Interfacial photocrosslinking of polymer particles possessing nucleobase photoreactive groups for hollow/capsule polymer fabrication

Herein, polystyrene-based particles possessing nucleobases in polymer side chains were prepared and nucleobase groups were applied to the interfacial photocrosslinking as photoreactive groups for the first time for fabricating hollow/capsule particles.

Carboxy-Functionalized pH Responsive Capsule Polymer Particles Fabricated by Particulate Interfacial Photocrosslinking

pH-responsive capsule particles show promise for various applications, such as self-healing materials, micro/nanoreactors, and drug delivery systems. Herein, carboxy-functionalized capsule polymer particles possessing neutral-alkali pH responsive controlled release capability were...

Core–shell Microgels Having Zwitterionic Hydrogel Core and Temperature-responsive Shell Prepared via Inverse Miniemulsion RAFT Polymerization

Stimuli-responsive core–shell microgels are of significant interest because of their fascinating applications due to the different swelling/shrinkage properties of their core and shell networks. Because such stimuli-responsive core–shell microgels are...

Zwitterionic Nanocapsules with Salt- and Thermo-Responsiveness for Controlled Encapsulation and Release

Intelligent polymer nanocapsules that can not only encapsulate substances efficiently but also release them in a controllable manner hold great potential in many applications. To date, although intensive efforts have been made to develop intelligent polymer nanocapsules, how to construct the well-defined core/shell structure with high stability via a straightforward method remains a considerable challenge. In this work, the target novel zwitterionic nanocapsules (ZN_Cs) with a stable hollow structure were synthesized by inverse reversible addition fragmentation transfer (RAFT) miniemulsion interfacial polymerization. The shell gradually grew from the water/oil interface due to the interfacial polymerization, accompanied by the cross-linking of the polyzwitterionic networks, where the core/shell structure could be well-tuned by adjusting the precursor compositions. The resultant ZN_Cs exhibited a salt-/thermo-induced swelling behavior through the phase transition of the external zwitterionic polymers. To further investigate the functions of ZN_Cs, different substances, such as methyl orange and bovine serum albumin (BSA), were encapsulated into the ZN_Cs with a high encapsulation efficiency of 89.3 and 93.6%, respectively. Interestingly, the loaded substances can be controllably released in aqueous solution triggered by salt or temperature variations, and such responsiveness also can be utilized to bounce off the bacteria adhered on target surfaces. We believe that these designed salt- and thermo-responsive intelligent polymer nanocapsules with well-defined core/shell structures and antifouling surfaces should be a promising platform for biomedical and saline related applications.

Preparation of Salt-Responsive Hollow Hydrophilic Polymer Particles by Inverse Suspension Polymerization

Hydrophilic polymer particles with a hollow structure have potential applications such as carriers for hydrophilic drugs. However, there are few reports on preparation and morphology control of such particles via a simple method. In this study, hollow hydrophilic polymer particles were prepared by inverse suspension polymerization for water droplets containing 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) anions, 1-vinylimidazole (VIm) cations, oligo(ethylene glycol) diacrylate (OEGDA), dextran, and an initiator via the self-assembling phase-separated polymer (SaPSeP) method developed in our lab. The inner morphology of the particle could be controlled (as single- or multi-hollow structures) by changing the concentrations of the OEGDA and the dextran. The obtained hollow particles could encapsulate a hydrophilic fluorescent substance in their hollow region when the substance was added to the primary droplets before polymerization. In addition, the poly(AMPS-co-VIm-co-OEGDA) shell of the particles exhibited an ionic cross-linked structure, which could be stimulated by salt. The poly(AMPS-co-VIm-co-OEGDA) hollow particles with the encapsulated substance released the substance when salt was added to the dispersion. These results indicated that the applicability of the SaPSeP method can be broadened for morphology control of the hydrophilic polymer particles encapsulating water-soluble materials.

Nanoemulsions for synthesis of biomedical nanocarriers

Nanoemulsions are kinetically stabilized emulsions with droplet sizes in the nanometer scale. These nanodroplets are able to confine spaces in which reactions of polymerization or precipitation can take place, leading to the formation of particles and capsules that can act as nanocarriers for biomedical applications. This review discusses the different possibilities of using nanoemulsions for preparing biomedical nanocarriers. According to the chemical nature, nanocarriers prepared in nanoemulsions are classified in polymeric, inorganic, or hybrid. The main synthetic strategies for each type are revised, including miniemulsion polymerization, nanoemulsion-solvent evaporation, spontaneous emulsification, sol-gel processes, and combination of different techniques to form multicomponent materials.

