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This research reports the success of the fabrication of hydrophobically modified chitosan cryogel. Chitosan was modified with alkyl groups through reductive animation. By varying the alkyl chain length and the substitution degree, the resulting cryogel could be optimized for strength, and the adsorption and release of hydrophobic dye, a model for hydrophobic medicines. By optimizing these attributes, the hydrogel was found to have the potential as a biomedical material.

Hypothesis In our previous study, we prepared millimeter-sized spherical hard capsules by solidifying droplets of liquid monomer or polymer solution placed on superamphiphobic surface. Application of liquid marbles in place of the naked droplets for capsule preparation has a great potential to increase encapsulation efficiency of high volatile ingredients. Further, interfacial thermodynamic prediction of internal configuration of capsules from spreading coefficients may be effective to prepare core/shell capsule. Experiments Droplets of liquid monomer containing a volatile ingredient were rolled on superamphiphobic powders to prepare liquid marbles and solidified by photopolymerization. For preparation of core/shell capsules, the liquid marbles injected with an immiscible water droplet were also solidified. Findings A volatile ingredient could be encapsulated with higher efficiency than our previous method. Interfacial thermodynamic prediction of internal configuration of capsules from spreading coefficients indicated successful formation of core/shell capsules. However, photopolymerization of the liquid marbles in a static condition resulted in formation of not only core/shell capsules but also acorn-type capsules. Furthermore, the core/shell capsules were distorted and the shell thickness was not uniform. Rolling of the liquid marbles, which generated centrifugal force inside of the liquid marbles, was effective to prepare spherical capsules with highly uniform shell thickness.

Hydrogels have become popular as drug carriers. Controlled release of the drugs from hydrogels can reduce dosage, inducing prevention of side effects. However, the hydrophilicity of hydrogels interferes with controlled release of hydrophobic drugs such as anticancer agents or antibiotics. In this study, we developed hydrophobically-modified gelatin (HMG) hydrogel, which was cross-linked only by hydrophobic interaction. HMG does not require toxic chemical cross-linkers to form hydrogel. In addition, the HMG hydrogel has hydrophobic chambers in its structure which hydrophobic drugs can adsorb to and desorb from. In order to control the amount of hydrophobic drugs adsorbed into the hydrogel, hydrophobic alkyl chains with different lengths (C4-C12) were incorporated into gelatin molecules. Uranine was used as a model for hydrophobic drugs. The adsorption test exhibited that the amount of uranine adsorbed in HMG hydrogels could be controlled by varying hydrophobic alkyl chain length and that the drug could be released in a controlled manner. These results show that HMG hydrogels are promising carriers of hydrophobic drugs.

Moist wounds were known to heal more rapidly than dry wounds. Hydrogel wound dressings were suitable for the moist wound healing because of their hyperhydrous structure. Chitosan was a strong candidate as a base material for hydrogel wound dressings because the polymer had excellent biological properties that promoted wound healing. We previously developed physically-crosslinked chitosan cryogels, which were prepared solely by freeze-thawing of a chitosan-gluconic acid conjugate (CG) aqueous solution, for wound treatment. The CG cryogels were disinfected by immersing in 70% ethanol before applying to wounds in our previous study. In the present study, we examined the influence of autoclave sterilization (121°C, 20 min) on the characteristics of CG cryogel because complete sterilization was one of the fundamental requirements for medical devices. We found that optimum value of gluconic acid content of CG, defined as the number of the incorporated gluconic acid units per 100 glucosamine units of chitosan, was 11 for autoclaving. An increased crosslinking level of CG cryogel on autoclaving enhanced resistance of the gels to enzymatic degradation. Furthermore, the autoclaved CG cryogels retained favorable biological properties of the pre-autoclaved CG cryogels in that they showed the same hemostatic activity and efficacy in repairing full-thickness skin wounds as the pre-autoclaved CG cryogels. These results showed the great potential of autoclavable CG cryogels as a practical wound dressing.

Immobilization of microbial cells in hydrophobic resin capsules for various bioprocesses such as metabolite production allows for greater efficiency than use of free cells. Conventional emulsion solvent evaporation (ESE) technique can seriously damage microbial cells in capsules by organic solvents. To overcome this issue, we applied an air drying technique on superamphiphobic surfaces for encapsulating microbial cells. Amphiphobic surface means water- and oil-repellent surface. Our data show that air drying allows capsules to be prepared without using water, and reduces cell contact with organic solvents. These features of air drying contribute to significant reduction of cell damage caused by solvents compared with ESE. Our results show that air drying is a promising technique for immobilization of living microbial cells in hydrophobic resin capsules.

