Aggregation behavior and interaction of an amphiphilic drug imipramine hydrochloride with cationic surfactant cetyltrimethylammonium bromide: Light scattering studies

Synthesis, Characterization, and Aqueous Properties of an Amphiphilic Terpolymer with a Novel Nonionic Surfmer

A series of surfactive amphiphilic polymer PAADs were prepared from the copolymerization of sodium acrylate, dodecyl polyoxyethylene acrylate (DPA, a surfmer), and acrylamide under the action of a mixed initiating agent consisting of ammonium persulfate-sodium bisulfite/2,2′-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride. The aggregative behaviors of PAADs were explored by 13C nuclear magnetic resonance, a viscometer, and a surface tension instrument. It was found that the apparent viscosity and surface activity of PAADs were significantly improved by the increase of average sequence length of hydrophobic micro blocks, strong intermolecular hydrophobic association, or the formation of mixed micelles between hydrophobic micro blocks and micromolecular surface-active agent. The introduction of long-chain alkyls on molecular chains prolonged the average sequence length of hydrophobic micro blocks in molecular chains and enhanced the hydrophobic association between molecular chains and the tight arrangement of molecular chains on water surfaces, thereby increasing the surface activity. Moreover, the anionic monomer sodium acrylate on molecular chains, via electrostatic repulsion, promoted the conversion from intrachain association to intermolecular association and thereby facilitated the formation of dense interfacial films, enhancing the surface activity of water solutions. Then, the anion surfmer sodium dodecylbenzenesulfonate interacted with the hydrophobic micro blocks on the molecular chains to form mixed micelles, which accelerated the interchain association and enhanced the polymer surface activity. The novel polymeric micelle with higher viscosifying ability and surface activity was expected to be a promising oil drive agent for tertiary oil recovery.

Silica Ouzo Effect: Amphiphilic Drugs Facilitate Nanoprecipitation of Polycondensed Mercaptosilanes

Amphiphilic drugs are therapeutic agents whose molecular structures contain both hydrophobic and hydrophilic portions. Here we report a systematic study on how amphiphilic drugs can assist in silica nanoprecipitation. 3-Mercaptopropyltrimethoxysilane (MPTMS) was used as the sole silica material and 12 amphiphilic drugs spanning a wide spectrum of therapeutic categories were included. MPTMS polycondensation was conducted in a DMSO-based organic phase. After a sufficient time, particle formation was induced by injecting a small amount of the organic phase into a water solution containing various amphiphiles. The results show that all amphiphilic drugs studied exerted concentration-dependent facilitating effect on nanoparticle formation. Under certain preparation conditions, the particle solution showed physical stability over a long period and the formed particles could be as small as 100 nm. By systematically varying drug concentrations and injection volumes, the ability of each amphiphile to promote nanoprecipitation can be quantified and compared, based on two novel indices: the area under the critical volume-concentration curve (AUC) and the critical stabilization concentration (CSC). We demonstrate that both ability indices significantly correlated with the drug's log P and critical micelle concentrations (CMC). Furthermore, we have optimized the aging and particle purification condition and extensively characterized our system through comprehensive TEM and zeta-potential measurements, as well as determinations for drug entrapment and release. In conclusion, we have established a quantitative structure-activity relationship for amphiphilic small-molecular drugs in their ability to interact with poly(mercaptopropyl)silsesquioxane species and form nanoparticles via solvent shifting. We speculate that both hydrophobic and electrostatic interactions play important roles in the formation and stabilization of nanoparticles.

Cationic sulfonium functionalization renders Znsalens with high fluorescence, good water solubility and tunable cell-permeability

Introducing cationic sulfonium to the Znsalens skeleton circumvents aggregation arising from intermolecular Zn⋯O interactions (found between Zn and the phenoxyl group of another Znsalen molecule).