Cross-Linker-Controlled Ostwald Ripening in Emulsion Polymerization of Hollow Copolymer Nanoparticles

We propose a synthesis method for hollow copolymer nanoparticles, in which the size is controllable by the wettability of the materials designed by relative energy difference (RED). We investigated the influence of cross-linkers in RED and the hollow polymer nanoparticle synthesis. The size of the nanoparticles was characterized by scanning electron microscopy and transmission electron microscopy images. The diameter size of the hollow copolymer (styrene-co-methyl methacrylate) changes from 400 to 141 nm and the average core-vacancy sizes changes from 330 to 71 nm as increasing the feed ratio of the cross-linker, divinyl benzene, from 0.07 to 0.43. Cross-linkers in polymerization precipitates a polymerization reaction to produce seed copolymer particles quickly. The seed copolymer is a more transferrable medium through the surfactants across emulsion droplets and inhibits emulsion growth by unstable concentration variations of seed copolymers in emulsions. Therefore, Ostwald ripening was reduced by a higher feeding ratio of the cross-linker in the copolymer, which tends to produce smaller sized hollow nanoparticles.

Size-Controllable, Single-Step, and Scalable Synthesis of Hollow Polymer Nanoparticles

Hollow polymer nanoparticles are of great importance in various industrial fields such as drug delivery vehicles in pharmaceutics, high thermal insulation materials for heat flow blocking and energy savings, and materials with unique optical properties. While the fabrication methods for hollow polymer nanoparticles have been studied and developed by numerous researchers, most synthesis methods require a rather complicated process, including a thorough core-washing step to formulate pores inside the particles. Single-step synthesis methods were developed to overcome this practical issue by utilizing the sacrificial solvent filling the pores temporarily and having it naturally evaporate without further process; however, such processes could not produce sub-200 nm diameter particles, which limit the application for high surface area applications. Herein, we have developed an innovative synthesis method that can overcome the particle size limitation by utilizing a sacrificial solvent for pore formation and a recondensation inhibitor. Pseudo-state Ostwald ripening was realized by selecting the sacrificial solvent with less affinity to the copolymer of hollow polymer particles, thus inhibiting the particle growth during polymerization. We have successfully obtained 120 nm diameter hollow PS-PMMA copolymer particles in large quantity via the single-step preparation of emulsion polymerization.

Poly(ε-caprolactone) (PCL) Hollow Nanoparticles with Surface Sealability and On-Demand Pore Generability for Easy Loading and NIR Light-Triggered Release of Drug

A new system for the easy loading and NIR light-triggered release of drugs is introduced. It consists of poly(ε-caprolactone) (PCL) hollow nanoparticles with surface openings containing a biodegradable fatty acid with phase-change ability and a biocompatible photothermal agent. These openings, which can enhance the connectivity between the interior and the exterior, enable the easy loading of drug molecules into the interior voids, and their successive sealing ensures a stable encapsulation of the drug. Upon exposure to an external NIR light irradiation, the photothermal agent generates heat that raises the local temperature of the hollow particles above the melting point of the fatty acid, leading to the formation of nanopores on their shells, and consequently, the instant release of the encapsulated drug molecules through the pores. The synergistic activity of the hyperthermia effect from the photothermal agent and the NIR-triggered release of the drug molecules results in noticeable anticancer efficacy.

All Wrapped up: Stabilization of Enzymes within Single Enzyme Nanoparticles

Enzymes are extremely useful in many industrial and pharmaceutical areas due to their ability to catalyze reactions with high selectivity. In order to extend their lifetime, significant efforts have been made to increase their stability using protein- or medium engineering as well as by chemical modification. Many researchers have explored the immobilization of enzymes onto carriers, or entrapment within a matrix, framework or nanoparticle with the hope of constricting the movement of the enzyme and shielding it from aggressive environments, thus delaying the denaturation. These strategies often balance three competing interests: (i) maintaining high enzymatic activity, (ii) ensuring good long-term stability against temperature, dehydration, organic solvents, and or aggressive pH, and (iii) enabling a tuning or reversible switching of enzyme activity. In most cases, multiple enzymes will be contained within a single nanoparticle or matrix, but in recent years researchers have begun to wrap up individual enzymes within single enzyme nanoparticles (SENs). In these nanoparticles the enzyme is stabilized by a thin shell, typically a polymer, prepared either by in situ polymerization from the enzyme surface or by assembling a preformed polymer around it. Because of the increased control over the environment directly around the enzyme, and the possibility of more directly controlling substrate diffusion, many SENs show remarkable stability while retaining high initial activities even for quite fragile enzymes. Moreover, the activity of the enzyme can often be more easily fine-tuned by adjusting the layer properties. We postulate that this emerging field will offer exciting and elegant opportunities to both extend the catalytic lifetime of enzymes in aggressive solvents, temperatures and pH, and enable their activity to be switched on and off on demand by modulation of the outer material layer.

