Hydrogel Formation Research Articles

Frontal polymerization of acrylamide/GelMA/gelatin hydrogels with controlled mechanical properties and inherent self-recovery

Low mechanical resistance represents one of the significant problems of hydrogels, limiting their applicability in many fields. One approach to overcome this issue is synthesizing interpenetrating polymeric networks. In this work, the frontal polymerization technique was used to synthesize two series of novel hydrogels: (i) poly(acrylamide) (PAAm)-based hydrogels copolymerised/crosslinked with methacrylate gelatin (GelMA) (AAm-GelMA copolymer networks), and (ii) semi-IPN made of AAm-GelMA copolymer networks and a physically crosslinked gelatin network. With the final objective of improving the rheological, mechanical, morphological, thermal, and swelling properties of PAAm hydrogels, GelMA with two different degrees of methacrylation (30 and 75 mol%) was used. Interactions between GelMA chains, which give rise to physical network formation (i.e., GelMA-GelMA interactions), resulted in very efficient crosslinking for PAAm-based hydrogels, requiring a significantly lower methacrylic group concentration (0.04 mol%) for hydrogel formation compared to N, N′-methylene-bis-acrylamide (1 mol%), which is the agent typically used as a crosslinker for PAAm. Furthermore, the degree of GelMA methacrylation markedly affected the properties of the hydrogels. For example, regarding the swelling degree, hydrogels containing 22 wt% of GELMA30 had an SR% of 2870, while those containing the same amount of GELMA75 swelled much less (870 %). The introduction of gelatin as a secondary network in semi-IPNs influenced the rheological and mechanical properties, resulting in increased hydrogel modulus and stiffness attributed to enhanced physical interactions within the network. Finally, dynamic rheological shear strain and cyclic loading compression tests demonstrated exceptional recovery capabilities in all hydrogel formulations: samples subjected to alternating low (0.1 %) and high (300 % or 10 %) shear strain demonstrated a complete and prompt recovery of G′ and G″ values.

Lignin-coated liquid metals-induced synthesis of deep eutectic solvent-based hydrogels with environmentally tolerant for strain sensors

In the work, alkali lignin (AL) was used as a coating layer for dispersing liquid metals (LM) in a ternary DES (choline chloride/ethylene glycol/water) system and generating free radical-catalyzed acrylic acid (AA) polymerization. The preparation of flexible sensors had high electrical conductivity (0.33 S·m-1), excellent self-healing and mechanical properties (84.7 KPa). The presence of AL facilitated the dispersion of LM in the DES system and the formation of a flexible hydrogel without the addition of an initiator. Moreover, DES was used as the liquid component of the PAA-AL2@LM2 hydrogel made it more environmentally tolerant and had better water retention. Even at -20 °C, the hydrogel exhibited low electrical resistance (131.4 Ω). The moisture loss of the prepared hydrogel was only 9% after 7 days at room temperature. This work exploited the significant advantages of DES and lignin-based materials in dispersing LM to provide a new technique for the preparation of metal-polymer composite hydrogels, which has great potential in the field of flexible sensors.

Thermally Induced Gelling Systems Based on Patchy Polymeric Micelles

AbstractThermogels that exhibit a sol‐gel transition at body temperature represent a promising class of injectable biomaterials for biomedical applications. Thermogels reported thus far are generally composed of amphiphilic block copolymer micelles with an isotropic thermosensitive surface that induces intermicellar aggregation upon heating. Despite the promise, these hydrogels exhibit low mechanical strengths due to their uncontrollable aggregation resulting in void formation. To gain better control over intermicellar assembly, herein a novel thermogel design concept is presented based on patchy polymeric micelles bearing multiple thermosensitive surface domains. These domains serve as “patches” to bridge the micelles to form a percolated network structure. Patchy micelles are prepared from a binary mixture of amphiphilic block copolymers: Poly(N‐acryloylmorpholine)‐b‐poly(N‐benzylacrylamide) (PAM‐PBzAM) and poly (N‐isopropyl acrylamide)‐b‐poly(N‐benzylacrylamide) (PNIPAM‐PBzAM), where PBzAM, PAM and PNIPAM are the hydrophobic, hydrophilic and thermosensitive blocks, respectively. At 25 °C, the polymers self‐assembled into mixed shell micelles having a phase‐separated shell with PAM‐ and PNIPAM‐rich domains. At 37 °C, the PNIPAM domains undergo a hydrophilic‐to‐hydrophobic transition to induce intermicellar assembly into entangled worm‐like structures resulting in hydrogel formation. Patchy micelles form a homogeneous network structure without voids. The micelle design significantly affects the inter‐micellar assembly, the thermogelling behavior, and the mechanical properties of the hydrogels.

