Spongy Hydrogels Research Articles

Preparation and evaluation of chitosan/MCM-41-based spongy hydrogels loaded with tea tree oil

In this study, chitosan, polyvinyl alcohol, gelatin, MCM-41 and tea tree oil (TTO) were used as raw materials. MCM-41-based spongy hydrogels loaded with TTO were synthesized by physical cross-linking method. The TTO was first adsorbed into MCM-41 s. Then different contents of MCM-41 s were added to the hydrogel, which affected the properties of the hydrogel. The structure of hydrogels was analyzed by scanning electron microscopy (SEM) and attenuated total internal reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The mechanical properties of hydrogels were determined by swelling, degradation and ductility evaluation. The antibacterial effect and biocompatibility were determined by in vitro antibacterial and cytotoxicity examinations. In this study, the mechanical property of the hydrogels was enhanced with the increasing content of MCM-41 s. The hydrogels exhibited an excellent antibacterial effect attributed to the synergistic interaction between TTO and chitosan. Furthermore, the hydrogels showed superior biocompatibility property. In conclusion, the hydrogels prepared in this study have great potential for expanding their applications in the bacteriostatic field.

Facile synthesis of self-healing poly-acrylic acid/TiO2 hybrid hydrogel for photocatalytic hydrogenation of 4-nitrophenol to 4-aminophenol

Self-healing poly-acrylic acid/TiO2 (PT) hybrid hydrogel with different water amount have been simply fabricated by UV light irradiation. The cross-linking (matrix) formation of PT hydrogels was formed due to UV light absorption by TiO2 generating the radical species to polymerize acrylic acid monomer to poly-acrylic acid. XRD analysis successfully revealed the presence of TiO2 in the hydrogel. Meanwhile, the polymerization of acrylic acid to poly-acrylic acid was revealed by FTIR analysis. It is obvious that the physical appearance of as-prepared PT hydrogels with different water amount was different, where a rigid hydrogel was obtained with less water amount and a spongy hydrogel was formed with more water amount. The highest self-healing efficiency achieved ∼85% exhibited by PT-4 hydrogel in which the self-healing ability is due to hydrogen bond occurred between TiO2 and carboxylic functional groups in poly-acrylic acid. For the application, the healed PT-4 hydrogel demonstrated the capability to convert toxic 4-nitrophenol to 4-aminophenol through photocatalytic hydrogenation reaction within 2 h UV light irradiation.

Novel pH-responsive chitosan/sodium alginate/PEG based hydrogels for release of sodium ceftriaxone

pH-sensitive hydrogels have gained attraction in many biomedical fields. In this study, pH-sensitive hydrogels based on polyelectrolyte complex of chitosan/sodium alginate/PEG with 1,4-diaminobutane as a cross-linking agent were blended by solution casting method. FTIR was conducted to study the interactions among the polymer chains and crosslinker. The influence of the cross-linker concentration on the swelling behavior of the hydrogels was studied. SEM images exhibited the spongy hydrogel matrix and the drug entrapped in the hydrogel is also observed in drug loaded sample. TGA was conducted to check the effect of cross-linking density on the thermal stability of the hydrogel matrix. The release profile of sodium ceftriaxone (CTX) as a model drug in the solutions of PBS, SGF and SIF was investigated. In SGF, drug was released more than 10% in 30 min, while in PBS and SIF, the drug was released in a controlled manner. The comparison of UV spectra of pure and released drug confirmed its chemical stability in the developed hydrogels. The release profile according to the pharmacopeia standards designated the prepared hydrogels as a suitable candidate for drug release applications.

