Special Issue "Smart Hydrogels for (Bio)printing Applications"

A special issue of Gels (ISSN 2310-2861).

Deadline for manuscript submissions: closed (15 November 2018)

Special Issue Editors

Guest Editor
Prof. Dr. Sandra Van Vlierberghe

Polymer Chemistry & Biomaterials Research Group, Centre of Macromolecular Chemistry, Ghent University, Krijgslaan 281, S4 Bis, Ghent 9000, Belgium
Website 1 | Website 2 | E-Mail
Interests: hydrogels; 3D printing; electrospinning; two-photon polymerization; proteins; polysaccharides; tissue engineering; hydrogel functionalization
Guest Editor
Prof. Dr. Dirk Kuckling

Organic and Macromolecular Chemistry, Department of Chemistry, University of Paderborn, Warburger Str. 100, D-33098 Paderborn, Germany
Website | E-Mail
Fax: +49 5251 603245
Interests: controlled polymer synthesis; polymer characterization; smart polymers; hydrolgels; actuators and sensors

Special Issue Information

Dear Colleagues,

We would like to invite you to contribute a communication, full article or review to this Special Issue, entitled “Smart Hydrogels for (Bio)Printing Applications”. All smart hydrogel types, ranging from natural to synthetic and semi-synthetic, are highly welcome. Responsivity to various triggers will be covered, including temperature, pH, light, etc., as well multi-responsive hydrogels. All aspects of the developmental process will be included in this Special Issue, starting from the hydrogel synthesis and characterization up to the engineering aspects associated with the production of 3D scaffolds.

A plethora of applications characteristic for the smart hydrogels will be tackled, including biomedical purposes, photonics, environmental, food applications, etc.

We look forward to receiving your contribution before 15 November 2018, but extensions may be granted upon request. 

Prof. Dr. Sandra Van Vlierberghe
Prof. Dr. Dirk Kuckling
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Gels is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) is waived for well-prepared manuscripts submitted to this issue. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • 3D printing (inkjet printing, two-photon polymerization, fused deposition modelling, etc.)
  • smart
  • hydrogel
  • temperature-responsive
  • pH-responsive
  • photo-responsive

Published Papers (4 papers)

