Tissue-Specific Bioink from Xenogeneic Sources for 3D Bioprinting of Tissue Constructs

3D bioprinting brings new aspirations to the tissue engineering and regenerative medicine research community. However, despite its huge potential, its growth towards translation is severely impeded due to lack of suitable materials, technological barrier, and appropriate validation models. Recently, the use of decellularized extracellular matrices (dECM) from animal sources is gaining attention as printable bioink as it can provide a microenvironment close to the native tissue. Hence, it is worth exploring the use of xenogeneic dECM and its translation potential for human application. However, extensive studies on immunogenicity, safety-related issues, and animal welfare-related ethics are yet to be streamlined. In addition, the regulatory concerns need to be addressed with utmost priority in order to expedite the use of xenogeneic dECM bioink for 3D bioprinted implantable tissues for human welfare

3D printed in vitro disease models

The vital goal of most biomedical research is to understand the cellular and molecular mechanisms of human disease or to develop novel and innovative therapies or diagnostics. Although animal models, such as transgenic mice, provides crucial clues of many diseases, many of them fail to recapitulate the human disease condition precisely. Furthermore, it is hard to recognize crucial cellular and molecular contributors to disease or gain greater insights in whole-animal models. Recent advances in tissue engineering and microfabrication technologies have generated huge interest in researchers to develop novel in vitro disease models to solve this problem. Among various microfabrication techniques, 3D printing is one such technique that enables researchers to build 3D in vitro tissue models, where the intrinsic cellular morphologies and functions can be reconstituted. These models allow the researchers to vary the specific cellular and molecular factors independently while simultaneously measuring system-level responses in real time. In this chapter, we provide some proof of concept examples of such efforts for engineering disease models. We also discuss the recently developed tools and technologies in 3D printing to develop these models and emphasize opportunities and challenges involved in combining these technologies. © 2017 Elsevier Ltd. All rights reserved

Inkjet-based 3D bioprinting

Three-dimensional (3D) bioprinting techniques, developed over the past two decades, have the potential to fabricate living, patient-specific tissues and organs for use in regenerative medicine (Kesti et al. 2016). Inkjet-based bioprinting is one of the oldest yet promising technologies, which combines the solid freeform fabrication process and precise cell placement in 2D and 3D. Typically, inkjet printing takes digital data of an image or character from a computer and reproduces it on to a material or substrate using ink drops in a noncontact mode (Mohebi and Evans 2002). In addition to its wide application in automation office tool, it has also been widely used in microengineering for printing electronic materials (Sirringhaus et al. 2000). Inkjet printer deposits controlled volume of ink in a layer-by-layer fashion to predefined locations on successive layers to form a 3D construct (Xu et al. 2008). Drop-on-demand (DOD) printers, a commonly used inkjet printers, are used for biological and nonbiological applications. The idea of printing of biological substances was introduced by Klebe after using HP thermal DOD inkjet printer to deposit collagen and fibronectin in 1988 (Klebe 1988). Later, Thomas Boland customized the thermal inkjet printer for printing living cells in a viable state (Wilson and Boland 2003). After this, scientists have made great progress in patterning molecules such as DNA, depositing proteins (Eric et al. 2009, Ilkhanizadeh et al. 2007, Miller et al. 2006), and printing tissues and organs by inkjet printing (Okamoto et al. 2000). The current focus of inkjet bioprinting is fabrication of 3D structures with clinically significant heights to extend its effectiveness in the direction of clinical applications. In this chapter, we discuss about the principle of inkjet bioprinting technology, types of inkjet printers in use, materials used for printing, and the critical parameters involved in this technique. Then, challenges associated with techniques and the future perspectives are also discussed

Integrated 3D Printing-Based Framework—A Strategy to Fabricate Tubular Structures with Mechanocompromised Hydrogels

Several hollow organs perform various crucial functions in the body and must be replaced, repaired, or augmented in many disease conditions. Fabrication of tissue analogues to these hollow organs is incredibly challenging. Still, recent advancements in biofabrication have allowed researchers to pursue the development of several hollow organs such as blood vessels, esophagus, trachea, urethra, and others. Materials like collagen, alginate, elastin, silk, fibrin, etc., have been predominantly used for organ development. However, the focus has been duly shifted toward decellularized extracellular matrix (dECM) to develop tissue-specific hydrogels because they provide relevant biochemical cues to promote cellular activity. Still, the dECM-based hydrogels are mechanically weak to fabricate self-supporting tubular structures. Here, an innovative approach using the stereolithography apparatus (SLA) 3D printed framework has been implemented to achieve a self-supporting tubular structure using caprine esophagus muscle dECM hydrogel. A significant improvement in the mechanical stability of the biofabricated tissue has been observed within 7 days of culture. Interestingly, the encapsulated L929 mouse fibroblasts transdifferentiated into myofibroblasts because of the cues provided by the muscle dECM. Overall, the potential of an SLA-based 3D printing strategy to fabricate frameworks, especially for fabricating tubular organs/tissues using mechanocompromised hydrogel, has been demonstrated here. © 2021 American Chemical Society