Electrochemically assisted hydrogel deposition, shaping and detachment

This work describes a facile approach allowing Dibenzoyl-l-Cystine (DBC) based hydrogel controlled deposition and controlled detachments over a conducting support. The method itself is an electrochemically assisted approach, where the water oxidation at the electrode surface results in a local pH drop inducing DBC gelation and hydrogel formation. We have comprehensively described the possibility of the hydrogel shaping by alternating the anodic deposition potential, DBC concentration and finally the working electrode geometry. The latter includes macro-electrodes in a form of platinum discs having diameter equal to 200 and 500 μm; hexagonal arrays of circular platinum microelectrodes with a diameter of a single electrode equal to 5 or 10 μm and custom made platinum microelectrodes, having the shape of circles, triangles and squares, that are used to shape the microgels. Over the course of our work we were able to define the conditions to form a number of different hydrogel shapes such as: (i) flat and planar deposits; (ii) hemispherical deposits with an oxygen bubble pocket; (iii) spongy hydrogel structures or (iv) hemispherical micro-cups build from radially oriented DBC fibres directionally growing from the support. Furthermore, we were also able to remotely form and then detach the hydrogel deposit in the initial formulation solution using only an electrochemical trigger. Our work represents a solid proof of concept and opens a number of new avenues for the electrochemically assisted soft matter fabrication down to micrometre scale.

Spongy hydrogels clean textured paintings

Washing away the dirt from an artistic masterpiece is especially tricky when the surface is not flat. New materials can help.

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Superelastic three-dimensional nanofiber-reconfigured spongy hydrogels with superior adsorption of lanthanide ions and photoluminescence

Materials combining high-water-content, robust mechanical performances, and multifunctionality, such as adsorption separation, photoluminescence and anti-fouling, are highly desirable for various applications. Electrospun nanofibrous hydrogels have emerged as attractive candidates; however, it has remained a great challenge to achieve these properties in three-dimensional (3D) bulk nanofibrous hydrogels. Here we report a facile and effective top-down approach to construct water-rich and superelastic 3D nanofiber-reconfigured spongy hydrogels (NRSHs) with hierarchically cellular architectures by combining sodium alginate/polyacrylamide (SA/PAM) electrospun nanofibers and the freeze-drying process of homogenized nanofiber dispersion, followed by chemically cross-linked with pyromellitic dianhydride (PMDA). The resulting SA/PAM NRSHs exhibit a comprehensive property of high water capacity, complete recovery from 80% strain, and stress retention of ∼90% after 100 compression cycles due to the synergistic effects of its cellular structures, well-hydrated and robust bonded nanofibrous skeleton. Furthermore, the well-designed NRSHs with abundant carboxyl groups perform superior adsorption behavior towards lanthanide ions (Ln3+) and excellent regenerability, the maximum equilibrium adsorption capacities for Eu3+ and Tb3+ reach up to 492.9 and 472.9 mg/g, respectively. Notably, benefiting from the typical 4f transition luminescence features of Ln, the obtained Ln3+-SA/PAM NRSHs are endowed with outstanding photoluminescent performance independent of compression deformation, tunable compression stress towards different Ln3+ concentration, desirable shapes and tunable emission color, simultaneously. The fabrication of such fascinating NRSHs will provide new prospects to design and develop multifunctional 3D bulk hydrogels for various applications, such as adsorbents, luminescent patterning, underwater fluorescent devices, sensors and bioengineering.

Stem Cell-Containing Hyaluronic Acid-Based Spongy Hydrogels for Integrated Diabetic Wound Healing

The detailed pathophysiology of diabetic foot ulcers is yet to be established and improved treatments are still required. We propose a strategy that directs inflammation, neovascularization, and neoinnervation of diabetic wounds. Aiming to potentiate a relevant secretome for nerve regeneration, stem cells were precultured in hyaluronic acid-based spongy hydrogels under neurogenic/standard media before transplantation into diabetic mice full-thickness wounds. Acellular spongy hydrogels and empty wounds were used as controls. Re-epithelialization was attained 4 weeks after transplantation independently of the test groups, whereas a thicker and more differentiated epidermis was observed for the cellular spongy hydrogels. A switch from the inflammatory to the proliferative phase of wound healing was revealed for all the experimental groups 2 weeks after injury, but a significantly higher M2(CD163+)/M1(CD86+) subtype ratio was observed in the neurogenic preconditioned group that also failed to promote neoinnervation. A higher number of intraepidermal nerve fibers were observed for the unconditioned group probably due to a more controlled transition from the inflammatory to the proliferative phase. Overall, stem cell-containing spongy hydrogels represent a promising approach to enhance diabetic wound healing by positively impacting re-epithelialization and by modulating the inflammatory response to promote a successful neoinnervation.