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Research

Open AccessArticle Viscoelastic Oxidized Alginates with Reversible Imine Type Crosslinks: Self-Healing, Injectable, and Bioprintable Hydrogels
Received: 30 August 2018 / Revised: 12 November 2018 / Accepted: 15 November 2018 / Published: 21 November 2018
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Abstract
Bioprinting techniques allow for the recreation of 3D tissue-like structures. By deposition of hydrogels combined with cells (bioinks) in a spatially controlled way, one can create complex and multiscale structures. Despite this promise, the ability to deposit customizable cell-laden structures for soft tissues [...] Read more.
Bioprinting techniques allow for the recreation of 3D tissue-like structures. By deposition of hydrogels combined with cells (bioinks) in a spatially controlled way, one can create complex and multiscale structures. Despite this promise, the ability to deposit customizable cell-laden structures for soft tissues is still limited. Traditionally, bioprinting relies on hydrogels comprised of covalent or mostly static crosslinks. Yet, soft tissues and the extracellular matrix (ECM) possess viscoelastic properties, which can be more appropriately mimicked with hydrogels containing reversible crosslinks. In this study, we have investigated aldehyde containing oxidized alginate (ox-alg), combined with different cross-linkers, to develop a small library of viscoelastic, self-healing, and bioprintable hydrogels. By using distinctly different imine-type dynamic covalent chemistries (DCvC), (oxime, semicarbazone, and hydrazone), rational tuning of rheological and mechanical properties was possible. While all materials showed biocompatibility, we observed that the nature of imine type crosslink had a marked influence on hydrogel stiffness, viscoelasticity, self-healing, cell morphology, and printability. The semicarbazone and hydrazone crosslinks were found to be viscoelastic, self-healing, and printable—without the need for additional Ca2+ crosslinking—while also promoting the adhesion and spreading of fibroblasts. In contrast, the oxime cross-linked gels were found to be mostly elastic and showed neither self-healing, suitable printability, nor fibroblast spreading. The semicarbazone and hydrazone gels hold great potential as dynamic 3D cell culture systems, for therapeutics and cell delivery, and a newer generation of smart bioinks. Full article
(This article belongs to the Special Issue Smart Hydrogels for (Bio)printing Applications)
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Open AccessFeature PaperArticle Low-Cost Microfluidic Sensors with Smart Hydrogel Patterned Arrays Using Electronic Resistive Channel Sensing for Readout
Received: 2 August 2018 / Revised: 3 October 2018 / Accepted: 9 October 2018 / Published: 19 October 2018
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Abstract
There is a strong commercial need for inexpensive point-of-use sensors for monitoring disease biomarkers or environmental contaminants in drinking water. Point-of-use sensors that employ smart polymer hydrogels as recognition elements can be tailored to detect almost any target analyte, but often suffer from [...] Read more.
There is a strong commercial need for inexpensive point-of-use sensors for monitoring disease biomarkers or environmental contaminants in drinking water. Point-of-use sensors that employ smart polymer hydrogels as recognition elements can be tailored to detect almost any target analyte, but often suffer from long response times. Hence, we describe here a fabrication process that can be used to manufacture low-cost point-of-use hydrogel-based microfluidics sensors with short response times. In this process, mask-templated UV photopolymerization is used to produce arrays of smart hydrogel pillars inside sub-millimeter channels located upon microfluidics devices. When these pillars contact aqueous solutions containing a target analyte, they swell or shrink, thereby changing the resistance of the microfluidic channel to ionic current flow when a small bias voltage is applied to the system. Hence resistance measurements can be used to transduce hydrogel swelling changes into electrical signals. The only instrumentation required is a simple portable potentiostat that can be operated using a smartphone or a laptop, thus making the system suitable for point of use. Rapid hydrogel response rate is achieved by fabricating arrays of smart hydrogels that have large surface area-to-volume ratios. Full article
(This article belongs to the Special Issue Smart Hydrogels for (Bio)printing Applications)
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Open AccessFeature PaperArticle Extrusion-Based 3D Printing of Poly(ethylene glycol) Diacrylate Hydrogels Containing Positively and Negatively Charged Groups
Received: 29 June 2018 / Revised: 30 July 2018 / Accepted: 8 August 2018 / Published: 14 August 2018
Cited by 1 | PDF Full-text (1595 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Hydrogels are an interesting class of materials used in extrusion-based 3D printing, e.g., for drug delivery or tissue engineering. However, new hydrogel formulations for 3D printing as well as a detailed understanding of crucial formulation properties for 3D printing are needed. In this [...] Read more.
Hydrogels are an interesting class of materials used in extrusion-based 3D printing, e.g., for drug delivery or tissue engineering. However, new hydrogel formulations for 3D printing as well as a detailed understanding of crucial formulation properties for 3D printing are needed. In this contribution, hydrogels based on poly(ethylene glycol) diacrylate (PEG-DA) and the charged monomers 3-sulfopropyl acrylate and [2-(acryloyloxy)ethyl]trimethylammonium chloride are formulated for 3D printing, together with Poloxamer 407 (P407). Chemical curing of formulations with PEG-DA and up to 5% (w/w) of the charged monomers was possible without difficulty. Through careful examination of the rheological properties of the non-cured formulations, it was found that flow properties of formulations with a high P407 concentration of 22.5% (w/w) possessed yield stresses well above 100 Pa together with pronounced shear thinning behavior. Thus, those formulations could be processed by 3D printing, as demonstrated by the generation of pyramidal objects. Modelling of the flow profile during 3D printing suggests that a plug-like laminar flow is prevalent inside the printer capillary. Under such circumstances, fast recovery of a high vicosity after material deposition might not be necessary to guarantee shape fidelity because the majority of the 3D printed volume does not face any relevant shear stress during printing. Full article
(This article belongs to the Special Issue Smart Hydrogels for (Bio)printing Applications)
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Graphical abstract

Open AccessArticle A Methylcellulose Hydrogel as Support for 3D Plotting of Complex Shaped Calcium Phosphate Scaffolds
Received: 16 July 2018 / Revised: 8 August 2018 / Accepted: 9 August 2018 / Published: 11 August 2018
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Abstract
3D plotting is an additive manufacturing technology enabling biofabrication, thus the integration of cells or biologically sensitive proteins or growth factors into the manufacturing process. However, most (bio-)inks developed for 3D plotting were not shown to be processed into clinically relevant geometries comprising [...] Read more.
3D plotting is an additive manufacturing technology enabling biofabrication, thus the integration of cells or biologically sensitive proteins or growth factors into the manufacturing process. However, most (bio-)inks developed for 3D plotting were not shown to be processed into clinically relevant geometries comprising critical overhangs and cavities, which would collapse without a sufficient support material. Herein, we have developed a support hydrogel ink based on methylcellulose (mc), which is able to act as support as long as the co-plotted main structure is not stable. Therefore, 6 w/v %, 8 w/v % and 10 w/v % mc were allowed to swell in water, resulting in viscous inks, which were characterized for their rheological and extrusion properties. The successful usage of 10 w/v % mc as support ink was proven by multichannel plotting of the support together with a plottable calcium phosphate cement (CPC) acting as main structure. CPC scaffolds displaying critical overhangs or a large central cavity could be plotted accurately with the newly developed mc support ink. The dissolution properties of mc allowed complete removal of the gel without residuals, once CPC setting was finished. Finally, we fabricated a scaphoid bone model by computed tomography data acquisition and co-extrusion of CPC and the mc support hydrogel. Full article
(This article belongs to the Special Issue Smart Hydrogels for (Bio)printing Applications)
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Graphical abstract

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