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ABSTRACT: A lamellar hydrogel with high toughness, exhibiting ternary stimuli-responsive structural color changes has been synthesized. The gel consists of alternating hard layers of a polymeric surfactant (PDGI) and soft layers of interpenetrating networks of poly(acrylamide)-poly(acrylic acid). Reversible, wide range switching of the stop-band position was achieved using different external stimuli of temperature, pH, and stress/strain.
Advanced Materials 05/2013; · 13.88 Impact Factor
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Macromolecules 04/2013; · 5.17 Impact Factor
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ABSTRACT: BACKGROUND: It has been a common belief that articular cartilage tissue cannot regenerate in vivo. Recently, however, we have found that spontaneous hyaline cartilage regeneration can be induced in vivo by implanting a synthetic double-network (DN) hydrogel, which is composed of poly-(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) and poly-(N,N'-dimethyl acrylamide) (PDMAAm). However, the mechanism of this phenomenon has not been clarified. Recently, we have found that single-network PAMPS and PDMAAm gels can induce chondrogenic differentiation of ATDC5 cells in vitro even in a maintenance medium. In the in vivo condition, there is a strong possibility that the induction effect of the gel itself is enhanced by some molecules which exist in the joint. We have noticed that the joint fluid naturally contains hyaluronic acid (HA). The purpose of this study is to clarify in vitro effects of supplementation of HA on the differentiation effect of the PAMPS and PDMAAm gels. METHODS: We cultured the ATDC5 cells on the PAMPS gel, the PDMAAm gel, and the polystyrene (PS) dish surface with the maintenance medium without insulin for 7 days. HA having a molecular weight of approximately 800 kDa was supplemented into the medium so that the concentration became 0.00, 0.01, 0.10, or 1.00 mg/mL. We evaluated the cultured cells with phase-contrast microscopy and PCR analyses. RESULTS: On the PAMPS gel, supplementation with HA of 0.01 and 0.10 mg/mL significantly increased expression of type-2 collagen mRNA (p = 0.0008 and p = 0.0413) and aggrecan mRNA (p = 0.0073 and p = 0.0196) than that without HA. On the PDMAAm gel, supplementation with HA of 1.00 mg/mL significantly reduced expression of these genes in comparison with the culture without HA (p = 0.0426 and p = 0.0218). CONCLUSIONS: The in vitro induction effects of the PAMPS and PDMAAm gels on chondrogenic differentiation of ATDC5 cells are significantly affected by HA, depending on the level of concentration. These results suggested that there is a high possibility that HA plays an important role in the in vivo spontaneous hyaline cartilage regeneration phenomenon induced by the PAMPS/PDMAAm DN gel.
BMC Musculoskeletal Disorders 02/2013; 14(1):56. · 1.58 Impact Factor
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ABSTRACT: BACKGROUND: A double-network (DN) gel, which is composed of poly(2-acrylamido-2-methylpropanesulfonic acid) and poly(N,N'-dimethyl acrylamide), can induce hyaline cartilage regeneration in vivo in a large osteochondral defect. The purpose of this study was to clarify the influence of the thickness of the implanted DN gel on the induction ability of hyaline cartilage regeneration. METHODS: Thirty-eight mature rabbits were used in this study. We created an osteochondral defect having a diameter of 4.3-mm in the patellofemoral joint. The knees were randomly divided into 4 groups (Group I: 0.5-mm thick gel, Group II: 1.0-mm thick gel, Group III: 5.0-mm thick gel, and Group IV: untreated control). Animals in each group were further divided into 3 sub-groups depending on the gel implant position (2.0-, 3.0-, or 4.0-mm depth from the articular surface) in the defect. The regenerated tissues were evaluated with the Wayne's gross and histological grading scales and real time PCR analysis of the cartilage marker genes at 4 weeks. RESULTS: According to the total Wayne's score, when the depth of the final vacant space was set at 2.0 mm, the scores in Groups I, II, and III were significantly greater than that Group IV (p < 0.05), although there were no significant differences between Groups I and IV at a 3.0-mm deep vacant space. The expression levels of type-2 collagen in Groups II and III were significantly higher (p < 0.05) than that in Group IV. CONCLUSIONS: The 1.0-mm thick DN gel sheet had the same ability to induce hyaline cartilage regeneration as the 5.0-mm thick DN gel plug. However, the induction ability of the 0.5-mm thick sheet was significantly lower when compared with the 1.0-mm thick gel sheet. The 1.0-mm DN gel sheet is a promising device to establish a cell-free cartilage regeneration strategy that minimizes bone loss from the gel implantation.
