Bioprinted Scaffolds Research Articles

Coaxial 3D bioprinting of tri-polymer scaffolds to improve the osteogenic and vasculogenic potential of cells in co-culture models.

The crosstalk between osteoblasts and endothelial cells is critical for bone vascularization and regeneration. Here, we used a coaxial 3D bioprinting method to directly print an osteon-like structure by depositing angiogenic and osteogenic bioinks from the core and shell regions of the coaxial nozzle, respectively. The bioinks were made up of gelatin, gelatin methacryloyl (GelMA), alginate, and hydroxyapatite (HAp) nanoparticles and were loaded with human umbilical vascular endothelial cells (HUVECs) and osteoblasts (MC3T3) in the core and shell regions, respectively. Conventional monoaxial 3D bioprinting was used as a control method, where the hydrogels, HAp nanoparticles, MC3T3 cells, and HUVECs were all mixed in one bioink and printed from the core nozzle. As a result, the bioprinted scaffolds were composed of cell-laden fibers with either a core-shell or homogenous structure, providing a non-contact (indirect) or contact (direct) co-culture of MC3T3 cells and HUVECs, respectively. Both structures supported the 3D culture of HUVECs and osteoblasts over a long period. The scaffolds also supported the expression of osteogenic and angiogenic factors. However, the gene expression was significantly higher for the core-shell structure than the homogeneous structure due to the well-defined distribution of osteoblasts and endothelial cells and the formation of vessel-like structures in the co-culture system. Our results indicated that the coaxial bioprinting technique, with the ability to create a non-contact co-culture of cells, can provide a more efficient bioprinting strategy for printing highly vascularized and bioactive bone structures.

Preparation and Characterisation of Cellulose Nanocrystal/Alginate/Polyethylene Glycol Diacrylate (CNC/Alg/PEGDA) Hydrogel Using Double Network Crosslinking Technique for Bioprinting Application

In this study, we aimed to prepare and characterise hydrogel formulations using cellulose nanocrystals (CNCs), alginate (Alg), and polyethylene glycol diacrylate (PEGDA). The CNC/Alg/PEGDA formulations were formed using a double network crosslinking approach. Firstly, CNC was extracted from oil palm trunk, and the size and morphology of the CNCs were characterised using TEM analysis. Secondly, different formulations were prepared using CNCs, Alg, and PEGDA. The mixtures were crosslinked with Ca2+ ions and manually extruded using a syringe before being subjected to UV irradiation at 365 nm. The shear-thinning properties of the formulations were tested prior to any crosslinking, while the determination of storage and loss modulus was conducted post extrusion after the Ca2+ ion crosslink using a rheometer. For the analysis of swelling behaviour, the constructs treated with UV were immersed in PBS solution (pH 7.4) for 48 h. The morphology of the UV crosslinked construct was analysed using SEM imaging. The extracted CNC exhibited rod-like structures with an average diameter and length of around 7 ± 2.4 and 113 ± 20.7 nm, respectively. Almost all CNC/Alg/PEGDA formulations (pre-gel formulation) displayed shear-thinning behaviour with the power-law index η < 1, and the behaviour was more prominent in the 1% [w/v] Alg formulations. The CNC/Alg/PEGDA with 2.5% and 4% [w/v] Alg displayed a storage modulus dominance over loss modulus (G′ > G″) which suggests good shape fidelity. After the hydrogel constructs were subjected to UV treatment at 365 nm, only the F8 construct [4% CNC: 4% Alg: 40% PEGDA] demonstrated tough and flexible characteristics that possibly mimic the native articular cartilage property due to a similar water content percentage (79.5%). In addition, the small swelling ratio of 4.877 might contribute to a minimal change of the 3D construct’s geometry. The hydrogel revealed a rough and wavy surface, and the pore size ranged from 3 to 20 µm. Overall, the presence of CNCs in the double network hydrogel demonstrated importance and showed positive effects towards the fabrication of a potentially ideal 3D bioprinted scaffold.

