Visible light-induced hydrogelation is attractive for various biomedical applications. In this study, hydrogels of alginate with phenolic hydroxyl groups (Alg-Ph) were obtained by irradiating a solution containing the polymer, ruthenium II trisbipyridyl chloride ([Ru(bpy)]) and sodium persulfate (SPS), with visible light. The hydrogelation kinetics and the mechanical properties of the resultant hydrogels were tunable by controlling the intensity of the light and the concentrations of [Ru(bpy)] and SPS. With appropriate concentrations of [Ru(bpy)] and SPS, the hydrogel could be obtained following approximately 10 s of irradiation using a normal desktop lamp. The hydrogelation process and the resultant hydrogel were cytocompatible; mouse fibroblast cells enclosed in the Alg-Ph hydrogel maintained more than 90% viability for 1 week. The solution containing Alg-Ph, [Ru(bpy)] and SPS was useful as a bioink for stereolithographic bioprinting. Cell-laden hydrogel constructs could be printed using the bioprinting system equipped with a visible light projector without a significant decrease in cell viability in the presence of photoabsorbent Acid Red 18. The hydrogel construct including a perfusable helical lumen of 1 mm in diameter could be fabricated using the printing system. These results demonstrate the significant potential of this visible light-induced hydrogelation system and the stereolithographic bioprinting using the hydrogelation system for tissue engineering and regenerative medicine.

Bioprinting has a great potential to fabricate three-dimensional (3D) functional tissues and organs. In particular, the technique enables fabrication of 3D constructs containing stem cells while maintaining cell proliferation and differentiation abilities, which is believed to be promising in the fields of tissue engineering and regenerative medicine. We aimed to demonstrate the utility of the bioprinting technique to create hydrogel constructs consisting of hyaluronic acid (HA) and gelatin derivatives through irradiation by visible light to fabricate 3D constructs containing human adipose stem cells (hADSCs). The hydrogel was obtained from a solution of HA and gelatin derivatives possessing phenolic hydroxyl moieties in the presence of ruthenium(II) tris-bipyridyl dication and sodium ammonium persulfate. hADSCs enclosed in the bioprinted hydrogel construct elongated and proliferated in the hydrogel. In addition, their differentiation potential was confirmed by examining the expression of pluripotency marker genes and cell surface marker proteins, and differentiation to adipocytes in adipogenic differentiation medium. Our results demonstrate the great potential of the bioprinting method and the resultant hADSC-laden HA/gelatin constructs for applications in tissue engineering and regenerative medicine.

Composite hydrogels of hyaluronic acid and gelatin attract great attention in biomedical fields. In particular, the composite hydrogels obtained through processes that are mild for cells are useful in tissue engineering. In this study, hyaluronic acid/gelatin composite hydrogels obtained through a blue light-induced gelation that is mild for mammalian cells were studied for the effect of the content of each polymer in the precursor solution on gelation, properties of resultant hydrogels, and behaviors of human adipose stem cells laden in the hydrogels. Control of the content enabled gelation in less than 20 s, and also enabled hydrogels to be obtained with 0.5–1.2 kPa Young’s modulus. Human adipose stem cells were more elongated in hydrogels with a higher rather than lower content of hyaluronic acid. Stem cell marker genes, Nanog, Oct4, and Sox2, were expressed more in the cells in the composite hydrogels with a higher content of hyaluronic acid compared with those in the hydrogel composed of gelatin alone and on tissue culture dishes. These results are useful for designing conditions for using gelatin/hyaluronic acid composite hydrogels obtained through blue light-induced gelation suitable for tissue engineering applications.

When irradiated, fullerene efficiently generates reactive oxygen species (ROS) and is an attractive photosensitizer for photodynamic therapy (PDT). Ideally, photosensitizers for PDT should be water-soluble and tumor-specific. Because cancer cells endocytose glucose more effectively than normal cells, the characteristics of fullerene as a photosensitizer were improved by combining it with glucose. The cytotoxicity of PDT was studied in several cancer cell lines cultured with C(60)-(Glc)1 (D-glucose residue pendant fullerene) and C(60)-(6Glc)1 (a maltohexaose residue pendant fullerene) subsequently irradiated with UVA(1). PDT alone induced significant cytotoxicity. In contrast, PDT with the glycoconjugated fullerene exhibited no significant cytotoxicity against normal fibroblasts, indicating that PDT with these compounds targeted cancer cells. To investigate whether the effects of PDT with glycoconjugated fullerene were because of the generation of singlet oxygen ((1)O(2)), NaN(3) was added to cancer cells during irradiation. NaN(3) extensively blocked PDT-induced apoptosis, suggesting that PDT-induced cell death was a result of the generation of (1)O(2). Finally, to investigate the effect of PDT in vivo, melanoma-bearing mice were injected intratumorally with C(60)-(Glc)1 and irradiated with UVA(1). PDT with C(60)-(Glc)1 suppressed tumor growth. These findings indicate that PDT with glycoconjugated fullerene exhibits tumor-specific cytotoxicity both in vivo and in vitro via the induction of (1)O(2).

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. Except for surgical resection, no effective treatment strategies have been established. Photodynamic therapy (PDT) consists of intravenous administration of a photosensitizer, activated by a specific wavelength of light, which produces reactive oxygen species that directly kill tumor cells. We analyzed the efficacy of PDT using a newly developed photosensitizer, 5,10,15,20-tetrakis, for the GIST treatment. Various photosensitizers were administered in vitro to GIST (GIST-T1) and fibroblast (WI-38) cells, followed by irradiation, after which cell death was compared. We additionally established xenograft mouse models with GIST-T1 tumors and examined the accumulation and antitumor effects of these photosensitizers in vivo. In vitro, the expression of the glucose transporters GLUT1, GLUT3, and GLUT4, the cellular uptake of H 2 TFPC-SGlc, and apoptosis mediated by PDT with H 2 TFPC-SGlc were significantly higher in GIST-T1 than in WI-38 cells. In vivo, H 2 TFPC-SGlc accumulation was higher in xenograft tumors of GIST-T1 cells than in the adjacent normal tissue, and tumor growth was significantly suppressed following PDT. PDT with novel H 2 TFPC-SGlc is potentially useful for clinical applications about the treatment of GIST. Mol Cancer Ther; 13(4); 767-75. Ó2014 AACR.