October 21, 2020 by admin 0 Comments

Design and manufacturing of bioprinted gellan gum-based constructs representative of the articular cartilage

Authors
Gianluca Ciardelli, Piergiorgio Gentile, Chiara Tonda Turo
Abstract
Articular cartilage (AC) is a highly specialized tissue which exhibit topographical heterogeneity in terms of matrix composition and mechanical properties. Due to its avascular nature AC shows limited regenerative ability, therefore representing an excellent subject for tissue engineering (TE). Particularly, bioprinting is an emerging additive manufacturing technology that has already demonstrated its potential use in regenerative medicine and cartilage TE. It allows to recapitulate the tissues microstructure by a controlled deposition of “bioinks”, suspensions of cells alone or encapsulated in biomaterials. As cells source, mesenchymal stem cells and chondrocytes, both naturally found in AC, are mainly selected. Hydrogels are largely used as biomaterials for their ability to resemble soft tissues extracellular matrix (ECM), providing an ideal micro-environment for the embedded cells survival, proliferation and differentiation. Hydrogels are produced from synthetic and natural polymers, including gellan gum (GG), a biocompatible polysaccharide that has gained interest in cartilage TE because of its structural similarity to cartilage glycosaminoglycans (GAGs) and chondrogenic potential. The aim of this work was the design and manufacturing of 3D constructs mimicking AC by extrusion bioprinting. Particularly, this thesis objectives (OBJ) were: the synthesis and characterization (physico-chemical, morphological, mechanical) of methacrylated GG-based hydrogels subjected to a dual physical and photo-chemical crosslinking (OBJ1); the subsequent biofabrication via Rokit INVIVO bioprinter of in vitro constructs (OBJ2) and biological characterization of cell-laden constructs in terms of cells viability and AC tissue formation (OBJ3). The final stage of this work dealt with the manufacturing of osteoarthritis (OA) in vitro models, via culturing healthy models in cytokine-enriched culture medium, for future analysis on novel OA therapeutic treatments. Firstly, the success of GG methacrylate (GGMA) synthesis was demonstrated through FTIR and XPS analysis. Then, 4 photo-curable hydrogels were prepared: pure GGMA 2% w/v (GG2) and 3% w/v (GG3), and GGMA (respectively 2% w/v and 0.75% w/v) combined with 5% w/v manuka honey (GG/MH) and 10% w/v gelatin (GG/GEL). Gelation analysis at room temperature showed that GG3 and GG/GEL underwent sol-gel transition in ~1 minute, while GG2 and GG/MH in ~3 minute. Water uptake (WU) analysis demonstrated the strong hydrophilic nature of these hydrogels, reaching WU values up to ~1700%. Morphological analysis evidenced that they had an interconnected porous morphology with a mean pore diameter in the range 100-200 μm, suitable for AC applications. Similarly, mechanical analysis showed that hydrogels had a compressive Young’s modulus between ~25 and ~16 kPa, comparable to other natural hydrogels found in literature. GG2 and GG/MH hydrogels were selected as bioinks encapsulating human TERT immortalised stem cells differentiated into chondrocytes (Y201-C; 7x106 cells/ml). The double-crosslinked bioinks were successfully printed into stable constructs. Live/Dead assay demonstrated high cell viability for both bioprinted constructs. The GAGs quantification assay showed that Y201-C GAGs production increased over time in both hydrogels. Finally, scanning electron microscopy analysis showed that cells exhibited a typical chondrocytes rounded-shaped morphology and tended to aggregate in both healthy and OA GG2 constructs .

August 30, 2019 by admin 0 Comments

Bioprinting Technologies in Tissue Engineering

Authors
Bengi Yilmaz, Aydin Tahmasebifar, Erkan Türker Baran
Abstract
Bioprinting technology is a strong tool in producing living functional tissues and organs from cells, biomaterial-based bioinks, and growth factors in computer-controlled platform. The aim of this chapter is to present recent progresses in bioprinting of nerve, skin, cardiac, bone, cartilage, skeletal muscle, and other soft tissues and highlight the challenges in these applications. Various composite bioinks with bioactive ceramic-based scaffolds having patient-specific design and controlled micro-architectures were used at clinical and preclinical applications successfully for regeneration of bone. In nerve tissue engineering, bioprinting of alginate- and gelatin-based gel bioinks by extrusion presented a controllable 3D microstructures and showed satisfactory cytocompatibility and axonal regeneration. Bioprinting of cardiac progenitors in biopolymers resulted in limited success, while the use of bioinks from extracellular matrix induced satisfactory results in cardiac regeneration. Osteochondral scaffold bioprinting is challenging due to the complex hierarchical structure and limited chondral regeneration. Therefore, current approaches focused on osteochondral scaffold with vascular network and mimicking hierarchical structures. The applications of bioprinting in other types of tissues were also studied, and results showed significant potentials in regeneration of tissues such as cornea, liver, and urinary bladder.

June 1, 2019 by admin 0 Comments

Characterization of the biomechanical properties of canine trachea using a customized 3D-printed apparatus

Authors
Jennifer Sang-jee Lee (a, 1), Jonghyun Park (b, 1), Dong-A Shin (b), Yoon-jong Ryu (a), Hee Chan Kim (c, d, e), Jung Chan Lee (c, d, e), Seong Keun Kwon (a)
Abstract
Objectives The canine trachea is considered to be an excellent preclinical model for tracheal research due to its similar mechanical and dimensional characteristics to the human trachea. However, normative biomechanical properties have yet to be defined and it is one of the main reasons tracheal reconstruction has not succeeded in animal models at large scale. Variation and inaccurate measurement due to a lack of proper apparatus for mechanical tests further prevent determination of normative mechanical data of the trachea. The goal of this study was to overcome these shortcomings by designing the measuring apparatus using 3D-printing technology. Using this apparatus, we determined the normative biomechanical properties of the canine trachea. Methods Whole tracheas were obtained from thirteen mongrel dogs. Biomechanical measurements were performed to determine the radial compressive strength and tensile strength of the intact trachea, and the elastic modulus of the tracheal cartilage. Results Structural parameter data indicated the canine trachea to have inner-diameters similar to those of the human trachea and other widely used animal models. The compressive strength was 4.24 N while the tensile strength was 29.96 N. The elastic modulus of the cartilage portion of the trachea was 1.58 N without showing a significant difference in value based on the location of the trachea. Conclusions This study delineates a comprehensive and foundational characterization of the biomechanical properties of both the intact and cartilage portion of the canine trachea. The parameters were in agreement with those of the human trachea, confirming the canine trachea to be an excellent preclinical model for tracheal research.