Composite Bioinks With Mesoporous Bioactive Glasses-A Critical Evaluation of Results Obtained by In Vitro Experiments.

Besides osteoconductivity and a high degradation rate, mesoporous bioactive glasses (MBGs) are specific for their highly ordered channel structure and high specific surface area, making them suitable as drug and/or growth factor delivery systems. On the other hand, the mesoporous channel structure and MBG composition can have an effect on common cell evaluation assays, leading to inconclusive results. This effect is especially important when MBG is mixed in composite bioinks, together with cells. Additionally, the hydrogel component of the ink can influence the degradation of MBG, leading to different ion releases, which can additionally affect the analyses. Hence, our aim here was to show how the MBG structure and composition influence common cell viability and differentiation assays when calcium (Ca)- or magnesium (Mg)-containing glass is part of an alginate-based composite bioink. We suggested pre-labeling of cells with DiI prior to bioprinting and staining with calcein-AM to allow identification of metabolically active cells expressing signals in both green and red channels, allowing the use of fluorescence imaging for cell viability evaluations in the presence of high amounts (7 wt %) of MBGs. The release and uptake of ions during degradation of CaMBG and MgMBG were significantly changed by alginate in the composite bioinks, as confirmed by higher release and uptake from bulk glasses. Additionally, we detected a burst release of Mg2+ from composites only after 24 h of incubation. Furthermore, we demonstrated that released ions and the mesoporous channel structure affect the measurement of lactate dehydrogenase (LDH) and alkaline phosphatase activity (ALP) in bioprinted composite scaffolds. Measured LDH activity was significantly decreased in the presence of CaMBG. On the other hand, the presence of MgMBG induced increased signal measured for the ALP. Taken together, our findings show how composite bioinks containing MBGs can interfere with common analyses, obtaining misleading results.

3D bioprinted scaffolds for diabetic wound-healing applications

The treatment strategy required for the effective healing of diabetic foot ulcer (DFU) is a complex process that is requiring several combined therapeutic approaches. As a result, there is a significant clinical and economic burden associated in treating DFU. Furthermore, these treatments are often unsuccessful, commonly resulting in lower-limb amputation. The use of drug-loaded scaffolds to treat DFU has previously been investigated using electrospinning and fused deposition modelling (FDM) 3D printing techniques; however, the rapidly evolving field of bioprinting is creating new opportunities for innovation within this research area. In this study, 3D-bioprinted scaffolds with different designs have been fabricated for the delivery of an antibiotic (levoflocixin) to DFU. The scaffolds were fully characterised by a variety of techniques (e.g. SEM, DSC/TGA, FTIR, and mechanical characterisation), demonstrating excellent mechanical properties and providing sustained drug release for 4 weeks. This proof of concept study demonstrates the innovative potential of bioprinting technologies in fabrication of antibiotic scaffolds for the treatment of DFU.Graphical abstract

Three-Dimensional Bioprinted MR-Trackable Regenerative Scaffold for Postimplantation Monitoring on T1-Weighted MRI.

