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Microscopic, fiber-shaped cell aggregates, have been used as building blocks for fabricating macroscopic three-dimensional tissue architectures, in the field of tissue engineering. In this study, we examined the occurrence of necrotic regions in the most widely used, fiber-shaped cell aggregates, approximately 100 μm in diameter. Alginate hydrogel hollow microfibers were used as templates for the cell aggregates. We demonstrated negligible necrotic region formation occurred in the cell aggregates formed in the hollow microfibers. Furthermore, we improved on previously-reported methods for preparing the hollow microfibers to avoid common microfiber tangling during the fiber preparation process.

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.

Injectable hydrogels have advantages over pre-formed hydrogels in biomedical applications. In our previous study, we showed usefulness of sugar beet pectin (SBP) as an injectable gel material. However, the in vivo biodegradability of the gels was low because animals lack suitable hydrolytic enzymes of SBP. In this study we developed SBP-based injectable gels with higher in vivo biodegradability than the previous SBP gels by incorporating biodegradable gelatin into the latter. An aqueous solution with dissolved SBP and gelatin rapidly (< 1 min) formed gels through a horseradish peroxidase-catalyzed oxidative coupling reaction between feruloyl moieties on the SBP molecules and phenolic moieties on the gelatin molecules. Gelation time and mechanical properties of the gels were tunable by adjusting the polymer concentrations. The gels containing doxorubicin, an anti-cancer drug, successfully suppressed the growth of a solid tumor created by subcutaneous injection of mouse melanoma B16F1 cells into nude mice. These results indicate that injectable and biodegradable SBP/gelatin gels are useful in biomedical applications.

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.