Gelatin molecules have been chemically crosslinked using potentially cytotoxic reagents to prepare stable hydrogels. Hydrophobic interaction is a means of forming physical crosslinks that is a good candidate for enhancing the stability of gelatin hydrogels without using cytotoxic chemicals. In this study, we proposed a new method to fabricate hydrogels from hydrophobically-modified gelatin (HMG) with high content of hydrophobic segments. HMG was first dissolved in dimethyl sulfoxide and poured into a vial with the desired shape. After the solution was freeze-dried, the solid construct was hydrated. The HMG hydrogel containing basic fibroblast growth factor promoted angiogenesis in vivo, indicating that the positively charged hydrophilic growth factor formed an electrostatic complex with negatively charged HMG hydrogel and was gradually released in vivo with the degradation of the hydrogel. In addition, we showed that the hydrophobic segments of HMG enhanced the adsorption of fluorescein sodium, a model for hydrophobic therapeutic agents, to the hydrogel through hydrophobic interaction. Furthermore, in vitro experiments indicated that the hydrophobic agents would be released from the hydrogel in a controlled manner in vivo. These results show that the HMG hydrogel has significant potential as a carrier for both charged hydrophilic drugs and hydrophobic drugs.

Microcapsules and porous polymer particles containing extractants, which are functional molecules to extract target ions or molecules by specific interaction using in solvent extraction process, are expected to be an effective separation medium of various substances from aqueous solution in hydrometallurgical process of harmful or valuable metals and in environmental protection processes from various pollutants. The preparation method, encapsulating materials and application area of these materials has been developed and extended in recent years. Recent topics of this field was been presented. The research on the polymeric particles for separation medium investigated by authors was introduced and showed the structural effect of the polymeric particles containing extractant on the separation performance of metal ion and chiral separation of amino acids by porous particles impregnated with phospholipids.

We demonstrate a method to create surfactant-free core–shell microcapsules in a hydrophilic polydimethylsiloxane microfluidic device. An ultraviolet light curable polymer was used to encapsulate an oil core. These microcapsules ensure contamination-free compartmentation of the core material without any surfactant, while maintaining the monodispersed generation at a rate of 100 microcapsules per second. The device fabrication process is greatly simplified without the alignment of microchannels and hydrophobic/hydrophilic surface treatment. After drying, physically shaking the collection chamber can crack the capsule to release the liquid core material. Such solid microcapsules with a liquid core are ideal for the storage and delivery of oil-based materials in skincare products or reagents for biochemical assays.

Magnetic manipulation of paramagnetic particles had great potential for efficient bioprocessing. In this study, we stirred microliter-volume water droplets formed on a superhydrophobic surface as micro-bioreactors by using paramagnetic magnetite microparticles manipulated by an external magnetic field. We showed that magnetite microparticles in the droplets spontaneously formed rod-like aggregates, which were like commercial stir bars, in an external magnetic field and spun with rotating of magnetic field. Increasing the rotating rate of the magnetic field and increasing the concentration of the microparticles caused the microparticles to fixate at the air/water interface of the droplets and their rotation at the interface with rotating of magnetic field. The active mixing enhanced the enzyme reaction and microorganism proliferation in the droplets. These results demonstrated that manipulating the magnetite microparticles by an external magnetic field efficiently mixed the small droplets as micro-bioreactors.

Spherical capsules have been used in various fields because of their many advantages. In many industrial applications, hydrophobic hard resins (e.g., polyacrylate, epoxy and polystyrene) are used as a shell material for stable packaging of ingredients within capsules. However, it is difficult to encapsulate ingredients in such capsules without loss by conventional techniques. The purpose of this study was to encapsulate hydrophobic ingredients within polyacrylate resin capsules with ultrahigh efficiency. In our methodology, a small volume of resin monomer solution containing the ingredients was first placed on a superoleophobic material and the resulting spherical droplets were then solidified by polymerization of the monomer. Doxorubicin (an anticancer drug), α-tocopherol (an antioxidant) and tetradecane (a phase change material used for heat storage) could be encapsulated in spherical hard capsules with almost no loss by heat and photopolymerization. We showed that tetradecane in the capsules had almost identical thermal properties to pure tetradecane. These results demonstrate that our technique is promising for encapsulation of hydrophobic ingredients in hard resin capsules.