A three-dimensional (3D) bioprinted tissue scaffold is a promising therapeutic that goes beyond providing physical support for tissue regeneration by enabling precise spatial control over scaffold geometry and integration of different materials/cells. Critically important is in vivo confirmation of correct scaffold placement and retention during the initial 24hours postimplantation, to detect unwanted implant migration. To incorporate a safe, efficient MR contrast agent into a bioprinting workflow, and to achieve bright-contrast scaffold monitoring in vivo postimplantation. In vitro and animal in vivo longitudinal study. Two female Sprague Dawley rats (~200 g) for labeled and unlabeled scaffold implantation in the subcutaneous dorsal space flanking the vertebral column. A 7.0 T/T1 -weighted spin echo (SE) sequence and T1 mapping using turbo SE with variable repetition times (TRs). Cell viability and proliferation were assessed over 2 weeks after labeling bioprinted gelatin/alginate scaffolds with MnPNH2 (0.5 mM, 24hours). In vitro MRI was performed 0, 12, and 24hours postlabeling in nine labeled and three unlabeled (control) scaffolds to monitor T1 evolution. In vivo MRI was performed immediately and 24hours postimplantation to assess T1 . Acute inflammation near surgical site was monitored in one rat to 3 days. One-way analysis of variance with Tukey-Kramer post hoc analysis (P < 0.01). Cell viability was unaffected by bioprinting/labeling: viability exceeded 90% in all scaffolds after 1 week. In vitro T1 's were significantly lower in labeled scaffolds compared to control (207 msec vs. 2257 msec) immediately postlabeling and 24hours later (1227 msec vs. 2257 msec). In vivo T1 's were significantly different (243.6msec vs. 2414.6msec) immediately postimplantation, and no differences emerged compared to respective in vitro control/labeled counterparts. The 24-hours imaging and gross pathology confirmed migration of scaffolds beyond the imaging field. We report an MR-detectable, cell-compatible bioprinted scaffold, utilizing a T1 -weighting contrast agent for high-resolution, postimplantation scaffold tracking. 2 TECHNICAL EFFICACY: Stage 1.

Human menstrual blood-derived stem cells combined with a new 3D bioprinted composite scaffold for spinal cord injury treatment

Spinal cord injury (SCI) regeneration and repair is a worldwide medical issue, and stem cell therapy is an emerging treatment strategy. Previously, our research group found that transplanting menstrual blood-derived mesenchymal stem cells (MenSCs) can promote axon regeneration in rats SCI. However, the SCI pathological microenvironment inhibits stem cell survival after transplantation. The acellular spinal cord is the most similar to the spinal cord in terms of three-dimensional structure and natural biological activity, and it can efficiently regulate axon growth and promote synapse formation. Based on recent progress in the understanding of scar-free spinal cord repair in neonatal mice, it was postulated that in the acellular spinal cord microenvironment of neonatal rats, it would be more active ingredients to promote axon regeneration and inhibit glial scars, than in the adult rat. The hypothesis was formulated that a new 3D bioprinted scaffold with neonatal acellular spinal cord/GelMA hydrogel/MenSCs would efficiently repair SCI. The neonatal acellular spinal cord can provide a dual bionic microenvironment for axon regeneration, optimizing bioactive composition and microstructure, and the GelMA hydrogel guarantees the scaffold's mechanical properties. Then, using 3D bioprinting technology, the pore size of the scaffold can be precisely controlled, and the spinal cord conduction tract path may be stimulated. Moreover, a tissue-engineered spinal cord can be constructed by planting MenSCs in the pores. Overall, our hypothesis suggests that 3D bioprinted neonatal acellular spinal cord/GelMA hydrogel composite scaffold coupled with MenSCs might have more beneficial therapeutic effects on spinal cord injury rehabilitation.

3D Bio-Printed Bone Scaffolds Incorporated with Natural Antibacterial Compounds

3D Bioprinting plays an irreplaceable role in bone tissue engineering. Shellac and curcumin are two natural compounds that are widely used in the food and pharmaceutical sectors. In this study, a new composite scaffold with good biocompatibility and antibacterial ability was manufactured by adding shellac and curcumin into the traditional bone scaffold through low-temperature three-dimensional printing (LT-3DP), and its impact on the osteoimmune microenvironment was evaluated.

Novel Digital Light Processing Printing Strategy Using a Collagen-Based Bioink with Prospective Cross-Linker Procyanidins.

Three-dimensional (3D) bioink plays a vital role in the construction of tissues and organs by 3D bioprinting. Collagen has outstanding biocompatibility and is widely used in the field of tissue engineering. However, due to poor mechanical properties and slow self-assembly, it is challenging to manufacture high-precision 3D bioprinted collagen scaffolds. Herein, a novel digital light processing (DLP) bioink which can satisfy the printing of complex structures has been developed. This photocurable bioink is based on collagen and supplemented with a small amount of procyanidins (PA) as a cross-linking agent. The low concentration of collagen gives the bioink good fluidity and excellent biocompatibility, and a small amount of PA increases the cross-linking density of the system to obtain better mechanical properties. Using commercial digital light processing (DLP) printers, this collagen-based ink can effectively print structures with micrometer resolution, and the fidelity of the 3D structures can reach above 90%. Cells were able to be loaded in the bioink and distributed uniformly in the collagen scaffold in an unscathed way. This photocurable collagen bioink has broad application potential in DLP 3D bioprinting.