Research Progress of the Molecularly Imprinted Cryogel

Abstract Cryogel is an elastic, loose, and porous spongy hydrogel prepared via addition polymerization from monomers or cross-linking reaction of a polymer at a temperature lower than the freezing point of the solvent. Cryogel has mainly been used in the form of molecular imprinting cryogel based solid phase extraction in analytical chemistry, which combines the advantages of high selectivity of the molecularly imprinted technique with the porous structure, high throughput of a cryogel. Cryogel has a unique advantage of keeping the biological activities of proteins while used in separating and purifying proteins. Molecularly imprinted cryogel can act as the stationary phase in a packed column or a monolith column, as well as the adsorbent in a separation membrane. A variety of molecules, including small molecule, macromolecule, and certain fragment of macromolecule, can act as template molecules. Even inorganic ions can be used as template. Thus, both simple template and complex template can be used. When we employ more than a molecule (or an ion) as co-template simultaneously, the method is termed as mixed template. In addition, high abundance components themselves of a complex sample may act as a mixed template, which is named as the pending template. Further, while an analogue, an isotopic label, or a fragment of the target substance acts as a template, the method is defined as the dummy template.

Hydrogel ophthalmic implants

A new nontoxic spongy hydrogel material containing immobilized α-chymotrypsin has been obtained via precipitation polymerization of hydroxyethyl methacrylate. From this material, drains for the therapy of secondary glaucoma and eyeball endoprostheses have been made. The positive results of biomedical studies and sanitary-chemical evaluation of the material have made it possible to recommend the obtained products for clinical use.

超巨大多糖類サクランの構造物性とバイオミメチックな機能創出

Cyanobacteria, which live in the rivers and sea, produce and secrete polysaccharides with functional groups such as carboxylic acid, sulfates, phosphates and amines that are responsible for ionic adsorption. Aphanothece sacrum,whose extracellular polysaccharide creates a jelly-like material (gels) which protects the cells, is mass cultured in fresh water only in Japan, and is grown with adsorbing metal ions from groundwater. The fact motivated us in the biomimetics concept to develop a metal-recycle material of the extracellular polysaccharide, which was here extracted by a successful alkaline elution method. The extracted polysaccharide was a new product and then it was named as “sacran”. Sacran adsorbed various multivalent metals as expected and formed the gels whose structure was formed a fibrous nanostructural network containing water revealed by cryogenic-TEM images. Freeze-drying of sacran formed spongy materials capable of In3+ preferential adsorption to form hydrogels from the mixed solution of In3+ and Sn4+ with concentrations below 40 mM. Electrolytic refinement of indium was made using the ion-complex hydrogels at room temperature to obtain indium metal foil at a pure grade over 99.9%. Thus epochal energy-saving methods for indium refinement were established using spongy hydrogels of cyanobacterial polyanions.

Macroporous StarPEG-Heparin Cryogels

Macroporous scaffolds with adaptable mechanical and biomolecular properties can be instrumental in enabling cell-based therapies. To meet these requirements, a cryostructuration method was adapted to prepare spongy hydrogels based on chemically cross-linked star-shaped poly(ethylene glycol) (starPEG) and heparin. Subzero temperature treatment of the gel forming reaction mixtures and subsequent lyophilization of the incompletely frozen gels resulted in macroporous biohybrid cryogels showing rapid swelling, porosity of up to 92% with interconnected large pores (30-180 μm), low bulk stiffness, and high mechanical stability upon compression. The applicability of the cryogel scaffolds was investigated using human umbilical vein endothelial cells. Cell attachment and three-dimensional spreading resulted in evenly distributed viable cells within the macroporous starPEG-heparin materials, demonstrating the significant translational potential of the developed three-dimensional cell carriers.

