Preparation of albumin—PAA nanocapsules and their controlled release behavior for drugs

New kinds of narrowly distributed protein‐based nanoparticles, bovine serum albumin‐Poly (acrylic acid) (BSA/PAA) nanospheres, and nanocapsules were prepared via in situ polymerization, swelling, and re‐aggregation. The structure and morphology of the nanospheres were characterized by UV‐Vis, FT‐IR, DLS, and TEM. The stability of the BSA/PAA nanospheres and nanocapsules was increased when their skeletons were fixed by cross‐linked agents. The nanospheres carried a positive charge and their size was about 80–110 nm. The protein‐based nanocapsules were stimuli‐responsive with pH value and their hydrodynamic diameter varied from 70 to 230 nm with changes of pH. In vitro release experiments of Rhodamine B and Doxorubicin hydrochloride showed that these biopolymer nanoparticles provided a controlled release of the entrapped drugs for 300 hr. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation of highly dispersed core/shell-type titania nanocapsules containing a single Ag nanoparticle

Core/shell-type titania nanocapsules containing a single Ag nanoparticle were prepared. Ag nanoparticles were prepared using the reduction of silver nitrate with hydrazine in the presence of cetyltrimethylammonium bromide (CTAB) as protective agent. The sol-gel reaction of titanium tetraisopropoxide (TTIP) was used to prepare core/shell-type titania nanocapsules with CTAB-coated Ag nanoparticles as the core. TEM observations revealed that the size of the core (Ag particle) and the thickness of the shell (titania) of the core/shell particles obtained are about 10 nm and 5-10 nm, respectively. In addition, the nanocapsules were found to be dispersed in the medium as individual particles without aggregation. Moreover, titania coating caused the surface plasmon absorption of Ag nanoparticles to shift toward the longer wavelength side.     

Synthesis, Characterization, and Long-Term Stability of Hollow Polymer Nanocapsules with Nanometer-Thin Walls

Hollow polymer nanocapsules are produced by the polymerization within hydrophobic interior of lipid bilayers that act as temporary self-assembled scaffolds. Pore-forming templates are co-dissolved with monomers in the bilayers to create pores with controlled size and chemical environment. Polymerization was monitored with UV spectroscopy and dynamic light scattering. High resolution magic angle spinning NMR characterization provided detailed structural information about nanocapsules. Spherical shape was confirmed by electron microscopy. Medium-sized molecules can be entrapped within porous nanocapsules. No release of encapsulated molecules was observed within 240 days.     

Ship-in-a-bottle entrapment of molecules in porous nanocapsules

Size-selective pores in the shells of hollow polymer nanocapsules enable combined assembly and entrapment of molecules. Small building blocks enter the capsule through the pores. The assembled molecules, which are larger than the pores, remain entrapped in the nanocapsules. Porous nanometre-thin walls permit unhindered functionalization of entrapped molecules.     

Synthesis of Monodisperse Hollow Carbon Nanocapsules by Using Protective Silica Shells

Monodisperse hollow carbon nanocapsules (<200 nm) with mesoporous shells were synthesized by coating their outer shells with silica to prevent aggregation during their high‐temperature annealing. Monodispersed silica nanoparticles were used as starting materials and octadecyltrimethoxysilane (C18TMS) was used as a carbon source to create core–shell nanostructures. These core–shell nanoparticles were coated with silica on their outer shell to form a second shell layer. This outer silica shell prevented aggregation during calcination. The samples were characterized by TEM, SEM, dynamic light scattering (DLS), UV/Vis spectroscopy, and by using the Brunauer–Emmett–Teller (BET) method. The as‐synthesized hollow carbon nanoparticles exhibited a high surface area (1123 m² g^?1) and formed stable dispersions in water after the pegylation process. The drug‐loading and drug‐release properties of these hollow carbon nanocapsules were also investigated.     

Temperature-responsive ionic-crosslinked polymeric nanocapsules via 'self-templating' approach

The temperature-responsive ionic-crosslinked polymeric nanocapsules (TRICNs) were fabricated via the 'self-templating' approach from the poly(tert-butyl acrylate-co-N-isopropylacrylamide-co-acrylic acid) (poly(tBA-co-NIPAm-co-AA)) terpolymer nanoparticles prepared via the emulsifier-free emulsion polymerization. After the surface carboxyl groups of the terpolymer nanoparticles were crosslinked with calcium ions, the TRICNs were achieved after the cores of the shell-crosslinked nanoparticles had been etched by being dissolved with acetone. Transmission electron microscope (TEM) showed the particle size of the individual nanocapsules was about 200 nm with the inner diameter of about 140 nm. The lower critical solution temperature (LCST) of the TRICNs was found to be about 31°C from the dynamic light scattering (DLS) analysis. Furthermore, the nanocapsules could disintegrate in acidic media while they were stable in the neutral or alkaline media.     