Reductively Responsive Gel Capsules Prepared Using a Water-Soluble Zwitterionic Block Copolymer Emulsifier

Utilizing the unique solubility of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), which is soluble in only water and alcohol, we synthesized a water-soluble block copolymer emulsifier composed of a hydrophilic PMPC block and an amphiphilic poly[oligo(ethylene glycol) methacrylate] (POEGMA) block via reversible addition-fragmentation chain transfer (RAFT) polymerization. Water-in-oil (W/O) emulsions were successfully formed in the presence of the resulting PMPC- b-POEGMA, which acted as a stabilizer of water droplets in a chloroform continuous phase because the PMPC and POEGMA blocks were distributed to the water and chloroform phases, respectively. Next, the amphiphilic poly[poly(ethylene glycol) methacrylate] (PPEGMA) gel layer, which contained bis(2-methacryloyl)oxyethyl disulfide as a reductively responsive cross-linker, was prepared by inverse miniemulsion periphery RAFT polymerization from the PMPC- b-POEGMA that stabilized the W/O emulsions. The resulting PPEGMA gel capsules were colloidally stable in not only chloroform but also water without additional hydrophilic surface modification. The drug-release behavior from the PPEGMA gel capsules in response to dithiothreitol (DTT), which is a reducing agent, was investigated using fluorescein-conjugated dextran (FITC-Dex) as a model drug. The FITC-Dex release rate from the gel capsules in a phosphate buffer solution (pH 7.4, 20 mM) with DTT was fast compared to that without DTT. The reductively responsive FITC-Dex release is attributed to the cleavage of disulfide bonds that act as cross-links in the PPEGMA gel layer. The fascinating properties of the PPEGMA gel capsules suggest that they can provide a useful platform for designing drug carriers for protein and gene delivery and nanobioreactors.

Hollow polymer particles: a review

Herein, the basic principles, such as the definitions, classifications, and properties, of hollow polymer particles (HPPs) are critically investigated.

Efficient Pathway for Preparing Hollow Particles: Site-Specific Crosslinking of Spherical Polymer Particles with Photoresponsive Groups That Play a Dual Role in Shell Crosslinking and Core Shielding

Site-specific a posteriori photocrosslinking of homogeneous spherical polymer particles and subsequent removal of the particle core-the self-templating strategy-has been developed as an efficient pathway for hollow particle formation. In this approach, homogeneous polymer particles containing linear polymers bearing post-crosslinkable side-chain groups are first synthesized, and the photoinduced crosslinking occurred only at the shell region in the homogeneous polymer particles. Our fundamental studies clarified that the remaining non-crosslinked photoresponsive groups in the shell region played a crucial role in shielding the core region from photoirradiation. The shell-selective crosslinking was successfully applied to hollow polymer particle formation by core removal. This facile route to polymeric hollow particle formation via a self-templating strategy has great potential to be used as an alternative because the route has high mass productivity and high simplicity as a result of the non-use of additional sacrificial template particles and highly toxic solvents.

Carbon nanospheres mediated delivery of nuclear matrix protein SMAR1 to direct experimental autoimmune encephalomyelitis in mice

Owing to the suppression of immune responses and associated side effects, steroid based treatments for inflammatory encephalitis disease can be detrimental. Here, we demonstrate a novel carbon nanosphere (CNP) based treatment regime for encephalomyelitis in mice by exploiting the functional property of the nuclear matrix binding protein SMAR1. A truncated part of SMAR1 ie, the DNA binding domain was conjugated with hydrothermally synthesized CNPs. When administered intravenously, the conjugate suppressed experimental animal encephalomyelitis in T cell specific conditional SMAR1 knockout mice (SMAR(-/-)). Further, CNP-SMAR1 conjugate delayed the onset of the disease and reduced the demyelination significantly. There was a significant decrease in the production of IL-17 after re-stimulation with MOG. Altogether, our findings suggest a potential carbon nanomaterial based therapeutic intervention to combat Th17 mediated autoimmune diseases including experimental autoimmune encephalomyelitis.

