Controllable preparation of epoxy-functionalized magnetic polymer latexes with different morphologies by modified miniemulsion polymerization

Synthesis of poly(acrylic acid) coated magnetic nanospheres via a multiple polymerization route

Magnetic nanospheres are versatile candidates for both fundamental and practical applications. Before they are applied in more complicated fields, their surface must be modified by several functionalities. However, the surface modification can be affected by the magnetic nanoparticles (MNP) embedded in the polymer matrix. Herein, the synthesis of poly(acrylic acid) coated magnetic nanospheres via a multiple polymerization route is described. During the synthesis process, seed emulsion polymerization was applied to redistribute the MNP in the polymer matrix, and the relationship between the structure of magnetic nanospheres and the thickness of the grafted poly(acrylic acid) layer was investigated. The development of size, morphology and magnetic properties of the nanospheres were characterized by transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, X-ray diffraction and vibrating sample magnetometry. This work would pave the way to design and preparation of new structure of functional magnetic nanospheres with precise surface modification.

Enrichment of human Vγ9Vδ2 T lymphocytes by magnetic poly(divinylbenzene-co-glycidyl methacrylate) colloidal particles conjugated with specific antibody

γδ T cells play a significant role in protection against cancer. Purification of γδ T cells is needed for insight when studying their anti-cancer functionality and their utilization in adoptive cell therapy. To improve the purification of γδ T cells, in this work, a composite material based on magnetic nanoparticles was developed for purification of Vγ9Vδ2 T cells, the predominant subset of γδ T lymphocytes in human peripheral blood. The epoxy-functionalized magnetic poly(divinylbenzene-co-glycidyl methacrylate) particles (mPDGs) were bio-conjugated with anti-human Vδ2 antibody to provide specific recognition sites for T cell receptors of Vγ9Vδ2 T cells. Using fluorescence-activated cell sorting (FACS) analysis, separation of Vγ9Vδ2 T cells from peripheral blood mononuclear cells of healthy donors was confirmed with high purity [89.77% (range 87.00–91.80, n = 3)]. More interestingly, the immobilized particles did not affect the viability of purified cells as high cell viability was indicated (>90%). By combining the properties of magnetic nanoparticles with specific antibodies, these immobilized particles were shown to be used as a cell-friendly purification tool of Vγ9Vδ2 T lymphocytes without any limits for the further use of cells. The purified Vγ9Vδ2 T cells using the antibody-immobilized epoxy-functionalized mPDGs could be used directly without a detachment step for further cultivation and expansion. This highlights the advantages of this method in allowing the study of cell function and further investigation of such rare T cell populations in immunotherapy.

Schematic procedure of Vγ9Vδ2 T cell purification using antibody-immobilized epoxy-functionalized mPDGs.

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.

Facile and green synthesis of core-shell structured magnetic chitosan submicrospheres and their surface functionalization

Submicrometer-sized magnetite colloid nanocrystal clusters (MCNCs) provide a new avenue for constructing uniformly sized and highly magnetic composite submicrospheres. Herein, a facile and eco-friendly method is described for the synthesis of Fe3O4@poly(acrylic acid) (PAA)/chitosan (CS) core-shell submicrospheres using MCNCs bearing carboxyl groups as the magnetic cores. It is based on the self-assembly of positively charged CS chains on the surface of the oppositely charged MCNCs dispersed in the aqueous solution containing acrylic acid (AA) and a cross-linker N,N'-methylenebis(acrylamide) (MBA), followed by radical induced cross-linking copolymerization of AA and MBA along the CS chains. The resulting polymer shell comprises a medium shell of cross-linked PAA/CS polyelectrolyte complexes and an outer shell of protonated CS chains. It was found that the shell thickness could be tuned by varying either the concentration of radical initiator or the molar ratio of AA to aminoglucoside units of CS. To the surface of thus obtained Fe3O4@PAA/CS particles, Au nanoparticles, a variety of functional groups such as fluorescein, carboxyl, quaternary ammonium, and aliphatic bromide, and even functional polymer chains were successfully introduced. Therefore, such Fe3O4@PAA/CS submicrospheres may be used as versatile magnetic functional scaffolds in biorelated areas like bioseparation and medical assay, considering the unique features of CS like nontoxicity and biocompatibility.