3D Bio-Printability of Hybrid Pre-Crosslinked Hydrogels.

Maintaining shape fidelity of 3D bio-printed scaffolds with soft biomaterials is an ongoing challenge. Here, a rheological investigation focusing on identifying useful physical and mechanical properties directly related to the geometric fidelity of 3D bio-printed scaffolds is presented. To ensure during- and post-printing shape fidelity of the scaffolds, various percentages of Carboxymethyl Cellulose (CMC) (viscosity enhancer) and different calcium salts (CaCl2 and CaSO4, physical cross-linkers) were mixed into alginate before extrusion to realize shape fidelity. The overall solid content of Alginate-Carboxymethyl Cellulose (CMC) was limited to 6%. A set of rheological tests, e.g., flow curves, amplitude tests, and three interval thixotropic tests, were performed to identify and compare the shear-thinning capacity, gelation points, and recovery rate of various compositions. The geometrical fidelity of the fabricated scaffolds was defined by printability and collapse tests. The effect of using multiple cross-linkers simultaneously was assessed. Various large-scale scaffolds were fabricated (up to 5.0 cm) using a pre-crosslinked hybrid. Scaffolds were assessed for the ability to support the growth of Escherichia coli using the Most Probable Number technique to quantify bacteria immediately after inoculation and 24 h later. This pre-crosslinking-based rheological property controlling technique can open a new avenue for 3D bio-fabrication of scaffolds, ensuring proper geometry.

Non-destructive mechanical assessment for optimization of 3D bioprinted soft tissue scaffolds

Non-destructive mechanical assessment for optimization of 3D bioprinted soft tissue scaffolds

307.7: 3D Bioprinting of Functional Islets With Adipose-derived Stromal Cells in an Alginate/Nanocellulose Scaffold

Islet isolation procedure destroys islet vasculature and extra cellular matrix molecules, which can negatively affect islet function post transplantation. Developing scaffold that favors islet micro-environment is one solution to preserve islet function post isolation. 3D bioprinting of islets using hydrogel-based bioinks has been reported previously. However, modifying bioinks and presence of supporting cells such as adipose-derived stromal cells (ASCs) can improve survival and reduce cellular stress in islet scaffolds. We designed an implantable multi-layered 3D bioprinted scaffold for human or mouse islets -/+ human ASCs (1.2 ×106 ASCs/scaffold). Cells were embedded in alginate/nanocellulose bioink and printed with INKREDIBLE 3D Bioprinter from CELLINK AB. Micro-CT was used to study the distribution of islets inside scaffolds. In vitro cell viability and function were assessed using FDA/PI staining and glucose stimulated insulin secretion on day 1, 8 and 14 post print. The level of secreted human- and mouse-specific cytokines, IP-10, MCP-1 and GRO-α were measured on day 1, 8 and 14 post print. Islet scaffolds -/+ ASCs were transplanted intraperitoneal (IP) in diabetic immune-compromised mouse model and followed for 60 days post transplantation. We printed 100 islets/scaffold for in vitro and 400 islets/scaffold for in vivo studies. In vitro viability analysis revealed viable islets and ASCs throughout the studies. However, scaffolds with human and mouse islets + ASCs showed improved insulin secretion in response to glucose compared to the islet alone group on day 1, 8 and 14 post print (selected data points for human islets-day 8: islet+ASC, basal insulin 2387 ± 1262, stimulated insulin 4312 ± 606.8, recovery insulin post stimulation 1637 ± 100.1 pmol/L, * p< 0.05 vs stimulated insulin. Islet alone, basal insulin 2358 ± 887.9, stimulated insulin 1149 ± 352.6, recovery insulin post stimulation 999.0 ± 267.7 pmol/L, n=4). This is followed by significant reduction in the level of both human and mouse IP-10, MCP-1 and GRO-α in islet+ASC group compared to the islet alone group on day 1, 8 and 14 post print. IP transplantation of mouse islets -/+ ASCs to diabetic mice normalizes random blood glucose in both groups starting from day 6 post transplantation for islet+ASC group and day 40 for islet alone group. We detected c-peptide in both groups on day 3 and 13 post transplantation. However, at termination of the studies, the level of c-peptide was significantly higher in islet+ASC compared to the islet alone group (islet+ASC 94.01 ± 14.47 vs. islet alone 27.08 ± 18.93, p<0.05). This study presents a successful multi-layered scaffold design for islets and ASCs. Presence of ASCs in the scaffold can create a favorable micro-environment for the islets, resulting in reduced islet loss and improved islet function.

