Ribeiro Suzie, Hussain Nasir, Florence Alexander T
The School of Pharmacy, University of London, 29/39 Brunswick Square, London, WC 1N 1AX, UK.
Int J Pharm. 2005 Jul 25;298(2):354-60. doi: 10.1016/j.ijpharm.2005.03.036.
Biodegradable PLGA particles of less than 1 microm can encapsulate DNA and DNA-dendron complexes (dendriplexes) providing sustained DNA release for transfecting cells in gene delivery. Two polylysine-based dendrons prepared by solid state peptide synthesis were used to condense pRedN-1 DNA (7.5 kbp), a fluorescent protein vector. The dendrons had 16 free surface amino groups attached to seven lysine groups, bound to a lipid core, one containing three C18 chains and the other a single C10 chain. Increased lipophilicity and molar charge ratios are key factors in producing compact and reproducible dendriplexes, shown by the hydrodynamic diameter which is of the order of 800 nm (p.d.>0.5) at a 2:1 molar charge ratio, a value which decreases to around 200 nm at a 5:1 charge ratio. At lower charge ratios the dendriplexes are negative and have a zeta potential in order of -18 mV. As the ratio increases (5:1, 10:1) the complexes bear a positive potential (13+/-2 mV). This suggests that at the 2:1 ratio the DNA is not fully condensed. The DNA was radiolabelled with 35S dCTP (deoxycytidinetriphosphate) with the removal of the un-incorporated radiolabelled nucleotides. The encapsulation efficiency of dendriplexes in PLGA particles is higher than that for uncomplexed DNA. When the results are normalised for DNA content and particle surface area, complexation of the DNA was found to decrease release rate.
小于1微米的可生物降解聚乳酸-羟基乙酸共聚物（PLGA）颗粒能够包裹DNA和DNA-树枝状聚合物复合物（树枝状复合物），在基因递送中为转染细胞提供持续的DNA释放。通过固态肽合成制备的两种基于聚赖氨酸的树枝状聚合物用于凝聚pRedN-1 DNA（7.5千碱基对），一种荧光蛋白载体。这些树枝状聚合物有16个连接到7个赖氨酸基团上的游离表面氨基，与脂质核心相连，一个脂质核心含有三条C18链，另一个含有一条C10链。增加的亲脂性和摩尔电荷比是产生紧密且可重复的树枝状复合物的关键因素，这通过流体动力学直径得以体现，在2:1的摩尔电荷比下，流体动力学直径约为800纳米（多分散性>0.5），在5:1的电荷比下该值降至约200纳米。在较低电荷比时，树枝状复合物带负电，zeta电位约为 -18毫伏。随着比例增加（5:1、10:1），复合物带有正电位（13±2毫伏）。这表明在2:1的比例下DNA未完全凝聚。DNA用3̅5̅S dCTP（脱氧胞苷三磷酸）进行放射性标记，并去除未掺入的放射性标记核苷酸。树枝状复合物在PLGA颗粒中的包封效率高于未复合的DNA。当结果根据DNA含量和颗粒表面积进行归一化时，发现DNA的复合会降低释放速率。
