Kato Riku, Frusawa Hiroshi
Faculty of Pharmaceutical Science, Nagasaki International University, Huis Ten Bosch, Nagasaki 859-3298, Japan.
Research Center for Materials Science and Engineering, Kochi University of Technology, Tosa-Yamada, Kochi 782-8502, Japan.
Materials (Basel). 2015 Jul 8;8(7):4176-4190. doi: 10.3390/ma8074176.
We investigated the individual properties of various polyion-coated bubbles with a mean diameter ranging from 300 to 500 nm. Dark field microscopy allows one to track the individual particles of the submicron bubbles (SBs) encapsulated by the layer-by-layer (LbL) deposition of cationic and anionic polyelectrolytes (PEs). Our focus is on the two-step charge reversals of PE-SB complexes: the first is a reversal from negatively charged bare SBs with no PEs added to positive SBs encapsulated by polycations (monolayer deposition), and the second is overcharging into negatively charged PE-SB complexes due to the subsequent addition of polyanions (double-layer deposition). The details of these phenomena have been clarified through the analysis of a number of trajectories of various PE-SB complexes that experience either Brownian motion or electrophoresis. The contrasted results obtained from the analysis were as follows: an amount in excess of the stoichiometric ratio of the cationic polymers was required for the first charge-reversal, whereas the stoichiometric addition of the polyanions lead to the electrical neutralization of the PE-SB complex particles. The recovery of the stoichiometry in the double-layer deposition paves the way for fabricating multi-layered SBs encapsulated solely with anionic and cationic PEs, which provides a simple protocol to create smart agents for either drug delivery or ultrasound contrast imaging.
我们研究了平均直径在300至500纳米范围内的各种聚离子包覆气泡的个体特性。暗场显微镜能够追踪通过阳离子和阴离子聚电解质（PEs）的逐层（LbL）沉积封装的亚微米气泡（SBs）的单个颗粒。我们关注的是PE-SB复合物的两步电荷反转：第一步是从未添加PEs的带负电荷的裸SBs反转到被聚阳离子封装的带正电荷的SBs（单层沉积），第二步是由于随后添加聚阴离子（双层沉积）而使PE-SB复合物过度充电成为带负电荷的复合物。通过分析经历布朗运动或电泳的各种PE-SB复合物的多条轨迹，已阐明了这些现象的细节。分析得出的对比结果如下：第一次电荷反转需要超过阳离子聚合物化学计量比的量，而聚阴离子的化学计量添加导致PE-SB复合颗粒的电中和。双层沉积中化学计量的恢复为制造仅用阴离子和阳离子PEs封装的多层SBs铺平了道路，这为创建用于药物递送或超声造影成像的智能试剂提供了一个简单的方案。
