Gels | Special Issue : 3D Printing of Gels: Applications and Properties

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12 pages, 3964 KiB

Open AccessArticle

Evaluation of Fused Deposition Modeling Materials for 3D-Printed Container of Dosimetric Polymer Gel

by Minsik Lee, Seonyeong Noh, Jun-Bong Shin, Jungwon Kwak and Chiyoung Jeong

Gels 2024, 10(2), 146; https://doi.org/10.3390/gels10020146 - 14 Feb 2024

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Abstract

Accurate dosimetric verification is becoming increasingly important in radiotherapy. Although polymer gel dosimetry may be useful for verifying complex 3D dose distributions, it has limitations for clinical application due to its strong reactivity with oxygen and other contaminants. Therefore, it is important that [...] Read more.

Accurate dosimetric verification is becoming increasingly important in radiotherapy. Although polymer gel dosimetry may be useful for verifying complex 3D dose distributions, it has limitations for clinical application due to its strong reactivity with oxygen and other contaminants. Therefore, it is important that the material of the gel storage container blocks reaction with external contaminants. In this study, we tested the effect of air and the chemical permeability of various polymer-based 3D printing materials that can be used as gel containers. A methacrylic acid, gelatin, and tetrakis (hydroxymethyl) phosphonium chloride gel was used. Five types of printing materials that can be applied to the fused deposition modeling (FDM)-type 3D printer were compared: acrylonitrile butadiene styrene (ABS), co-polyester (CPE), polycarbonate (PC), polylactic acid (PLA), and polypropylene (PP) (reference: glass vial). The map of R2 (1/T2) relaxation rates for each material, obtained from magnetic resonance imaging scans, was analyzed. Additionally, response histograms and dose calibration curves from the R2 map were evaluated. The R2 distribution showed that CPE had sharper boundaries than the other materials, and the profile gradient of CPE was also closest to the reference vial. Histograms and dose calibration showed that CPE provided the most homogeneous and the highest relative response of 83.5%, with 8.6% root mean square error, compared with the reference vial. These results indicate that CPE is a reasonable material for the FDM-type 3D printing gel container. Full article

(This article belongs to the Special Issue 3D Printing of Gels: Applications and Properties)

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17 pages, 4176 KiB

Open AccessArticle

Cryosectioning of Hydrogels as a Reliable Approach to Increase Yield and Further Tune Mechanical Properties

by África Martínez-Blanco, Sergio Noé, Lourdes Carreras-Vidal, Jorge Otero and Núria Gavara

Gels 2023, 9(10), 834; https://doi.org/10.3390/gels9100834 - 20 Oct 2023

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Abstract

Decellularized extracellular matrix (dECM) hydrogels have emerged as promising materials in tissue engineering. The steps to produce dECM hydrogels containing the bioactive epitopes found in the native matrix are often laborious, including the initial harvesting and decellularization of the animal organ. Furthermore, resulting [...] Read more.

Decellularized extracellular matrix (dECM) hydrogels have emerged as promising materials in tissue engineering. The steps to produce dECM hydrogels containing the bioactive epitopes found in the native matrix are often laborious, including the initial harvesting and decellularization of the animal organ. Furthermore, resulting hydrogels often exhibit weak mechanical properties that require the use of additional crosslinkers such as genipin to truly simulate the mechanical properties of the desired study tissue. In this work, we have developed a protocol to readily obtain tens of thin dECM hydrogel cryosections attached to a glass slide as support, to serve as scaffolds for two-dimensional (2D) or three-dimensional (3D) cell culture. Following extensive atomic force microscopy (AFM)-based mechanical characterization of dECM hydrogels crosslinked with increasing genipin concentrations (5 mM, 10 mM, and 20 mM), we provide detailed protocol recommendations for achieving dECM hydrogels of any biologically relevant stiffness. Given that our protocol requires hydrogel freezing, we also confirm that the approach taken can be further used to increase the mechanical properties of the scaffold in a controlled manner exhibiting twice the stiffness in highly crosslinked arrays. Finally, we explored the effect of ethanol-based short- and long-term sterilization on dECM hydrogels, showing that in some situations it may give rise to significant changes in hydrogel mechanical properties that need to be taken into account in experimental design. The hydrogel cryosections produced were shown to be biocompatible and support cell attachment and spreading for at least 72 h in culture. In brief, our proposed method may provide several advantages for tissue engineering: (1) easy availability and reduction in preparation time, (2) increase in the total hydrogel volume eventually used for experiments being able to obtain 15–22 slides from a 250 µL hydrogel) with a (3) reduction in scaffold variability (only a 17.5 ± 9.5% intraslide variability provided by the method), and (4) compatibility with live-cell imaging techniques or further cell characterization of cells. Full article