BMC Musculoskeletal Disorders 01/2013; 14(1):50. · 1.58 Impact Factor
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ABSTRACT: Expanding undifferentiated induced pluripotent stem (iPS) cells in vitro is a basic requirement for application of iPS cells in both fundamental research and clinical regeneration. In this study, we intended to establish a simple, low cost and efficient method for the long-term self-renewal of mouse induced pluripotent stem (miPS) cells without using feeder-cells and adhesive proteins. Three scaffolds were selected for the long-term subculture of miPS cells over two months starting from passages 14 to 29: 1) a gelatin coated polystyrene (Gelatin-PS) that is a widely used scaffold for self-renewal of mouse embryonic stem (mES) cells; 2) a neutral hydrogel poly(N,N-dimethylacrylamide) (PDMAAm); and 3) a negatively charged hydrogel poly(2-acrylamido-2-methyl-propane sulfonic acid sodium salt) (PNaAMPS). Each passaged miPS cells on these scaffolds were cryopreserved successfully and the revived cells showed high viability and proliferation. The passaged miPS cells maintained a high undifferentiated state on all three scaffolds and a high level of pluripotency by expressing differentiation markers in vitro and forming teratomas in SCID mice with derivatives of all three germ layers. Compared to Gelatin-PS, the two hydrogels exhibited much better self-renewal performance in terms of high proliferation rate and level of expression of undifferentiated gene markers as well as efficiency in pluripotent teratoma formation. Furthermore, the PNaAMPS hydrogel demonstrated a slightly higher efficiency and simpler operation of cell expansion than the PDMAAm hydrogel. To conclude, PNaAMPS hydrogel is an excellent feeder-free scaffold because of its simplicity, low cost and high efficiency in expanding a large number of miPS cells in vitro. Copyright © 2012 John Wiley & Sons, Ltd.
Journal of Tissue Engineering and Regenerative Medicine 11/2012; · 3.28 Impact Factor
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ABSTRACT: Biopolymers such as actin, microtubules and DNA are well known for their fascinating in vivo selforganization
phenomena. Considerable efforts have been devoted to mimicking their organization
process in vitro that produced ring-shaped or toroid structures in an irreversible manner. However,
understanding the factors that lead to formation of such assembled structures deserves more
investigation to achieve a unified insight into the assembly process, particularly of the microtubules.
Here, we report an active assembly process of microtubules (MTs) at an air–buffer interface that
resulted in ring-shaped microtubule structures with a narrow size distribution and a high yield. Using
an ‘‘air–buffer interface control system’’ combined with the newly developed ‘‘inert chamber system
(ICS)’’ we have also successfully observed the reversible conformational transition between ring- and
linear-shaped microtubules at the air–buffer interface. This is the first ever direct in situ observation of a
reversible assembly process of MTs and probably provides us with valuable discernment to understand
the in vivo organizational behavior of biopolymers.
Soft Matter 11/2012; 8(42):10863-10867. · 4.39 Impact Factor
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ABSTRACT: We introduce here an ATP (adenosine triphosphate)-fueled nano-biomachine constructed from actin and myosin gels. Various types
of chemically cross-linked actin gel, which are tens of times larger in size than native actin filaments (F-actin), were formed
by complexing with cation-polymers and placed on a chemically cross-linked myosin gel. By adding dilute solution of ATP, they
moved along the myosin gel with a velocity as high as that of native F-actin by coupling to ATP hydrolysis. Formation mechanism
and structure of actin complexes as well as those of myosin gels were studied in detail and elucidated with the specific characteristics
of the motility. These results demonstrate that one can construct nano-biomachines fueled by chemical energy of ATP with controlled
motility.