Magnetic hydrogel scaffold based on hyaluronic acid/chitosan and gelatin natural polymers.

Owing to their native extracellular matrix-like features, magnetic hydrogels have been proven to be promising biomaterials as tissue engineering templates In the present work, magnetic hydrogels scaffold based on chitosan, gelatin, hyaluronic acid, containing Fe3O4 as magnetic nanoparticles (IONPs) were prepared. The prepared hydrogels were loaded with ciprofloxacin hydrochloride as a model drug. The magnetic hydrogel was prepared using different volumes of chitosan, 1%, gelatin, 10%, and hyaluronic acid, 1% in glutaraldehyde as the crosslinking agent and Fe3O4 as magnetic nanoparticles. The hydrogel scaffold and magnetic scaffold hydrogel samples were characterized by scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), and Fourier-transform infrared spectroscopy (FTIR). The porosity, mechanical properties, swelling degree, and antibacterial activity of the hydrogel scaffold were also determined as well as the drug release profiles of the hydrogels. SEM imaging revealed that the magnetic hydrogel scaffold showed a relatively rough morphology with an irregular surface. The data obtained indicated that the hydrogel surface has three-dimensional porous microstructures and the porosity varied depending on the hydrogel formulation. The breaking load of the hydrogel scaffold increased from 1.361 Kgf to 4.98 Kgf by increasing the glutaraldehyde concentration from 0.2 mL to 0.8 mL. Swelling degree values in water were from 250 to 2000% after 24h. The antibacterial activity of the hydrogel scaffold ranged from 54% to about 97% for Gram-positive bacteria (S. aureus) and from about 26-92% for Gram-negative bacteria (E. coli). The ciprofloxacin hydrochloride loaded hydrogel has a sustained release of ciprofloxacin hydrochloride over 10h. The presence of IONPs gave a faster release of ciprofloxacin hydrochloride.

Double-crosslinked hydrogels and hydrogel beads formed by garlic protein hydrolysates for bioactive encapsulation and gastrointestinal delivery.

Garlic protein is one of the main components of garlic. It has several beneficial characteristics. This study aimed to characterize a double crosslinked hydrogel formed with alginate, calcium ions (Ca2+), and garlic protein hydrolysates (GPH), and to develop hydrogel beads for targeted delivery of bioactive constituents to the gastrointestinal tract. The results indicated that the degree of GPH hydrolysis was approximately 3% following trypsin treatment. The inner structure of the double crosslinked hydrogel showed a honeycomb pattern, with solid-like gel rheology and improved texture properties at a 4% (w/v) GPH concentration. The GPH-based hydrogel beads demonstrated pH sensitivity, swelling in near-neutral and alkaline environments, and the encapsulated paclitaxel (PTX) exhibited an amorphous phase with preferential release in intestinal conditions. The GPH group also achieved greater drug encapsulation efficiency than a soy protein hydrolysate (SPH) group, and proteomic analysis suggested that lower molecular weight and peptide charge favored the formation of peptide-integrated double crosslinking hydrogels. This work indicated that GPH was helpful and could inspire the development of drug delivery systems involving GPH with the required mechanical strength and target-release properties. © 2024 Society of Chemical Industry.

Development and In Vitro Characterization of Azadirachta Indica Gum Grafted Polyacrylamide Based pH-Sensitive Hydrogels to Improve the Bioavailability of Lansoprazole.

