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20 pages, 7152 KiB

Open AccessArticle

Three-Dimensional Printing of Red Algae Biopolymers: Effect of Locust Bean Gum on Rheology and Processability

by Sónia Oliveira, Isabel Sousa, Anabela Raymundo and Carlos Bengoechea

Gels 2024, 10(3), 166; https://doi.org/10.3390/gels10030166 - 23 Feb 2024

Viewed by 858

Seaweeds, rich in high-value polysaccharides with thickening/gelling properties (e.g., agar, carrageenan, and alginate), are extensively used in the food industry for texture customization and enhancement. However, conventional extraction methods for these hydrocolloids often involve potentially hazardous chemicals and long extraction times. In this [...] Read more.

Seaweeds, rich in high-value polysaccharides with thickening/gelling properties (e.g., agar, carrageenan, and alginate), are extensively used in the food industry for texture customization and enhancement. However, conventional extraction methods for these hydrocolloids often involve potentially hazardous chemicals and long extraction times. In this study, three red seaweed species (Chondrus crispus, Gelidium Corneum, and Gracilaria gracilis) commercialized as food ingredients by local companies were chosen for their native gelling biopolymers, which were extracted using water-based methodologies (i.e., (1) hydration at room temperature; (2) stirring at 90 °C; and (3) centrifugation at 40 °C) for production of sustainable food gels. The potential use of these extracts as bioinks was assessed employing an extrusion-based 3D printer. The present work aimed to study the gelation process, taken place during printing, and assess the effectiveness of the selected green extraction method in producing gels. To improve the definition of the printed gel, two critical printing parameters were investigated: the addition of locust bean gum (LBG) at different concentrations (0, 0.5, 1, 1.5, 2, and 2.5%) and printing temperature (30, 40, 60, and 80 °C). Rheological results from a controlled-stress rheometer indicated that gels derived from G. corneum and G. gracilis exhibited a lower gel strength (lower G′ and G″) and excessive material spreading during deposition (lower viscosity) than C. crispus. Thus, G′ was around 5 and 70 times higher for C. crispus gels than for G. corneum and G. gracilis, respectively. When increasing LBG concentration (0.5 to 2.5% w/w) and lowering the printing temperature (80 to 30 °C), an enhanced gel matrix definition for G. corneum and G. gracilis gels was found. In contrast, gels from C. crispus demonstrated greater stability and were less influenced by these parameters, showcasing the potential of the seaweed to develop sustainable clean label food gels. Eventually, these results highlight the feasibility of using algal-based extracts obtained through a green procedure as bioinks where LBG was employed as a synergic ingredient. Full article

(This article belongs to the Special Issue Hydrogels for 3D Printing)

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12 pages, 2479 KiB

Open AccessArticle

Polydopamine Blending Increases Human Cell Proliferation in Gelatin–Xanthan Gum 3D-Printed Hydrogel

by Preetham Yerra, Mario Migliario, Sarah Gino, Maurizio Sabbatini, Monica Bignotto, Marco Invernizzi and Filippo Renò

Gels 2024, 10(2), 145; https://doi.org/10.3390/gels10020145 - 14 Feb 2024

Viewed by 1047

Abstract

Background: Gelatin–xanthan gum (Gel–Xnt) hydrogel has been previously modified to improve its printability; now, to increase its ability for use as cell-laden 3D scaffolds (bioink), polydopamine (PDA), a biocompatible, antibacterial, adhesive, and antioxidant mussel-inspired biopolymer, has been added (1–3% v/v) [...] Read more.