Reversible Clustering of Gold Nanoparticles under Confinement

A limiting factor of solvent‐induced nanoparticle self‐assembly is the need for constant sample dilution in assembly/disassembly cycles. Changes in the nanoparticle concentration alter the kinetics of the subsequent assembly process, limiting optical signal recovery. Herein, we show that upon confining hydrophobic nanoparticles in permeable silica nanocapsules, the number of nanoparticles participating in cyclic aggregation remains constant despite bulk changes in solution, leading to highly reproducible plasmon band shifts at different solvent compositions.     

Spatially controlled self-assembly of gold nanoparticles encased in alpha-helical polypeptide nanospheres

Gold nanoparticles (Au-NPs) are encased in aqueous nanospheres of alpha-helical poly(gamma-benzyl L-glutamate)s (PBLG, number average degree of polymerization: n = 32), with spatially controlled self-assembly structures of solid core-shell nanospheres or double-layered hollow nanocapsules.     

乳化剂在双重乳液合成含胰岛素纳米胶囊中的作用

Insulin entrapped nanocapsules to use polylactide （PLA） as the encapsulating material were prepared through a modified water-in-oil-in-water （W/O/W） emulsification and solvent evaporation method, The average particle size of PLA nanocapsules obtained was decreased to （181.5 ± 8.4） nm, and capably adjusted from 180 to 370 nm by using different types and content of nonionic emulsifiers. The influence of emulsifiers on property of nanocapsules was discussed in detail. The effects of spans and tweens to modify the size of the nanocapsules were different, which can be due to the distribution of the surfactants on the inner interface between the inner water and oil of the double emulsion. The encapsulation efficiency and drug release of nanocapsules were affected obviously by the content and type of emulsifiers.     

Self-assembly of a peptide rod-coil: a polyproline rod and a cell-penetrating peptide Tat coil

Peptide rod-coil molecules, composed of a stiff polyproline rod and a hydrophilic cell-penetrating peptide Tat coil, self-assemble into nanocapsules and mediate efficient intracellular delivery of entrapped hydrophilic molecules.     

Preparation and Characterization of Polymeric Nanocapsules Produced by in Situ Polymerization From Nanoemulsions Produced by Direct Emulsification

Polymeric nanoparticles constitute an important drug delivery system with controlled release profile. This article describes a new way to produce polymeric nanocapsules using a vegetable oil nanoemulsion as template. The process occurs in two steps: First, a nanoemulsion was obtained with a low-energy method based on phase inversion emulsification, using 2-ethylhexyl acrylate as lipophilic monomer. The in situ polymerization of the nanoemulsion droplets is induced by the addition of polymerization catalyzers. The mean size of the polymeric nanoparticles was evaluated by photon correlation spectroscopy and atomic force microscopy. Both techniques showed the formation of polymeric nanocapsules with a mean particle size less than 300 nm.     

Synergistic co-entrapment and triggered release in hollow nanocapsules with uniform nanopores

We describe a new co-entrapment and release motif based on the combination of noncovalent and steric interactions in materials with well-defined nanopores. Individual components enter hollow nanocapsules through nanopores in the capsule shell. Their complex, larger than the pore size, remains entrapped. The dissociation of the complex upon external stimulus releases entrapped components. Reversible formation of complexes between diaza-18-crown-6 and metal ions was used to demonstrate the feasibility of new approach to co-entrapment and triggered release.     

Retracted: Control of Nanoparticle Release by Membrane Composition for Dual-Responsive Nanocapsules

Stimulus-responsive polymeric nanocapsules usable as cell mimics can be engineered to precisely control cargo release. This work reports the release behavior of post-loaded nanoparticles through permeable membranes of stable pH and temperature dual-responsive polymeric nanocapsules (CP1, CP2, and CP3) with the same membrane thickness but different membrane composition, prepared by layer-by-layer assembly and surface-initiated single electron transfer living radical polymerization, respectively. These nanocapsules differ in their tunable membrane permeability for post-loaded nanoparticles as protein mimics, tailored by pH and temperature stimuli. Release mechanisms are dominated by membrane composition, such as polyelectrolyte multilayer membrane for CP1, pure cationic membrane for CP2, and valve-like functions for CP3. Thus, one can postulate the main locations of post-loaded protein mimics in the different nanocapsules. Understanding the post-loading and diffusion mechanism of nanoparticles through permeable membranes in cell mimics paves the way for the construction of new “smart” synthetic protocells with control over the exchange of bioactive nanoparticles between different compartments.     

A personal journey on using polymerization in aqueous dispersed media to synthesize polymers with branched structures

Several projects were discussed to demonstrate the intriguing power of radical polymerization in aqueous dispersed media to regulate the branched structures in functional polymeric nanomaterials.     

A new class of silica cross-linked micellar core-shell nanoparticles

Micellar nanoparticles made of surfactants and polymers have attracted wide attention in the materials and biomedical community for controlled drug delivery, molecular imaging, and sensing; however, their long-term stability remains a topic of intense study. Here we report a new class of robust, ultrafine silica core-shell nanoparticles formed from silica cross-linked, individual block copolymer micelles. Compared with pure polymeric micelles, the main advantage of the new core-shell nanoparticles is that they have significantly improved stability and do not break down during dilution. We also studied the drug loading and release properties of the silica cross-linked micellar particles, and we found that the new core-shell nanoparticles have a slower release rate which allows the entrapped molecules to be slowly released over a much longer period of time under the same experimental conditions. A range of functional groups can be easily incorporated through co-condensation with the silica matrix. The potential to deliver hydrophobic agents into cancer cells has been demonstrated. Because of their unique structures and properties, these novel core-shell nanoparticles could potentially provide a new nanomedicine platform for imaging, detection, and treatment, as well as novel colloidal particles and building blocks for mutlifunctional materials.     