The present study intended to develop a pH-responsive hydrogel based on Neem gum (Ng) to improve Lansoprazole (LSP) oral bioavailability. Azadirachta Indica seed extract was used to obtain Ng. pH-responsive hydrogel formulations (F1-F9) were prepared using different Ng ratios, Acrylamide (AAm), and methylene-bis-acrylamide (MBA). The formulated hydrogels were characterized through FTIR, thermal analysis, swelling ratio, SEM, sol-gel ratios, In-Vitro drug release, and cytotoxicity analysis. Azadirachta Indica was extracted to produce a powder containing 21.5 % Ng. Prepared hydrogels showed maximum swelling at pH 7.4, whereas the swelling at an acidic pH was insignificant. LSP-loaded hydrogel demonstrated a regulated release of LSP for up to 24 h and indicated a Super Case II transport release mechanism. During the cytotoxic evaluation, the delivery system showed minimal cytotoxicity towards normal cells, while percent cytotoxicity was carried out for a longer duration (up to 96 h). The present study revealed Azadirachta indica gum-based pH-responsive hydrogel as a promising technique for precisely delivering LSP.

Extremely Ultrahigh Stretchable Starch‐Based Hydrogels with Continuous Hydrogen Bonding

AbstractNatural polysaccharides‐based hydrogels have drawn extensive attention yet have been plagued by less desirable stretchability due to their inherent nature. Here, ultra‐stretchable starch‐based hydrogels (amylopectin/polyacrylamide, AAM) are developed by constructing reversible intramolecular physical interactions. This strategy endows the hydrogel with exceedingly ultrahigh deformation due to a continuous hydrogen bonding network. It can be stretched from less than 0.5 to >300 cm without breakage that the elongation exceeds 600 times the original length. The elongation collected by the universal testing machine reaches up to 36 000% without breakage outperforming previous reports and demonstrating extraordinary stretchability. Furthermore, an interwoven structure of hydrogen bonding interaction and trace covalent bonds make the stress of hydrogel reach 0.28 MPa, accompanied by an ultra‐high strain of 22 500% and significant toughness (47 MJ·m−3). The hydrogel displays high transparency (≈93%), low‐temperature resistance, moisturizing property, and extraordinary interfacial adhesion property. Intriguingly, the aqueous precursor can act as inks to prepare various forms of hydrogel within minutes through the facile writing or drawing method. This hydrogel verifies strong potential in both fields of human motion sensor (After long‐term or low‐temperature conditions) and energy storage. This study will facilitate the progress of ultra‐stretchable or multifunctional hydrogels.

Formulation, E-Beam Crosslinking, and Comprehensive Characterisation of Lavender Oil-Enriched Hydrogels

This study focused on the formulation, electron beam (e-beam) crosslinking, and characterisation of hydrogels enriched with lavender oil (LO) to enhance their structural and functional properties for biomedical applications. Stable hydrogels were synthesised using water-soluble polymers and suitable ratios of Tween 80 and Isopropyl alcohol (IPA) as surfactant and co-surfactant, respectively, via e-beam irradiation at doses up to 70 kGy. The most effective crosslinking was achieved with a radiation dose of 30 kGy, depending on the concentrations of surfactants and LO. LO-enriched hydrogels exhibited enhanced superabsorbent swelling (7700% to 18,000%) and faster equilibrium rates than the control hydrogel. Structural analysis revealed a flexible spongiform porous architecture with larger mesh sizes (156 nm to 246 nm) and adequate elastic moduli (130 to 308 Pa). Degradation tests aligned with swelling data, demonstrating a degradation rate of 12% after 35 days, indicating an appropriate balance of stability and degradation. These findings suggest that e-beam technology, in conjunction with LO and surfactant addition, can effectively tailor hydrogel properties for biomedical applications, making them promising candidates for further research in wound care, drug delivery systems, and other biological applications.

Generating Tooth Organoids Using Defined Bioorthogonally Cross-Linked Hydrogels.