Background: Gelatin–xanthan gum (Gel–Xnt) hydrogel has been previously modified to improve its printability; now, to increase its ability for use as cell-laden 3D scaffolds (bioink), polydopamine (PDA), a biocompatible, antibacterial, adhesive, and antioxidant mussel-inspired biopolymer, has been added (1–3% v/v) to hydrogel. Methods: Control (CT) and PDA-blended hydrogels were used to print 1 cm² grids. The hydrogels’ printability, moisture, swelling, hydrolysis, and porosity were tested after glutaraldehyde (GTA) crosslinking, while biocompatibility was tested using primary human-derived skin fibroblasts and spontaneously immortalized human keratinocytes (HaCaT). Keratinocyte or fibroblast suspension (100 µL, 2.5 × 10⁵ cells) was combined with an uncrosslinked CT and PDA blended hydrogel to fabricate cylinders (0.5 cm high, 1 cm wide). These cylinders were then cross-linked and incubated for 1, 3, 7, 14, and 21 days. The presence of cells within various hydrogels was assessed using optical microscopy. Results and discussion: PDA blending did not modify the hydrogel printability or physiochemical characteristics, suggesting that PDA did not interfere with GTA crosslinking. On the other hand, PDA presence strongly accelerated and increased both fibroblast and keratinocyte growth inside. This effect seemed to be linked to the adhesive abilities of PDA, which improve cell adhesion and, in turn, proliferation. Conclusions: The simple PDA blending method described could help in obtaining a new bioink for the development of innovative 3D-printed wound dressings. Full article

(This article belongs to the Special Issue Hydrogels for 3D Printing)

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23 pages, 10853 KiB

Open AccessArticle

A New Method for the Production of High-Concentration Collagen Bioinks with Semiautonomic Preparation

by Jana Matejkova, Denisa Kanokova, Monika Supova and Roman Matejka

Gels 2024, 10(1), 66; https://doi.org/10.3390/gels10010066 - 15 Jan 2024

Cited by 1 | Viewed by 1081

Abstract

It is believed that 3D bioprinting will greatly help the field of tissue engineering and regenerative medicine, as live patient cells are incorporated into the material, which directly creates a 3D structure. Thus, this method has potential in many types of human body [...] Read more.

It is believed that 3D bioprinting will greatly help the field of tissue engineering and regenerative medicine, as live patient cells are incorporated into the material, which directly creates a 3D structure. Thus, this method has potential in many types of human body tissues. Collagen provides an advantage, as it is the most common extracellular matrix present in all kinds of tissues and is, therefore, very natural for cells and the organism. Hydrogels with highly concentrated collagen make it possible to create 3D structures without additional additives to crosslink the polymer, which could negatively affect cell proliferation and viability. This study established a new method for preparing highly concentrated collagen bioinks, which does not negatively affect cell proliferation and viability. The method is based on two successive neutralizations of the prepared hydrogel using the bicarbonate buffering mechanisms of the 2× enhanced culture medium and pH adjustment by adding NaOH. Collagen hydrogel was used in concentrations of 20 and 30 mg/mL dissolved in acetic acid with a concentration of 0.05 and 0.1 wt.%. The bioink preparation process is automated, including colorimetric pH detection and adjustment. The new method was validated using bioprinting and subsequent cultivation of collagen hydrogels with incorporated stromal cells. After 96 h of cultivation, cell proliferation and viability were not statistically significantly reduced. Full article

(This article belongs to the Special Issue Hydrogels for 3D Printing)

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31 pages, 7805 KiB

Open AccessArticle

Alginate–Gelatin Hydrogel Scaffolds; An Optimization of Post-Printing Treatment for Enhanced Degradation and Swelling Behavior

by Christina Kaliampakou, Nefeli Lagopati, Evangelia A. Pavlatou and Costas A. Charitidis

Gels 2023, 9(11), 857; https://doi.org/10.3390/gels9110857 - 28 Oct 2023

Cited by 1 | Viewed by 1516

Abstract

The generation of 3D structures comprises three interlinked phases: material development, the printing process, and post-printing treatment. Numerous factors control all three phases, making the optimization of the entire process a challenging task. Until now, the state of the art has mainly focused [...] Read more.