A personal journey on using polymerization in aqueous dispersed media to synthesize polymers with branched structures

This short review is dedicated to celebrate Prof.Shoukuan Fu's 80 th birthday by discussing several of my accomplished projects over the past twenty years,which all applied radical polymerization in aqueous dispersed media for producing polymers with branched structures.These projects include the use of microemulsion polymerization for syntheses of fluorescent nanoparticles,hairy nanoparticles and hyperbranched polymers;the use of miniemulsion polymerization for synthesis of star polymers and light-emitting nanoparticles;the use of seeded emulsion polymerization for synthesis of hairy nanoparticles and hyperstar polymers;and the use of precipitation polymerization for synthesis of hollow polymer nanocapsules.Discussion of these projects demonstrates intriguing features of polymerization in biphasic dispersed media via either conventional radical polymerization or controlled radical polymerization to effectively regulate the branched structure of functional polymers.     

Rotaxane‐Like Structures Threaded through the Pores of Hollow Porous Nanocapusles

Nanocapsules with molecules threaded through the porous shells may lead to advanced cell‐mimicking functional devices. Herein, we show the feasibility of synthesizing such hybrid nanostructures by using vesicle‐templated polymer nanocapsules with controlled nanopores. Ship‐in‐a‐bottle assembly inside a nanocapsule created an internal unit. An external unit was then connected to an entrapped internal unit through pre‐attached linker threaded through a nanopore in the shell of the nanocapsule. Both internal and external units are larger than the pore size and cannot cross the shell, producing a rotaxane‐like structure. Successful synthesis was achieved with fairly short linkers (six and ten carbon atoms in a chain), creating an opportunity for facile synthesis of functional devices capable of cross‐shell communication.     

"Two-in-one" fabrication of Fe3O4/MePEG-PLA composite nanocapsules as a potential ultrasonic/MRI dual contrast agent

A new method for the fabrication of Fe(3)O(4) nanoparticles enveloped by polymeric nanocapsules is proposed. This method is characterized by combining a double emulsification with the interfacial coprecipitation of iron salts to form Fe(3)O(4)/polymer composite nanocapsules in a single step. To demonstrate the viability of this approach, methoxy poly(ethylene glycol)-poly(lactide) (MePLEG) was chosen as the shell material for Fe(3)O(4)/MePLEG nanocapsules. In addition to the versatility offered for fabricating nanocapsules with different shell materials, the method was found to be convenient for adjusting the magnetite content of the nanocapsules from 0 to 43%. In addition to their confirmed T(2)-weighted magnetic resonance imaging (MRI) enhancement, the resultant composite nanocapsules display much more obvious acoustic responses than MePLEG nanocapsules in an acoustic investigation. Furthermore, the low toxicity of these composite nanocapsules, as confirmed by our study, combined with their magnetic and acoustic properties ensure that these composite nanocapsules have great potential in acting as ultrasonic/MRI dual contrast agents.     

Simple but Precise Engineering of Functional Nanocapsules through Nanoprecipitation

A general, rapid, and undemanding method to generate at will functional oil‐filled nanocapsules through nanoprecipitation is reported. On the basis of polymer and hexadecane/water/acetone phase diagrams, the composition can be set so that polymer chains preferentially stick at the interface of the oil droplets to create nanocapsules. The nanocapsules can be decorated with biorelevant molecules (biotin, fluorescent tags, metal nanoparticles) within the shell and loaded with hydrophobic molecules in a simple one‐pot procedure.     

Monodisperse cobalt ferrite nanomagnets with uniform silica coatings

Ferro- and ferrimagnetic nanoparticles are difficult to manipulate in solution as a consequence of the formation of magnetically induced nanoparticle aggregates, which hamper the utility of these particles for applications ranging from data storage to bionanotechnology. Nonmagnetic shells that encapsulate these magnetic particles can reduce the interparticle magnetic interactions and improve the dispersibility of the nanoparticles in solution. A route to create uniform silica shells around individual cobalt ferrite nanoparticles--which uses poly(acrylic acid) to bind to the nanoparticle surface and inhibit nanoparticle aggregation prior to the addition of a silica precursor--was developed. In the absence of the poly(acrylic acid) the cobalt ferrite nanoparticles irreversibly aggregated during the silica shell formation. The thickness of the silica shell around the core-shell nanoparticles could be controlled in order to tune the interparticle magnetic coupling as well as inhibit magnetically induced nanoparticle aggregation. These ferrimagnetic core-silica shell structures form stable dispersion in polar solvents such as EtOH and water, which is critical for enabling technologies that require the assembly or derivatization of ferrimagnetic particles in solution.