Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
Anal Chem. 2012 Mar 6;84(5):2179-87. doi: 10.1021/ac202434c. Epub 2012 Feb 17.
Iontophoresis uses electricity to deliver solutes into living tissue. Often, iontophoretic ejections from micropipets into brain tissue are confined to millisecond pulses for highly localized delivery, but longer pulses are common. As hippocampal tissue has a ζ-potential of approximately -22 mV, we hypothesized that, in the presence of the electric field resulting from the iontophoretic current, electroosmotic flow in the tissue would carry solutes considerably farther than diffusion alone. A steady state solution to this mass transport problem predicts a spherically symmetrical solute concentration profile with the characteristic distance of the profile depending on the ζ-potential of the medium, the current density at the tip, the tip size, and the solute electrophoretic mobility and diffusion coefficient. Of course, the ζ-potential of the tissue is defined by immobilized components of the extracellular matrix as well as cell-surface functional groups. As such, it cannot be changed at will. Therefore, the effect of the ζ-potential of the porous medium on ejections is examined using poly(acrylamide-co-acrylic acid) hydrogels with various magnitudes of ζ-potential, including that similar to hippocampal brain tissue. We demonstrated that nearly neutral fluorescent dextran (3 and 70 kD) solute penetration distance in the hydrogels and OHSCs depends on the magnitude of the applied current, solute properties, and, in the case of the hydrogels, the ζ-potential of the matrix. Steady state solute ejection profiles in gels and cultures of hippocampus can be predicted semiquantitatively.
电渗析利用电流将溶质输送到活组织中。通常，通过微管将离子电渗喷射到脑组织中的喷射持续时间为毫秒级，以实现高度局部化的输送，但较长的脉冲很常见。由于海马组织的 ζ 电位约为-22 mV，我们假设，在离子电渗电流产生的电场存在的情况下，组织中的电渗流将溶质输送得更远，远远超过单纯的扩散。这种质量传输问题的稳态解预测了一个球形对称的溶质浓度分布，其特征距离取决于介质的 ζ 电位、尖端的电流密度、尖端尺寸以及溶质的电泳迁移率和扩散系数。当然，组织的 ζ 电位是由细胞外基质的固定成分以及细胞表面的功能基团定义的。因此，它不能随意改变。因此，使用具有不同 ζ 电位的聚（丙烯酰胺-co-丙烯酸）水凝胶来研究多孔介质的 ζ 电位对喷射的影响，包括类似于海马脑组织的 ζ 电位。我们证明，几乎中性的荧光葡聚糖（3 和 70 kD）溶质在水凝胶和 OHSCs 中的穿透距离取决于施加电流的大小、溶质的性质，以及在水凝胶的情况下，基质的 ζ 电位。凝胶和海马组织培养物中的稳态溶质喷射分布可以半定量地预测。