The generation of 3D structures comprises three interlinked phases: material development, the printing process, and post-printing treatment. Numerous factors control all three phases, making the optimization of the entire process a challenging task. Until now, the state of the art has mainly focused on optimizing material processability and calibration of the printing process. However, after the successful Direct Ink Writing (DIW) of a hydrogel scaffold, the post-printing stage holds equal importance, as this allows for the treatment of the structure to ensure the preservation of its structural integrity for a duration that is sufficient to enable successful cell attachment and proliferation before undergoing degradation. Despite this stage’s pivotal role, there is a lack of extensive literature covering its optimization. By studying the crosslinking factors and leveling the post-treatment settings of alginate–gelatin hydrogel, this study proposes a method to enhance scaffolds’ degradation without compromising the targeted swelling behavior. It introduces an experimental design implementing the Response Surface Methodology (RSM) Design of Experiments (DoE), which elucidated the key parameters influencing scaffold degradation and swelling, and established an alginate ratio of 8% and being immersed for 15 min in 0.248 M CaCl₂ as the optimal level configuration that generates a solution of 0.964 desirability, reaching a degradation time of 19.654 days and the swelling ratio of 50.00%. Full article

(This article belongs to the Special Issue Hydrogels for 3D Printing)

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13 pages, 2635 KiB

Open AccessArticle

Role of pH and Crosslinking Ions on Cell Viability and Metabolic Activity in Alginate–Gelatin 3D Prints

by Andrea Souza, Matthew Parnell, Brian J. Rodriguez and Emmanuel G. Reynaud

Gels 2023, 9(11), 853; https://doi.org/10.3390/gels9110853 - 27 Oct 2023

Viewed by 1266

Abstract

Alginate–gelatin hydrogels are extensively used in bioengineering. However, despite different formulations being used to grow different cell types in vitro, their pH and its effect, together with the crosslinking ions of these formulations, are still infrequently assessed. In this work, we study how [...] Read more.

Alginate–gelatin hydrogels are extensively used in bioengineering. However, despite different formulations being used to grow different cell types in vitro, their pH and its effect, together with the crosslinking ions of these formulations, are still infrequently assessed. In this work, we study how these elements can affect hydrogel stability and printability and influence cell viability and metabolism on the resulting 3D prints. Our results show that both the buffer pH and crosslinking ion (Ca²⁺ or Ba²⁺) influence the swelling and degradation rates of prints. Moreover, buffer pH influenced the printability of hydrogel in the air but did not when printed directly in a fluid-phase CaCl₂ or BaCl₂ crosslinking bath. In addition, both U2OS and NIH/3T3 cells showed greater cell metabolic activity on one-layer prints crosslinked with Ca²⁺. In addition, Ba²⁺ increased the cell death of NIH/3T3 cells while having no effect on U2OS cell viability. The pH of the buffer also had an important impact on the cell behavior. U2OS cells showed a 2.25-fold cell metabolism increase on one-layer prints prepared at pH 8.0 in comparison to those prepared at pH 5.5, whereas NIH/3T3 cells showed greater metabolism on one-layer prints with pH 7.0. Finally, we observed a difference in the cell arrangement of U2OS cells growing on prints prepared from hydrogels with an acidic buffer in comparison to cells growing on those prepared using a neutral or basic buffer. These results show that both pH and the crosslinking ion influence hydrogel strength and cell behavior. Full article

(This article belongs to the Special Issue Hydrogels for 3D Printing)

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12 pages, 2449 KiB

Open AccessArticle

Characterization of Bioinks Prepared via Gelifying Extracellular Matrix from Decellularized Porcine Myocardia

by Héctor Sanz-Fraile, Carolina Herranz-Diez, Anna Ulldemolins, Bryan Falcones, Isaac Almendros, Núria Gavara, Raimon Sunyer, Ramon Farré and Jorge Otero

Gels 2023, 9(9), 745; https://doi.org/10.3390/gels9090745 - 13 Sep 2023

Viewed by 979

Abstract

Since the emergence of 3D bioprinting technology, both synthetic and natural materials have been used to develop bioinks for producing cell-laden cardiac grafts. To this end, extracellular-matrix (ECM)-derived hydrogels can be used to develop scaffolds that closely mimic the complex 3D environments for [...] Read more.

