Microelectrophoresis based on the dynamic light scattering (DLS) effect has been a major tool for assessing and controlling the conditions for stability of colloidal systems. However, both the DLS methods for characterization of the hydrodynamic size of dispersed submicron particles and the theory behind the electrokinetic phenomena are associated with fundamental and practical approximations that limit their sensitivity and information output. Some of these fundamental limitations, including the spherical approximation of DLS measurements and an inability of microelectrophoretic analyses of colloidal systems to detect discrete charges and differ between differently charged particle surfaces due to rotational diffusion and particle orientation averaging, are revisited in this work. Along with that, the main prospects of these two analytical methods are mentioned. A detailed review of the role of zeta potential in processes of biochemical nature is given too. It is argued that although zeta potential has been used as one of the main parameters in controlling the stability of colloidal dispersions, its application potentials are much broader. Manipulating surface charges of interacting species in designing complex soft matter morphologies using the concept of zeta potential, intensively investigated recently, is given as one of the examples. Branching out from the field of colloid chemistry, DLS and zeta potential analyses are now increasingly finding application in drug delivery, biotechnologies, physical chemistry of nanoscale phenomena and other research fields that stand on the frontier of the contemporary science. Coupling the DLS-based microelectrophoretic systems with complementary characterization methods is mentioned as one of the prosperous paths for increasing the information output of these two analytical techniques.

Intracellular delivery of non-transported therapeutic agents has traditionally been thought possible only for low molecular weight (<500 DA) hydrophobic molecules. Higher molecular weight agents including oligonucleotides, proteins, DNA, liposomes, and nanoparticles do not readily enter the cytoplasm. However, the human immunodeficiency virus (HIV) trans-acting transcriptional activator (TAT) protein enters the cytosol by way of an 11 amino acid cationic peptide (TATp). When this cationic sequence is attached to a variety of small pharmacological agents, including paramagnetic ions[1,2] and proteins,[3-6] they are delivered into cells. Further, TATp modification of large cargo, such as proteins, polymers, and nanoparticles, may enable them to internalize into cells as well. The size limitations for cargo delivered by a single TATp are currently undetermined, but multiple TATp attached to polymers, nanoparticles, liposomes, and phage can definitely mediate their internalization. This process appears to follow an endocytotic or potocytic pathway and does not directly transfer the cargo into the cytoplasm of the cell. Here we review recent publications in which multiple TATp have been attached to and resulted in the successful intracellular delivery of nanoparticles.

The uncontrolled aggregation of amorphous calcium phosphate (ACP) particulate fillers and their uneven distribution within polymer matrices can have adverse effects on the properties of ACP composites. In this paper we assessed the influence of non-ionic and anionic surfactants and poly(ethylene oxide) (PEO) introduced during the preparation of ACP on the particle size distribution and compositional properties of ACP. In addition, the mechanical strength of polymeric composites utilizing such fillers with a photo-activated binary methacrylate resin was evaluated. Zirconia-hybridized ACP (Zr-ACP) filler and its corresponding composite served as controls for this study. Surfactant- and PEO-ACPs had an average water content of 16.8 % by mass. Introduction of the anionic surfactant reduced the median particle diameter about 45 % (4.1 μm vs. 7.4 μm for the Zr-ACP control). In the presence of PEO, however, the d(m) increased to 14.1 μm. There was no improvement in the biaxial flexure strength (BFS) in any of the dry composite specimens prepared with the surfactant- and/or PEO-ACPs compared to those formulated with Zr-ACP. The BFS of wet composite specimens decreased by 50 % or more after a month-long exposure to saline solutions. Other types of surfactants and/or polymers as well as alternative surface modification protocols need to be explored for their potential to provide better dispersion of ACP into the matrix resin and better mechanical performance ACP composites.

Molecular dynamics simulations were used to characterize the binding of the chiral drugs chlorthalidone and lorazepam to the molecular micelle poly-(sodium undecyl-(L)-leucine-valine). The project's goal was to characterize the nature of chiral recognition in capillary electrophoresis separations that use molecular micelles as the chiral selector. The shapes and charge distributions of the chiral molecules investigated, their orientations within the molecular micelle chiral binding pockets, and the formation of stereoselective intermolecular hydrogen bonds with the molecular micelle were all found to play key roles in determining where and how lorazepam and chlorthalidone enantiomers interacted with the molecular micelle.