Agarose gels were superior to calcium-alginate gels for immobilizing Rhodococcus erythropolis CS98 strain to remove cesium from water. Suitable incubation time of the immobilized cells in cesium solutions, cell number in the gels and volume ratio of the cesium solution to the gels for efficient cesium removal were identified.

Collagen extracted from tissues by alkaline treatment has a di erent isoelectric point (pI≈5) than the commonly-used acidor pepsin-treated collagen (pI≈9). In this study, the feasibility of using the alkali-treated collagen (AC) as a carrier of basic broblast growth factor (bFGF) for enhancement of angiogenesis was examined. AC hydrogels were prepared by chemically crosslinking AC molecules using glutaraldehyde (GA). We investigated the e ects of GA concentration in AC gels on the degree of swelling of the gels in an aqueous environment and on the in vivo degradation rate of the gels. Horse cytochrome c (pI: 9.6), a model for bFGF (pI: 9.6), electrostatically adsorbed to the AC gels. Subcutaneously-implanted AC gels incorporating bFGF led to enhanced angiogenesis compared with bFGF-free gels. Thus, AC gels incorporating bFGF appear to be useful materials for (i) the enhancement of angiogenesis and (ii) tissue engineering sca olds.

Growth factor (GF)-immobilizable materials were developed as a practical hepatocyte transplantation method for reconstructing a tissue-like structure in liver tissue engineering. Two GF-immobilizable scaffolds, namely single hepatocyte-embedded, heparin-immobilized, collagen-gel-filled polyurethane foam, and hepatocyte spheroid-embedded, heparin-immobilized, collagen-gel-filled polyurethane foam were developed by covalently incorporating heparin into collagen gel, using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide/N-hydroxysuccinimide for hepatocyte transplantation. Seventy percent partial hepatectomy (PH) was performed at the same time after hepatocyte transplantation. Angiogenesis efficiency and viability of transplanted cells are discussed in terms of normalized hemoglobin content, nuclear density and histological observations after transplantation. In summary, the normalized hemoglobin content and viability of transplanted cells were higher in GF-immobilized scaffolds with PH pretreatment than in the other scaffolds with/without PH pretreatment. These materials have the potential for in vivo hepatocyte transplantation, as GFs released from remnant liver were easily incorporated into the heparin-immobilized collagen gel system. These GF–heparin complexes may promote the survival of embedded cells. Furthermore, the transplantation of spheroids promoted increased angiogenesis compared with hepatocytes, and resulted in sufficient vascularization for cell survival.

The construction of a functional liver-tissue equivalent using tissue engineering is a very important goal because the liver is a central organ in the body. However, the construction of functional organ-scale liver tissue is impossible because it requires a high-density blood vessel network. In this study, we focused on decellularization technology to solve this problem. Decellularized liver tissue with a fine vascular tree network template was obtained using Triton X-100. The distance between each vascular structure was less than 1 mm. Endothelialization of the blood vessel network with human umbilical vein endothelial cells (HUVECs) was successfully performed without any leakage of HUVECs to the outside of the vessel structure. Furthermore, hepatocytes/spheroids could be located around the blood vessel structure. This study indicates that decellularized liver tissue is a potential scaffold for creating a practical liver tissue using tissue engineering technology.

Poly(vinyl alcohol) (PVA) gel beads crosslinked with sodium phosphate or boric acid have been widely utilized for microorganism immobilization. We previously utilized sodium sulfate to induce crosslinking of PVA for preparing immobilized yeast cells in PVA beads. In this study, we compared the toxicities of sodium sulfate and conventional crosslinkers (sodium phosphate and boric acid) toward Pseudomonas putida F1 (PpF1) and the performance of the corresponding immobilized PpF1 in PVA beads. The toxicity of sodium sulfate to PpF1 was lower than those of the conventional crosslinkers. PVA–sodium sulfate beads showed a higher gel fraction of PVA and a lower swelling ratio in water than PVA–sodium phosphate beads, which indicates that the former had higher stability. PpF1 immobilized in the PVA–sodium sulfate beads completely degraded the pollutant trichloroethylene (TCE) with an initial concentration (0.42 mg/l) within the most common range of TCE concentration found in contaminated field sites.