Generating teeth in vitro requires mimicking tooth developmental processes. Biomaterials are essential to support 3D tooth organoid formation, but their properties must be finely tuned to achieve the required biomimicry for tooth development. For the first time, we used bioorthogonally cross-linked hydrogels as defined 3D matrixes for tooth developmental engineering, and we highlighted how their properties play a pivotal role in enabling 3D tooth organoid formation in vitro. We prepared hydrogels by mixing gelatin precursors modified either with tetrazine (Tz) or norbornene (Nb) moieties. We tuned the hydrogel properties (E = 2-7 kPa; G' = 500-1500 Pa) by varying the gelatin concentration (8% vs 12% w/V) and stoichiometric ratio (Tz:Nb = 1 vs 0.5). We encapsulated dental epithelial-mesenchymal cell pellets in a library of hydrogels and identified a hydrogel formulation that enabled successful growth kinetics and morphogenesis of tooth germs, introducing a defined tunable platform for tooth organoid engineering and modeling.

ADVANCING TOPICAL POSACONAZOLE DELIVERY: BOX BEHNKEN DESIGN MICROSPONGE HYDROGEL OPTIMIZATION AND EXTENSIVE IN VIVO INVESTIGATION

Objective: The primary aim of this study was to develop a novel hydrogel formulation containing Posaconazole (PCZ) encapsulated within microsponges. Furthermore, the study aimed to assess the permeation properties of this formulation in vivo using a mouse model. Methods: To achieve this aim, a series of seventeen trials were conducted using the Box Behnken Design methodology. These trials were designed to optimize the production of PCZ Microsponges (PCZ MS), which were subsequently incorporated into a hydrogel matrix. Skin permeation studies were then performed to evaluate the ability of the PCZ microsponge-based hydrogel to deliver the drug across the skin barrier. These studies involved comparison with a standard hydrogel formulation lacking microsponges. Results: This study assessed the efficacy of microsponge gel formulation PM-3 for drug entrapment, yield, and sustained release compared to a conventional gel. PM-3 displayed the highest entrapment efficiency of 98.5% and a yield of 95.62%, indicating a direct correlation with the 1:1 drug-polymer ratio. Moreover, PM-3 exhibited sustained drug release over 12 h, releasing 83.82% of PCZ compared to 65.31% with the normal gel, suggesting its potential for prolonged therapeutic action. These findings underscore the promise of microsponge-based hydrogels, like PM-3, in enhancing therapeutic outcomes through sustained drug release, warranting further exploration for clinical applications. Conclusion: The findings of this study highlight the promising potential of microsponge-based hydrogels as effective carriers for localized drug delivery, particularly in the context of treating skin fungal infections.

Ionically crosslinked Sodium alginate – Galactoxyloglucan hydrogel beads as a controlled release system for sustainable urea delivery

The prolonged usage of chemical fertilizers often causes deleterious effects on the environment, and it remains an alarming issue in agricultural practices. Smart delivery of fertilizers achieved by hydrogels proved their efficiency in reducing risk in action. In this study, we investigated the optimization of urea-encapsulated hydrogel formulations and evaluated their physical and chemical attributes for agricultural applications. The proposed hydrogel formulation consists of ionically crosslinked two promising plant biopolymers (galactoxyloglucan and sodium alginate) which are specifically developed for the controlled release of urea fertilizer. The FT-IR analysis of the hydrogel beads confirmed the presence of biopolymer functional groups and urea. XRD analysis indicated the amorphous nature of the biopolymers. TGA revealed a thermal stability of up to 350°C. SEM images showed the porous structure of the hydrogel beads. To investigate the controlled release of urea, two kinetic models were employed: Korsmeyer-Peppas and Peppas-Sahlin. The results indicated a controlled release mechanism. The hydrogel beads demonstrated excellent water retention properties, maintaining soil moisture for up to 16 days. Additionally, degradability results demonstrated that in the soil environment, the hydrogel beads were degraded completely in 21 days. Therefore, we are confident that the formulated hydrogel bead exhibits eco-friendly and bio-compatible characteristics, which potentially mitigate the risks associated with urea fertilizers.

A Dry Patch with In Situ Solid-to-Gel Transformation for All-in-One Skin Wound Care.

