Bin Mu

Fabrication of Flocculation-Resistant pH/Ionic Strength/Temperature Multiresponsive Hollow Microspheres and Their Controlled Release

pH/ionic strength/temperature multiresponsive hollow microspheres were successfully prepared by the Ce(IV) initiated grafting polymerization of N-isopropylacrylamide (NIPAm) onto the multilayered polyelectrolyte shells encapsulating the polystyrene sulfonate (PSS) microsphere templates fabricated by the layer-by-layer assembly of chitosan (CS) and alginate (SAL), after etching the templates by dialysis. The hollow structure of the obtained multiresponsive hollow microspheres was characterized by transmission electron microscopy (TEM), which indicated that the inner diameter of the hollow microspheres was about 200 nm. The environmental responsive properties of the multiresponsive hollow microspheres were characterized with dynamic light scattering (DLS) in an aqueous system. The introduction of poly(N-isopropylacrylamide) (PNIPAm) brushes onto the pH/ionic strength dual-responsive hollow microspheres achieved temperature-responsive characteristics. It also could prevent flocculation among the obtained multiresponsive hollow microspheres in a solution with higher salt concentration. Their controlled release of drug molecules (a model hydrophobic drug, dipyridamole (DIP)) was also investigated.

Biocompatible Magnetic and Molecular Dual-Targeting Polyelectrolyte Hybrid Hollow Microspheres for Controlled Drug Release

Well-defined biocompatible magnetic and molecular dual-targeting polyelectrolyte hybrid hollow microspheres have been accomplished via the layer-by-layer (LbL) self-assembly technique. The hybrid shell was fabricated by the electrostatic interaction between the polyelectrolyte cation, chitosan (CS), and the hybrid anion, citrate modified ferroferric oxide nanoparticles (Fe3O4-CA), onto the uniform polystyrene sulfonate microsphere templates. Then the magnetic hybrid core/shell composite particles were modified with a linear, functional poly(ethylene glycol) (PEG) monoterminated with a biotargeting molecule (folic acid (FA)). Afterward the dual targeting hybrid hollow microspheres were obtained after etching the templates by dialysis. The dual targeting hybrid hollow microspheres exhibit exciting pH response and stability in high salt-concentration media. Their pH-dependent controlled release of the drug molecule (anticancer drug, doxorubicin (DOX)) was also investigated in different human body fluids. As expected, the cell viability of the HepG2 cells which decreased more rapidly was treated by the FA modified hybrid hollow microspheres rather than the unmodified one in the in vitro study. The dual-targeting hybrid hollow microspheres demonstrate selective killing of the tumor cells. The precise magnetic and molecular targeting properties and pH-dependent controlled release offers promise for cancer treatment.

Stimuli-responsive multilayer chitosan hollow microspheres via layer-by-layer assembly

Novel stimuli-responsive multilayer chitosan hollow microspheres with chitosan as the unique component have been fabricated by the sequential layer-by-layer electrostatic assembly technique from the sacrificial templates (polystyrene sulfonate, PSS) with chitosan (CS) as the polycation and carboxymethyl chitosan (CMCS) as the polyanion, respectively. Their hollow structure was confirmed by the TEM analysis. The DLS analysis indicated that the multilayer chitosan microcapsules were pH and ionic strength dual-responsive. Due to the biocompatibility of the single component chitosan used, the multilayer chitosan microcapsules are expected to be used in the controlled release of drugs.

Crosslinked polymeric nanocapsules from polymer brushes grafted silica nanoparticles via surface-initiated atom transfer radical polymerization.

The crosslinked polymeric nanocapsules with inner diameter of about 20-50nm were prepared successfully by the post-treatment of the poly(methyl acrylate) (PMA) brushes grafted silica nanoparticles (SN-PMA) produced with the surface-initiated atom transfer radical polymerization (SI-ATRP) technique. The PMA chains grafted were modified with amino groups by being treated with ethanediamine (EDA). Then the silica nanoparticles (SN) templates were removed by being etched with hydrofluoric acid (HF) to produce the crosslinked polymeric nanocapsules after the aminated poly(methyl acrylate) (APMA) chains on the SN templates were crosslinked with hexamethylene diisocyanate (HDI). Transmission electron microscopy (TEM) analyses were used to estimate the size of the polymeric nanocapsules.

Facile Preparation of Crosslinked Polymeric Nanocapsules via Combination of Surface-Initiated Atom Transfer Radical Polymerization and Ultraviolet Irradiated Crosslinking Techniques.

