-cationic polymer complexation is crucial for nonviral gene delivery. Although physicochemical characterization of the interaction between DNA and cationic polymers has recently attracted more attention in the nonviral DNA delivery field, the literature on the effect of varying polycation charge density on DNA-cationic polymer complexation is still scarce. Thus, the aim of this study was to systematically assess the influence of the degree of ionization of a weak cationic polyelectrolyte (poly[2(dimethylamino)ethyl methacrylate] or DMAEMA homopolymer) on its ability to form complexes with DNA. This was achieved by varying the solution pH from 4.0 to 8.0 and analyzing the resulting effects on the binding affinity, thermodynamic properties, complex size, and morphology. Lowering the solution pH led to higher degrees of ionization for the cationic polymer and hence greater binding affinities with DNA, as judged by the increased propensity of the former to displace ethidium bromide from DNA and also by relatively low monomer:nucleotide molar ratio (0.8:1) required to retard the migration of free DNA. Isothermal titration microcalorimetry studies further confirmed that a stronger interaction occurred at low pH than at high pH. By decreasing the pH from 8.0 to 6.6, K-obs increased from 7.8 x 10(5) to 20.4 x 10(5) M-1. More efficient condensation at low pH was demonstrated by the reduction of ethidium bromide fluorescence in the loading wells from gel electrophoresis, decreased complex sizes without agglomeration occurring at high polymer/DNA ratios, together with discrete and dense spherical complexes observed in TEM studies. This may be attributed to the presence of electrostatic stabilization from excess cationic polymer chains, which provide a repulsive shell around the polyrner/DNA complex. The physicochemical data indicate that the increased degree of ionization for the DMAEMA homopolymer at lower pH results in higher binding affinity, smaller and more compact complexes, and more efficient condensation. These findings therefore highlight the importance of the degree of ionization on DNA complex formation for weak cationic polyelectrolytes.