Understanding the mechanism of action of poly(amidoamine)s as endosomolytic polymers: Correlation of physicochemical and biological properties
Understanding the mechanism of action of poly(amidoamine)s as endosomolytic polymers: Correlation of physicochemical and biological properties
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DOI：
10.1021/bm049936g
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发表时间：
2004-07-01
影响因子：
6.2
通讯作者：
Duncan, R
中科院分区：
文献类型：
--
作者：
Griffiths, PC;Paul, A;Duncan, R
生物响应性聚酰胺胺S(PAA)S目前正在开发用于细胞内蛋白质和基因递送的内溶聚合物。在这里，首次使用小角中子散射(SANS)系统地研究了内溶聚合物PAA ISA 23的随pH的构象变化。ISA23的旋转半径被确定为pH和反离子的函数，目的是将聚合物构象的变化与用大鼠红细胞溶血试验评估的膜活性相关联。随着pH的降低，ISA23的回转半径在pH=3附近增大到最大值(R-g接近80埃)，然后再次减小。在高pH和高离子强度下，聚合物带负电荷，并采用相当紧凑的结构(R-g类似于20埃)，推测聚合物线圈外部有解离的羧基。在低pH值下，线圈再次坍塌(R-g<；20埃)，可能是由于高离子强度的影响。结论是，盐型的性质对聚合物卷曲的大小没有直接的影响，但它确实间接地决定了普遍的pH，从而决定了聚合物的构象。脉冲梯度自旋回波核磁共振测量与SANS对旋转半径的估计很好地一致，尽管ISA23的多分散性确实使数据解释/比较复杂化。这些结果支持提出的PaaS的作用模式，即从中性pH(细胞外)到酸性pH(内酶体和溶酶体)环境的卷曲膨胀。然而，结果确实表明，聚合物上的电荷与溶血活性更密切相关，而不是聚合物构象。
Bioresponsive poly(amidoamine)s (PAA)s are currently under development as endosomolytic polymers for intracellular delivery of proteins and genes. Here for the first time, small-angle neutron scattering (SANS) is used to systematically investigate the pH-dependent conformational change of an endosomolytic polymer, the PAA ISA 23. The radius of gyration of the ISA23 was determined as a function of pH and counterion, the aim being to correlate changes in polymer conformation with membrane activity assessed using a rat red blood cell haemolysis assay. With decreasing pH, the ISA23 radius of gyration increased to a maximum (R-g similar to 80 Angstrom) around pH = 3, before subsequently decreasing once more. At high pH and therefore high ionic strengths, the polymer is negatively charged and adopts a rather compact structure (R-g similar to 20 Angstrom), presumably with the dissociated carboxylic groups on the exterior of the polymer coil. At low pH, the coil again collapses (R-g < 20 Angstrom), presumably due to the effects of the high ionic strength. It is concluded that the nature of the salt form has no direct hearing on the size of the polymer coil, but it does indirectly determine the prevailing pH and, hence, polymer conformation. Pulsed-gradient spin-echo NMR measurements were in good agreement with the SANS estimates of the radius of gyration, although ISA23 polydispersity does complicate the data interpretation/comparison. These results support the proposed mode of action of PAAs, namely a coil expansion on passing from a neutral pH (extracellular) to an acidic pH (endosomal and lysosomal) environments. The results do, however, suggest that the charge on the polymer shows a closer correlation with the haemolysis activity rather than the polymer conformation.