Burkholderia cepacia lipase was immobilized in silicates forming from n -butyl-substituted precursors within a silica monolith from methyl-substituted precursors. The resultant preparation gave about 12 times higher rates of transesterification of ( R , S )-1-phenylethanol with vinyl acetate and an approximately two-fold increase in the enantioselectivity toward ( R )-1-phenylethanol, as compared to a non-immobilized counterpart. The highest enzymatic activity and enantioselectivity (reaching 250) were found at a low water activity of 0.11. The continuous-flow kinetic resolution of ( R , S )-1-phenylethanol was successfully conducted using lipase-immobilized silica monolith micro-bioreactors with various inside diameters ranging from 0.25 to 1.6 mm. The reactor performance during continuous operation was consistent with the prediction from the batch reactor. A steady state conversion of 40% and enantiomeric excess more than 98% were maintained over a time period of 15 days.

In situ gellable hydrogels are more attractive in many biomedical and biopharmaceutical applications than pre-formed hydrogels because they can be implanted simply by injection and allow homogeneous incorporation of bioactive materials. In this study, the potential suitability of in situ gellable sugar beet pectin (SBP) for biomedical and biopharmaceutical applications was investigated. SBP aqueous solution gelled within 1 min after addition of appropriate amounts of horseradish peroxidase (HRP) and H 2 O 2 via HRP-catalyzed oxidative coupling reaction of feruloyl groups on SBP molecules. The resultant gels gradually degraded under simulated physiological condition. L929 fibroblast cells encapsulated in the gels were scarcely damaged during the gelation process. A subcutaneously injected mixture of SBP, HRP and H 2 O 2 solutions successfully gelled, and the gel did not induce necrosis in the surrounding tissue 1 week after implantation. These results demonstrate that the in situ gellable SBP gels are useful for biomedical and biopharmaceutical applications.

Poly(vinyl alcohol) (PVA) hydrogel beads crosslinked with boric acid have been widely utilized for microorganism immobilization. However, a drawback of the method for preparing conventional PVA–boric acid beads is that microorganisms enclosed in the PVA matrix are drastically damaged by boric acid during the bead preparation process. In the present study, we utilized sodium sulfate as an inducer for crosslinkage of PVA for fabricating microorganism-enclosing PVA hydrogel beads to avoid the drastic decrease in cell viability caused by saturated boric acid solution. First, PVA was crosslinked by boric acid for a short time. Subsequently, the molecules were further crosslinked using sodium sulfate. X-ray diffraction analysis indicated that sodium sulfate promoted crystallization of PVA, which contributed to gelation of PVA solution. Moreover, the toxicity of sodium sulfate to Saccharomyces cerevisiae was lower than that of boric acid. The stability in water of the PVA–sodium sulfate beads was superior to the stability of PVA–boric acid beads. The ethanol fermentation rate of the PVA–sodium sulfate hydrogel beads enclosing the yeast cells was 2–3 times as fast as that of PVA–boric acid beads. The PVA–sodium sulfate beads could be reused 10 times in repeated ethanol fermentation tests.

We aimed to develop cell-embedded gel-filled macroporous scaffold (CGS) culture technology as a fundamental technology for the construction of large-scale tissue-like structures, which will be indispensable for practical liver tissue engineering. Tissue transglutaminase (tTGase) from guinea pig liver showed no cytotoxicity toward primary hepatocytes, and hepatocyte-embedded gelatin gel cultures could be realized. The albumin production activities in tTGase-mediated hepatocyte-embedded gelatin gel cultures were similar to those in collagen gel cultures, representing an established hepatocyte culture method for the expression of liver-specific functions. Therefore, it was expected that a hepatocyte-embedded gelatin gel culture system enabling high liver-specific function expression could be created. The CGS culture system was created by incubating a suspension of hepatocytes and tTGase-containing gelatin-filled hydrophilic-treated scaffolds at 37 °C. The albumin production activities in CGS with poly( l -lactic acid) macroporous scaffold (porosity = 68.4%) were inferior to those in tTGase–gelatin gel cultures because of a diffusion problem. However, the activities were similar between CGS with macroporous polyurethane foam (porosity = 98.8%) and tTGase–gelatin gel cultures, even under stationary conditions. On the other hand, further functional improvements of hepatocytes were achieved in HGF- or HGF/heparin-containing gel cultures. Based on these results, tTGase-mediated CGS cultures are expected to become a fundamental technology for the creation of engineered liver tissues.