Gold nanoparticle-enhanced luminescence of silicon quantum dots co-encapsulated in polymer nanoparticles

The preparation of two-component polymer composite nanoparticles encapsulating both Si quantum dots (SiQDs) and Au nanoparticles (AuNPs) by a single step miniemulsion polymerization of divinylbenzene is described. This simple and robust method affords well-defined polymer composite nanoparticles with mean diameters in a range of 100-200 nm and with narrow polydispersity indices as determined by dynamic light scattering and transmission electron microscopy. The successful encapsulation of AuNPs within poly(divinylbenzene) was confirmed by UV-visible spectroscopy and from TEM images. Plasmon-enhanced fluorescence of the luminescence of the SiQDs by AuNPs encapsulated within the polymer composite nanoparticles was evaluated by confocal microspectroscopy, and luminescence enhancements of up to 15 times were observed. These observations indicate that the luminescence of the SiQDs is enhanced by the proximity of the AuNPs. The polymer composite nanoparticles were successfully ink-jet printed onto a glass substrate, which demonstrates that these composites are processable in printing applications.

Reactive magnetic poly(divinylbenzene-co-glycidyl methacrylate) colloidal particles for specific antigen detection using microcontact printing technique

Epoxy-functionalized magnetic poly(divinylbenzene-co-glycidyl methacrylate) colloidal particles (mPDGs) were prepared by co-polymerization of 1,4-divinylbenzene and glycidyl methacrylate monomers. The reaction was conducted by batch emulsion polymerization in the presence of an oil in water magnetic emulsion as a seed. The chemical composition, morphology, iron oxide content, magnetic properties, particle size and colloidal stability of the prepared magnetic polymer particles were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, thermal gravimetric analysis, vibrating sample magnetometry, dynamic light scattering, and zeta potential determination, respectively. The prepared mPDGs were immobilized on a self-assembled monolayer of 3-aminopropyltriethoxysilane (APTES)/octadecyltrichlorosilane (OTS), which were patterned on glass using microcontact printing technique, forming mPDGs-APTES/OTS reactive surface. This construction (mPDGs-APTES/OTS) was used as a solid support for immunoassay. The immobilized magnetic particles were bioconjugated with monoclonal anti-human IL-10 antibody to provide specific and selective recognition sites for the recombinant human IL-10 protein (antigen). Fluorescence microscopic examination was carried out to follow this immunoassay using fluorescently labeled anti-human IL-10 antibody. The results obtained proved the successful use of mPDGs-APTES/OTS microcontact printed surfaces in an immunoassay, which can be exploited and integrated into microsystems in order to elaborate medical devices (e.g. biosensors) which could provide rapid analysis at high sensitivity with low volumes of analyte.

Development of a stable dual functional coating with low non-specific protein adsorption and high sensitivity for new superparamagnetic nanospheres

To overcome major challenges of non-specific protein adsorption on nanoparticles for nanosensing and nanodiagnosis, an efficient method for robust chemical modification was developed to achieve excellent specific biorecognition and long-term stability in complex biomedia. This method is demonstrated by a highly specific and sensitive immunoassay (IA), using superparamagnetic nanospheres (NSs) with high magnetite content. The non-specific protein adsorption on the NSs was suppressed dramatically when modified with dual functional poly(carboxybetaine methacrylate) (polyCBMA) via surface-initiated atom transfer radical polymerization (SI-ATRP) and chemically grafted with antibodies of the β subunit of human chorionic gonadotrop (anti-β-hCG). The response to hCG of IA NSs with polyCBMA coatings was highly consistent in either phosphate-buffered saline (PBS) or 50% fetal bovine serum (FBS), which is far less variable than the response of the IA NSs without polyCBMA coatings. After all, a very robust platform for IA NSs with excellent specific biorecognition was obtained. It is expected that this method for nanoparticle modification could be widely used in ultrasensitive nanosensing and nanodiagnosis in the future.