Polymer Science Series A 04/2012; 51(6):689-700. · 0.84 Impact Factor
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ABSTRACT: The purpose of this study was to determine the in vivo cartilage induction effect of the poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) single-network (SN) gel and poly(N,N'-dimethyl acrylamide) (PDMAAm) SN gel in comparison with that of the PAMPS/PDMAAm double-network (DN) gel. An osteochondral defect created in rabbit trochlea was treated with PAMPS/PDMAAm DN, PAMPS SN, or PDMAAm SN gel implantation or left untreated. The gel was implanted into the defect so that a 2-mm depth remained. The defects were examined by histologic and immunohistochemical evaluations, surface assessment using confocal laser scanning microscopy, and real-time polymerase chain reaction analysis at 4 weeks. Samples were quantitatively evaluated with a scoring system reported by Wayne et al. The PAMPS/PDMAAm DN gel-implanted defect was filled with the hyaline-like cartilage tissue. The PAMPS SN gel-implanted defect was filled inhomogenously with hyaline/fibrocartilage tissue. The histology score of the defect treated with PAMPS/PDMAAm DN gel was significantly higher than those treated with PAMPS and PDMAAm SN gels, and the untreated defect (p = 0.0408, p < 0.0001, and p < 0.0001, respectively) and the scores of the defect treated with PAMPS SN gel were significantly higher than those treated with PDMAAm SN gel and the untreated defect (p = 0.0026 and p = 0.0026, respectively). These results suggested that the PAMPS SN gel has an ability that can induce hyaline cartilage regeneration in vivo, but that the PDMAAm SN gel does not. The current study indicates that the chondrogenic potential of a negatively charged PAMPS gel component plays an important role in the cartilage regeneration ability of the PAMPS/PDMAAm DN gel in vivo.
Journal of Biomedical Materials Research Part A 04/2012; 100(9):2244-51. · 2.63 Impact Factor
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Polymer Journal 04/2012; · 1.26 Impact Factor
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ABSTRACT: Marine sessile organisms easily adhere to submerged solids such as rocks, metals and plastics,
but not to seaweeds and fishes, which are covered with soft and wet ‘hydrogel’. Inspired by
this fact, we have studied long-term antifouling properties of hydrogels against marine sessile
organisms. Hydrogels, especially those containing hydroxy group and sulfonic group, show
excellent antifouling activity against barnacles both in laboratory assays and in the marine
environment. The extreme low settlement on hydrogels in vitro and in vivo is mainly caused
by antifouling properties against the barnacle cypris.
SCIENCE AND TECHNOLOGY OF ADVANCEDMATERIALS. 01/2012; 12.
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ABSTRACT: Over the last few decades, the in vitro motility assay has been performed to probe the biophysical and chemo-mechanical properties as well as the self-organization process of biomolecular motor systems such as actin-myosin and microtubule-kinesin. However, aggression of the reactive oxygen species (ROS) and concomitant termination of the activity of biomolecular motors during investigation remains a drawback of this assay. Despite enzymatic protection that makes use of a combination of glucose, glucose oxidase, and catalase, the active lifetime of biomolecular motors is found to be only a few hours and this short lifetime restricts further study on those systems. We have solved this problem by using a newly developed system of the in vitro motility assay that is conducted in an inert nitrogen gas atmosphere free of ROS. Using microtubule-kinesin as a model system we have shown that our system has prolonged the active lifetime of the biomolecular motor until several days and even a week by protecting it from oxidative damage.
Langmuir 11/2011; 27(22):13659-68. · 4.19 Impact Factor
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ABSTRACT: We study the sliding friction of poly(vinyl alcohol) (PVA) gel against glass substrate in hyaluronan (HA) aqueous solution with various concentrations and two molecular weights. The frictional stress decreases with increase of concentration of HA at low sliding velocity, and the lowest friction appears in HA 10c* (c* is the overlap concentration) solution; after that, it increases slightly with the concentration. By assuming that a continuous HA lubricant layer is formed at the interface, which screens PVA adsorption to substrate, we estimate the thickness of the lubrication film in concentrated HA solution. In addition, we perform frictional measurement in poly(ethylene oxide) (PEO) aqueous solutions and proteoglycan solutions. By comparing the frictional behavior with that in HA solutions, we observe a universal relationship between the zero-shear rate viscosity of polymer solution and the friction at low sliding velocity region, regardless the change in the lubricating polymer species.