3D Bioprinting: Recent Trends and Challenges

3D bioprinting is an additive biomanufacturing technology having potential to fast-forward the translational research, as it has the capability to fabricate artificial tissues and organs that closely mimic biological tissues or organs. As an emerging area of research in the field of tissue engineering, 3D bioprinting has scope in the development of implantable tissues and organs, construction of tissue/organ models and high-throughput diseased/cancer models for pharmaceutical and toxicological studies. Further, this area has diversified with the continuous upgradation of 3D bioprinters and biomaterials, which play major roles in the architectural quality and functionality of bioprinted construct. Addressing these technological complexities requires an integrated approach involving expertise from different areas of science and engineering with lateral thinking. In this review, we highlight the recent trends in 3D bioprinting of tissues and organs including recent developments in usage of material, printers and printing technologies. In addition, importance has been given to various target tissues printed using this technology with an emphasis on bioprinted tissue/cancer models

3D Tissue Modelling of Orthopaedic Tissues

Bones are organs of the skeletal system, providing shape, mechanical support and facilitating movement. They are well known for their self-healing abilities; however, large-scale bone defects cannot be healed completely by the body, and in most cases, external intervention is needed to repair the defects. Among different treatment options such as autografts and allografts, bone tissue engineering is becoming widespread. The essential idea is to apply the concepts of tissue engineering, i.e. the interplay of cells, scaffolds and biological molecules to form a ‘tissue engineering construct’ (TEC), which can promote bone repair and regeneration. The key players in bringing research and clinical practice together are the design and manufacturing technologies. The ability of 3D printing technology to make customized medical devices will make it the core manufacturing technology for bone tissue engineering in future generations

Influence of Liver Extracellular Matrix in Predicting Drug-Induced Liver Injury: An Alternate Paradigm

In vitro drug-induced liver injury (DILI) models are promising tools for drug development to predict adverse events during clinical usage. However, the currently available DILI models are not specific or not able to predict the injury accurately. This is believed to be mainly because of failure to conserve the hepatocyte phenotype, lack of longevity, and difficulty in maintaining the tissue-specific microenvironment. In this study, we have assessed the potential of decellularized liver extracellular matrix (DLM) in retaining the hepatic cellular phenotype and functionality in the presence of a tissue-specific microenvironment along with its role in influencing the effect of the drug on hepatic cells. We show that DLM helps maintain the phenotype of the hepatic cell line HepG2, a well-known cell line for secretion of human proteins that is easily available. Also, the DLM enhanced the expression of a metabolic marker carbamoyl phosphate synthetase I (CPS1), a regulator of urea cycle, and bile salt export pump (BSEP), a marker of hepatocyte polarity. We further validated the DLM for its influence on the sensitivity of cells toward different classes of drugs. Interestingly, the coculture model, in the presence of endothelial cells and stellate cells, exhibited a higher sensitivity for both acetaminophen and trovafloxacin, a toxic compound that does not show any toxicity on preclinical screening. Thus, our results demonstrate for the first time that a multicellular combination along with DLM can be a potential and reliable DILI model to screen multiple drugs. © 2022 American Chemical Society. All rights reserved

Decellularized extracellular matrix hydrogels – cell behavior as function of matrix stiffness

Cells in their native environment are exposed to a milieu of biochemical and physical forces. Cellular physiology and function are affected by dynamic cell – cell and cell – matrix interactions and communication. Cells bind to the cellular or matrix components through receptors, causing changes in the cytoskeleton, which is then translated into information that controls cell behavior such as cellular proliferation, differentiation or migration. Physical properties like matrix stiffness and micro- and nano-topographies play an important role in determining cell behavior. This review explores the effect of matrix stiffness on cell behavior, especially when using decellularized extracellular matrix hydrogels as scaffolds for tissue regeneration. Since the mechanical strength of decellularized extracellular matrix hydrogels is lower than that of native tissue, tuning these properties to achieve conditions similar to the in vivo microenvironment can improve the performance of the decellularized extracellular matrix hydrogels as scaffolds in tissue engineering

Tissue/organ-derived bioink formulation for 3D bioprinting

Tissue/organ-derived bioink formulations open up new avenues in 3D bioprinting research with the potential to create functional tissue or organs. Printing of tissue construct largely depends on material properties, as it needs to be fabricated in an aqueous environment while encapsulating living cells. The decellularized extracellular matrix bioinks proved to be a potential option for functional tissue development in vivo and as an alternative to chemically cross-linked bioinks. However, certain limitations such as printability and limited mechanical strength need to be addressed for enhancing their widespread applications. By drawing knowledge from the existing literature, emphasis has been given in this review to the development of decellularized extracellular matrix bioinks and their applications in printing functional tissue constructs