Hydrogel-based dressing materials offer significant potential in expediting skin wound healing. Nevertheless, they face several challenges: poor adhesion to wound tissues, difficulties in preservation under ambient conditions, and limited multifunctionality to support all wound healing stages. In this work, a dry patch is designed to address these persistent issues by featuring an in situ solid-to-gel transformation and Janus wet tissue adhesiveness. The HGP patch integrates a wet adhesive layer combining dopamine-conjugated hyaluronic acid (HD) and poly(acrylic acid) (PAA), a drug-loading layer comprising gelatin (Gel), and a nonadhesive gelation layer of poly(vinyl alcohol) (PVA) and sodium alginate (SA). This hierarchical structural design confers exceptional wound adhesion, hemostatic capabilities, and antibacterial and antioxidant activities, as well as immune regulatory properties. These attributes collectively support accelerated skin wound healing, particularly in cases complicated by bacterial infections. This research charts an approach to engineer hydrogel-based wound dressings through on-site hydrogel formation, thus advancing the treatment of wounds afflicted with complex infections.

Hydronium-Crosslinked Inorganic Hydrogel Comprised of 1D Lepidocrocite Titanate Nanofilaments.

When a few drops of acid (hydrochloric, acrylic, propionic, acetic, or formic) are added to a colloid comprised of 1D lepidocrocite titanate nanofilaments (1DLs)-2 × 2 TiO6 octahedra in cross-section-a hydrogel forms, in many cases, within seconds. The 1DL synthesis process requires the reaction between titanium diboride with tetramethylammonium (TMA+), hydroxide. Using quantitative nuclear magnetic resonance (qNMR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), the mass percent of TMA+ after synthesis is determined to be ≈ 13.1±0.1%. The TMA+ is completely removed from the gels after 2 water soak cycles, resulting in the first completely inorganic, TiO2-based hydrogels. Ion exchanging the TMA+ with hydronium results in gels with relatively strong hydrogen bonds. The hydrogels' compression strengths increased linearly with 1DL colloid concentration. At a 1DL concentration of 45gL-1, the compressive strength, at 80% deformation when acrylic acid is used, is ≈325kPa. The strengths are ≈ 50% greater after the TMA+ is removed. The removal of all residual organic components in the hydrogels, including TMA+, is confirmed by qNMR, Fourier-transformed infrared spectroscopy (FTIR), and TGA/DSC. The 1DL phase is retained after gelation, TMA+ removal, and 80% compression.

Comprehensive Review of Hydrogel Synthesis, Characterization, and Emerging Applications

Hydrogels play a crucial role due to their high-water content and 3D structure, which make them ideal for various applications in biomedicine, sensing, and beyond. They can be prepared from a variety of biomaterials, polymers, and their combinations, allowing for versatility in properties and applications. Hydrogels include natural types derived from collagen, gelatin, alginate, and hyaluronic acid, as well as synthetic types based on polyethylene glycol (PEG), polyvinyl alcohol (PVA), and polyacrylamide (PAAm). Each type possesses distinct properties, such as mechanical strength, biodegradability, and biocompatibility, which can be tailored for applications such as wound healing, contact lenses, 3D bioprinting, and tissue engineering. The high-water content of hydrogels mimics natural tissue environments, promoting cell growth and allowing nutrient and waste exchange, which supports the development of functional tissues. They serve as scaffolds in tissue engineering applications, including wound healing, cartilage and bone regeneration, vascular tissue engineering, and organ-on-a-chip systems. Additionally, hydrogels can encapsulate and deliver therapeutic agents, such as growth factors or drugs, to specific target sites in the body. Hydrogels can be prepared through three primary methods: physical crosslinking, which relies on non-covalent interactions such as physical entanglements or hydrogen bonding; chemical crosslinking, which forms covalent bonds between polymer chains to create a stable structure; and irradiation-based crosslinking, where UV irradiation induces rapid hydrogel formation. The choice of crosslinking method depends on the desired properties and applications of the hydrogel. By providing a biomimetic environment, hydrogels facilitate cell growth and differentiation, support tissue formation, and aid in the regeneration of damaged or diseased tissues while delivering therapeutic agents. This review focuses on the critical advancements in processing routes for hydrogel development, summarizing the characterization and application of hydrogels. It also details key applications, including wound healing and cartilage and bone regeneration, as well as the challenges and future perspectives in the field.