A facile approach for the preparation of crosslinked polymeric nanocapsules was developed by the combination of the surface-initiated atom transfer radical polymerization and ultraviolet irradiation crosslinking techniques. The well-defined polystyrene grafted silica nanoparticles were prepared via the SI-ATRP of styrene from functionalized silica nanoparticles. Then the grafted polystyrene chains were crosslinked with ultraviolet irradiation. The cross-linked polystyrene nanocapsules with diameter of 20–50 nm were achieved after the etching of the silica nanoparticle templates with hydrofluoric acid. The strategy developed was confirmed with Fourier transform infrared, thermogravimetric analysis, and transmission electron microscopy.

Disintegration-controllable stimuli-responsive polyelectrolyte multilayer microcapsules via covalent layer-by-layer assembly

The disintegration-controllable stimuli-responsive polyelectrolyte multilayer microcapsules have been fabricated via the covalent layer-by-layer assembly between the amino groups of chitosan (CS) and the aldehyde groups of the oxidized sodium alginate (OSA) onto the sacrificial templates (polystyrene sulfonate, PSS) which was removed by dialysis subsequently. The covalent crosslinking bonds of the multilayer microcapsules were confirmed by FTIR analysis. The TEM analysis showed that the diameter of the multilayer microcapsules was <200nm. The diameter of the multilayer microcapsules decreased with the increasing of the pH values or the ionic strength. The pH and ionic strength dual-responsive multilayer microcapsules were stable in acidic and neutral media while they could disintegrate only at strong basic media.

Encapsulation of drug microparticles with self-assembled Fe3O4/alginate hybrid multilayers for targeted controlled release†

The magnetic-targeted drug-delivery system was developed with the Fe(3)O(4) nanoparticles as the self-assembling material to form the hybrid multilayer shells. Layer-by-Layer stepwise self-assembly of the natural polyelectrolytes sodium alginate and the Fe(3)O(4) nanoparticles was used to create the magnetic hybrid multilayers around drug microparticles (~400 nm in diameter) for the purpose of targeted controlled release. The obtained drug microparticles encapsulated with hybrid multilayers were characterized with dynamic light scattering, transmission electron microscope, and vibrating sample magnetometer. UV-vis spectroscopy was employed to monitor the drug releasing behaviors in pH 1.8 and 7.4 buffer solutions. It was found that the release of drug molecules from the pH-sensitive magnetic-targeted drug-delivery system was mainly dependent on the following factors: the permeability of the hybrid multilayer shells and the solubility of the drug molecules in the bulk solutions. The results revealed that it could achieve the quick and continuous controlled release via the magnetically-guide to the target tissue of organism.

Biocompatible and Biodegradable Polymeric Nanocapsules from Poly(α,β-malic acid)-Grafted Nano-silica Templates

A green strategy for the preparation of biocompatible and biodegradable polymeric nanocapsules containing lots of functional carboxyl groups is developed by the surface polycondensation of α,β-malic acid from silica nanoparticles as the sacrificial templates. After the poly(α,β-malic acid) grafted silica nanoparticles are cross-linked with glycerol, the nano-silica templates are etched with hydrofluoric acid to produce the biocompatible and biodegradable polymeric nanocapsules. The hollow structure of the polymeric nanocapsules with an inner diameter about 20–100 nm is validated by transmission electron microscopy.

Polymeric Nanocapsule from Silica Nanoparticle@Cross-linked Polymer Nanoparticles via One-Pot Approach

A facile strategy was developed here to prepare cross-linked polymeric nanocapsules (CP nanocapsules) with silica nanoparticles as templates. The silica nanoparticle@cross-linked polymer nanoparticles were prepared by the encapsulation of the silica nanoparticles by the one-pot approach via surface-initiated atom transfer radical polymerization of hydroxyethyl acrylate in the presence ofN,N′-methylenebisacrylamide as a cross-linker from the initiator-modified silica nanoparticles. After the silica nanoparticle templates were etched with hydrofluoric acid, the CP nanocapsules with particle size of about 100 nm were obtained. The strategy developed was confirmed with Fourier transform infrared, thermogravimetric analysis and transmission electron microscopy.

Preparation of Photo-Sensitive Degradable Polymeric Nanocapsules from Dendrimer Grafted Nano-Silica Templates

The poly-hydroxylated photo-sensitive degradable polymeric nanocapsules were prepared by the condensation of the A2-type monomer 4, 4′-Azobenzene dibenzoyl chloride (ADC) and the B3-type monomer triethanolamine (TEA) from the sacrificial nano-silica templates by a divergent approach. After the dendrimer molecules grafted on the silica nanoparticles were cross-linked with ADC, which is both the monomer and the cross-linker in this approach developed subsequently, the silica templates were removed by being etched with hydrofluoric (HF) to produce the photo-sensitive degradable polymeric nanocapsules. The hollow structure of the polymeric nanocapsules with the inner diameter about 20–100 nm is characterized by transmission electron microscopy (TEM). The photo-responsive behavior of the nanocapsules is confirmed by UV-Vis spectroscopy.