Since the emergence of 3D bioprinting technology, both synthetic and natural materials have been used to develop bioinks for producing cell-laden cardiac grafts. To this end, extracellular-matrix (ECM)-derived hydrogels can be used to develop scaffolds that closely mimic the complex 3D environments for cell culture. This study presents a novel cardiac bioink based on hydrogels exclusively derived from decellularized porcine myocardium loaded with human-bone-marrow-derived mesenchymal stromal cells. Hence, the hydrogel can be used to develop cell-laden cardiac patches without the need to add other biomaterials or use additional crosslinkers. The scaffold ultrastructure and mechanical properties of the bioink were characterized to optimize its production, specifically focusing on the matrix enzymatic digestion time. The cells were cultured in 3D within the developed hydrogels to assess their response. The results indicate that the hydrogels fostered inter-cell and cell-matrix crosstalk after 1 week of culture. In conclusion, the bioink developed and presented in this study holds great potential for developing cell-laden customized patches for cardiac repair. Full article

(This article belongs to the Special Issue Hydrogels for 3D Printing)

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19 pages, 5150 KiB

Open AccessArticle

Microbial Polysaccharide-Based Formulation with Silica Nanoparticles; A New Hydrogel Nanocomposite for 3D Printing

by Maria Minodora Marin, Ioana Catalina Gifu, Gratiela Gradisteanu Pircalabioru, Madalina Albu Kaya, Rodica Roxana Constantinescu, Rebeca Leu Alexa, Bogdan Trica, Elvira Alexandrescu, Cristina Lavinia Nistor, Cristian Petcu and Raluca Ianchis

Gels 2023, 9(5), 425; https://doi.org/10.3390/gels9050425 - 19 May 2023

Cited by 2 | Viewed by 1684

Abstract

Natural polysaccharides are highly attractive biopolymers recommended for medical applications due to their low cytotoxicity and hydrophilicity. Polysaccharides and their derivatives are also suitable for additive manufacturing, a process in which various customized geometries of 3D structures/scaffolds can be achieved. Polysaccharide-based hydrogel materials [...] Read more.

Natural polysaccharides are highly attractive biopolymers recommended for medical applications due to their low cytotoxicity and hydrophilicity. Polysaccharides and their derivatives are also suitable for additive manufacturing, a process in which various customized geometries of 3D structures/scaffolds can be achieved. Polysaccharide-based hydrogel materials are widely used in 3D hydrogel printing of tissue substitutes. In this context, our goal was to obtain printable hydrogel nanocomposites by adding silica nanoparticles to a microbial polysaccharide’s polymer network. Several amounts of silica nanoparticles were added to the biopolymer, and their effects on the morpho-structural characteristics of the resulting nanocomposite hydrogel inks and subsequent 3D printed constructs were studied. FTIR, TGA, and microscopy analysis were used to investigate the resulting crosslinked structures. Assessment of the swelling characteristics and mechanical stability of the nanocomposite materials in a wet state was also conducted. The salecan-based hydrogels displayed excellent biocompatibility and could be employed for biomedical purposes, according to the results of the MTT, LDH, and Live/Dead tests. The innovative, crosslinked, nanocomposite materials are recommended for use in regenerative medicine. Full article

(This article belongs to the Special Issue Hydrogels for 3D Printing)

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Review

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35 pages, 4956 KiB

Open AccessReview

3D-Printed Hydrogel for Diverse Applications: A Review

by Arpana Agrawal and Chaudhery Mustansar Hussain

Gels 2023, 9(12), 960; https://doi.org/10.3390/gels9120960 - 07 Dec 2023

Cited by 6 | Viewed by 2043

Abstract

Hydrogels have emerged as a versatile and promising class of materials in the field of 3D printing, offering unique properties suitable for various applications. This review delves into the intersection of hydrogels and 3D printing, exploring current research, technological advancements, and future directions. [...] Read more.

Hydrogels have emerged as a versatile and promising class of materials in the field of 3D printing, offering unique properties suitable for various applications. This review delves into the intersection of hydrogels and 3D printing, exploring current research, technological advancements, and future directions. It starts with an overview of hydrogel basics, including composition and properties, and details various hydrogel materials used in 3D printing. The review explores diverse 3D printing methods for hydrogels, discussing their advantages and limitations. It emphasizes the integration of 3D-printed hydrogels in biomedical engineering, showcasing its role in tissue engineering, regenerative medicine, and drug delivery. Beyond healthcare, it also examines their applications in the food, cosmetics, and electronics industries. Challenges like resolution limitations and scalability are addressed. The review predicts future trends in material development, printing techniques, and novel applications. Full article

