Popa Raluca, Vrânceanu M, Nikolaus S, Nirschl H, Leneweit G
Carl Gustav Carus-Institute, Society for the Promotion of Cancer Therapy, Am Eichhof 30, 75223 Niefern-Oschelbronn, Germany.
Langmuir. 2008 Nov 18;24(22):13030-6. doi: 10.1021/la8024777. Epub 2008 Oct 25.
We studied the effect of poly(ethylene glycol) (PEG) on the extrusion of large, multilamellar nanocapsules (also called liposomes or vesicles) through nanochannels with a length of 6 microm. For the generation of the nanocapsules, we used a lipid mixture with lecithin consisting of saturated and unsaturated fatty acids (dipalmitoylphosphatidylcholine (DPPC) and dioleoylphosphatidylcholine (DOPC)), cholesterol, and 2-8 mol % PEG linked to a lipid anchor (distearoylphosphatidylethanolamine (DSPE)) or the plain lipid anchor without PEG. An increase in PEG leads to a decrease of the critical tension for nanocapsule rupture (lysis tension) between 20-30%, whereas the pure lipid anchor does not produce any differences. We interpret these findings to be produced by a partial intrusion of the polymeric chain into the phospholipid bilayer of the nanocapsule which weakens its tensile strength. We evaluate statistically the discrepancies of lysis tensions found for different channels widths (50-100 nm) and two or four channels in series. Comparing our results on the flow resistance of either nanocapsules or pure water with lubrication theory, we find that the calculated viscous forces are not sufficient to account for the measured friction of nanocapsules. This shows that the nanocapsules are decelerated in the nanochannels by van der Waals interactions between channel and capsule walls and the intermediate water layer. The strength of these forces is 24 times higher for PEG and 94 times higher for the pure lipid anchor than the respective calculated viscous forces alone, showing that nanocapsule flow in nanochannels cannot be considered under the classical continuum assumption of the intermediate water layer.
我们研究了聚乙二醇（PEG）对大型多层纳米胶囊（也称为脂质体或囊泡）通过长度为6微米的纳米通道挤出的影响。为了制备纳米胶囊，我们使用了一种脂质混合物，其包含由饱和脂肪酸和不饱和脂肪酸组成的卵磷脂（二棕榈酰磷脂酰胆碱（DPPC）和二油酰磷脂酰胆碱（DOPC））、胆固醇，以及与脂质锚定基团（二硬脂酰磷脂酰乙醇胺（DSPE））连接的2 - 8摩尔% PEG或不含PEG的纯脂质锚定基团。PEG含量的增加会导致纳米胶囊破裂的临界张力（裂解张力）降低20 - 30%，而纯脂质锚定基团则不会产生任何差异。我们认为这些发现是由聚合物链部分侵入纳米胶囊的磷脂双层中，从而削弱其拉伸强度所导致的。我们对不同通道宽度（50 - 100纳米）以及串联的两个或四个通道所测得的裂解张力差异进行了统计学评估。将我们关于纳米胶囊或纯水流动阻力的结果与润滑理论进行比较，我们发现计算出的粘性力不足以解释所测得的纳米胶囊摩擦力。这表明纳米胶囊在纳米通道中由于通道壁与胶囊壁以及中间水层之间的范德华相互作用而减速。对于PEG，这些力的强度比单独计算的粘性力高24倍，对于纯脂质锚定基团则高94倍，这表明纳米通道中纳米胶囊的流动不能在中间水层的经典连续介质假设下进行考虑。
