The effect of riboflavin-induced collagen photocrosslinking on the scaffold printing accuracy, namely on the area of formed niches and filament thickness, as well as on the degradation time and biocompatibility of scaffolds, has been studied. The thickness of the filaments in the riboflavin-modified scaffolds was 13–29

The aim of the study was to compare type I collagen-based and methacryloyl gelatin-based (GelMA) hydrogels by their ability to form hyaline cartilage in animals after subcutaneous implantation of scaffolds. Materials and Methods Chondrocytes were isolated from the costal cartilage of newborn rats using 0.15% collagenase solution in DMEM. The cells was characterized by glycosaminoglycan staining with alcian blue. Chondrocyte scaffolds were obtained from 4% type I porcine atelocollagen and 10% GelMA by micromolding and then implanted subcutaneously into the withers of two groups of Wistar rats. Histological and immunohistochemical studies were performed on days 12 and 26 after implantation. Tissue samples were stained with hematoxylin and eosin, alcian blue; type I and type II collagens were identified by the corresponding antibodies. Results The implanted scaffolds induced a moderate inflammatory response in both groups when implanted in animals. By day 26 after implantation, both collagen and GelMA had almost completely resorbed. Cartilage tissue formation was observed in both animal groups. The newly formed tissue was stained intensively with alcian blue, and the cells were positive for both types of collagen. Cartilage tissue was formed among muscle fibers. Conclusion The ability of collagen type I and GelMA hydrogels to form hyaline cartilage in animals after subcutaneous implantation of scaffolds was studied. Both collagen and GelMA contributed to formation of hyaline-like cartilage tissue type in animals, but the chondrocyte phenotype is characterized as mixed. Additional detailed studies of possible mechanisms of chondrogenesis under the influence of each of the hydrogels are needed.

3D-bioprinting is a promising technology for a tissue scaffold fabrication in the case of damaged tissue/organ replacement. Collagen is one of the most appropriate hydrogel for the purpose, due to its exceptional biocompatibility. However, the use of collagen with conventionally low concentration makes bioprinting process difficult and does not provide its high accuracy. The purpose of the study was evaluation of suitability of collagen with high concentration in case of chondrocyte-laden scaffold fabrication via 3D-bioprinting for cartilage regeneration in vitro and in vivo. The results of the study showed that inherent porosity of 4% collagen was not enough for cell survival in the case of long-term incubation in vitro. With the beginning of the scaffold incubation, cell migration to the surface and out of the scaffold was observed. The residual cells died mostly within 4 weeks. As for in vivo study, in 2 weeks after implantation of the scaffold, a weak granulomatous inflammation was observed. In 6 weeks, a connective tissue was formed in the area of implantation. In the tissue, macrophages and groups of small cells with round nuclei were found. In accordance with morphological criteria, these cells could be considered as young chondrocytes. However, its amount was not enough to initiate the formation of cartilage.

During biofabrication, a tissue scaffold may require temporary support. The aim of this study was to develop an approach of human thyroid cartilage scaffold temporal support formation. The scaffold 3D-model was based on DICOM images. XY plane projections were used to form scaffold supporting part. To verify the technique, collagen hydrogel was chosen as the main scaffold component. Gelatin was applied for the supporting part. To test the applicability of the approach, a model of thyroid cartilage scaffold with the support was printed. The scaffold corresponded to a given model, although some discrepancy in geometry was observed during verification by computed tomography.

Cancer radiotherapy effectiveness largely depends on tumor cells radiosensitivity. Inherent or acquired radioresistance of tumor cells is important challenge in radiation therapy. Response of tumor cells to fractionated radiation therapy has been investigated by many research groups. At present time the use of protons for cancer research and treatment has expanded rapidly. In this connection research on sensitivity of tumor cells to proton beam therapy is an urgent task. The aim of the study was to assess sensitivity of irradiated with electrons or protons B16 melanoma cells to the next electron beam or proton beam irradiation at comparable total doses. Studies with the use of stable tumor cell lines with acquired radioresistance may be useful for the develop-ment of effective treatment plan tailored to the patients with relapses or metastases that have oc-curred after prior unsuccessful radiotherapy with standard types of radiation. Protons were pro-vided by Prometeus installation scanning beam and the electron beam of the accelerator Novac-11. Cells radiosensitivity was measured by clonogenic assay. The resistance of cells first irradiat-ed with protons and electrons to the next irradiation with protons and electrons was estimated by clonogenic assay. DNA damages, cell size, proliferative activity and cell cycle phase distribution were also evaluated. The study demonstrated that fractionated irradiation of B16 cells with elec-trons at the total dose of 60 Gy causes significant reduction of cells radiosensitivity to the next ir-radiation with protons, radiosensitivity of irradiated cells to the second irradiation with electrons remains the same. In contrast, the first fractionated irradiation of cells with protons at the total dose of 50 Gy does not affect the radiosensitivity of the cells to the next irradiation with electrons or protons.