On Going to a New Era of Microgel Exhibiting Volume Phase Transition.

The discovery of phenomena of volume phase transition has had a great impact not only on bulk gels but also on the world of microgels. In particular, research on poly(-isopropylacrylamide) (PNIPAM) microgels, whose transition temperature is close to body temperature, has made remarkable progress in almost 35 years. This review presents some breakthrough findings in microgels that exhibit volume phase transitions and outlines recent works on the synthesis, structural analysis, and research direction of microgels.

Micro hydrogels: preparation, properties, and applications.

A micro hydro-gel is a submicron- or micron-sized network polymer particle that is insoluble in water but highly swellable. This review presents the following topics: preparation, properties, and applications of micro hydrogels. First, two types of preparation methods for micro hydrogels are presented: (i) particle-forming polymerization and (ii) molecular assembly of polymer chains dissolved in water.

Enhancement of sensitivity of SPR protein microarray using a novel 3D protein immobilization.

We discovered a novel method to prepare a protein-based hydrogel, that is, a "Three-Dimensional Nanostructured Protein Hydrogel (3D NPH)", which is composed of protein-polymer hybrid nanoparticles. In this study, we propose a novel protein microarray whose 3D NPH spots were prepared by dispensing a small volume of the solution of protein-polymer mixture on a substrate. The dispensed solution had a short time for cross-linking before its drying-up and the resulting 3D NPH had loosely cross-linked, thin spongy structure.

Thermosensitive pickering emulsion stabilized by poly(N-isopropylacrylamide)-carrying particles.

Poly(N-isopropylacrylamide) (PNIPAM)-carrying particles were characterized as thermosensitive Pickering emulsifiers. Emulsions were prepared from various oils, such as heptane, hexadecane, trichloroethylene, and toluene, with PNIPAM-carrying particles. PNIPAM-carrying particles preferentially formed oil-in-water (O/W)-type emulsions with a variety of oils.

Development of novel magnetic nano-carriers for high-performance affinity purification.

We developed novel magnetic nano-carriers around 180 nm in diameter for affinity purification. Prepared magnetic nano-carriers possessed uniform core/shell/shell nano-structure composed of 40 nm magnetite particles/poly(styrene-co-glycidyl methacrylate (GMA))/polyGMA, which was constructed by admicellar polymerization. By utilizing relatively large 40 nm magnetite particles with large magnetization, the magnetic nano-carriers could show good response to permanent magnet.

Impact of initiators in preparing magnetic polymer particles by miniemulsion polymerization.

Sub-micron sized polystyrene particles containing magnetite more than 30 wt.% were prepared by miniemulsion polymerization with commercially available ferricolloid. The effects of some water-soluble initiators and/or oil-soluble initiators on the particles characteristics, such as the size, morphology, magnetic properties and colloidal stability, were studied.

Hybrid microgels with reversibly changeable multiple brilliant color.

We report reversibly color changeable hybrid microgels that tune multiple brilliant colors due to interparticle interactions of SPR using several structured nanoparticles. The interparticle interactions were brought out using the thermosensitive swelling/deswelling property of microgel. We employ N-isopropylacrylamide (NIPAM) and glycidyl methacrylate (GMA) copolymerized microgels (NG microgels) as templates for in situ synthesis of Au nanoparticles.

Gold nanoparticle localization at the core surface by using thermosensitive core-shell particles as a template.

We report novel thermosensitive hybrid core-shell particles via in situ gold nanoparticle formation using thermosensitive core-shell particles as a template. This method for the in situ synthesis of gold nanoparticles with microgel interiors offers the advantage of eliminating or significantly reducing particle aggregation. In addition, by using thermosensitive microgel structures in which the shell has thermosensitive and gel properties in water--whereas the core itself is a water-insoluble polymer--we were able to synthesize the gold nanoparticles only at the surface of the core, which had reactive sites to bind metal ions.

Affinity identification of delta-opioid receptors using latex nanoparticles.

Three types of latex nanoparticles carrying naltrindole (NTI) derivatives were synthesized as probes for the affinity isolation of their binding proteins including the delta-opioid receptor. The effect of the attachment of NTI to different positions on the linker was investigated. Only latex nanoparticles in which the NTI derivative was linked through the phenol group were useful for isolating the recombinant delta-opioid receptor solubilized from CHO cell membrane.

Colored thin films prepared from hydrogel microspheres.

Ordered 2-D structures composed of poly(N-isopropylacrylamide) (PNIPAM) microgel particles that had regularity on a sub-micrometer length scale were prepared. By using sterically stabilized PNIPAM microgel particles as components, the ordered array was formed by a self-assembly process. The particle array was prepared by depositing a droplet of the microgel dispersion on a substrate.

Modification of gold nanoparticle composite nanostructures using thermosensitive core-shell particles as a template.

We report the formation of novel thermosensitive hybrid core-shell particles via in situ synthesis of gold nanoparticles using thermosensitive core-shell particles as a template. The template core-shell particles, with cores composed mainly of poly(glycidyl methacrylate) (GMA) and shells composed mainly of poly(N-isopropylacrylamide) (PNIPAM), were synthesized in aqueous medium, and functional groups such as thiol groups were incorporated into each particle. We found that these particles containing thiol groups were effective for the in situ synthesis of gold nanoparticles in long-term storage.