Calcium-alginate hydrogel hollow microfibers have a potential to be utilized in various fields such as tissue engineering. In this study, we developed a new technique for exquisite control of inner diameter (id) as well as outer diameter (od) of the microfibers using a coaxial triple cylinder. Aqueous solutions of dextran (core solution), sodium alginate (sample solution) and CaCl 2 (sheath solution) were extruded simultaneously from the inner, intermediate and outer cylinders, respectively. The ratio of id to od could be controlled only by the ratio of flow volume of core solution to total flow volume of core and sample solutions (core volume ratio). The od depended on core volume ratio, flow velocities of core and sample solution at the tip of the intermediate cylinder, tip id of intermediate cylinder and flow velocity of sheath solution. Two types of mammalian cells could be separately located in the hollow core and the gel part of the microfibers. We confirmed that the cell-enclosing process scarcely influenced the viability of the enclosed cells. Although we did not perform long-term culture of the cell-enclosing microfibers in this study, these results indicate that our system has a high potential to fabricate biomimetic scaffold for tissue-engineered tubular tissues.

Polymeric microcapsules enclosing Saccharomyces cerevisiae were prepared by radical suspension polymerization via water-in-oil-in-water emulsion. Trimethylolpropane trimethacrylate and 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) were used as monomer and radical initiator, respectively. A culture medium with suspended yeast cells, monomer solution with the dissolved radical initiator, and poly(vinyl alcohol) aqueous solution were used as inner aqueous phase, oil phase, and outer aqueous phase, respectively. The influence of microcapsule preparation parameters on the viability of encapsulated cells and encapsulation efficiency was investigated. The radical polymerization process did not cause significant damage to encapsulated yeast cells. Decreased weight ratio of aqueous phase to oil phase resulted in increased encapsulation efficiency of the cells. The diameter of the microcapsules could be controlled by varying the agitation rate.

In the present study, we attempted to prepare phase-change material (PCM)-loaded polyurea microcapsules several hundred micrometres in diameter via oil-in-water emulsion polymerisation. An oil phase with two types of isocyanate monomers (2,4-toluene diisocyanate (TDI) and phenyl isocyanate (PI)) and tetradecane as PCM was dispersed in an aqueous phase with hexamethylene diamine (HMD). The polyurea shell of microcapsules was formed by reaction of the isocyanate monomers with the amine groups derived from HMD and hydrolysed isocyanate monomers. A suitably adjusted agitation rate made it possible to prepare the required microcapsules. An increased molar ratio of TDI to PI in oil phase resulted in improvement of microcapsule morphology. Increased weight ratio of tetradecane to the two isocyanate monomers (TDI and PI) led to an increase in the PCM content in the microcapsules, which is preferable for practical applications. An examination using differential scanning calorimetry analyser demonstrated that the polyurea shell of the microcapsules scarcely influenced the thermal properties of encapsulated tetradecane.

The immobilization of plant growth-promoting bacteria in biodegradable polymeric supports is effective in providing them with a suitable microenvironment for increased survival, compared to free bacteria, in agricultural land. In this study, we optimized the preparation parameters for bacteria-enclosing calcium alginate gel beads with a view to large-scale production. An emulsion system was used and the optimization was based on alginate bead recovery and entrapment efficiency of viable bacteria. Lactic acid bacteria were used as a plant growth-promoting bacteria. The optimized conditions were as follows: the concentration of calcium chloride in the aqueous phases was 1.1% (w/v), the volume ratio of alginate solution to total aqueous phases was 0.93, and the agitation time was 0.5–1.0 h. The mean diameter of the beads could be controlled (approximately from 100 to 300 μm) by varying the agitation rate.

Reduction of the amount of pesticides applied to agricultural land is essential for environmental conservation. It can be accomplished by immobilization of the pesticides in polymer supports, which prevents their volatilization, degradation and leaching losses, and provides controlled release of the chemicals. In the present study, acetamiprid, a novel pesticide, was encapsulated in PLA-based microspheres using the solvent evaporation method via oil-in-oil (O/O) emulsion. Silicon oil and an acetonitrile solution with dissolved synthetic polymer(s) and acetamiprid were used as an outer and inner oil phases, respectively. The entrapment efficiency of the pesticide in the case of PLA microspheres decreased with increasing the concentration of the pesticide in the inner oil phase. The amount of acetamiprid released from the microspheres was less than 18 %. On the other hand, incorporation of poly(-caprolactone) (PCL) into the PLA microspheres resulted in increased amount of releasable pesticide (approximately 89 %). These results indicate that the PCL/PLA microsphere is a promising immobilization support of the acetamiprid for practical application.