Synthesis of microcapsules using inverse emulsion periphery RAFT polymerization via SPG membrane emulsification

Synthesis of polymeric capsules with good control over the particle size and size distribution is demonstratedviaa novel approach involving SPG membrane emulsification.

Functional characterizations of interactive recombinant PTEN–silica nanoparticles for potential biomedical applications

Nanosystem mediated successful stabilization and delivery of functional recombinant PTEN.

Radical polymerization of miniemulsions induced by compressed gases

Pressurization of a macroemulsion comprising a vinyl monomer/water/surfactant can result in formation of a transparent miniemulsion without use of high energy mixing, suitable for synthesis of polymeric nanoparticlesviaminiemulsion polymerization.

Synthesis of crosslinked polymeric nanocapsules using catanionic vesicle templates stabilized by compressed CO2

The synthesis of polymeric nanocapsules in the approximate diameter range 40-100 nm (TEM/SEM) using catanionic surfactant vesicle templates stabilized by subcritical CO2 is demonstrated. Near equimolar aqueous solutions of the surfactants sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) experienced immediate vesicle destabilization and precipitation in the absence of CO2. However, pressurization with CO2 (5 MPa) dramatically enhanced the stability of the initial vesicles, and enabled swelling of the bilayers with hydrophobic monomers via diffusion loading (loading of monomers into preformed bilayers). Subsequent radical crosslinking polymerization of the monomers n-butyl methacrylate/tert-butyl methacrylate/ethylene glycol dimethacrylate contained within the bilayers was conducted at room temperature using UV-initiation under CO2 pressure. The hollow structure of the resultant nano-objects was confirmed by successful encapsulation and retention of the dye Nile Blue. It is demonstrated that using this method, polymeric nanocapsules can be successfully prepared using diffusion loading of up to 94 wt% monomer (rel. to surfactant) stabilized by CO2.

Biocompatible Glycopolymer Nanocapsules via Inverse Miniemulsion Periphery RAFT Polymerization for the Delivery of Gemcitabine

Encapsulation of hydrophilic cancer drugs in polymeric nanocapsules was achieved in a one-pot process via the inverse miniemulsion periphery RAFT polymerization (IMEPP) approach. The chosen guest molecule was gemcitabine hydrochloride, which is used as the first-line treatment of pancreatic cancer. The resulting nanocapsules were confirmed to be ∼200 nm, with excellent encapsulation (∼96%) and loading (∼12%) efficiency. Postpolymerization reaction was successfully conducted to create glyocopolymer nanocapsules without any impact on the loads as well as the nanocapsules size or morphology. The loaded nanocapsules were specifically designed to be responsive in a reductive environment. This was confirmed by the successful disintegration of the nanocapsules in the presence of glutathione. The gemcitabine-loaded nanocapsules were tested in vitro against pancreatic cancer cells (AsPC-1), with the results showing an enhancement in the cytotoxicity by two fold due to selective accumulation and release of the nanocapsules within the cells. The results demonstrated the versatility of IMEPP as a tool to synthesize functionalized, loaded-polymeric nanocapsules suitable for drug-delivery application.

A solvent-free thermosponge nanoparticle platform for efficient delivery of labile proteins

Protein therapeutics have gained attention recently for treatment of a myriad of human diseases due to their high potency and unique mechanisms of action. We present the development of a novel polymeric thermosponge nanoparticle for efficient delivery of labile proteins using a solvent-free polymer thermo-expansion mechanism with clinical potential, capable of effectively delivering a range of therapeutic proteins in a sustained manner with no loss of bioactivity, with improved biological half-lives and efficacy in vivo.

Synthesis of pH-Responsive Nanocapsules via Inverse Miniemulsion Periphery RAFT Polymerization and Post-Polymerization Reaction

We report herein the versatility of inverse miniemulsion periphery RAFT polymerization (IMEPP) and postpolymerization reaction in producing pH-responsive nanocapsules with different functionalities. The robustness of the polymeric nanocapsules was confirmed by their ability to undergo reactions, be dried, and be redispersed in various solvents without any changes in size and core-shell morphology. Nanocapsules bearing carboxylic acid (COOH) functionalities were produced via hydrolysis, while nanocapsules bearing tertiary-amine (N-X₃) functionalities were synthesized via aminolysis. The responsive behavior of the nanocapsules was tested in aqueous solution with pHs ranging from 3 to 12. Nanocapsules with COOH functionalities were found to swell under basic conditions due to the deprotonated carboxylate ions. In contrast, nanocapsule with tertiary amine functionalities underwent swelling in acidic conditions.