Bioprinting a thick and cell-laden partially oxidized alginate-gelatin scaffold with embedded micro-channels as future soft tissue platform

Despite all the advancements in tissue engineering, one of the unsolved challenges is the mass transfer limitation. Therefore, the subject of pre-vascularization in the engineered tissues gets more attention to avoid necrotic core formation. In this study, we considered a design for interconnected channels with a muscle tissue-like structure, in silico and in vitro. A sequence of simple steps make it possible for us to use the same material, gelatin, as both a sacrificial material and one of the main components of the scaffold simultaneously. We defined a new approach to quantify the repeatability of a new combination of hydrogels (Partially Oxidized Alginate + Gelatin) for extrusion-based bioprinting. Additionally, the mechanical properties, hydrogel porosity, degradation time, and swelling ratio were also evaluated. Based on all these test results, the scaffold with the optimum properties was chosen for the bioprinting of adipose derived mesenchymal stem cells (ADMSCs) in the scaffolds with and without the channels. This bioprinted scaffold with microchannels showed promising mimicry of the microenvironment, leading to higher survival and proliferation rates of the cells by up to 250%. Based on these results, it has the potential to serve as a platform for further research in vascularization, healthy/disease modelling, and stem cell differentiation.

The Role of Mesenchymal Stromal Cells in the Management of Knee Chondral Defects.

Mesenchymal stromal cells (MSCs) are a subset of progenitor cells that help to promote tissue healing and regeneration through the secretion of various cytokines and growth factors. Although technically pluripotent, MSCs in vivo rarely repair damaged tissue through direct differentiation and engraftment. Augmentation of traditional marrow stimulation techniques with MSCs has been theorized to improve repair tissue quality and defect fill. Clinical trials evaluating this technique are limited but have shown modest improvements compared with isolated marrow stimulation. Various scaffolds also have been utilized in combination with MSCs to treat focal chondral defects. Although the techniques described are heterogeneous, many have shown promising early clinical outcomes. Newer techniques involving 3-dimensional bioprinted scaffolds seeded with MSCs allow for the recreation of complex architecture, more closely resembling articular cartilage. These techniques are evolving and have not yet been studied in human clinical trials.

Spinal Cord Injury Management through the Combination of Stem Cells and Implantable 3D Bioprinted Platforms.

Spinal cord injury (SCI) has a major impact on affected patients due to its pathological consequences and absence of capacity for self-repair. Currently available therapies are unable to restore lost neural functions. Thus, there is a pressing need to develop novel treatments that will promote functional repair after SCI. Several experimental approaches have been explored to tackle SCI, including the combination of stem cells and 3D bioprinting. Implanted multipotent stem cells with self-renewing capacity and the ability to differentiate to a diversity of cell types are promising candidates for replacing dead cells in injured sites and restoring disrupted neural circuits. However, implanted stem cells need protection from the inflammatory agents in the injured area and support to guide them to appropriate differentiation. Not only are 3D bioprinted scaffolds able to protect stem cells, but they can also promote their differentiation and functional integration at the site of injury. In this review, we showcase some recent advances in the use of stem cells for the treatment of SCI, different types of 3D bioprinting methods, and the combined application of stem cells and 3D bioprinting technique for effective repair of SCI.