(This article belongs to the Special Issue 3D Printing of Gels: Applications and Properties)

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16 pages, 6142 KiB

Open AccessArticle

Vat Photopolymerization 3D Printing of Hydrogels with Re-Adjustable Swelling

by Pedro Liz-Basteiro, Felipe Reviriego, Enrique Martínez-Campos, Helmut Reinecke, Carlos Elvira, Juan Rodríguez-Hernández and Alberto Gallardo

Gels 2023, 9(8), 600; https://doi.org/10.3390/gels9080600 - 25 Jul 2023

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Abstract

Vat photopolymerization typically prints highly crosslinked networks. Printing hydrogels, which are also networks but with a high swelling capacity in water and therefore with low crosslinking density, is a challenge for this technique. However, it may be of interest in medicine and in [...] Read more.

Vat photopolymerization typically prints highly crosslinked networks. Printing hydrogels, which are also networks but with a high swelling capacity in water and therefore with low crosslinking density, is a challenge for this technique. However, it may be of interest in medicine and in other areas, since it would allow for the preparation of this type of 3D-shaped material. In this work, an approach for printing hydrogels via vat photopolymerization that uses a mixture of stable and hydrolysable crosslinkers has been evaluated so that an initial highly crosslinked network can be printed, although after hydrolysis it becomes a network with low crosslinking. This approach has been studied with PEO/PEG-related formulations, that is, with a PEG-dimethacrylate as a stable crosslinker, a PEO-related derivative carrying β-aminoesters as a degradable crosslinker, and PEG-methyl ether acrylate and hydroxyethyl acrylate as monofunctional monomers. A wide family of formulations has been studied, maintaining the weight percentage of the crosslinkers at 15%. Resins have been studied in terms of viscosity, and the printing process has been evaluated through the generation of Jacobs working curves. It has been shown that this approach allows for the printing of pieces of different shapes and sizes via vat photopolymerization, and that these pieces can re-ajust their water content in a tailored fashion through treatments in different media (PBS or pH 10 buffer). Full article

(This article belongs to the Special Issue 3D Printing of Gels: Applications and Properties)

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11 pages, 2149 KiB

Open AccessArticle

Cryopreservation of 3D Bioprinted Scaffolds with Temperature-Controlled-Cryoprinting

by Linnea Warburton and Boris Rubinsky

Gels 2023, 9(6), 502; https://doi.org/10.3390/gels9060502 - 20 Jun 2023

Cited by 2 | Viewed by 1935

Abstract

Temperature-Controlled-Cryoprinting (TCC) is a new 3D bioprinting technology that allows for the fabrication and cryopreservation of complex and large cell-laden scaffolds. During TCC, bioink is deposited on a freezing plate that descends further into a cooling bath, keeping the temperature at the nozzle [...] Read more.