Spongy Hydrogels of Cyanobacterial Polyanions Mediate Energy-Saving Electrolytic Metal-Refinement

The freeze-drying of anionic megamolecules extracted from gelatinous cyanobacteria, Aphanothece sacrum, formed spongy materials capable of metal adsorption to form hydrogels. Cryogenic-transmission electron microscopy demonstrated that thicker nanofibers were formed in sacran/In3+ complexes than in sacran/Sn4+. The preferential sorption of In3+ into the hydrogels occurred in the mixed solution of In3+ and Sn4+ with concentrations below 40 mM. Since In3+ was condensed in the sponges, electrolytic refinement of indium was made using the ion-complex hydrogels at room temperature to obtain indium metal foil at a pure grade over 99.9%. Furthermore, the sponges were recovered and used again, to successfully obtain highly pure indium metal, in even the second and third trials. Thus epochal energy-saving methods for indium refinement were established using spongy hydrogels of cyanobacterial polyanions.

Growing polymer hydrogels

A new nontoxic spongy hydrogel material is synthesized via the precipitative polymerization of hydroxyethyl methacrylate, and implants for the ophthalmic reconstructive surgery are created on its basis. The obtained endoprostheses are well compatible with eye-socket tissues. The copolymerization of hydroxyethyl methacrylate with acrylamide yields a material that is able to increase its degree of swelling in aqueous solutions. As a result, implants that controllably change in size during use may be created.

Are 2 photons better than 1?

The detailed pathophysiology of diabetic foot ulcers is yet to be established and improved treatments are still required. We propose a strategy that directs inflammation, neovascularization, and neoinnervation of diabetic wounds. Aiming to potentiate a relevant secretome for nerve regeneration, stem cells were precultured in hyaluronic acid-based spongy hydrogels under neurogenic/standard media before transplantation into diabetic mice full-thickness wounds. Acellular spongy hydrogels and empty wounds were used as controls. Re-epithelialization was attained 4 weeks after transplantation independently of the test groups, whereas a thicker and more differentiated epidermis was observed for the cellular spongy hydrogels. A switch from the inflammatory to the proliferative phase of wound healing was revealed for all the experimental groups 2 weeks after injury, but a significantly higher M2(CD163+)/M1(CD86+) subtype ratio was observed in the neurogenic preconditioned group that also failed to promote neoinnervation. A higher number of intraepidermal nerve fibers were observed for the unconditioned group probably due to a more controlled transition from the inflammatory to the proliferative phase. Overall, stem cell-containing spongy hydrogels represent a promising approach to enhance diabetic wound healing by positively impacting re-epithelialization and by modulating the inflammatory response to promote a successful neoinnervation.

Cryogenic Designing of Biocompatible Blends of Polyvinyl alcohol and Starch with Macroporous Architecture

The present paper discusses synthesis, characterization, and blood compatibility studies of macroporous cryogels of PVA and starch. Biocompatible spongy porous hydrogels of polyvinyl alcohol–starch have been synthesized by repeated freezing–thawing methods and characterized by Infra red (FTIR) and environmental scanning electron microscopy (ESEM) techniques, respectively, to gain insights for structural and morphological features. The FTIR analysis of prepared cryogels indicated that starch was introduced into the network of cryogel possibly via formation of hydrogen bonds between the PVA and starch clusters. The “cryogels” were evaluated for their water uptake potentials and influence of various factors such as chemical architecture of the spongy hydrogels, pH and temperature of the swelling bath were investigated on the degree of water sorption by the cryogels. The hydrogels were also swollen in salt solutions and various simulated biological fluids. The biocompatibility of the prepared cryogels was judged by in vitro methods of blood–clot formation viz. percent haemolysis and protein (BSA) adsorption. The cryogels were also studied for their pores morphology and percent porosity and the effect of chemical composition on the extent of porosity was also investigated.

