AC-Electrokinetic Characterization and Induced Encapsulation Release of Micelles in Aqueous Suspensions

Micelles and polymers vesicles have been of increasing interest as drug delivery systems for controlled release, specific cell targeting, and medical diagnostics. In addition, AC-electrokinetic techniques have emerged as a viable option for colloidal and biocolloidal manipulation. In this work, we examine the dielectrophoresis (DEP) characteristics of complex micellar nanoparticles under non-uniform AC-electric field of varied ac-field frequencies (5 kHz-20 MHz) and amplitudes (0.1-10 Vpp) by fluorescence correlation spectroscopy (FCS) at a single-molecule resolution. We focus on the AC-field induced transport of sodium tetradecyl sulfate (STS) and sodium dodecyl sulfate (SDS) micelles tagged with various fluorescent and drug encapsulates in aqueous media. We observe a strong AC-frequency dependence of micelle concentration between two microelectrodes, from which the DEP crossover frequency is determined. Surprisingly, we also observe an AC-field induced dissociation of the micelle structure and a resulting release of fluorescent encapsulates at a characteristic low AC-field frequency of approximately 1-10 kHz, where the dissociation has been found to be dependent on the surface charge of the interior encapsulate.