10/2011;
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ABSTRACT: We have recently found a phenomenon that spontaneous regeneration of a hyaline cartilage-like tissue can be induced in a large osteochondral defect by implanting a double-network (DN) hydrogel plug, which was composed of poly-(2-Acrylamido-2-methylpropanesulfonic acid) and poly-(N, N'-Dimetyl acrylamide), at the bottom of the defect. The purpose of this study was to clarify gene expression profile of the regenerated tissue in comparison with that of the normal articular cartilage.
We created a cylindrical osteochondral defect in the rabbit femoral grooves. Then, we implanted the DN gel plug at the bottom of the defect. At 2 and 4 weeks after surgery, the regenerated tissue was analyzed using DNA microarray and immunohistochemical examinations.
The gene expression profiles of the regenerated tissues were macroscopically similar to the normal cartilage, but showed some minor differences. The expression degree of COL2A1, COL1A2, COL10A1, DCN, FMOD, SPARC, FLOD2, CHAD, CTGF, and COMP genes was greater in the regenerated tissue than in the normal cartilage. The top 30 genes that expressed 5 times or more in the regenerated tissue as compared with the normal cartilage included type-2 collagen, type-10 collagen, FN, vimentin, COMP, EF1alpha, TFCP2, and GAPDH genes.
The tissue regenerated by using the DN gel was genetically similar but not completely identical to articular cartilage. The genetic data shown in this study are useful for future studies to identify specific genes involved in spontaneous cartilage regeneration.
BMC Musculoskeletal Disorders 09/2011; 12:213. · 1.58 Impact Factor
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09/2011: pages 2689 - 2717; , ISBN: 9783527631421
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ABSTRACT: The microtubule (MT)-kinesin system has been proposed as the building block of biomolecular motor based artificial biomachines. Considerable efforts have been devoted to integrate this system that produced a variety of ordered structures including the ring-shaped MT assembly which is being considered as a promising candidate for the further development of the biomachines. However, lack of proper knowledge that might help tune the direction of motion of ring-shaped microtubule assembly from counterclockwise to clockwise direction, and vice versa, significantly restricted their potential applications. We report our success in controlling the direction of rotational motion of ring-shaped MT assembly by altering the preparation conditions of microtubules. The change in the direction of rotation of MT rings could be interpreted in terms of the accompanied structural rearrangement of the MT lattice. For achieving handedness-regulated efficient biomachines having tunable asymmetric property, our study will be significantly directive.
Biomacromolecules 09/2011; 12(10):3394-9. · 5.48 Impact Factor
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ABSTRACT: The poor mechanical properties remain the largest barrier to traditional synthetic hydrogels for extensive practical applications, such as tissue scaffolds. In this work, we have synthesized the hydrogel films in the presence of microgel precursors of various chemical species with different charges. The hydrogels fabricated have a novel two-phase composite structure, where the continuous phase is a loosely cross-linked polyacrylamide (PAAm) matrix and the disperse phase is virtually double-network (DN) microgels. Named as microgel-reinforced (MR) hydrogels, they exhibited dramatic enhancement in mechanical strength and toughness, in comparison to the hydrogels with no microgels. MR hydrogels showed the comparable mechanical properties with the conventional bicontinuous DN hydrogels. By visualizing the embedded microgels before, during, and after the elongation, mesoscale fractures of the microgels phase were confirmed, which should effectively blunt the crack and enhance the fracture propagation resistance. Therefore, we conclude that the essential reinforcement principle of MR gels roots in the sacrificial bonds effect contributed by the microgels. This work provides a novel universal pathway to synthesize hydrogel thin films with high strength and toughness from various microgels and may open a new avenue for the application of hydrogels in various fields, such as fast responsive actuators, fuel cell films, wound dressings, etc.
