Molecular Mobility of Polyrotaxane Surfaces Alleviates Oxidative Stress-Induced Senescence in Mesenchymal Stem Cells.

Polyrotaxane is a supramolecular assembly consisting of multiple cyclic molecules threaded by a linear polymer. One of the unique properties of polyrotaxane is molecular mobility, cyclic molecules moving along the linear polymer. Molecular mobility of polyrotaxane surfaces affects cell spreading, differentiation, and other cell-related aspects through changing subcellular localization of yes-associated proteins (YAPs). Subcellular YAP localization is also related to cell senescence derived from oxidative stress, which is known to cause cancer, diabetes, and heart disease. Herein, the effects of polyrotaxane surface molecular mobility on subcellular YAP localization and cell senescence following H2 O2 -induced oxidative stress are evaluated in human mesenchymal stem cells (HMSCs) cultured on polyrotaxane surfaces with different molecular mobilities. Oxidative stress promotes cytoplasmic YAP localization in HMSCs on high-mobility polyrotaxane surfaces; however, low-mobility polyrotaxane surfaces more effectively maintain nuclear YAP localization, exhibiting lower senescence-associated ß-galactosidase activity and senescence-related gene expression and DNA damage than that seen with the high-mobility surfaces. These results suggest that the molecular mobility of polyrotaxane surfaces regulates subcellular YAP localization, thereby protecting HMSCs from oxidative stress-induced cell senescence. Applying the molecular mobility of polyrotaxane surfaces to implantable scaffolds can provide insights into the prevention and treatment of diseases caused by oxidative stress.

Suppressed Migration and Enhanced Cisplatin Chemosensitivity in Human Cancer Cell Lines by Tuning the Molecular Mobility of Supramolecular Biomaterials.

Cancer cells recognize physical cues transmitted from the surrounding microenvironment, and accordingly alter the migration and chemosensitivity. Cell adhesive biomaterials with tunable physical properties can contribute to the understanding of cancer cell responses, and development of new cancer therapies. Previously, it was reported that polyrotaxane-based surfaces with molecular mobility effectively modulate cellular functions via the yes-associated protein (YAP)-related signaling pathway. In the present study, the impact of molecular mobility of polyrotaxane surfaces on the migration and chemosensitivity of lung (A549), pancreatic (BxPC-3), and breast cancer (MDA-MB-231) cell lines is investigated, and it is found that the cellular spreading of adherent A549 and BxPC-3 cells and nuclear YAP translocation are promoted on low-mobility surfaces, suggesting that cancer cells alter their subcellular YAP localization in response to molecular mobility. Furthermore, low-mobility surfaces suppress cellular migration more than high-mobility surfaces. Additionally, low-mobility surfaces promote the cisplatin chemosensitivity of each cancer cell line to a greater extent than high-mobility surfaces. These results suggest that the molecular mobility of polyrotaxane surfaces suppresses cellular migration and enhances chemosensitivity via the subcellular translocation of YAP in cancer cells. Biointerfaces based on polyrotaxanes can thus be a new platform for elucidating cancer cell migration and chemoresistance mechanisms.

Supramolecular Surface Coatings with Acetylated Polyrotaxane-Based Triblock Copolymers for Thermal Regulation of Cell Adhesion and Fabrication of Cell Sheets.

Polyrotaxanes (PRXs) containing acetylated α-cyclodextrins exhibit a temperature-dependent phase transition in aqueous solutions across their lower critical solution temperature (LCST) of approximately 26.6 °C. To gain insights into the interactions of acetylated PRXs (Ac-PRXs) with biological components, thermoresponsive supramolecular surfaces were prepared by coating tissue culture polystyrene (TCPS) surfaces with Ac-PRX triblock copolymers, and their surface properties across the LCST were evaluated. The wettability and protein adsorption of Ac-PRX-coated surfaces changed significantly between 10 and 37 °C, whereas the uncoated TCPS and unmodified PRX-coated surfaces did not alter the wettability and protein adsorption at 10 and 37 °C. The adhesion, proliferation, morphology, and adhesion strength of NIH/3T3 cells on Ac-PRX-coated surfaces were found to be similar to those of the uncoated and unmodified PRX-coated surfaces. However, the adhesion strength of NIH/3T3 cells on Ac-PRX-coated surfaces decreased drastically at 10 °C. Consequently, the cells spontaneously detached from the Ac-PRX-coated surfaces without enzymatic treatment. Additionally, when incubating confluent cells at 10 °C, the cells detached from Ac-PRX-coated surfaces as cell sheets while retaining extracellular matrix proteins. The findings of this study provide new directions for the design of thermoresponsive supramolecular biointerfaces for applications in bioseparation and cell manipulation.

