Structure and thermodynamics of mixed polymeric micelles with crystalline cores: tuning properties via co-assembly

Mixed Micelles with Galactose Ligands for the Oral Delivery of Berberine to Enhance Its Bioavailability and Hypoglycemic Effects

Diabetes mellitus (DM) has become an epidemic disorder that is an escalating public health risk. Currently, DM treatment is highly challenging due to temporary medical relief rather than a permanent cure. This article reports a ligand-anchored mixed micellar system formed by phospholipids and N -oleoyl-D-galactosamine aiming to enhance the oral bioavailability and hypoglycemic effects of berberine, an antidiabetic agent with poor absorption. Berberine-loaded mixed micelles (BBMMs) were prepared through a solvent diffusion technique. The resulting BB-MMs were characterized by particle size, potential, morphology, entrapment efficiency (EE) and in vitro release. The oral pharmacokinetics and hypoglycemic efficacy of BB-MMs were evaluated in rats and compared with a berberine suspension. As a result, BB-MMs prepared with the preferable formulation had a particle size of approximately 100 nm with an EE of over 85%. BB-MMs exhibited sustained drug release owing to the entrapment in the micelles. After oral administration, BB-MMs ameliorated the pharmacokinetic profile of berberine and significantly enhanced its oral bioavailability (317.17% relative to the suspension). The pharmacological effect (PE) of BB-MMs was approximately 3.44 times greater than that of the suspension. In addition, in situ single-pass intestinal perfusion and cellular testing results illustrated that BB-MMs had good intestinal permeability and cellular uptake. Our findings demonstrate that the oral bioavailability and hypoglycemic effects of berberine could be largely enhanced by encapsulation into mixed micelles with a galactose moiety. Thus, galactosylated micelles may be promising for developing berberine nanomedicines to fight DM.

Spherical Micelles with Nonspherical Cores: Effect of Chain Packing on the Micellar Shape

Self-assembly of amphiphilic polymers into micelles is an archetypical example of a "self-confined" system due to the formation of micellar cores with dimensions of a few nanometers. In this work, we investigate the chain packing and resulting shape of C n -PEOx micelles with semicrystalline cores using small/wide-angle X-ray scattering (SAXS/WAXS), contrast-variation small-angle neutron scattering (SANS), and nuclear magnetic resonance spectroscopy (NMR). Interestingly, the n-alkyl chains adopt a rotator-like conformation and pack into prolate ellipses (axial ratio ϵ ≈ 0.5) in the "crystalline" region and abruptly arrange into a more spheroidal shape (ϵ ≈ 0.7) above the melting point. We attribute the distorted spherical shape above the melting point to thermal fluctuations and intrinsic rigidity of the n-alkyl blocks. We also find evidence for a thin dehydrated PEO layer (≤1 nm) close to the micellar core. The results provide substantial insight into the interplay between crystallinity and molecular packing in confinement and the resulting overall micellar shape.

Tale of Two Tails: Molecular Exchange Kinetics of Telechelic Polymer Micelles

Telechelic polymers contain two chain ends that are able to promote self-assembly into "flowerlike" or interconnected micellar structures. Here, we investigate the molecular exchange kinetics of such micelles using time-resolved small-angle neutron scattering. We show that the activation energies of monofunctional and telechelic chain exchange are identical. This demonstrates that the two chain ends are not simultaneously released in a single event. Instead, the results show that, contrary to regular micelles, the kinetics occurs in a multistep process involving a collision-induced single-molecule exchange mechanism where the exchange rate is directly proportional to the polymer concentration. We show that this novel mechanism can be quantitatively explained by a simple kinetic model.