Development of bioactive catechol functionalized nanoparticles applicable for 3D bioprinting

Efficient wound treatments to target specific events in the healing process of chronic wounds constitute a significant aim in regenerative medicine. In this sense, nanomedicine can offer new opportunities to improve the effectiveness of existing wound therapies. The aim of this study was to develop catechol bearing polymeric nanoparticles (NPs) and to evaluate their potential in the field of wound healing. Thus, NPs wound healing promoting activities, potential for drug encapsulation and controlled release, and further incorporation in a hydrogel bioink formulation to fabricate cell-laden 3D scaffolds are studied. NPs with 2 and 29 M % catechol contents (named NP2 and NP29) were obtained by nanoprecipitation and presented hydrodynamic diameters of 100 and 75 nm respectively. These nanocarriers encapsulated the hydrophobic compound coumarin-6 with 70% encapsulation efficiency values. In cell culture studies, the NPs had a protective effect in RAW 264.7 macrophages against oxidative stress damage induced by radical oxygen species (ROS). They also presented a regulatory effect on the inflammatory response of stimulated macrophages and promoted upregulation of the vascular endothelial growth factor (VEGF) in fibroblasts and endothelial cells. In particular, NP29 were used in a hydrogel bioink formulation using carboxymethyl chitosan and hyaluronic acid as polymeric matrices. Using a reactive mixing bioprinting approach, NP-loaded hydrogel scaffolds with good structural integrity, shape fidelity and homogeneous NPs dispersion, were obtained. The in vitro catechol NPs release profile of the printed scaffolds revealed a sustained delivery. The bioprinted scaffolds supported viability and proliferation of encapsulated L929 fibroblasts over 14 days. We envision that the catechol functionalized NPs and resulting bioactive bioink presented in this work offer promising advantages for wound healing applications, as they: 1) support controlled release of bioactive catechol NPs to the wound site; 2) can incorporate additional therapeutic functions by co-encapsulating drugs; 3) can be printed into 3D scaffolds with tailored geometries based on patient requirements.

Recent advances in three-dimensional bioprinted nanocellulose-based hydrogel scaffolds for biomedical applications

Recent advances in three-dimensional bioprinted nanocellulose-based hydrogel scaffolds for biomedical applications

Mechanically tunable photo-cross-linkable bioinks for osteogenic differentiation of MSCs in 3D bioprinted constructs

3D bioprinting technique renders a plausible solution to tissue engineering applications, mainly bone tissue regeneration, which could provide the microenvironment with desired physical, chemical, and mechanical properties. However, the mechanical and structural stability of current natural polymers is a critical issue in the fabrication of bone tissue-engineered scaffolds. To overcome these issues, we have developed 3D bioprintable semi-synthetic polymers derived from natural (sodium alginate, A) and synthetic (polyethylene glycol, PEG) biopolymers. In order to enhance the cross-linking properties and biocompatibility, we have functionalized these polymers with acrylate and methacrylate chemical moieties. These selected combination of natural and synthetic polymers improved the mechanical strength due to the synergistic effect of covalent as well as ionic bond formation in the hydrogel system, which is evident from the tested tensile data. Further, the feasibility of 3D bioprinting of acrylate and methacrylate functionalized PEG and hydrogels have been tested for the biocompatibility of the fabricated structures with human umbilical cord mesenchymal stem cells (UMSCs). Further, these bioprinted scaffolds were investigated for osteogenic differentiation of UMSCs in two types of culture conditions: namely, i) with osteoinduction media (with OIM), ii) without osteoinduction media (w/o OIM). We have examined the osteoinductivity of scaffolds with the activity of alkaline phosphatase (ALP) content, and significant changes in the ALP activity was observed with the stiffness of developed materials. The extent osteogenic differentiation was observed by alizarin red staining and reverse transcription PCR analysis. Elevated levels of ALP, RUNX2 and COL1 gene expression has been observed in without OIM samples on week 1 and week 3. Further, our study showed that the synthesized alginate methacrylate (AMA) without osteoinduction supplement with young's modulus of 0.34 MPa has a significant difference in ALP quantity and gene expression over the other reported literature. Thus, this work plays a pivotal role in the development of 3D bioprintable and photo-cross-linkable hydrogels in osteogenic differentiation of mesenchymal stem cells.