Independent Roles of Molecular Mobility and Zeta Potential on Supramolecular Surfaces in the Sequence of RAW264.7 Macrophage Responses.

Surface properties of biomaterials affect the morphologies and inflammatory responses of macrophages. Recently, biomaterial design utilizing these properties has been explored to build a scaffold for balancing the immune system in vivo. In the present study, polyrotaxane surfaces with different functional groups including methyl, amino, and sulfo groups are utilized to clarify the effect of molecular mobility and zeta potential of these surfaces on RAW264.7 macrophage responses. At 24 h post-seeding, the majority of the cells adhere onto each surface, and the initial spreading is suppressed by more negatively-charged polyrotaxane surfaces. From 24 to 48 h of incubation, the spreading areas on the unmodified and methylated surfaces significantly increase, whereas those on the aminated and sulfonated surfaces remain unchanged. These results suggest that the initially cellular spreading process depends on the zeta potential, while the subsequent spreading process is governed by the molecular mobility. After lipopolysaccharide stimulation, the less mobile surfaces induce higher expression of inflammation-related genes than highly mobile surfaces, suggesting that molecular mobility is the main factor modulating the inflammatory activity in macrophages. These findings indicate that the zeta potential and molecular mobility of polyrotaxane surfaces may play independent roles in the sequence of macrophage responses.

Phototethering of Collagen onto Polyetheretherketone Surfaces to Enhance Osteoblastic and Endothelial Performance.

Polyetheretherketone (PEEK) is a candidate material for bone implants as an alternative to metals. However, PEEK exhibits poor osseointegration and low endothelial compatibility. This study demonstrates the phototethering of collagen onto PEEK surfaces to facilitate osteoblastic and vascular endothelial performance. In particular, collagen with methacryloyl groups is covalently tethered to the PEEK surface via surface-initiated photopolymerization. This process is simpler than the conventional method of collagen-tethering and can be extended to the surface-patterning treatment of collagen. The collagen is confirmed to be tethered to the PEEK surface using attenuated total reflection Fourier transform infrared measurements, bicinchoninic acid assays, and atomic force microscopic observations. When human bone marrow-derived mesenchymal stem cells (HbmMSCs) are cultured on collagen-tethered PEEK (COL-PEEK) surfaces, the cells favorably adhere and proliferate. After inducing osteogenic differentiation, the cells on the COL-PEEK surfaces show higher expression levels of osteoblast-related genes and mineralization than those on the PEEK surface. Moreover, the tethering of collagen greatly improves endothelial proliferation. The COL-PEEK surfaces promotes endothelial networking in coculture with HbmMSCs. These results suggest that COL-PEEK is highly compatible with both osteoblasts and vascular endothelial cells. COL-PEEK is a promising implant that induces osteogenesis and angiogenesis to repair bone tissues.

Post-Cross-Linking of Collagen Hydrogels by Carboxymethylated Polyrotaxanes for Simultaneously Improving Mechanical Strength and Cell Proliferation.

To improve the mechanical properties of collagen hydrogels, which are widely utilized as biomaterials, post-cross-linking of collagen hydrogels was performed using polyrotaxane (PRX) as a cross-linker. Herein, carboxymethyl group-modified PRXs (CMPRs) composed of carboxymethylated α-cyclodextrins (α-CDs) threaded along poly(ethylene glycol) (PEG) capped with bulky stoppers were used to cross-link via reaction with the amino groups in the collagen. Four series of CMPRs with different α-CD threading ratios and axle PEG molecular weights were used for the post-cross-linking of the collagen hydrogels to verify the optimal CMPR chemical compositions. The post-cross-linking of the collagen hydrogels with CMPRs improved the swelling ratios and mechanical properties, such as viscoelasticity and tensile strength. Among the tested CMPRs, CMPRs with an axle PEG molecular weight of 35,000 (PEG35k) resulted in better mechanical properties than CMPRs with a PEG10k axis. Additionally, the cell adhesion and proliferation were greatly improved on the surface of the collagen hydrogels post-cross-linked with CMPRs with the PEG35k axle. These findings suggest that the molecular weight of an axle polymer in CMPRs is a more important parameter than the α-CD threading ratios. Accordingly, the post-cross-linking of hydrogels with PRXs is promising for improving the mechanical properties and biomaterial functions of collagen hydrogels.

