FIGURE 6 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
| (A) Pr and Dr values and (B-I) optical microscope images of the cross-hatch scaffold printed with formulated inks under different printing parameters: (B and C) printed with 1.5% GrowInk-N + 2% GGMMA-PBS with a layer height of 0.07 mm and an input flow rate of 100 and 110%, respectively, (D and E) printed with 1.5% GrowInk-N+5% GelMA-PBS with a layer height of 0.07 mm and an input flow rate of 100 and 110%, respectively, (F and G) printed with 1.5% GrowInk-T + 2% GGMMA-PBS with a layer height of 0.07 mm and an input flow rate of 100 and 110%, respectively, (H and I) printed with 1.5% GrowInk-T + 5% GelMA-PBS with a layer height of 0.07 mm and an input flow rate of 110 and 120%, respectively. Scale bar: 1 mm)
Source publication
Biomaterial inks based on cellulose nanofibers (CNFs) and photo-crosslinkable biopolymers have great potential as a high-performance ink system in light-aided, hydrogel extrusion-based 3D bioprinting. However, the colloidal stability of surface charged nanofibrils is susceptible to mono-cations in physiological buffers, which complexes the applicat...
Contexts in source publication
Context 1
... the outcome square pores would display varying degrees of circularity. As observed in Figure 6, all inks displayed an under-gelation status under different printing conditions, in which the Pr values were in the range from 0.8 to 1.0. In this case, the diffusion rate (Dr) value should also be considered to evaluate their printability because filament spreading would also lead to printing failure by losing printing accuracy. ...
Context 2
... this case, the diffusion rate (Dr) value should also be considered to evaluate their printability because filament spreading would also lead to printing failure by losing printing accuracy. As observed in Figures 6D and E, the Pr values did not display a noticeable difference between the two scaffolds of 1.5% GrowInk-N + 5% GelMA-PBS that were printed with a constant layer height of 0.07 mm but at different input flow rates; however, the filament spreading resulted in almost closure of pores in the grid as the input flow increased. Hence, the Dr value was carried out to evaluate the pore closure effect caused by filament spreading during the printing by comparing the outcome pore area with its theoretical area ( Habib et al., 2018). ...
Context 3
... this study, 10-layer cross-hatch scaffolds were printed under the given printing conditions for the ink formulations that showed promising extrudability. As shown in Figure 6, Dr values increased with the increase in the input flow rate for the same formulation, which indicated a more severe spreading of the filaments and closure of the pore. Meanwhile, Dr values decreased with an increase in the layer height. ...
Similar publications
Gelatin is a biopolymer widely used to synthesize hydrogels for biomedical applications, such as tissue engineering and bioinks for 3D bioprinting. However, as with other biopolymer-based hydrogels, gelatin-hydrogels do not allow precise temporal control of the biomolecule distribution to mimic biological signals involved in biological mechanisms....
Citations
... The filament width of the printed structures was measured in five different locations for each collected image. Moreover, the filament spreading ratio (S), 47 defined as the width of the printed filament divided by the needle diameter, and the printability index (Pr), 48 defined by comparing the circularity of a square (π/4) with the outcome pores, were measured for each bioink at each time point using Equations VI and VII: Finally, to assess the possibility of developing selfstanding internally crosslinked structures using the optimized bioink, ADA/Alg/Gel_50/25/25 formulation was printed into 3D grid structures with square mesh geometry (strand distance: 5 mm), obtaining 3D square samples (10 × 10 mm 2 ; five layers), and into hollow 3D cylindrical structures (diameter ∅: 3 mm; 10 layers). In vitro experiments with AHCFs were conducted in complete medium composed of DMEM, supplemented with 10% FBS, 1% L-glutamine, and 1% penicillin/streptomycin, at 37°C in 5% CO 2 atmosphere. ...
Cardiovascular diseases represent a global challenge due to heart-limited regenerative capabilities. 3D-bioprinted cell-laden constructs are a promising approach as cardiac patches or in vitro models. However, developing bioinks with optimal mechanical, rheological, and biological properties remains challenging. Although alginate (Alg)-based bioinks have been extensively explored, such hydrogels lack cell adhesion properties and degradability. Additionally, 3D Alg structures are usually obtained by microextrusion bioprinting, exploiting conventional external crosslinking methods, which introduce inhomogeneities and unpredictability in construct formation. This work exploits Alg internal ionic gelation mechanism to obtain homogeneous self-standing multilayered 3D-printed constructs without employing support baths or post-printing crosslinking treatments. Alg was blended with oxidized alginate (ADA) and gelatin (Gel) to achieve degradable and cell-adhesive hydrogels for cardiac tissue engineering. Firstly, ADA/Alg bioink composition was tailored to achieve cardiac tissue-like viscoelastic properties. Then, the amount of Gel in ADA/Alg hydrogels was optimized to support cell adhesion, producing shear thinning inks with tunable viscoelastic properties (storage modulus [G']: 650-1300 Pa) and degradation profile (40-80% weight loss after 21 days in phosphate-buffered saline [PBS]) by varying Gel concentration. ADA/Alg/Gel hydrogels displayed shear thinning behavior, suitable for 3D bioprinting depending on the ink stabilization time, due to the gradual pH-triggered release of calcium ions over time. Adult human cardiac fibroblast (AHCF) and H9C2-laden ADA/Alg/Gel bioinks were successfully printed, producing scaffolds with high shape fidelity and good cell viability post-printing. Finally, the highest Gel content (25% [w/w]) supported cell adhesion after 24 h of incubation, displaying potential for cardiac tissue modeling. This research presents a comprehensive framework for advancing the design of bioink.