Formulation of Asiatic acid-loaded polymeric chitosan-based hydrogel for effective MRSA infection control and enhanced wound healing in zebrafish models

BackgroundWound healing relies on a controlled inflammatory process vital for tissue regeneration. Chronic wounds, characterized by persistent inflammation and high infection risk, pose significant challenges in healthcare. Hydrogel dressings offer promise in wound care; however, the understanding of their role in managing inflammation and infection remains unclear. This study aimed to elucidate these processes and assess the efficacy of Asiatic acid (AA)-infused hydrogels in reducing inflammation and preventing infection. The unique properties of AA suggest its potential to modulate inflammation, promote tissue regeneration, and inhibit microbial colonization, thereby paving the way for specialized dressings that optimize healing outcomes. MethodsThe investigation encompassed the antibacterial, anti-biofilm, antioxidant activity, and biocompatibility of AA using a fibroblast cell line. A hydrogel incorporating AA was developed and characterized through scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), contact angle analysis, tensile testing, swelling capacity, and thermal stability assessments. Biodegradability was evaluated via enzymatic degradation, alongside controlled drug release and antibacterial efficacy against MRSA. In vivo studies using a zebrafish model examined wound healing and immune response. ResultsResults confirmed AA's potent antibacterial activity against MRSA and its effectiveness in disrupting mature biofilms. Additionally, AA exhibited strong antioxidant activity and biocompatibility. Morphological analysis revealed a pore structure conducive to wound healing, and the hydrogel demonstrated enhanced tensile strength, swelling properties, and thermal stability. In vivo, the AA-infused hydrogel accelerated wound closure, re-epithelialization, and immune response, supporting its potential for advanced wound care applications. In conclusion, the AA-infused chitosan hydrogel emerges as a promising candidate for advanced wound care therapies.

In Situ Gelling Eye Drops of Tacrolimus with Improved Ocular Delivery and Therapeutic Efficacy.

In situ gelling eye drops of tacrolimus (FK506 Gel) were developed to address the formulation challenge of tacrolimus for anterior ocular inflammatory diseases. Both in silico and in vitro investigations were conducted to screen a suitable cyclodextrin species to increase the drug solubility. Guanosine was employed as the gelator and combined with inclusion complexes of tacrolimus in the presence of borate anions to obtain FK506 Gel, which gelated when came into contact with cations in tear fluid and led to the formation of a nanofibrous hydrogel. The versatility of our design to improve the solubility and ocular retention of the hydrophobic drug was demonstrated in vivo with coumarin 6 as a model drug. A mouse dry eye model was used to evaluate the therapeutic effects of FK506 Gel, which, in combination with the biocompatibility study, suggested that FK506 Gel served as a superior treatment for anterior ocular inflammatory diseases.

Enhancing the viscoelastic properties of bacterial cellulose hydrogels through ultrasonic and enzymatic modification of xyloglucan

Bacterial cellulose (BC) hydrogels exhibit nanofibril porous network with good viscoelasticity for use as food ingredients and medical materials. Xyloglucan (XG), a hemicellulose with branching residues, can hybridize with BC to improve the hydrogel's extensibility. Thus, modifying the molecular structure of XG can fine-tune the viscoelastic properties of BC hydrogels. In this study, tamarind seed XG subjected to ultrasonic and enzymatic treatment was hybridized with BC to form composite materials. The results indicated that incorporating modified XG reduced the modulus and enhanced the viscous behaviour of BC to varying degrees. XG modified via ultrasonic treatment demonstrated a higher binding efficiency (19–22 %) with cellulose compared to enzymatically treated XG (11–13 %). The enzymatically treated XG improved the maximum elongation ratio to 57 %, but reduced the storage modulus to 30 kPa. Although ultrasonic-treated XG had a similar effect on the shear modulus, it had less impact on the extensibility of BC, with an elongation ratio of 38 %. Additionally, the incorporation of modified XG also regulated the nonlinear viscoelasticity of BC. These findings advance our understanding of the application of XG as a regulator of mechanical and rheological properties, broadening its utility in BC hydrogel formulations for the food industry and medical material development.