09/2011;
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ABSTRACT: Biological motors, driven by the conversion of chemical energy into mechanical energy, are much more efficient than man-made machines. The development of such efficient biomimetic motor systems in vitro is currently a vital need. However, great difficulty lies in how to integrate the sophisticated functions of the constituent components to obtain a performance as in the case of natural living systems. Based on 'active' and 'passive' self-organization principles, it has been demonstrated that the functions of motor protein systems can be integrated to obtain complex hierarchical structures that can work as actuators. Most of the works discussed here concern two-dimensional behavior, and recent works aim to explore the three-dimensional features of such artificial bio-mechanical systems.
Macromolecular Bioscience 07/2011; 11(10):1314-24. · 3.89 Impact Factor
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ABSTRACT: We studied the ability of surfactants to reduce friction by boundary lubrication for a bulk hydrogel sliding on a solid surface in an aqueous solution. A piece of negatively charged polyelectrolyte hydrogel was slid across solid surfaces with various levels of hydrophobicity, using a strain-controlled parallel-plate rheometer in water. A dramatic reduction in the sliding friction, especially in the low velocity region, was detected by the addition of a surfactant to the water medium. This friction reduction was only observed in gel-solid friction but not in solid-solid friction, indicating that the soft and wet nature of the gel surface was crucial for this surfactant-induced friction reduction. This phenomenon reveals that surfactants can remain at the gel-mated interface, thus preventing direct interfacial interaction between the sliding surfaces, and significantly decreasing the frictional stress. The reported dramatic reduction in friction highlights the frictional characteristics of soft and wet hydrogel materials.
Journal of Physics Condensed Matter 07/2011; 23(28):284107. · 2.55 Impact Factor
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ABSTRACT: In this paper, settlement, metamorphosis, and long term growth of barnacles on soft substrates with
a wide elasticity range (modulus 0.01–0.47 MPa) as well as with the variation in wettability were
investigated for the first time in vitro, in the laboratory environment. Tough double-network (DN)
hydrogels and polydimethylsiloxane (PDMS) were used as the soft hydrophilic substrates and
hydrophobic substrates, respectively, and polystyrene (PS), a hard and hydrophobic substrate, was
used as a control. It was observed that (1) the initial settlement and metamorphosis of cyprid larvae
dramatically increase with the substrate elastic modulus while not showing an explicit dependence on
the substrate wettability; (2) the growth rate of barnacles on both DN gels and PDMSs does not show
an explicit dependence on the elasticity of the soft substrates, while it shows a slightly higher value on
the hydrophobic PDMSs than on the hydrophilic DN gels; (3) the growth rate on these soft substrates is
explicitly lower than that on the rigid PS substrate at the late stage of the growth; (4) the ‘‘self-release’’
phenomenon of barnacles was observed for the PDMS substrate with a modulus higher than 0.01 MPa.
Based on these observations, the antifouling effects of the soft substrates on barnacles were discussed.
Soft Matter 07/2011; 7(16):7281-7290. · 4.39 Impact Factor
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ABSTRACT: Differentiation of embryoid bodies (EBs) into particular cell lineages has been extensively studied. There is an increasing interest in the effect of soft hydrogel scaffolds on the behavior of EBs, such as the initial adhesion, dynamic morphology change, and differentiation. In this study, without adding any other bioactive factors in the serum-containing medium, dynamic behaviors of mouse EBs loaded on the surface of hydrogels with different surface charge and chemical structures are investigated. EBs adhered quickly to negatively charged poly(sodium p-styrene sulfonate) (PNaSS) hydrogels, which facilitates EBs spreading, migration, and differentiation into three germ layers with high efficiency of cardiomyocytes differentiation, similar to that on gelatin coated polystyrene (PS) culture plate. While on neutral poly(acrylamide) (PAAm) hydrogels, EBs maintained the initial spherical morphology with high expression of pluripotency-related markers in the short culture periods, and then showed the significantly greater levels of selected endoderm markers after long-time culture. EBs cultured on negatively charged poly(2-acrylamido-2-methyl-propane sulfonic acid sodium salt) (PNaAMPS) gels demonstrated the analogous behaviors with that of neutral PAAm gels at early differentiation phase (day 4+1). Then, their adhesion, spreading and differentiation were quite similar to that on negatively charged PNaSS gels. The correlation between surface properties of hydrogels and EBs differentiation was discussed.
Tissue Engineering Part A 06/2011; 17(17-18):2343-57. · 4.64 Impact Factor