Improved epithelial cell-cell adhesion using molecular mobility of supramolecular surfaces.

Cells can sense the surrounding microenvironmental properties including contact with biomaterials. Although in vitro cell fates in response to the physical properties of cell-adhesive materials have been widely reported, their influence on cell-cell adhesion is unclear. Here, we investigated the role of molecular mobility on polyrotaxane surfaces in epithelial cell-cell adhesion. Polyrotaxane surfaces with high mobility induced cytoplasmic yes-associated protein (YAP) localization in epithelial cells, whereas those with low mobility induced nuclear YAP localization, suggesting that YAP localization is switched by the mobility of the polyrotaxane surface. The cytoplasmic YAP localization increased the expression of tight junction-associated genes. A scratch assay revealed that although the epithelial cells on the low mobile surface rapidly initiated their migration, the cells on the highly mobile surface delayed their migration. Thus, this finding suggests that polyrotaxane surfaces with higher mobility induce cytoplasmic YAP localization, leading to stronger cell-cell adhesion. The polyrotaxane biointerface is promising as a powerful tool to improve the physical immune system and repair biological tissues.

Tissue Adhesion-Anisotropic Polyrotaxane Hydrogels Bilayered with Collagen.

Hydrogels are promising materials in tissue engineering scaffolds for healing and regenerating damaged biological tissues. Previously, we developed supramolecular hydrogels using polyrotaxane (PRX), consisting of multiple cyclic molecules threaded by an axis polymer for modulating cellular responses. However, since hydrogels generally have a large amount of water, their adhesion to tissues is extremely weak. Herein, we designed a bilayered hydrogel with a PRX layer and a collagen layer (PRX/collagen hydrogel) to achieve rapid and strong adhesion to the target tissue. The PRX/collagen hydrogel was fabricated by polymerizing PRX crosslinkers in water with placement of a collagen sponge. The differences in components between the PRX and collagen layers were analyzed using Fourier transform infrared spectroscopy (FT-IR). After confirming that the fibroblasts adhered to both layers of the PRX/collagen hydrogels, the hydrogels were implanted subcutaneously in mice. The PRX hydrogel without collagen moved out of its placement site 24 h after implantation, whereas the bilayer hydrogel was perfectly adherent at the site. Together, these findings indicate that the bilayer structure generated using PRX and collagen may be a rational design for performing anisotropic adhesion.

Delayed Senescence of Human Vascular Endothelial Cells by Molecular Mobility of Supramolecular Biointerfaces.

Yes-associated protein (YAP), a transcriptional coactivator of the Hippo signaling pathway, has been widely implicated in vascular aging and diseases. For preventing vascular endothelial cell senescence, the design and development of biomaterials to regulate YAP activity are required. This study prepares polyrotaxane-coated surfaces with molecular mobility and clarifies the role of the mobility on vascular endothelial cell senescence through Hippo-YAP signaling. The polyrotaxane surface with high mobility induces cytoplasmic YAP localization in endothelial cells, whereas the surface with low mobility induces nuclear YAP localization. After serial cultivation of endothelial cells using polyrotaxane surfaces with different mobilities for 35 d, the endothelial cells aged on the polyrotaxane surface with high mobility exhibit higher proliferative potential, smaller spreading size, and lower activity of senescence-associated ß-galactosidase than those aged on the surface with low mobility. These findings suggest that cellular senescence can be delayed by modulating the molecular mobility on polyrotaxane surfaces.

Evaluation of Mechanical and Physical Properties of Light and Heat Polymerized UDMA for DLP 3D Printer.

The aims of this study were to investigate the feasibility of using a DLP 3D printer to fabricate a crown using scan data before tooth preparation, and to investigate the effect of additional heat curing on the mechanical properties of the urethane dimethacrylate (UDMA)-based 3D printed crown. A silicone fitting test was used to evaluate the internal adaptation of the crown. For ultimate tensile strength (UTS), the specimens were tested after 24 h storage in water at 37 °C or after 10,000 thermal cycles (TC) between 5-55 °C. For shear bond strength (SBS), a PMMA self-curing resin was filled into a Teflon ring mounted onto the polished UDMA specimens. The internal adaptation of the crowns fabricated with cement space was better than those with no cement space. There was no significant difference in UTS between light-curing and additional heat-curing groups after TC. As for the SBS, there was a significant difference after TC between the two groups. Crowns can be fabricated by a DLP 3D printer using pre-preparation scans with a cement space defined in the software. Additional heat curing of the UDMA-based crown reduced residual monomer and improved its mechanical properties.

