The extracellular matrix (ECM) comprises a complex milieu of proteins and other growth factors that provide mechanical, biophysical, and biochemical cues to cells. The ECM is organ specific, and its ...detailed composition varies across organs. Bioinks are material formulations and biological molecules or cells processed during a bioprinting process. Organ-derived decellularized ECM (dECM) bioinks have emerged as arguably the most biomimetic bioinks. Here, we review bioinks derived from different decellularized organs, the techniques used to obtain these bioinks, and the characterization methods used to evaluate their quality. We emphasize that obtaining a good-quality bioink depends on the choice of organ, animal, and decellularization method. Finally, we explore potential large-scale applications of bioinks and challenges in manufacturing such bioinks.
Many individual ECM components, including collagen, fibrin, gelatin, alginate, and others, have been used as bioinks, but the natural ECM offers many physical, chemical, and biological cues that are difficult to recapitulate using only a single or just a few components. dECM bioinks could be revolutionary in terms of offering a complete biomimetic ink.
dECM bioinks could be used to print more functional and relevant tissues, which would have applications for drug screening, disease modeling, and regenerative medicine.
A dECM bioink is a softer material with lower mechanical strength; therefore, to ensure the integrity of the bioprinted structure, it is important to fine-tune the mechanical properties of this bioink by mixing it with either natural or synthetic materials.
The dawn of commercial bioprinting is rapidly advancing the tissue engineering field. In the past few years, new bioprinting approaches as well as novel bioinks formulations have emerged, enabling ...biological research groups to demonstrate the use of such technology to fabricate functional and relevant tissue models. In recent years, several companies have launched bioprinters pushing for early adoption and democratisation of bioprinting. This article reviews the progress in commercial bioprinting since the inception, with a particular focus on the comparison of different available printing technologies and important features of the individual technologies as well as various existing applications. Various challenges and potential design considerations for next generations of bioprinters are also discussed.
Bioprinting is an emerging research field that has attracted tremendous attention for various applications; it offers a highly automated, advanced manufacturing platform for the fabrication of ...complex bioengineered constructs. Different bio-inks comprising multiple types of printable biomaterials and cells are utilized during the bioprinting process to improve the homology to native tissues and/or organs in a highly reproducible manner. This paper, presenting a first-time comprehensive yet succinct review of microvalve-based bioprinting, provides an in-depth analysis and comparison of different drop-on-demand bioprinting systems and highlights the important considerations for microvalve-based bioprinting systems. This review paper reports a detailed analysis of its printing process, bio-ink properties and cellular components on the printing outcomes. Lastly, this review highlights the significance of drop-on-demand bioprinting for various applications such as high-throughput screening, fundamental cell biology research, in situ bioprinting and fabrication of in vitro tissue constructs and also presents future directions to transform the microvalve-based bioprinting technology into imperative tools for tissue engineering and regenerative medicine.
Spheroid culture provides cells with a three‐dimensional environment that can better mimic physiological conditions compared to monolayer culture. Technologies involved in the generation of cell ...spheroids are continuously being innovated to produce spheroids with enhanced properties. In this paper, we review the manufacturing capabilities of current cell spheroid generation technologies. We propose that spheroid generation technologies should enable tight and robust process controls to produce spheroids of consistent and repeatable quality. Future technology development for the generation of cell spheroids should look into improvement in process control, standardization, scalability and monitoring, in addition to advanced methods of spheroid transfer and characterization.
Spheroid culture provides cells with a 3D environment that can better mimic physiological conditions compared to monolayer culture. We propose that spheroid generation technologies should enable tight and robust process controls to produce spheroids of consistent and repeatable quality. Future technology development for the generation of cell spheroids should look into improvement in process control, standardization, scalability and monitoring, in addition to advanced methods of spheroid transfer and characterization.