Matured Myofibers in Bioprinted Constructs with In Vivo Vascularization and Innervation.

For decades, the study of tissue-engineered skeletal muscle has been driven by a clinical need to treat neuromuscular diseases and volumetric muscle loss. The in vitro fabrication of muscle offers the opportunity to test drug-and cell-based therapies, to study disease processes, and to perhaps, one day, serve as a muscle graft for reconstructive surgery. This study developed a biofabrication technique to engineer muscle for research and clinical applications. A bioprinting protocol was established to deliver primary mouse myoblasts in a gelatin methacryloyl (GelMA) bioink, which was implanted in an in vivo chamber in a nude rat model. For the first time, this work demonstrated the phenomenon of myoblast migration through the bioprinted GelMA scaffold with cells spontaneously forming fibers on the surface of the material. This enabled advanced maturation and facilitated the connection between incoming vessels and nerve axons in vivo without the hindrance of a scaffold material. Immunohistochemistry revealed the hallmarks of tissue maturity with sarcomeric striations and peripherally placed nuclei in the organized bundles of muscle fibers. Such engineered muscle autografts could, with further structural development, eventually be used for surgical reconstructive purposes while the methodology presented here specifically has wide applications for in vitro and in vivo neuromuscular function and disease modelling.

Open-source CAD-CAM simulator of the extrusion-based bioprinting process

Extrusion-based Bioprinting (EBB) represents one of the most used Bioprinting technologies among researchers, thanks to its ease of use, wide variety of available materials, and affordable cost. Even though the technique has successfully been applied in bioprinting constructs for Tissue Engineering applications, there is still no consensus on which parameters have more influence of the accuracy of bioprinted scaffolds. Moreover, the literature lacks a rapid and robust method to consistently set the printing parameters before the actual printing phase, thus minimizing the trial-and-error process. In this context, we present a mathematical model for understanding the printability of a defined structure by depositing a given biomaterial ink through a specific EBB apparatus. The model takes into account different steps of the printing process, including extrusion, line formation and scaffold stabilization over time. The model was experimentally validated and implemented in an open-source software to guide the user in setting the correct printing parameters (i.e., printing speed, layer height and flow) based on scaffold dimensions, material properties (including rheological and mechanical ones) and printer set-up. To encourage the model use, we also propose a set of experiments to extract the relevant material properties for our model, and the software is available both as a stand-alone program (available at https://github.com/CentroEPiaggio/Rheology-GUI), as well as a webpage (available at https://www.prin-vision.it/printability-assessment).

Advances of Hydrogel-Based Bioprinting for Cartilage Tissue Engineering.

Bioprinting has gained immense attention and achieved the revolutionized progress for application in the multifunctional tissue regeneration. On account of the precise structural fabrication and mimicking complexity, hydrogel-based bio-inks are widely adopted for cartilage tissue engineering. Although more and more researchers have reported a number of literatures in this field, many challenges that should be addressed for the development of three-dimensional (3D) bioprinting constructs still exist. Herein, this review is mainly focused on the introduction of various natural polymers and synthetic polymers in hydrogel-based bioprinted scaffolds, which are systematically discussed via emphasizing on the fabrication condition, mechanical property, biocompatibility, biodegradability, and biological performance for cartilage tissue repair. Further, this review describes the opportunities and challenges of this 3D bioprinting technique to construct complex bio-inks with adjustable mechanical and biological integrity, and meanwhile, the current possible solutions are also conducted for providing some suggestive ideas on developing more advanced bioprinting products from the bench to the clinic.