Surface-tethering of methylated polyrotaxanes with 4-vinylbenzyl groups onto poly(ether ether ketone) substrates for improving osteoblast compatibility.

Poly(ether ether ketone) (PEEK) is a high-performance thermoplastic used for several industrial applications due to its excellent mechanical properties. However, the use of PEEK is limited to dental materials because of its poor implant-bone integration. In the present study, methylated polyrotaxanes (MePRXs) with 4-vinylbenzyl groups, which are supermolecules composed of methylated α-cyclodextrins and poly(ethylene glycol) chains end-capped with 4-vinylbenzyl groups, were covalently tethered onto PEEK surfaces using photo-induced polymerization to improve their osteoblast compatibility. The surface-tethering of MePRXs onto PEEK surfaces was confirmed by analyzing their attenuated total reflectance Fourier transform infrared spectra and contact angles. When mouse preosteoblasts were cultured on the MePRX-PEEK and bare PEEK surfaces, the MePRX-PEEK surfaces showed significantly better proliferation and osteoblast differentiation than the bare PEEK surfaces. These results suggest that surface modification of PEEKs using MePRXs improves their osteoblast compatibility.

Molecular mobility of polyrotaxane-based biointerfaces alters inflammatory responses and polarization in Kupffer cell lines.

A polyrotaxane is a supramolecular system composed of a linear polymer (e.g., poly(ethylene glycol): PEG) chain with bulky groups at both ends that threads through the cavities of multiple macrocyclic molecules (e.g., α-cyclodextrins: α-CD). Its structural properties allow for the threading α-CDs to move along the PEG chain, and the extent of mobility can be modulated by the number of threading α-CDs. In the present study, we prepared polyrotaxane-based surfaces with tunable mobilities, and evaluated the effect of molecular mobility on the activation of Kupffer cells. In particular, we analyzed the morphological changes and the gene expression of inflammatory cytokines in the presence of lipopolysaccharide (LPS), an immune-activator, using polyrotaxane-based surfaces with different molecular mobilities. Morphological changes were observed in the Kupffer cells depending on the number of threading α-CDs in the polyrotaxanes. This result suggests that the molecular mobility on the polyrotaxane surfaces acts as a mechanical cue for changing the morphology of Kupffer cells. Furthermore, the highly mobile surfaces with a small number of threading α-CDs promoted vacuolar formation in Kupffer cells and increased the gene expression of pro-inflammatory cytokines in the presence of LPS. These results suggest that polyrotaxane surfaces with tunable mobilities can be used as culture platforms for elucidating the mechanism by which mechanical cues contribute to the immune activity of Kupffer cells. Furthermore, by applying the molecular mobility of polyrotaxane to implantable scaffolds, it could be used as a tool for balancing the immune response in the living body.

Dual effect of molecular mobility and functional groups of polyrotaxane surfaces on the fate of mesenchymal stem cells.

Polyrotaxanes are supramolecular assemblies consisting of cyclic molecules (e.g., α-cyclodextrins) and linear polymer chains (e.g., poly[ethylene glycol]), in which cyclic molecules can move along the polymer chain. Here, we examined the effect of functional groups introduced into the α-cyclodextrins of polyrotaxane on cell responses such as adhesion, proliferation, and differentiation. Polyrotaxane-based triblock copolymers modified with methyl (CH3, hydrophobic, and nonionic), hydroxy (OH, hydrophilic and nonionic), amino (NH2, cationic), and sulfo (SO3H, anionic) groups were coated on the surface of the culture plate to fabricate polyrotaxane surfaces with different surface chemistries. The chemical compositions of each surface were determined via time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The contact angle hysteresis reflecting the molecular mobility and zeta potential of each polyrotaxane surface changed depending on the functional groups. When osteoblast and adipocyte differentiation was induced in human mesenchymal stem cells cultured on each polyrotaxane surface, the cells adhered to the SO3H-modified polyrotaxane surfaces exhibited osteoblast differentiation, whereas the cells adhered to the OH-, NH2-, and SO3H-modified polyrotaxane surfaces preferentially underwent adipocyte differentiation compared with those on the unmodified and CH3-modified polyrotaxane surfaces. Interestingly, the SO3H-modified polyrotaxane surfaces promoted both osteoblast and adipocyte differentiation. High molecular mobility and negative charge on the SO3H-modified polyrotaxane surfaces are expected to contribute to the facilitation of both osteoblast and adipocyte differentiation.