(This article belongs to the Special Issue Hydrogels for 3D Printing)

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35 pages, 6091 KiB

Open AccessReview

Biopolymers for Tissue Engineering: Crosslinking, Printing Techniques, and Applications

by David Patrocinio, Victor Galván-Chacón, J. Carlos Gómez-Blanco, Sonia P. Miguel, Jorge Loureiro, Maximiano P. Ribeiro, Paula Coutinho, J. Blas Pagador and Francisco M. Sanchez-Margallo

Gels 2023, 9(11), 890; https://doi.org/10.3390/gels9110890 - 10 Nov 2023

Viewed by 1536

Abstract

Currently, tissue engineering has been dedicated to the development of 3D structures through bioprinting techniques that aim to obtain personalized, dynamic, and complex hydrogel 3D structures. Among the different materials used for the fabrication of such structures, proteins and polysaccharides are the main [...] Read more.

Currently, tissue engineering has been dedicated to the development of 3D structures through bioprinting techniques that aim to obtain personalized, dynamic, and complex hydrogel 3D structures. Among the different materials used for the fabrication of such structures, proteins and polysaccharides are the main biological compounds (biopolymers) selected for the bioink formulation. These biomaterials obtained from natural sources are commonly compatible with tissues and cells (biocompatibility), friendly with biological digestion processes (biodegradability), and provide specific macromolecular structural and mechanical properties (biomimicry). However, the rheological behaviors of these natural-based bioinks constitute the main challenge of the cell-laden printing process (bioprinting). For this reason, bioprinting usually requires chemical modifications and/or inter-macromolecular crosslinking. In this sense, a comprehensive analysis describing these biopolymers (natural proteins and polysaccharides)-based bioinks, their modifications, and their stimuli-responsive nature is performed. This manuscript is organized into three sections: (1) tissue engineering application, (2) crosslinking, and (3) bioprinting techniques, analyzing the current challenges and strengths of biopolymers in bioprinting. In conclusion, all hydrogels try to resemble extracellular matrix properties for bioprinted structures while maintaining good printability and stability during the printing process. Full article

(This article belongs to the Special Issue Hydrogels for 3D Printing)

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21 pages, 3893 KiB

Open AccessEditor’s ChoiceReview

Essential Guide to Hydrogel Rheology in Extrusion 3D Printing: How to Measure It and Why It Matters?

by Helena Herrada-Manchón, Manuel Alejandro Fernández and Enrique Aguilar

Gels 2023, 9(7), 517; https://doi.org/10.3390/gels9070517 - 26 Jun 2023

Cited by 10 | Viewed by 5344

Abstract

Rheology plays a crucial role in the field of extrusion-based three-dimensional (3D) printing, particularly in the context of hydrogels. Hydrogels have gained popularity in 3D printing due to their potential applications in tissue engineering, regenerative medicine, and drug delivery. The rheological properties of [...] Read more.

Rheology plays a crucial role in the field of extrusion-based three-dimensional (3D) printing, particularly in the context of hydrogels. Hydrogels have gained popularity in 3D printing due to their potential applications in tissue engineering, regenerative medicine, and drug delivery. The rheological properties of the printing material have a significant impact on its behaviour throughout the 3D printing process, including its extrudability, shape retention, and response to stress and strain. Thus, understanding the rheological characteristics of hydrogels, such as shear thinning behaviour, thixotropy, viscoelasticity, and gelling mechanisms, is essential for optimising the printing process and achieving desired product quality and accuracy. This review discusses the theoretical foundations of rheology, explores different types of fluid and their properties, and discusses the essential rheological tests necessary for characterising hydrogels. The paper emphasises the importance of terminology, concepts, and the correct interpretation of results in evaluating hydrogel formulations. By presenting a detailed understanding of rheology in the context of 3D printing, this review paper aims to assist researchers, engineers, and practitioners in the field of hydrogel-based 3D printing in optimizing their printing processes and achieving desired product outcomes. Full article

(This article belongs to the Special Issue Hydrogels for 3D Printing)

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