In recent years, significant progress has been observed in the field of skin bioprinting, which has a huge potential to revolutionize the way of treatment in injury and surgery. Furthermore, it may be considered as an appropriate platform to perform the assessment and screening of cosmetic and pharmaceutical formulations. Therefore, the objective of this paper was to review the latest advances in 3D bioprinting dedicated to skin applications. In order to explain the boundaries of this technology, the architecture and functions of the native skin were briefly described. The principles of bioprinting methods were outlined along with a detailed description of key elements that are required to fabricate the skin equivalents. Next, the overview of recent progress in 3D bioprinting studies was presented. The article also highlighted the potential applications of bioengineered skin substituents in various fields including regenerative medicine, modeling of diseases, and cosmetics/drugs testing. The advantages, limitations, and future directions of this technology were also discussed.
At present, one of the main limitations of three-dimensional (3D) bioprinting in tissue engineering stems from a scarcity of biomaterials tailored for specific applications. Widely used hydrogels offer an optimal printability and a suitable environment for cell growth; however, they lack the mechanical strength required for non-soft tissues, for example, cartilage, tendons, and meniscus. This work investigated the physicochemical, mechanical, and biological characteristics of a 3D-printed polycaprolactone (PCL) reinforced with multiwalled carbon nanotubes (MWCNT) and “bamboo-like” carbon nanotubes (BCNT) with the following w/w % concentrations: 0.005%, 0.01%, 0.02%, and 0.2%. The materials were analyzed with subsequent techniques: Scanning electron microscopy, nanoindentation, parallel plate rheometry, and differential scanning calorimetry. Biological evaluations were performed with normal human articular chondrocytes by confocal microscopy and proliferation assay. The study revealed that the carbon nanotubes (CNT) addition improved the rheological properties of the material by increasing the setting temperature. Moderate enhancement was observed in terms of mechanical properties. The most significant difference was noted in cell adhesion and proliferation. Pure PCL did not facilitate cell growth and mainly apoptotic cells were observed on its surface. The addition of 0.01% MWCNT resulted in enhanced adhesion and proliferation; however, the morphology of the cells remained spherical, signifying a suboptimal surface for proliferation. Interestingly, PCL reinforced with 0.02% BCNT displayed excellent facilitation of cellular adhesion and proliferation, which is uncharacteristic of pure PCL. In summary, this study investigated the potential of CNT-reinforced PCL for 3D bioprinting and tissue engineering, highlighting key physicochemical, mechanical, and biological aspects of this biomaterial.
Articular cartilage and meniscus injuries are prevalent disorders with insufficient regeneration responses offered by available treatment methods. In this regard, 3D bioprinting has emerged as one of the most promising new technologies, offering novel treatment options. Additionally, the latest achievements from the fields of biomaterials and tissue engineering research identified constituents facilitating the creation of biocompatible scaffolds. In this study, we looked closer at hyaluronic acid and multi-walled carbon nanotubes as bioink additives. Firstly, we assessed the minimal concentrations that stimulate cell viability, and decrease reactive oxygen species and apoptosis levels in 2D cell cultures of normal human knee articular chondrocytes (NHAC) and human adipose-derived mesenchymal stem cells (hMSC-AT). In this regard, 0.25 mg/ml of hyaluronic acid and 0.0625 mg/ml of carbon nanotubes were selected as the most optimal concentrations. In addition, we investigated the protective influence of 2-phospho-L-ascorbic acid in samples with carbon nanotubes. Tests conducted on 3D bioprinted constructs revealed that only a combination of components positively impacted cell viability throughout the whole experiment. Gene expression analysis of COL1A1, COL6A1, HIF1A, COMP, RUNX2, and POU5F1 showed significant changes in the expression of all analyzed genes with a progressive overall loss of transcriptional activity in most of them.
The necessity to preserve meniscal function prompts the research and develop¬ment of novel treatment options, like three-dimensional (3D) bioprinting. However, bioinks for meniscal 3D bioprinting have not been extensively explored. Therefore, in this study, a bioink composed of alginate, gelatin, and carboxymethylated cellu¬lose nanocrystal (CCNC) was formulated and evaluated. Firstly, bioinks with varying concentrations of the aforementioned components were subjected to rheological analysis (amplitude sweep test, temperature sweep test, and rotation). The optimal bioink formulation of 4.0% gelatin, 0.75% alginate, and 1.4% CCNC dissolved in 4.6% D-mannitol was further used for printing accuracy analysis, followed by 3D bioprint¬ing with normal human knee articular chondrocytes (NHAC-kn). The encapsulated cells’ viability was > 98%, and collagen II expression was stimulated by the bioink. The formulated bioink is printable, stable under cell culture conditions, biocompatible, and able to maintain the native phenotype of chondrocytes. Aside from meniscal tissue bioprinting, it is believed that this bioink could serve as a basis for the devel¬opment of bioinks for various tissues.
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