Vesicle formation and stability in aqueous mixtures of the hydrolyzed copolymer of styrene-maleic anhydride and conventional single-tailed cationic surfactants

Dual stimuli-responsive polymeric hollow nanogels designed as carriers for intracellular triggered drug release

Dual stimuli-responsive hollow nanogel spheres serving as an efficient intracellular drug delivery platform were obtained from the spontaneous coassociation of two graft copolymers into the vesicle architecture in aqueous phase. Both copolymers comprise acrylic acid (AAc) and 2-methacryloylethyl acrylate (MEA) units as the backbone and either poly(N-isopropylacrylamide) (PNIPAAm) alone or both PNIPAAm and monomethoxypoly(ethylene glycol) (mPEG) chain segments as the grafts. The assemblies were then subjected to covalent stabilization within vesicle walls with ester-containing cross-links by radical polymerization of MEA moieties, thereby leading to hollow nanogel particles. Taking the advantage of retaining a low quantity of payload within polymer layer-enclosed aqueous chambers through the entire loading process, doxorubicin (DOX) in the external bulk phase can be effectively transported into the gel membrane and bound therein via electrostatic interactions with ionized AAc residues and hydrogen-bond pairings with PNIPAAm grafts at pH 7.4. With the environmental pH being reduced (e.g., from 7.4 to 5.0) at 37 °C, the extensive disruption of AAc/DOX complexes due to the reduced ionization of AAc residues within the gel layer and the pronounced shrinkage of nanogels enable the rapid release of DOX species from drug-loaded hollow nanogels. By contrast, the drug liberation at 4 °C was severally restricted, particularly at pH 7.4 at which the DOX molecules remain strongly bound with ionized AAc residues and PNIPAAm grafts. The in vitro characterizations suggest that the DOX-loaded hollow nanogel particles after being internalized by HeLa cells via endocytosis can rapidly release the payload within acidic endosomes or lysosomes. This will then lead to significant drug accumulation in nuclei (within 1 h) and a cytotoxic effect comparable to free drug. This work demonstrates that the novel DOX-loaded hollow nanogel particles show great promise of therapeutic efficacy for potential anticancer treatment.

Novel hybrid vesicles co-assembled from a cationic lipid and PAAc-g-mPEG with pH-triggered transmembrane channels for controlled drug release

This work presents an important example of novel hybrid vesicles with pH-triggered transmembrane channels prepared by co-assembly of poly(acrylic acid)-g-poly(monomethoxy ethylene glycol) (PAAc-g-mPEG) with a cationic lipid, didodecyldimethylammonium bromide (DDAB), via electrostatic interaction for effective doxorubicin (DOX) release.

Preparation of a panoscopic mimic diatom from a silicon compound

Inspired by biological design principles, a panoscopic mimic diatom was created by hierarchical self-assembly of reactive amphiphiles in a multiphase medium comprising hexadecane, ethanol, water, and hydrochloric acid. Through simple stirring at room temperature, mesolamellar macroporous capsules covering oil droplets were obtained in large quantity, which was confirmed by NMR spectroscopy, X-ray diffraction, scanning electron microscopy, and thermogravimetry. At the mesoscale, amphiphilic C(16)Si(OH)(3) assembled into bilayer lamellae through polycondensation, hydrophobic interaction, and H bonding. At the micrometer scale, the bilayer lamellae nucleated at the interface and grew into a polar phase, thus leading to delicate microcages or mimic diatoms. Moreover, the microcages tended to interconnect and fuse into a continuous coating at the centimeter scale, which provided hydrophobicity through the micropatterned surface. This paradigm for creating hierarchical materials with multiphases could lead to new "synthetic" material technologies and novel fascinating materials with anisotropic properties.

Vesicle aggregation in aqueous mixtures of negatively charged polyelectrolyte and conventional cationic surfactant

Vesicle aggregation induced by different environmental factors, including the addition of divalent metal ions, decrease of pH, and increase of temperature--was investigated through turbidity measurement, fluorescence measurement, and transmission electron microscope observation in aqueous solutions of hydrolyzed styrene-maleic anhydride copolymer (HSMA) mixed with dodecyltriethylammonium bromide (C(12)Et(3)). The vesicle aggregation can be explained by the dehydration of the vesicle surface through cations addition or temperature increase based on an analysis of the interaction between vesicles. Moreover, the steric repulsion was introduced to the system and the control of vesicle aggregation was achieved.