May 29, 2020 by admin 0 Comments

3D-Bioprinted Aptamer-Functionalized Bio-inks for Spatiotemporally Controlled Growth Factor Delivery

Authors
Deepti Rana, Vasileios D. Trikalitis (Contributor), Vincent R. Rangel (Contributor), Ajoy Kumar Kandar (Contributor), Nasim Salehi Nik (Contributor), Jeroen Rouwkema* (Contributor)
Abstract
Introduction Spatiotemporally controlled growth factors delivering systems are crucial for tissue engineering. However, most of the current strategies for growth factors delivery often focuses on the immobilization or coupling of growth factors within the engineered matrices (hydrogel) via various linker proteins or peptides. These systems provide passive release rates and growth factor delivery on demand, but fail to adapt their release rates in accordance with the tissue development. To overcome this limitation, the present study employed nucleic acid based aptamers for achieving spatiotemporally controlled growth factor delivery. Aptamers are affinity ligands selected from DNA/RNA libraries to recognize proteins with high affinity and specificity.1 Aptamer based growth factor delivery systems are able to load/release multiple growth factors on demand with high specificity. In the present study, the authors have 3D-bioprinted aptamer-functionalized bio-inks to evaluate their potential for growth factor sequestering, programmable release and for studying their effect on vascular network formation. Methods The aptamer-functionalized hydrogels were prepared via photo-polymerization of gelatin methacryloyl (GelMA) and acrydite functionalized aptamers having sequence specific for binding to vascular endothelial growth factor (VEGF165). Visible light photoinitiator, tris(2,2′-bipyridyl)dichloro-ruthenium(II) hexahydrate with sodium persulfate was used. The 3D-bioprinting experiments were carried out using Rokit Invivo 3D printer. The viscoelastic properties of the bio-inks were evaluated and compared with control GelMA bio-ink. To study the programmable growth factor release efficiency, VEGF antibody immunostaining was used. For studying the effect of triggered growth factor release on vascular network formation, human umbilical vein endothelial cells (HUVECs) and mesenchymal stem cells (MSCs) were encapsulated within the bio-inks. Results & Discussion The results obtained from VEGF antibody immunostainings confirmed the sequestration and triggered release of VEGF in response to complementary sequence addition from the 3D bioprinted construct after 5 days of culture. The bioprinted construct showed high cellular viability. The F-Actin/DAPI staining showed cellular sprouting and vascular network formation within the 3D printing aptamer functionalized bio-ink regions. In addition, the endothelial cells showed variations in cellular organization based on the VEGF bound aptamer availability within the bioprinted construct. These observations altogether confirms the bioactivity of VEGF bound aptamers within the printed constructs. Conclusions The present study shows the vasculogenic potential of 3D bioprinted aptamer-functionalized bio-inks via spatiotemporally controlling VEGF availability within the hydrogel system. Acknowledgements: This work is supported by an ERC Consolidator Grant under grant agreement no 724469. References 1. M.R. Battig, et. al., J. Am. Chem. Soc. 134 (2012) 12410-12413.

January 6, 2020 by admin 0 Comments

NiCHE Platform: Nature-Inspired Catechol-Conjugated Hyaluronic Acid Environment Platform for Salivary Gland Tissue Engineering

Authors
Sang-woo Lee, Ji Hyun Ryu, Min Jae Do, Eun Namkoong, Haeshin Lee* and Kyungpyo Park*
Abstract
Recently, there has been growing interest in replacing severely damaged salivary glands with artificial salivary gland functional units created in vitro by tissue engineering approaches. Although various materials such as poly(lactic-co-glycolic acid), polylactic acid, poly(glycolic acid), and polyethylene glycol hydrogels have been used as scaffolds for salivary gland tissue engineering, none of them is effective enough to closely recapitulate the branched structural complexity and heterogeneous cell population of native salivary glands. Instead of discovering new biomaterial candidates, we synthesized hyaluronic acid–catechol (HACA) conjugates to establish a versatile hyaluronic acid coating platform named “NiCHE (nature-inspired catechol-conjugated hyaluronic acid environment)” for boosting the salivary gland tissue engineering efficacy of the previously reported biomaterials. By mimicking hyaluronic acid-rich niche in the mesenchyme of embryonic submandibular glands (eSMGs) with NiCHE coating on substrates including polycarbonate membrane, stiff agarose hydrogel, and polycaprolactone scaffold, we observed significantly enhanced cell adhesion, vascular endothelial and progenitor cell proliferation, and branching of in vitro-cultured eSMGs. High mechanical stiffness of the substrate is known to inhibit eSMG growth, but the NiCHE coating significantly reduced such stiffness-induced negative effects, leading to successful differentiation of progenitor cells to functional acinar and myoepithelial cells. These enhancement effects of the NiCHE coating were due to the increased proliferation of vascular endothelial cells via interaction between CD44 and surface-immobilized HAs. As such, our NiCHE coating platform renders any kind of material highly effective for salivary gland tissue culture by mimicking in vivo embryonic mesenchymal HA. Based on our results, we expect the NiCHE coating to expand the range of biomaterial candidates for salivary glands and other branching epithelial organs.

March 7, 2019 by admin 0 Comments

Surface Engineered Biomimetic Inks Based on UV Cross-Linkable Wood Biopolymers for 3D Printing

Authors
Wenyang Xu, Xue Zhang, Peiru Yang, Otto Långvik, Xiaoju Wang*, Yongchao Zhang, Fang Cheng, Monika Österberg, Stefan Willför and Chunlin Xu*
Abstract
Owing to their superior mechanical strength and structure similarity to the extracellular matrix, nanocelluloses as a class of emerging biomaterials have attracted great attention in three-dimensional (3D) bioprinting to fabricate various tissue mimics. Yet, when printing complex geometries, the desired ink performance in terms of shape fidelity and object resolution demands a wide catalogue of tunability on the material property. This paper describes surface engineered biomimetic inks based on cellulose nanofibrils (CNFs) and cross-linkable hemicellulose derivatives for UV-aided extrusion printing, being inspired by the biomimetic aspect of intrinsic affinity of heteropolysaccharides to cellulose in providing the ultrastrong but flexible plant cell wall structure. A facile aqueous-based approach was established for the synthesis of a series of UV cross-linkable galactoglucomannan methacrylates (GGMMAs) with tunable substitution degrees. The rapid gelation window of the formulated inks facilitates the utilization of these wood-based biopolymers as the feeding ink for extrusion-based 3D printing. Most importantly, a wide and tunable spectrum ranging from 2.5 to 22.5 kPa of different hydrogels with different mechanical properties could be achieved by varying the substitution degree in GGMMA and the compositional ratio between GGMMA and CNFs. Used as the seeding matrices in the cultures of human dermal fibroblasts and pancreatic tumor cells, the scaffolds printed with the CNF/GGMMA inks showed great cytocompatibility as well as supported the matrix adhesion and proliferative behaviors of the studied cell lines. As a new family of 3D printing feedstock materials, the CNF/GGMMA ink will broaden the map of bioinks, which potentially meets the requirements for a variety of in vitro cell–matrix and cell–cell interaction studies in the context of tissue engineering, cancer cell research, and high-throughput drug screening.