Takao Aoyagi

Preparation of temperature-responsive, cationized, poly(ε-caprolactone)-based, cross-linked materials by a macromonomer design and positive charge control on the surface

AbstractIn this study, a convenient method to synthesize cationic macromonomers containing branched poly(ε-caprolactone) (PCL) was developed, and stable materials were derived by photo-cross-linking reactions. In fact, a bromomethyl-terminated modification was carried out at the hydroxyl end groups of the starting PCL; then, the terminal groups reacted with 2,2′-dimethylaminoethyl methacrylate to afford the objective macromonomers, which had N,N′-dimethylmethacrylamino groups at the chain ends. The resulting PCL-based materials were cross-linked by UV light irradiation and were stable against exposure to organic solvents and heating above the softening points. The surface properties of the cationic, PCL, cross-linked membrane were evaluated by measuring the zeta potentials and performing anionic dye adsorption tests using Acid Red 87. As expected, the cationic, PCL, cross-linked membrane surfaces showed a positive charge and greater dye adsorption than the naked PCL, which depended on the cationic contents and temperature. Over the softening point, the positive charge steeply increased. The morphologies of adhered human mesenchymal stem cells on the PCL materials with lower cationic contents were preliminarily observed and shown to be well dispersed. The PCL-based materials in this study could enhance cell interaction and be useful for scaffold or mechanobiology studies.This study demonstrated convenient preparation methods for the introduction of cationic and cross-linkable moieties into 2-branched and 4-branched PCL and their corresponding stable materials. The cationic content and the ratio of 2-branched and 4-branched monomers could be simultaneously controlled by incorporating non-cationic macromonomers. Zeta potential measurements proved that the cationic charge could be controlled by changing the temperatures. Human MSC adhesion was observed on the PCL materials with different cationic contents and lower contents of cationic contents seem to be preferable. Consequently, such materials are promising for biomaterials research.n

Production of hollow-type spherical bacterial cellulose as a controlled release device by newly designed floating cultivation

We developed a novel cultivating system for hollow-type spherical bacterial cellulose (HSBC) gel production without any molds or template. It consisted of floating aqueous medium droplet containing Gluconacetobacter xylinus (G. xylinus) at the boundary of two non-mixed silicone oil layers. The fibrils of bacterial cellulose (BC) were produced at the interface of water and oil phases. Fibril layers effectively thickened layer-by-layer and eventually formed a shell structure. The size of the HSBC gel can be controlled by the volume of dropped cell suspension. For cell suspensions of 50 μL and 10 μL, HSBC gels of approximately 4.0 mm and 2.5 mm were obtained, respectively. The shell of the HSBC gel is the gelatinous membrane formed by well-organized fibril networks; they comprised type-I crystal structure of cellulose. Additionally, we studied release profile of the fluorescein isothiocyanate-dextran (FITC-Dex) and observed that it released rapidly from the HSBC gels compared to from the BC gels obtained by the static culture method. The release behavior from HSBC gel agreed satisfactorily with Higuchi model. Therefore, the shell of HSBC gel is surely a thin gelatinous membrane of BC, and would be useful as a drug release device.

Dynamic alterations of hepatocellular function by on-demand elasticity and roughness modulation

Temperature-responsive cell culture substrates reported here can be dynamically programmed to induce bulk softening and surface roughness changes in the presence of living cells. Alterations in hepatocellular function following temporally controlled substrate softening depend on the extent of stiff mechanical priming prior to user-induced material transition.

A nanoparticle-preparation kit using ethylene glycol-based block copolymers with a common temperature-responsive block

A nanoparticle-preparation kit system for producing desired nanoparticles using ethylene glycol-based block copolymers with a common temperature-responsive block was developed. The injected nanoparticles were found to accumulate in the tumor tissue and showed high blood biocompatibility.

In vitro and in vivo assessment of delivery of hydrophobic molecules and plasmid DNAs with PEO-PPO-PEO polymeric micelles on cornea

The stability and bio-distribution of genes or drug complexes with poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO, Pluronic F-68) polymeric micelles (PM) are essential for an effective nanosized PM delivery system. We used Förster resonance energy transfer (FRET) pairs with PM and measured the FRET ratio to assess the stability of PM inxa0vitro and inxa0vivo on the cornea. The FRET ratio reached a plateau at 0.8 with 3% PM. Differential scanning calorimetry measurement confirmed the complex formation of FRET pairs with PM. Confocal imaging with the fluorophores fluorescein isothiocyanate isomer I (FITC) and rhodamine B base (RhB) also showed the occurrence of FRET pairs inxa0vitro. The fluorophores were mixed with 3% PM solution or the FITC-labeled PEO-PPO-PEO polymers (FITC-P) were mixed with RhB-labeled plasmids (RhB-DNA). In addition, the inxa0vitro corneal permeation of FRET pair complexes with PM reached a 0.8 FRET ratio. One hour after eye drop administration, FRET pairs colocalized in the cytoplasm, and surrounded and entered the nuclei of cells in the cornea, and the polymers were located in the corneal epithelial layers, as detected through anti-PEG immunohistochemistry. Furthermore, fluorescence colocalization in the cytoplasm and cell nucleus of the corneal epithelium was confirmed in tissues where RhB or RhB-DNA complexed with FITC-P was found to accumulate. We demonstrate that at a concentration of 3%, PM can encapsulate FRET pairs or RhB-DNA and retain their integrity within the cornea 1xa0h after administration, suggesting the feasibility and stability of PEO-PPO-PEO polymers as a vehicle for drug delivery.

An Intriguing Method for Fabricating Arbitrarily Shaped "Matreshka" Hydrogels Using a Self-Healing Template

This work describes an intriguing strategy for the creation of arbitrarily shaped hydrogels utilizing a self-healing template (SHT). A SHT was loaded with a photo-crosslinkable monomer, PEG diacrylate (PEGDA), and then ultraviolet light (UV) crosslinked after first shaping. The SHT template was removed by simple washing with water, leaving behind the hydrogel in the desired physical shape. A hierarchical 3D structure such as “Matreshka” boxes were successfully prepared by simply repeating the “self-healing” and “photo-irradiation” processes. We have also explored the potential of the SHT system for the manipulation of cells.