Cyclodextrin-Based Supramolecular Complexes of Osteoinductive Agents for Dental Tissue Regeneration.

Oral tissue regeneration has received growing attention for improving the quality of life of patients. Regeneration of oral tissues such as alveolar bone and widely defected bone has been extensively investigated, including regenerative treatment of oral tissues using therapeutic cells and growth factors. Additionally, small-molecule drugs that promote bone formation have been identified and tested as new regenerative treatment. However, treatments need to progress to realize successful regeneration of oral functions. In this review, we describe recent progress in development of regenerative treatment of oral tissues. In particular, we focus on cyclodextrin (CD)-based pharmaceutics and polyelectrolyte complexation of growth factors to enhance their solubility, stability, and bioactivity. CDs can encapsulate hydrophobic small-molecule drugs into their cavities, resulting in inclusion complexes. The inclusion complexation of osteoinductive small-molecule drugs improves solubility of the drugs in aqueous solutions and increases in vitro osteogenic differentiation efficiency. Additionally, various anionic polymers such as heparin and its mimetic polymers have been developed to improve stability and bioactivity of growth factors. These polymers protect growth factors from deactivation and degradation by complex formation through electrostatic interaction, leading to potentiation of bone formation ability. These approaches using an inclusion complex and polyelectrolyte complexes have great potential in the regeneration of oral tissues.

Preservation of heparin-binding EGF-like growth factor activity on heparin-modified poly(N-isopropylacrylamide)-grafted surfaces.

A heparin-modified poly(N-isopropylacrylamide) (PIPAAm)-grafted surface bound with heparin-binding epidermal growth factor-like growth factor (HB-EGF) was able to culture hepatocytes maintaining high albumin secretion and high expression of hepatocyte-specific genes. However, the activity of HB-EGF on the surface and its binding effects on hepatocytes remain unclear. In this study, we investigated the temperature-dependent interactions of HB-EGF and EGF receptor (EGFR) with heparin-modified PIPAAm to evaluate the activity of HB-EGF on the surface. Quartz crystal microbalance (QCM) measurements revealed that the amounts of adsorbed HB-EGF on either the heparin-modified PIPAAm-grafted surface (heparin-IC1) or PIPAAm-grafted surfaces were almost the same regardless of swelling/deswelling of grafted PIPAAm chains. The heparin-IC1 surface bound to HB-EGF at 37 °C had the ability to bind to hepatocytes through specific affinity interaction with EGFR, whose activation was confirmed by western blotting. However, the physisorbed HB-EGF on the PIPAAm surface greatly diminished its activity. Taken together, the introduction of heparin into grafted PIPAAm chains on the surface plays a pivotal role in holding HB-EGF while preserving its activity. Hydration and swelling of surface-grafted PIPAAm chains at 20 °C greatly diminished the attachment of hepatocytes with HB-EGF bound to heparin-IC1, whereas hepatocytes were able to bind to HB-EGF bound to heparin-IC1 at 37 °C. Thus, the equilibrated affinity interaction between EGFRs and surface-bound HB-EGF was considered to be attenuated by steric hindrance due to hydration and/or swelling of grafted PIPAAm chains.

Synergy of molecularly mobile polyrotaxane surfaces with endothelial cell co-culture for mesenchymal stem cell mineralization.

Stem cell-based bone tissue engineering is a promising strategy for the treatment of bone defects. Since regeneration of bone tissue takes a long time, promoting osteogenesis of stem cells is desired for earlier recovery from dysfunctions caused by bone defects. Here, we combined endothelial cell co-culture using the molecularly mobile sulfonated polyrotaxane (PRX) surfaces to enhance the mineralization of human bone marrow derived mesenchymal stem cells (HBMSCs). Sulfonated PRXs are composed of sulfopropyl ether-modified α-cyclodextrins (α-CDs) threaded on a polyethylene glycol chain. The molecular mobility of PRX, α-CDs moving along the polymer, can be modulated by the number of α-CDs. When osteoblastic differentiation was induced in HBMSCs and human umbilical vein endothelial cells (HUVECs), co-culture groups on sulfonated PRX surfaces with low molecular mobility showed the highest mineralization, which is about two times as high as co-culture groups on sulfonated PRX surfaces with high molecular mobility. Nuclear accumulation of yes-associated proteins in HBMSCs and cell-cell communication via cytokines or cadherin may play an important role in synergistically induced mineralization of HBMSCs.

Polyrotaxanes as emerging biomaterials for tissue engineering applications: a brief review.