Recent advances in the preparation of hybrid nanoparticles in miniemulsions

In this review, we summarize recent advances in the synthesis of hybrid nanoparticles in miniemulsions since 2009. These hybrid nanoparticles include organic-inorganic, polymeric, and natural macromolecule/synthetic polymer hybrid nanoparticles. They may be prepared through encapsulation of inorganic components or natural macromolecules by miniemulsion (co)polymerization, simultaneous polymerization of vinyl monomers and vinyl-containing inorganic precursors, precipitation of preformed polymers in the presence of inorganic constituents through solvent displacement techniques, and grafting polymerization onto, from or through natural macromolecules. Characterization, properties, and applications of hybrid nanoparticles are also discussed.

Engineered M13 bacteriophage nanocarriers for intracellular delivery of exogenous proteins to human prostate cancer cells

The size, well-defined structure, and relatively high folding energies of most proteins allow them to recognize disease-relevant receptors that present a challenge to small molecule reagents. While multiple challenges must be overcome in order to fully exploit the use of protein reagents in basic research and medicine, perhaps the greatest challenge is their intracellular delivery to a particular diseased cell. Here, we describe the genetic and enzymatic manipulation of prostate cancer cell-penetrating M13 bacteriophage to generate nanocarriers for the intracellular delivery of functional exogenous proteins to a human prostate cancer cell line.

Emerging methods for the fabrication of polymer capsules

Hollow polymer capsules are attracting increasing research interest due to their potential application as drug delivery vectors, sensors, biomimetic nano- or multi-compartment reactors and catalysts. Thus, significant effort has been directed toward tuning their size, composition, morphology, and functionality to further their application. In this review, we provide an overview of emerging techniques for the fabrication of polymer capsules, encompassing: self-assembly, layer-by-layer assembly, single-step polymer adsorption, bio-inspired assembly, surface polymerization, and ultrasound assembly. These techniques can be applied to prepare polymer capsules with diverse functionality and physicochemical properties, which may fulfill specific requirements in various areas. In addition, we critically evaluate the challenges associated with the application of polymer capsules in drug delivery systems.

Impact of self-assembled monolayer films with specific chemical group on bFGF adsorption and endothelial cell growth on gold surface

In this study, thiols ended with methyl, carboxyl, hydroxy, and amino groups are self-assembled on gold surfaces. The X-ray photoelectron spectroscopy test results show that chemical components on the self-assembled surface are similar to those in the theoretical calculations. The atomic force microscope test results show that the molecule assembled on the surface causes no significant variation in the surface roughness before and after the molecule assembly. The water surface contact angle increases with the increasing hydrophilicity of the end groups of the self-assembled monolayer. The surface zeta potential reveals that -COOH surface has the most electronegativity. The resulting substrates are then made to adsorb base fibroblast growth factor (bFGF). The quartz crystal microbalance test results show that the amounts of bFGF adsorbed onto different self-assembled surfaces are -COOH≈-OH>-CH₃ >-NH₂. According to cell culture experiments, endothelial cells have different morphologies after adhering to different surfaces. Furthermore, endothelial cells achieve the quickest proliferation on the -COOH self-assembled surface and the slowest proliferation on the -CH₃ self-assembled surface.

Responsive hybrid microcapsules by the one-step interfacial thiol-ene photopolymerization

We here demonstrated a general, convenient, and robust method to fabricate the hybrid microcapsules through the one-step thiol-ene photopolymerization at the interface between toluene and water. In the presence of amphiphilic polyhedral oligomeric silsesquioxane (POSS) containing thiol groups (PTPS) as reactive surfactants and trimethylolpropane triacrylate (TMPTA) as a cross-linker, the wall of hybrid microcapsules can be photo-cross-linked. The obtained hybrid microcapsules (HMCs) were well-characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and confocal laser scanning microscopy (CLSM). The results revealed that the obtained HMCs are uniform with the tunable size in diameter (2-4 μm) and wall thickness (55-120 nm). The size of HMCs increased with the increasing content of toluene. The wall thickness of HMCs decreased with the increasing content of toluene, while the wall thickness of HMCs increased with the increasing content of cross-linker TMPTA. Furthermore, HMCs are thermoresponsive in aqueous solution, can encapsulate both hydrophobic and dydrophilic dyes, and can be used in the controlled dispersion of dyes in different mediums. It is believed that this simple, robust, and general method to fabricate the hybrid microcapsules will extend the potential application fields of microcapsules, such as in the controlled dispersion and drug delivery.