Temperature-Controlled-Cryoprinting (TCC) is a new 3D bioprinting technology that allows for the fabrication and cryopreservation of complex and large cell-laden scaffolds. During TCC, bioink is deposited on a freezing plate that descends further into a cooling bath, keeping the temperature at the nozzle constant. To demonstrate the effectiveness of TCC, we used it to fabricate and cryopreserve cell-laden 3D alginate-based scaffolds with high cell viability and no size limitations. Our results show that Vero cells in a 3D TCC bioprinted scaffold can survive cryopreservation with a viability of 71%, and cell viability does not decrease as higher layers are printed. In contrast, previous methods had either low cell viability or decreasing efficacy for tall or thick scaffolds. We used an optimal temperature profile for freezing during 3D printing using the two-step interrupted cryopreservation method and evaluated drops in cell viability during the various stages of TCC. Our findings suggest that TCC has significant potential for advancing 3D cell culture and tissue engineering. Full article

(This article belongs to the Special Issue 3D Printing of Gels: Applications and Properties)

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11 pages, 2525 KiB

Open AccessArticle

Highly Thermally Resistant Bisamide Gelators as Pharmaceutical Crystallization Media

by Iván Torres-Moya, Abelardo Sánchez, Basanta Saikia, Dmitry S. Yufit, Pilar Prieto, José Ramón Carrillo and Jonathan W. Steed

Gels 2023, 9(1), 26; https://doi.org/10.3390/gels9010026 - 29 Dec 2022

Cited by 4 | Viewed by 1390

Abstract

Three simple bisamide derivatives (G1, G2 and G3) with different structural modifications were synthesized with easy synthetic procedures in order to test their gel behaviour. The outcomes showed that hydrogen bonding was essential in gel formation; for this reason, only [...] Read more.

Three simple bisamide derivatives (G1, G2 and G3) with different structural modifications were synthesized with easy synthetic procedures in order to test their gel behaviour. The outcomes showed that hydrogen bonding was essential in gel formation; for this reason, only G1 provided satisfactory gels. The presence of methoxy groups in G2 and the alkyl chains in G3 hindered the hydrogen bonding between N-H and C=O that occurred G1. In addition, G1 provided thermally and mechanical stable gels, as confirmed with T_sol and rheology experiments. The gels of G1 were also responsive under pH stimuli and were employed as a vehicle for drug crystallization, causing a change in polymorphism in the presence of flufenamic acid and therefore providing the most thermodynamically stable form III compared with metastable form IV obtained from solution crystallization. Full article

(This article belongs to the Special Issue 3D Printing of Gels: Applications and Properties)

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19 pages, 5585 KiB

Open AccessArticle

A Power Compensation Strategy for Achieving Homogeneous Microstructures for 4D Printing Shape-Adaptive PNIPAM Hydrogels: Out-of-Plane Variations

by Liyuan Tan, Hyunjin Lee, Li Fang and David J. Cappelleri

Gels 2022, 8(12), 828; https://doi.org/10.3390/gels8120828 - 15 Dec 2022

Cited by 2 | Viewed by 1464

Abstract

In the last decade, 3D printing has attracted significant attention and has resulted in benefits to many research areas. Advances in 3D printing with smart materials at the microscale, such as hydrogels and liquid crystalline polymers, have enabled 4D printing and various applications [...] Read more.

In the last decade, 3D printing has attracted significant attention and has resulted in benefits to many research areas. Advances in 3D printing with smart materials at the microscale, such as hydrogels and liquid crystalline polymers, have enabled 4D printing and various applications in microrobots, micro-actuators, and tissue engineering. However, the material absorption of the laser power and the aberrations of the laser light spot will introduce a decay in the polymerization degree along the height direction, and the solution to this problem has not been reported yet. In this paper, a compensation strategy for the laser power is proposed to achieve homogeneous and high aspect ratio hydrogel structures at the microscale along the out-of-plane direction. Linear approximations for the power decay curve are adopted for height steps, discretizing the final high aspect ratio structures. The strategy is achieved experimentally with hydrogel structures fabricated by two-photon polymerization. Moreover, characterizations have been conducted to verify the homogeneity of the printed microstructures. Finally, the saturation of material property is investigated by an indirect 3D deformation method. The proposed strategy is proved to be effective and can be explored for other hydrogel materials showing significant deformation. Furthermore, the strategy for out-of-plane variations provides a critical technique to achieve 4D-printed homogeneous shape-adaptive hydrogels for further applications. Full article