Designing of macroporous biocompatible cryogels of PVA–haemoglobin and their water sorption study

Macroporous polymeric materials are three-dimensional porous architectures having enormous utility in the areas of biomedical, biotechnological and separation sciences. Thus realizing the crucial role of macroporous polymeric materials in tissue engineering and allied fields the present paper discusses synthesis, characterization, and blood compatibility study of macroporous cryogels of PVA and haemoglobin. Biocompatible spongy and porous hydrogels of polyvinyl alcohol-haemoglobin have been synthesized by repeated freezing-thawing method and characterized by Infrared (FTIR), and ESEM techniques. The FTIR analysis of prepared cryogels indicated that haemoglobin was introduced into the cryogel possibly via hydrogen bonds formed amongst hydroxyl groups and amino groups present in PVA and haemoglobin, respectively. The 'cryogels' were evaluated for their water uptake potentials and influence of various factors such as chemical architecture of the spongy hydrogels, pH and temperature of the swelling bath were investigated on the degree of water sorption by the cryogels. The hydrogels were also swollen in salt solutions and various simulated biological fluids. The effect of drying temperature on its water sorption capacity was also studied. The biocompatibility of the prepared cryogels was judged by in vitro methods of blood-clot formation, percent haemolysis and protein (BSA) adsorption.

Preparation and characterization of a novel spongy hydrogel from aqueous Bombyx mori sericin

AbstractWe attempted to obtain a novel spongy hydrogel from aqueous Bombyxmori (B. Mori) sericin by using a freeze-thaw method without any cross-linking reagent. The aqueous sericin solution utilized was extracted from silkworm cocoons by using boiling method, and showed continuous molecular weight distribution mainly from 43 kDa to 212 kDa and even higher. To optimize the conditions for hydrogel preparation, the efficiency of hydrogel transformation from sericin solution were investigated by changing sericin concentration, freezing time, freezing temperature and frozen-thawed repetition. The porous characteristics of sericin hydrogel including the porosity, density and maximal water absorbency were performed by changing freezingn conditions. The pore size and morphology of hydrogels prepared at different concentration and freezing temperatures were observed with SEM. FTIR, XRD and DSC curves indicate that the hydrogel prepared at -20 °C and -80 °C adopt mainly random coil conformation.

Mathematics‐aided quantitative analysis of diffusion characteristics of pHEMA sponge hydrogels

AbstractThis study reports the current progress in quantitative analysis of the release characteristics of pHEMA spongy hydrogels using prednisolone 21‐hemisuccinate sodium salt as a model drug. Extraction of effective diffusion coefficients of the drug from various pHEMA matrices was made using a novel mathematical model that handles both boundary layer and initial burst effects. Drug loading level and entrapment efficiency were also determined. The computed diffusion coefficients and the drug loading capacity in relation to the device porous structure and drug concentration of the loading solution, as well as the size of device are discussed. Mathematical modelling proves to be a powerful tool not only for establishing and interpreting structure and performance relationships but also for handling experimental ambiguity. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.

Preparation and characterization of novel biocompatible cryogels of poly (vinyl alcohol) and egg-albumin and their water sorption study

Polyvinyl alcohol (PVA) and egg albumin are water-soluble, biocompatible and biodegradable polymers and have been widely employed in biomedical fields. In this paper, novel physically cross-linked hydrogels composed of poly (vinyl alcohol) and egg albumin were prepared by cyclic freezing/thawing processes of aqueous solutions containing PVA and egg albumin. The FTIR analysis of prepared cryogels indicated that egg albumin was successfully introduced into the formed hydrogel possibly via hydrogen bonds among hydroxyl groups, amide groups and amino groups present in PVA and egg albumin. The gels were also characterized thermally and morphologically by DSC and SEM-techniques, respectively. The prepared so called 'cryogels' were evaluated for their water uptake potential and influence of various factors such as chemical architecture of the spongy hydrogels, pH and temperature of the swelling bath were investigated on the degree of water sorption by the cryogels. The effect of salt solution and various simulated biological fluids on the swelling of cryogel was also studied. The in vitro biocompatibility of the prepared cryogel was also judged by methods such as protein (BSA) adsorption, blood clot formation and percentage hemolysis measurements.