Hydrogel fibers that possessed a cell-adhesive surface and were degradable via enzymatic reactions were developed for fabricating tubular constructs with smooth muscle cell (SMC) and endothelial cell (EC) layers, similar to native blood vessels, in collagen gels. The fibers were prepared by soaking hydrogel fibers prepared from a solution of sodium alginate and gelatin containing bovine ECs (BECs) in medium containing oxidized alginate (AO). BECs soaked in 8.0% (w/v) AO showed no reduction in viability within 3 h of soaking. Furthermore, mouse SMCs (MSMCs) adhered and proliferated on the AO-cross-linked hydrogels. Based on these results, we prepared AO-cross-linked hydrogel fibers containing BECs, covered their surface with MSMCs, and embedded them in collagen gels. We then degraded the fibers using alginate lyase to obtain channels in the collagen gels. Histological analysis of the released ECs using a specific fluorescent dye revealed the formation of tubular structures with layered BECs and MSMCs.

Microencapsulation of pesticides is a promising technique for avoiding high initial doses and multiple applications of the chemicals to agricultural land which cause environmental pollution. It is because the formulation is possible to improve the stability of the chemicals against environmental degradation and control the release rate. In the present study, polymeric microcapsules prepared by the solvent evaporation method via water-in-oil-in-water (W/O/W) emulsion were used as immobilization supports of acetamiprid, a water-soluble pesticide. The pesticide was loaded in the microcapsules by impregnating the polymeric supports with acetamiprid dissolved in an organic solvent. Increased volume ratio (ϕ) of inner aqueous phase to oil phase in the emulsion system contributed to more pores in the microcapsules and increase in the content of acetamiprid in the polymeric supports. Release rate of acetamiprid from the microcapsules could be controlled by changing ϕ.

Concern for the environment has increased interest in reducing the amount of pesticides applied to agricultural land. This can be accomplished by immobilization of the pesticides in polymer supports, which prevents volatilization, degradation and leaching losses, and provides controlled release of the pesticides. In the present study, acetamiprid, a novel pesticide, was enclosed in polylactide (PLA)-based microspheres using solvent evaporation method via oil-in-oil (O/O) emulsion. Amount of acetamiprid released from PLA microspheres was less than 5% in phosphate buffered saline. On the other hand, incorporation of water-soluble polymer, such as poly(ethylene glycol) (PEG) and poly(oxyethylene) diglycolic acid, into the PLA microspheres resulted in increased amount of released acetamiprid (∼70%). Planting hole application by greenhouse pot test demonstrated that the efficacy of the PLA/PEG microspheres enclosing acetamiprid against cotton aphids was superior to that of PLA microspheres enclosing acetamiprid. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

セラミックスやエレクトロニクス産業の分野で広く使用されている封着加工用鉛ガラスの無鉛化は急務な課題である．本研究ではわれわれの研究グループが報告した封着加工用鉛フリーガラスである，41.8 mol% V2O5–3.1 mol% ZnO–17.6 mol% BaO–37.5 mol% TeO2（以下VTEと略記）ガラスと53.0 mol% V2O5–4.0 mol% ZnO–22.4 mol% BaO–20.6 mol% P2O5（以下VPと略記）ガラスの2つの組成系の実用化に向けた評価試験の検討を行った．評価試験内容としては，平面蛍光管の封着加工後のサーマルショック試験，耐圧試験，連続点灯試験を行った．対象実験として従来の鉛ガラス（以下Pbと略記）で作製した平面蛍光管と比較した結果，サーマルショック試験および加圧試験では鉛ガラスで作製された平面蛍光管と同等の熱衝撃および圧力衝撃性を有していることがわかった．また，連続点灯試験においても鉛ガラスを使用したものと同等の発光特性を有することがわかった．

Nylon-polystyrene microcapsules with immobilized ferroelectric liquid crystalline segments were prepared, and permeability control of an encapsulated core material was investigated under an external electric field. A ferroelectric liquid crystal monomer possessing both mesogenicity and chirality responded effectively to the external electrical field. Permeation of the material (oxprenolol) contained in the inner aqueous core of the microcapsules was enhanced under a weak electric field (2 V). Furthermore, the permeability of oxprenolol did not depend on the external electric field in the absence of the ferroelectric liquid crystal segments. To clarify the controlled-release mechanism of the core material, the light transmittance of the polymer membranes was quantitatively evaluated under an external electric field using a handmade polarized light transmittance apparatus.