The field of tissue engineering and regeneration constantly explores the possibility of utilizing various biomaterials' properties to achieve effective and uneventful tissue repairs. Polyrotaxanes (PRXs) are supramolecular assemblies, which possess interesting mechanical property at a molecular scale termed as molecular mobility. This molecular mobility could be utilized to stimulate various cellular mechanosignaling elements, thereby altering the cellular functions. Apart from this, the versatile nature of PRXs such as the ability to form complex with growth factors and peptides, numerous sites for chemical modifications, and processability into different forms makes them interesting candidates for applications towards tissue engineering. This literature briefly reviews the concepts of PRXs and molecular mobility, the versatile nature of PRXs, and its emerging utility towards certain tissue engineering applications.

Biological Effects of Polyrotaxane Surfaces on Cellular Responses of Fibroblast, Preosteoblast and Preadipocyte Cell Lines.

Biointerfaces based on polyrotaxane (PRX), consisting of α-cyclodextrins (α-CDs) threaded on a poly(ethylene glycol) (PEG) chain, are promising functionalized platforms for culturing cells. PRXs are characterized by the molecular mobility of constituent molecules where the threading α-CDs can move and rotate along the PEG chain. Taking advantage of this mobility, we have previously succeeded in demonstrating the regulation of cellular responses, such as cellular adhesion, proliferation, and differentiation. In the present study, we investigated differences in the cellular responses to PRX surfaces versus commercially available tissue culture polystyrene (TCPS) surfaces using fibroblasts, preosteoblasts, and preadipocytes. PRX surfaces were found to more significantly promote cellular proliferation than the TCPS surfaces, regardless of the cell type. To identify the signaling pathways involved in the activation of cellular proliferation, a DNA microarray analysis was performed. PRX surfaces showed a significant increase in the integrin-mediated cell adhesion and focal adhesion pathways. Furthermore, PRX surfaces also promoted osteoblast differentiation more than TCPS. These results suggest that structural features of PRX surfaces act as mechanical cues to dominate cellular proliferation and differentiation.

Mobility Tuning of Polyrotaxane Surfaces to Stimulate Myocyte Differentiation.

Polyrotaxanes, consisting of poly(ethylene glycol) and α-cyclodextrins, are mechanically interlocked supermolecules. The structure allows α-cyclodextrins to move along the polymer, referred to as molecular mobility. Here, polyrotaxane-based triblock copolymers, composed of polyrotaxanes with different degrees of methylation and poly(benzyl methacrylate) at both terminals, are coated on culture surfaces to fabricate dynamic biointerfaces for myocyte differentiation. The molecular mobility increases with the degree of methylation and the contact angle hysteresis of water droplets and air bubbles. When the mouse myoblast cell line C2C12 is cultured on methylated polyrotaxane surfaces, the expression levels of myogenesis-related genes, myogenin (Myog) and myosin heavy chain (Myhc) are altered by the degree of methylation. Polyrotaxane surfaces with intermediate degrees of methylation promote the highest expression levels among all the surfaces. The polyrotaxane surface provides an appropriate environment for myocyte differentiation by accurately adjusting the degrees of methylation.

Cellular Orientation on Repeatedly Stretching Gelatin Hydrogels with Supramolecular Cross-Linkers.

The cytocompatibility of biological and synthetic materials is an important issue for biomaterials. Gelatin hydrogels are used as biomaterials because of their biodegradability. We have previously reported that the mechanical properties of gelatin hydrogels are improved by cross-linking with polyrotaxanes, a supramolecular compound composed of many cyclic molecules threaded with a linear polymer. In this study, the ability of gelatin hydrogels cross-linked by polyrotaxanes (polyrotaxane-gelatin hydrogels) for cell cultivation was investigated. Because the amount of polyrotaxanes used for gelatin fabrication is very small, the chemical composition was barely altered. The structure and wettability of these hydrogels are also the same as those of conventional hydrogels. Fibroblasts adhered on polyrotaxane-gelatin hydrogels and conventional hydrogels without any reduction or apoptosis of adherent cells. From these results, the polyrotaxane-gelatin hydrogels have the potential to improve the mechanical properties of gelatin without affecting cytocompatibility. Interestingly, when cells were cultured on polyrotaxane-gelatin hydrogels after repeated stress deformation, the cells were spontaneously oriented to the stretching direction. This cellular response was not observed on conventional hydrogels. These results suggest that the use of a polyrotaxane cross-linking agent can not only improve the strength of hydrogels but can also contribute to controlling reorientation of the gelatin.