Isotropic and Anisotropic Scaffolds for Tissue Engineering: Collagen, Conventional, and Textile Fabrication Technologies and Properties

In this review article, tissue engineering and regenerative medicine are briefly explained and the importance of scaffolds is highlighted. Furthermore, the requirements of scaffolds and how they can be fulfilled by using specific biomaterials and fabrication methods are presented. Detailed insight is given into the two biopolymers chitosan and collagen. The fabrication methods are divided into two categories: isotropic and anisotropic scaffold fabrication methods. Processable biomaterials and achievable pore sizes are assigned to each method. In addition, fiber spinning methods and textile fabrication methods used to produce anisotropic scaffolds are described in detail and the advantages of anisotropic scaffolds for tissue engineering and regenerative medicine are highlighted.

The Use of Collagen with High Concentration in Cartilage Tissue Engineering by Means of 3D-Bioprinting

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.

Solution-Based Processing for Scaffold Fabrication in Tissue Engineering Applications: A Brief Review

The fabrication of 3D scaffolds is under wide investigation in tissue engineering (TE) because of its incessant development of new advanced technologies and the improvement of traditional processes. Currently, scientific and clinical research focuses on scaffold characterization to restore the function of missing or damaged tissues. A key for suitable scaffold production is the guarantee of an interconnected porous structure that allows the cells to grow as in native tissue. The fabrication techniques should meet the appropriate requirements, including feasible reproducibility and time- and cost-effective assets. This is necessary for easy processability, which is associated with the large range of biomaterials supporting the use of fabrication technologies. This paper presents a review of scaffold fabrication methods starting from polymer solutions that provide highly porous structures under controlled process parameters. In this review, general information of solution-based technologies, including freeze-drying, thermally or diffusion induced phase separation (TIPS or DIPS), and electrospinning, are presented, along with an overview of their technological strategies and applications. Furthermore, the differences in the fabricated constructs in terms of pore size and distribution, porosity, morphology, and mechanical and biological properties, are clarified and critically reviewed. Then, the combination of these techniques for obtaining scaffolds is described, offering the advantages of mimicking the unique architecture of tissues and organs that are intrinsically difficult to design.

Advances in 3D Printing for Tissue Engineering

Tissue engineering (TE) scaffolds have enormous significance for the possibility of regeneration of complex tissue structures or even whole organs. Three-dimensional (3D) printing techniques allow fabricating TE scaffolds, having an extremely complex structure, in a repeatable and precise manner. Moreover, they enable the easy application of computer-assisted methods to TE scaffold design. The latest additive manufacturing techniques open up opportunities not otherwise available. This study aimed to summarize the state-of-art field of 3D printing techniques in applications for tissue engineering with a focus on the latest advancements. The following topics are discussed: systematics of the available 3D printing techniques applied for TE scaffold fabrication; overview of 3D printable biomaterials and advancements in 3D-printing-assisted tissue engineering.