A useful microorganism (lactic acid bacteria) was immobilized in biodegradable microcapsule utilizing the solvent evaporation technique of water-in-oil-in-water (W/O/W) emulsions. We optimized the preparation conditions of the microcapsule immobilizing a useful microorganism through the experiments. As a result, the optimized microcapsule could efficiently immobilize the microorganism with a high activity. The lactic acid production activity of the microcapsules prepared under the optimized condition was approximately nine times higher than that of a commercial soil conditioner. Soil application demonstrated that the microcapsules are effective for the disinfestation of the root-knot nematode.

A jetting technique in a liquid-liquid co-flowing stream was applied to the preparation of mammalian cell-enclosing calcium-alginate (Ca-alg) hydrogel fibers of several hundred micrometers in cross-sectional diameter. One percent alginate aqueous solution was extruded from needles (270, 480, 940 microm inner diameter) into a co-flowing laminar stream of 100 mM aqueous calcium chloride solution. The extruded alginate solution was stretched by the CaCl(2) solution, which is known as a "jetting process", and the Ca-alg hydrogel fibers were formed by gelation of the alginate solution through the uptake of calcium ions in the CaCl(2) solution. The cross-sectional diameter of the hydrogel fibers could be controlled from approximately 100-800 microm by changing the velocities of the alginate and CaCl(2) solution, and the inner diameter of the needle. Approximately 95% of bovine carotid artery vascular endothelial cells remained alive after the process of preparing hydrogel fibers in a co-flowing stream, demonstrating that the cell-enclosing process scarcely influences the viability of the enclosed cells.

We fabricated a scaffold of poly (lactic acid) and acidic gelatin, a sustained-release carrier of basic fibroblast growth factor (bFGF), which is a positive regulator of angiogenesis. After 1 week of implantation into mesentery of rats, blood vessels induced in the bFGF-containing scaffolds were almost double those in the bFGF-free scaffolds. Further, histological examination of hepatocyte-immobilizing scaffolds retrieved after 1 week of implantation into the mesentery of the rats that received a 70% hepatectomy revealed that the bFGF-containing scaffolds were more efficient for immobilized cell survival than the bFGF-free scaffolds. As well, hepatocytes in the bFGF-containing scaffolds kept their hepatospecific glycogen storage capacity.

A human hepatoblastoma cell line, Hep G2, showed albumin production activity, a hepatic function, when cocultured with three-dimensional endothelialized tubes in collagen gels. The albumin production rate of the collagen-based liver-like constructs increased with increasing length of the endothelialized tube in the construct.

Reconstructed liver has been desired as a liver substitute for transplantation. However, reconstruction of a whole liver has not been achieved because construction of a vascular network at an organ scale is very difficult. We focused on decellularized liver (DC-liver) as an artificial scaffold for the construction of a hierarchical vascular network. In this study, we obtained DC-liver and the tubular network structure in which both portal vein and hepatic vein systems remained intact. Furthermore, endothelialization of the tubular structure in DC-liver was achieved, which prevented blood leakage from the tubular structure. In addition, hepatocytes suspended in a collagen sol were injected from the surroundings using a syringe as a suitable procedure for liver cell inoculation. In summary, we developed a base structure consisting of an endothelialized vascular-tree network and hepatocytes for whole liver engineering.

We previously developed chitosan cryogels from chitosan-gluconic acid conjugate without using toxic additives for wound care. In this study, we improved physiological characteristics of the previous cryogels by incorporating poly(vinyl alcohol) that also form cryogels. Mechanical strength of the cryogels was more than two times higher than that of the previous cryogels. Furthermore, the incorporation of poly(vinyl alcohol) enhanced water retention and resistance to degradation of the gels by lysozyme. The cryogels retained the favorable biological properties of the previous cryogels that they accelerate infiltration of inflammatory cells into wound sites. Time period for repairing 50 % of initial area of partial-thickness skin wound treated with the cryogels (4.0 ± 1.1 days) was shorter than those with gauze (6.5 ± 0.3 days) or a commercial hydrogel dressing (5.7 ± 0.3 days). Finally, we confirmed that incorporation of basic fibroblast growth factor into the cryogels was effective to further accelerate wound healing (2.7 ± 1.0 days). These results demonstrate that the cryogels in this study are promising for wound care.