... On the other hand, the square mesh structure was used to quantify the printing fidelity by comparing the area and the shape of the mesh openings to the designed model. We introduce a formula (eq 1) that multiplies two parameters previously used to quantify printability: printability based on circularity 31,38 and the ratio of the area of the openings in the printed structure and the model 39 (details of the calculations and full experimental data can be found in the Supporting Information, Figure S3�Quantification of printability from mesh-like structures). We noted that although the quantification of printability based solely on circularity is useful in assessing large filament deformations, it fails in the absence of large filament variability because the resulting numerical differences are small. ...
Extrusion three-dimensional (3D) bioprinting is a
promising technology with many applications in the biomedical
and tissue engineering fields. One of the key limitations for the
widespread use of this technology is the narrow window of
printability that results from the need to have bioinks with
rheological properties that allow the extrusion of continuous
filaments while maintaining high cell viability within the materials
during and after printing. In this work, we use Carbopol (CBP) as
rheology modifier for extrusion printing of biomaterials that are
typically nonextrudable or present low printability. We show that
low concentrations of CBP can introduce the desired rheological
properties for a wide range of formulations, allowing the use of
polymers with different cross-linking mechanisms and the
introduction of additives and cells. To explore the opportunities and limitations of CBP as a rheology modifier, we used ink
formulations based on poly(ethylene glycol)diacrylate with extrusion 3D printing to produce soft, yet stable, hydrogels with tunable mechanical properties. Cell-laden constructs made with such inks presented high viability for cells seeded on top of cross-linked materials and cells incorporated within the bioink during printing, showing that the materials are noncytotoxic and the printed structures do not degrade for up to 14 days. To our knowledge, this is the first report of the use of CBP-containing bioinks to 3Dprint complex cell-laden structures that are stable for days and present high cell viability. The use of CBP to obtain highly printable inks can accelerate the evolution of extrusion 3D bioprinting by guaranteeing the required rheological properties and expanding the number of materials that can be successfully printed. This will allow researchers to develop and optimize new bioinks focusing on the biochemical, cellular, and mechanical requirements of the targeted applications rather than the rheology needed to achieve good printability.
... The concept of printability in 3D printing refers to the printed object's ability to retain its structural integrity and functionality postprinting. Hence, the printability degree depends on both the intrinsic factors of the chosen ink, mainly its rheological and mechanical properties, and the printing process-related factors such as flow rate, nozzle diameter, and deposition method [215][216][217]. Naghieh et al. [216] conducted a comprehensive review on the concept of printability, including its key issues and how to measure it in 3D bioprinting. ...
... As previously mentioned, printability is typically defined by observable characteristics in printed objects, although it is possible to quantitatively measure ink printability in the production of scaffolds via 3D bioprinting (Fig. 1g) [218]. Wang et al. [217] quantitatively evaluated the printability of two commercially obtained CNF inks (neutral CNF GrowInk-N and negatively charged CNF GrowInk-T) and biopolymers for photocrosslinking (methacryloyl gelatin (GelMA) and methacrylated galactoglucomannan (GGMMA)) in scaffold production via 3D bioprinting. The printability value (Pr value) is determined by the uniformity of the scaffold pores, and the diffusion rate (Dr value) given by the spreading of the post-printing filaments when they are in an under-gelation state. ...
... In additive manufacturing, it is common to find inks made up of a polymer, but CNs can be utilized as a reinforcing agent owing to their mechanical strength, viscoelastic behavior, and biodegradability [215]. Wang et al. [217] incorporated ENZ-CNF as a reinforcing agent in polylactic acid (PLA) for 3D printing of complex shapes using fused deposition modeling (FDM). The inclusion of ENZ-CNF (2.5 wt%) increased the thermal stability, tensile strength, and elongation at break of the composites compared to PLA-neat filaments, without compromising shape fidelity. ...