Human mesenchymal stromal cells (hMSCs) have demonstrated, in various preclinical settings, consistent ability in promoting tissue healing and improving outcomes in animal disease models. However, ...translation from the preclinical model into clinical practice has proven to be considerably more difficult. One key challenge being the inability to perform in situ assessment of the hMSCs in continuous culture, where the accumulation of the senescent cells impairs the culture's viability, differentiation potential and ultimately leads to reduced therapeutic efficacies. Histochemical Formula: see text-galactosidase staining is the current standard for measuring hMSC senescence, but this method is destructive and not label-free. In this study, we have investigated alternatives in quantification of hMSCs senescence, which included flow cytometry methods that are based on a combination of cell size measurements and fluorescence detection of SA-Formula: see text-galactosidase activity using the fluorogenic substrate, CFormula: see textFDG; and autofluorescence methods that measure fluorescence output from endogenous fluorophores including lipopigments. For identification of senescent cells in the hMSC batches produced, the non-destructive and label-free methods could be a better way forward as they involve minimum manipulations of the cells of interest, increasing the final output of the therapeutic-grade hMSC cultures. In this work, we have grown hMSC cultures over a period of 7 months and compared early and senescent hMSC passages using the advanced flow cytometry and autofluorescence methods, which were benchmarked with the current standard in Formula: see text-galactosidase staining. Both the advanced methods demonstrated statistically significant values, (r = 0.76, p Formula: see text 0.001 for the fluorogenic CFormula: see textFDG method, and r = 0.72, p Formula: see text 0.05 for the forward scatter method), and good fold difference ranges (1.120-4.436 for total autofluorescence mean and 1.082-6.362 for lipopigment autofluorescence mean) between early and senescent passage hMSCs. Our autofluroescence imaging and spectra decomposition platform offers additional benefit in label-free characterisation of senescent hMSC cells and could be further developed for adoption for future in situ cellular senescence evaluation by the cell manufacturers.
Drop-on-demand (DOD) bioprinting has attracted huge attention for numerous biological applications due to its precise control over material volume and deposition pattern in a contactless printing ...approach. 3D bioprinting is still an emerging field and more work is required to improve the viability and homogeneity of printed cells during the printing process. Here, a general purpose bio-ink was developed using polyvinylpyrrolidone (PVP) macromolecules. Different PVP-based bio-inks (0%-3% w/v) were prepared and evaluated for their printability; the short-term and long-term viability of the printed cells were first investigated. The Z value of a bio-ink determines its printability; it is the inverse of the Ohnesorge number (Oh), which is the ratio between the Reynolds number and a square root of the Weber number, and is independent of the bio-ink velocity. The viability of printed cells is dependent on the Z values of the bio-inks; the results indicated that the cells can be printed without any significant impairment using a bio-ink with a threshold Z value of ≤9.30 (2% and 2.5% w/v). Next, the cell output was evaluated over a period of 30 min. The results indicated that PVP molecules mitigate the cell adhesion and sedimentation during the printing process; the 2.5% w/v PVP bio-ink demonstrated the most consistent cell output over a period of 30 min. Hence, PVP macromolecules can play a critical role in improving the cell viability and homogeneity during the bioprinting process.
Technological advances have increasingly provided more and better treatment options for patients with severe burns. Here, we provide a bird’s-eye view of the product development process for ...third-degree burn wounds with considerations of the critical interaction with regulatory bodies, existing technological gaps, and future directions for skin substitutes.
Technological advances have increasingly provided more and better treatment options for patients with severe burns. Here, we provide a bird’s-eye view of the product development process for third-degree burn wounds with considerations of the critical interaction with regulatory bodies, existing technological gaps, and future directions for skin substitutes.
Three-dimensional (3D) pigmented human skin constructs have been fabricated using a 3D bioprinting approach. The 3D pigmented human skin constructs are obtained from using three different types of ...skin cells (keratinocytes, melanocytes and fibroblasts from three different skin donors) and they exhibit similar constitutive pigmentation (pale pigmentation) as the skin donors. A two-step drop-on-demand bioprinting strategy facilitates the deposition of cell droplets to emulate the epidermal melanin units (pre-defined patterning of keratinocytes and melanocytes at the desired positions) and manipulation of the microenvironment to fabricate 3D biomimetic hierarchical porous structures found in native skin tissue. The 3D bioprinted pigmented skin constructs are compared to the pigmented skin constructs fabricated by conventional a manual-casting approach; in-depth characterization of both the 3D pigmented skin constructs has indicated that the 3D bioprinted skin constructs have a higher degree of resemblance to native skin tissue in term of the presence of well-developed stratified epidermal layers and the presence of a continuous layer of basement membrane proteins as compared to the manually-cast samples. The 3D bioprinting approach facilitates the development of 3D in vitro pigmented human skin constructs for potential toxicology testing and fundamental cell biology research.
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