Poly(methyl methacrylate) (PMMA) microfibers were used as a template for development of a capillary-like network in agarose hydrogel. Microfibers with diameter 10-20 μm, which is comparable to the diameter of native capillary vessels, were fabricated using a wet spinning technique. The microfibers were embedded in agarose gel and dissolved by immersing the gel in dichloromethane. The resultant microchannels in the gel had the same diameter as the microfibers, and allowed an aqueous solution to be perfused through the gel. The methodology is promising for fabricating a capillary-like network in tissue engineering scaffolds of various water-soluble polymers.

Conventional chitosan hydrogels exhibit an acidic nature and contain unfavorable additives because (i) chitosan is soluble only in acidic solutions and (ii) toxic chemicals or proteins of non-human origin that serve as antigens are necessary for preparing chitosan hydrogels. These characteristics of the chitosan hydrogels limit their possibilities as wound dressings. In this study, a chitosan-gluconic acid conjugate is developed, soluble in an aqueous solution at neutral pH and gellable by freeze-thawing (cryogelation) without using additives. The viability of L929 fibroblasts cultured in the presence of the chitosan derivative for 24 h was >96%. The degradation rate of the corresponding chitosan cryogels by lysozyme was tunable via the derivative concentration in the gels. The gels had low cellular adhesiveness. The gels promoted the accumulation of inflammatory cells such as polymorphonuclear leukocytes, which have the potential to release chemical mediators effective for wound healing, in full-thickness skin wounds in rats and accelerated the healing of the wounds. These results demonstrate that cryogels are promising for wound care.

The aim of this study was to develop in situ gellable hydrogels composed of periodate oxidized citrus pectin (OP) for localized anticancer drug delivery and evaluate the potential of OP to inhibit cancer metastasis. Doxorubicin (Dox) was coupled to OP by imine bonds. Adipic dihydrazide (ADH) was used for cross-linking of the Dox-OP conjugates. The Dox-OP conjugate solution gelled within 2 min after addition of ADH. The release rate of Dox from the hydrogels was controllable by an additive amount of ADH. The released Dox retained anticancer activity. OP was shown to have a potency to prevent homotypic cancer cell aggregation compared to unmodified citrus pectin, strongly suggesting that OP released from hydrogels in vivo will inhibit cancer metastasis. These results indicate that OP hydrogels have the potential to prevent progression of primary cancer by the released Dox and generation of metastatic cancer by the released OP.

A hepatocyte growth factor (HGF)/heparin-immobilized collagen system was used as a synthetic extracellular matrix for hepatocyte culture. The albumin synthesis, nucleus numbers and morphology of the hepatocytes were determined separately to evaluate the hepatocyte number and hepatocyte-specific function under this system. The benefits of the HGF/heparin-immobilized collagen system for hepatocyte culture were confirmed by three types of culture methods in vitro, namely 2D film cultures, 2D gel cultures and 3D gel cultures. In 2D collagen film cultures, hepatocytes exhibited the highest albumin synthesis (1.42 microg/well/day) in HGF/heparin-immobilized collagen films at 7 days of culture. Heparin inhibited hepatocyte adhesion while HGF promoted hepatocyte migration, and spheroid formation was easily detected in HGF/heparin-immobilized collagen films. In 2D collagen gel cultures, albumin synthesis of around 15 microg/well/day was detected and maintained for more than 18 days on HGF/heparin-immobilized collagen gels. Similar findings were obtained in 3D HGF/heparin-immobilized collagen gel cultures, which exhibited albumin synthesis of up to 30 microg/well/day. The albumin synthesis by hepatocytes was two-fold higher in 3D gel cultures compared with 2D gel cultures, and was maintained for over 2 weeks compared with 2D film cultures using the HGF/heparin-immobilized collagen system. Taken together, the HGF/heparin-immobilized collagen system was effective for albumin synthesis by hepatocytes in both 2D film cultures and 3D gel cultures, and therefore shows good potential for tissue engineering use.