Development of polymer latex particles for selective cleavage of mismatched DNA and their application for DNA diagnosis.

We developed functional polymer latex particles that can catch and cleave mismatched DNA selectively and propose a new mismatch detection system using the functional particles. The aimed particles possess two functional units composed of mismatch binding protein (MutS) and an anthraquinone derivative (AQ), a light-activated agent that photocleaves dsDNA. Use of the functional particles made it possible to discriminate complementary and mismatched DNAs and photocleave mismatched DNA selectively.

High-performance fluorescent particles prepared via miniemulsion polymerization.

Highly fluorescent polymer particles were prepared with Eu beta-diketonates complex as a fluorophore by miniemulsion polymerization technique. Eu beta-diketonates complex has a long decay time, a large Stokes shift, and very narrow emission bands in comparison with other organic fluorescent compounds. Aqueous miniemulsion was prepared by mixing monomer, crosslinker, hydrophobe, and Eu beta-diketonates complex and then putting the mixture into an aqueous solution of surfactant, followed by ultrasonication.

Temperature-sensitive hairy particles prepared by living radical graft polymerization.

Four types of temperature-sensitive hairy particles were prepared by living radical graft polymerization using a photoiniferter. The hairs were poly(N-isopropylacrylamide) (N), poly(N-isopropylacrylamide)ran-poly(acrylic acid) (NA), and diblock copolymers composed of N and NA. The block copolymer was attached to the particle in different modes, that is, one has a N-block inner and a NA-block outer but the other has the inverse arrangement.

Point mutation detection with the sandwich method employing hydrogel nanospheres by the surface plasmon resonance imaging technique.

We propose a surface modification procedure to construct DNA arrays for use in surface plasmon resonance (SPR) imaging studies for the highly sensitive detection of a K-ras point mutation, enhanced with hydrogel nanospheres. A homobifunctional alkane dithiol was adsorbed on Au film to obtain the thiol surface, and ethyleneglycol diglycidylether (EGDE) was reacted to insert the ethyleneglycol moiety, which can suppress nonspecific adsorption during SPR analysis. Then streptavidin (SA) was immobilized on EGDE using tosyl chloride activation.

Self-assembly of poly(N-isopropylacrylamide)-carrying microspheres into two-dimensional colloidal arrays.

Droplets containing polymer particles were deposited on a substrate. Poly(N-isopropylacrylamide) (PNIPAM) hydrogel and particles with PNIPAM graft chains on the surface self-assembled into a two-dimensional (2-D) superlattice when their dilute dispersions were dried on substrates. The capillary force between the particles induced ordered array formation during water evaporation.

Selective ligand purification using high-performance affinity beads.

Since the development of affinity chromatography, affinity purification technology has been applied to many aspects of biological research, becoming an indispensable tool. Efficient strategies for the identification of biologically active compounds based on biochemical specificity have not yet been established, despite widespread interest in identifying chemicals that directly alter biomolecular functions. Here, we report a novel method for purifying chemicals that specifically interact with a target biomolecule using reverse affinity beads, a receptor-immobilized high-performance solid-phase matrix.

Design and synthesis of a solid-supported FR225659 derivative for its receptor screening.

[structure: see text] We describe the design and synthesis of latex particles attached to an FR225659 derivative to identify its receptor proteins. Two key building blocks were prepared by two-step degradation of FR225659 under basic conditions. The designed ligand showed an acceptable level of biological activity to make it of potential value for use in affinity-supported receptor identification.

Flow-stress-induced discrimination of a K-ras point mutation by sandwiched polymer microsphere-enhanced surface plasmon resonance.

The highly sensitive detection of a K-ras point mutation with the aid of DNA-carrying microspheres as a flow-stress receptor is proposed at the surface of a surface plasmon resonance (SPR) biosensor. Single-stranded DNAs were immobilized onto epoxy-group-derivatized gold surfaces and the hybridization of DNA targets was monitored. The subsequent interaction with DNA-carrying micospheres enhanced the SPR response.

Hydrogel-microsphere-enhanced surface plasmon resonance for the detection of a K-ras point mutation employing peptide nucleic acid.

Highly-sensitive detection of a K-ras point mutation in codon 12, frequently found in pancreatic cancer, based on DNA-carrying hydrogel microspheres as a response enhancer for surface plasmon resonance (SPR), is described. Acrylamide-based microspheres with carboxyl groups were conjugated with DNA probes. Use of the DNA-carrying microsphere in the sandwich method, that is, binding of the microspheres with target DNAs at the sensor surface, enhanced the SPR response as a combined result of increased dielectric constant by the DNA-carrying microspheres.

Total analysis and purification of cellular proteins binding to cisplatin-damaged DNA using submicron beads.

A high-performance affinity purification technique has been developed for cisplatin (CDDP)-damaged DNA binding proteins directly from crude nuclear extracts of HeLaS3 cell using novel submicron beads synthesized by copolymerization of styrene and glycidyl methacrylate (GMA). The beads dramatically decreased both nonspecific protein adsorption on solid surfaces and elution volume and simplified the handling procedure. Preparation of the beads for purification was carried out by immobilization of telomeric repeats, (TTAGGG)(n), on the surface after the reaction with CDDP.