Cellulose nanomaterials (CNs) are promising green materials due to their unique properties as well as their environmental benefits. Cellulose nanofibrils (CNFs) and nanocrystals (CNCs) are the most explored types of CNs. Although they share some fundamental properties, such as low density, biodegradability, biocompatibility, and low toxicity, they also have various distinct and unique properties, including, morphology, rheology, aspect ratio, crystallinity, mechanical, and optical properties. Therefore, several comparative studies have evaluated the performance of these distinct nanomaterials to determine the most suitable CN for different applications. Recently, various studies have reported the synergetic benefits of combining CNF and CNC, resulting in hybrid cellulose nanomaterials (HCNs). In this review, we first briefly cover aspects of properties driven applications and performance of CNs from both an individual and comparative perspective. Next, we comprehensively examine the potential of HCN-based materials, highlighting their performance for various applications. In conclusion, HCNs have been successfully explored in food packaging, electronic devices, 3D printing, biomedical, and other fields, resulting in materials with superior performance compared to neat CNF or CNC. Therefore, HCNs show great potential for the development of green materials with enhanced properties.
... Current cellulosebased bioink formulations often use second biopolymer networks, such as collagen (Xu, Molino, et al., 2019), alginate (Markstedt et al., 2015) or modified polysaccharides (Markstedt et al., 2017;Xu, Zhang, et al., 2019), to enable crosslinking of the formed hydrogels and to add structural stability. These formulations can be rapidly crosslinked during or after printing using direct chemical crosslinking (Markstedt et al., 2017), indirect crosslinking via UV-irradiation (Wang et al., 2021), physical crosslinking using an addition of multivalent salts (Markstedt et al., 2015) or pure physical entanglements depending on their overall composition. ...
Development of strong cellulose nanofibril (CNF) networks for advanced applications, such as in the biomedical field, is of high importance owing to the biocompatible nature and plant-based origin of cellulose nanofibrils. Nevertheless, lack of mechanical strength and complex synthesis methods hinder the application of these materials in areas where both toughness and manufacturing simplicity are required. In this work, we introduce a facile method for the synthesis of a low solid content (< 2 wt%), covalently crosslinked CNF hydrogel where Poly (N-isopropylacrylamide) (NIPAM) chains are utilized as crosslinks between the nanofibrils. The resulting networks have the capability to fully recover the shape in which they were formed after various drying and rewetting cycles. Characterization of the hydrogel and its constitutive components was performed using X-ray scattering, rheological investigations and uniaxial testing in compression. Influence of covalent crosslinks was compared with networks crosslinked by the addition of CaCl2. Among other things the results show that the mechanical properties of the hydrogels can be tuned by controlling the ionic strength of the surrounding medium. Finally, a mathematical model was developed based on the experimental results, which describes and predicts to a decent degree the large-deformation, elastoplastic behavior, and fracture of these networks.
... The presence of chitosan as micro-ribbons was essential to reduce the disintegration time, while chitosan as a powder could not provide this function. Increasing the contents of micro-ribbons made printing difficult, perhaps not only by increasing the viscosity [28] of molten polymer in the printer head [29], but also, by creating a rough surface on the surface of the filament, making it difficult for the filament to pass through the gear mechanism in the printer head. ...
Three-dimensional printing (3DP) allows production of novel fast dissolving oral films (FDFs). However, mechanical properties of the films may not be desirable when certain excipients are used. This work investigated whether adding chitosan micro-ribbons or cellulose microfibres will achieve desired FDFs by fused deposition modelling 3DP. Filaments containing polyvinyl alcohol (PVA) and paracetamol as model drug were manufactured at 170 °C. At 130 °C, filaments containing polyvinylpyrrolidone (PVP) and paracetamol were also created. FDFs were printed with plain or mesh patterns at temperatures of 200 °C (PVA) or 180 °C (PVP). Both chitosan micro-ribbons and cellulose micro-fibres improved filament mechanical properties at 1% w/w concentration in terms of flexibility and stiffness. The filaments were not suitable for printing at higher concentrations of chitosan micro-ribbons and cellulose micro-fibres. Furthermore, mesh FDFs containing only 1% chitosan micro-ribbons disintegrated in distilled water within 40.33 ± 4.64 s, while mesh FDFs containing only 7% croscarmellose disintegrated in 55.33 ± 2.86 s, and croscarmellose containing films showed signs of excipient scorching for PVA polymer. Cellulose micro-fibres delayed disintegration of PVA mesh films to 108.66 ± 3.68 s at 1% w/w. In conclusion, only chitosan micro-ribbons created a network of hydrophilic channels within the films, which allowed faster disintegration time at considerably lower concentrations.
... It is another area of research, which is known as four-dimensional printing (4DP), and more information is available elsewhere (Ahmed, 2019). Rando et al. (2020) Wang et al., 2021). In order to avoid these issues, the filament should be used to balance the surface tension, gravitational force, and applied stress perfectly. ...
Additive manufacturing, or three-dimensional printing (3DP) technology, has been recently explored in every field of science and technology for its unique features and ease of operation. 3DP technology has a wide range of applications in the food industry. This review envisages the recent interest in plant proteins and the development of meat analogues using additive manufacturing (3D printing), which is an exciting opportunity for the food industry and legume producers. The development of the formulation prior to printing requires a thorough rheological characterization for the smooth operation of the printer and fidelity. The steady flow properties and viscoelasticity of legume proteins, as well as their role in 3D printing, are elucidated. Finally, this review provides insights into the current state of legume protein-based 3D printing and food product development.