(This article belongs to the Special Issue 3D Printing of Gels: Applications and Properties)

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Review

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33 pages, 3926 KiB

Open AccessReview

Three-Dimensional Printing Strategies for Enhanced Hydrogel Applications

by Hossein Omidian and Kwadwo Mfoafo

Gels 2024, 10(4), 220; https://doi.org/10.3390/gels10040220 - 25 Mar 2024

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Abstract

This study explores the dynamic field of 3D-printed hydrogels, emphasizing advancements and challenges in customization, fabrication, and functionalization for applications in biomedical engineering, soft robotics, and tissue engineering. It delves into the significance of tailored biomedical scaffolds for tissue regeneration, the enhancement in [...] Read more.

This study explores the dynamic field of 3D-printed hydrogels, emphasizing advancements and challenges in customization, fabrication, and functionalization for applications in biomedical engineering, soft robotics, and tissue engineering. It delves into the significance of tailored biomedical scaffolds for tissue regeneration, the enhancement in bioinks for realistic tissue replication, and the development of bioinspired actuators. Additionally, this paper addresses fabrication issues in soft robotics, aiming to mimic biological structures through high-resolution, multimaterial printing. In tissue engineering, it highlights efforts to create environments conducive to cell migration and functional tissue development. This research also extends to drug delivery systems, focusing on controlled release and biocompatibility, and examines the integration of hydrogels with electronic components for bioelectronic applications. The interdisciplinary nature of these efforts highlights a commitment to overcoming material limitations and optimizing fabrication techniques to realize the full potential of 3D-printed hydrogels in improving health and well-being. Full article

(This article belongs to the Special Issue 3D Printing of Gels: Applications and Properties)

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61 pages, 12697 KiB

Open AccessReview

Recent Developments in 3D-(Bio)printed Hydrogels as Wound Dressings

by Olga Kammona, Evgenia Tsanaktsidou and Costas Kiparissides

Gels 2024, 10(2), 147; https://doi.org/10.3390/gels10020147 - 14 Feb 2024

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Abstract

Wound healing is a physiological process occurring after the onset of a skin lesion aiming to reconstruct the dermal barrier between the external environment and the body. Depending on the nature and duration of the healing process, wounds are classified as acute (e.g., [...] Read more.

Wound healing is a physiological process occurring after the onset of a skin lesion aiming to reconstruct the dermal barrier between the external environment and the body. Depending on the nature and duration of the healing process, wounds are classified as acute (e.g., trauma, surgical wounds) and chronic (e.g., diabetic ulcers) wounds. The latter take several months to heal or do not heal (non-healing chronic wounds), are usually prone to microbial infection and represent an important source of morbidity since they affect millions of people worldwide. Typical wound treatments comprise surgical (e.g., debridement, skin grafts/flaps) and non-surgical (e.g., topical formulations, wound dressings) methods. Modern experimental approaches include among others three dimensional (3D)-(bio)printed wound dressings. The present paper reviews recently developed 3D (bio)printed hydrogels for wound healing applications, especially focusing on the results of their in vitro and in vivo assessment. The advanced hydrogel constructs were printed using different types of bioinks (e.g., natural and/or synthetic polymers and their mixtures with biological materials) and printing methods (e.g., extrusion, digital light processing, coaxial microfluidic bioprinting, etc.) and incorporated various bioactive agents (e.g., growth factors, antibiotics, antibacterial agents, nanoparticles, etc.) and/or cells (e.g., dermal fibroblasts, keratinocytes, mesenchymal stem cells, endothelial cells, etc.). Full article

(This article belongs to the Special Issue 3D Printing of Gels: Applications and Properties)

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