A miniemulsion polymerization technique for encapsulation of silicon quantum dots in polymer nanoparticles

Miniemulsion polymerization techniques were used to encapsulate luminescent alkylated silicon quantum dots (Si-QDs) within polymer nanoparticles composed of styrene and 4-vinylbenzaldehyde monomers. The polymer nanoparticles had mean diameters in the range 90-150 nm depending on the reaction conditions, however all samples showed narrow particle size distributions, as determined by dynamic light scattering and atomic force microscopy. The Si-QDs were found to have a small, but beneficial effect on the polymerization process by reducing the polydispersity of the final polymer particles, which we attribute to co-surfactant action of the undecene used to form the alkyl capping layer on the Si-QDs. Confocal microspectroscopy was used to confirm that the luminescent alkylated Si-QDs were encapsulated within the polymer nanoparticles and also provided luminescence and Raman spectra which show peaks corresponding to both alkylated Si-QDs and the polymer nanoparticles. Treatment of the polymer nanoparticles with dilute aqueous sodium hydroxide solution, which is known to corrode Si and extinguish the luminescence of alkylated Si-QDs, results in only a partial reduction in luminescence suggesting that the majority of the alkylated Si-QDs are encapsulated sufficiently deep within the polymer matrix to protect them from alkaline attack. Miniemulsion polymerization of the monomers styrene and 4-vinylbenzaldehyde affords polymer nanoparticles displaying reactive aldehyde groups upon their surfaces, which could then be decorated with a selection of molecules through imine, oxime or hydrazone condensation reactions. We speculate that polymer-SiQD composite nanoparticles whose surfaces can be further decorated will increase the utility of luminescent Si-QDs in applications such as anti-counterfeiting and as probes of biological processes.

Facile one-pot synthesis and morphological control of asymmetric superparamagnetic composite nanoparticles

A one-pot colloidal reaction strategy was developed to synthesize asymmetric magnetic composite particles (AMCPs) with high anisotropy and magnetic content. The asymmetricity was established by having two portions of the particle composed of both polystyrene and silica, among which the latter was conjugated with magnetite nanoparticles. Phase separation was found to be critical in developing the asymmetric structure between the inorganic and polymer components during miniemulsion polymerization and the sol-gel reaction. Morphological control of the magnetic composite particles was achieved in a straightforward fashion by adjusting the processing parameters. These asymmetric nanomaterials with superparamagnetic and amphiphilic properties will have significant potential in biomedical applications.

Surfactant-free miniemulsion polymerization as a simple synthetic route to a successful encapsulation of magnetite nanoparticles

Due to the existing interest in new hybrid particles in the colloidal range based on both magnetic and polymeric materials for applications in biotechnological fields, this work is focused on the preparation of magnetic polymer nanoparticles (MPNPs) by a single-step miniemulsion process developed to achieve better control of the morphology of the magnetic nanocomposite particles. MPNPs are prepared by surfactant-free miniemulsion polymerization using styrene (St) as a monomer, hexadecane (HD) as a hydrophobe, and potassium persulfate (KPS) as an initiator in the presence of oleic acid (OA)-modified magnetite nanoparticles. The effect of the type of cross-linker used [divinylbenzene (DVB) and bis[2-(methacryloyloxy)ethyl] phosphate (BMEP)] together with the effect of the amount of an aid stabilizer (dextran) on size, particle size distribution (PSD), and morphology of the hybrid nanoparticles synthesized is analyzed in detail. The mixture of different surface modifiers produces hybrid nanocolloids with various morphologies: from a typical core-shell composed by a magnetite core surrounded by a polymer shell to a homogeneously distributed morphology where the magnetite is uniformly distributed throughout the entire nanocomposite.