Tailoring the mechanical properties of macro-porous PVA hydrogels for biomedical applications

Polyvinyl alcohol (PVA) is a biocompatible biopolymer with superior dimensional and mechanical stability when compared to naturally available biomaterials such as collagen and gelatin. Furthermore, PVA in hydrogel form behaves non-linearly during mechanical loading, generating a response like soft biological tissues. Generally, PVA hydrogels are fabricated using freeze-thaw cycles (FTCs) and changing the number of FTCs gives control over its mechanical properties. Porosity of the hydrogel is another important factor which determines its mechanical properties and is also evident in biological soft tissues. Incorporating macro-pores in PVA hydrogels substantially reduces the stiffness of the material and can mimic some porous tissues such as lung, liver, bone marrow, kidneys, urethra and penile tissues (corpus cavernosa). Within this study, we developed macro-porous PVA hydrogels using the freeze-thaw process followed by particulate leaching of sacrificial 3D-printed and milled PVA (m-PVA) filler particles. This fabrication method enables control over the porosity in macro-porous PVA hydrogels, which is crucial not only for tuning mechanical properties but also for mimicking the structure of spongy tissues, such as liver tissue and corpus cavernosum in the penile tissue, for example. We investigated the level of porosity in the specimen using optical microscopy to understand the distribution of the pores and the pore size. The tunability of the mechanical properties of PVA hydrogels is, a key finding of this study and is achieved using three factors: (i) weight percentage of sacrificial fillers, (ii) number of FTCs and (iii) concentration of PVA. These macro-porous PVA specimens have wide ranging biomedical applications as biological soft tissue analogues, or tissue engineering scaffolds, where the PVA hydrogel can be tuned to match the mechanical properties of these soft biological tissues.

Green Synthesis of Silver Nanoparticles with Roasted Green Tea: Applications in Alginate–Gelatin Hydrogels for Bone Regeneration

The incorporation of silver nanoparticles (AgNPs) into alginate–gelatin (Alg-Gel) hydrogels can enhance the properties of these materials for bone regeneration applications, due to the antimicrobial properties of AgNPs and non-cytotoxic concentrations, osteoinductive properties, and regulation of stem cell proliferation and differentiation. Here, the hydrogel formulation included 2% (w/v) sodium alginate, 4 µg/mL AgNPs, and 2.5% (w/v) gelatin. AgNPs were synthesized using a 2% (w/v) aqueous extract of roasted green tea with silver nitrate. The aqueous extract of roasted green tea for AgNP synthesis was characterized using HPLC and UHPLC-ESI-QTOF-MS/MS, and antioxidant capacity was measured in Trolox equivalents (TE) from 4 to 20 nmol/well concentrations. Stem cells from human exfoliated deciduous tooth cells were used for differentiation assays including positive (SHEDs/hydrogel with AgNPs) and negative controls (hydrogel without AgNPs). FTIR was used for hydrogel chemical characterization. Statistical analysis (p < 0.05, ANOVA) confirmed significant findings. Roasted green tea extract contained caffeine (most abundant), (−)-Gallocatechin, gallic acid, and various catechins. XRD analysis revealed FCC structure, TEM showed quasispheroidal AgNPs (19.85 ± 3 nm), and UV–Vis indicated a plasmon surface of 418 nm. This integration of nanotechnology and biomaterials shows promise for addressing bone tissue loss in clinical and surgical settings.

In Vivo Assessment of an Antioxidant Hydrogel Vitreous Substitute.

The vitreous humor undergoes liquefaction with age, resulting in complications that may require a vitrectomy, or surgical removal of the vitreous from the eye. Silicone oil, a common vitreous substitute, lacks properties similar to the natural vitreous. In particular, it lacks antioxidants that may be necessary to reduce oxidative stress in the eye. The purpose of this study was to evaluate antioxidant-loaded hydrogel vitreous substitutes in a pilot invivo study. Ascorbic acid and glutathione were loaded into synthesized PEGDA hydrogels. Following vitrectomy, experimental antioxidant hydrogels or silicone oil were injected into one eye of rabbits, while the other eye served as untreated or sham control. Ophthalmic assessments, including electroretinography, were performed. Levels of glutathione and ascorbic acid were higher in the eyes treated with the antioxidant-loaded hydrogel vitreous substitute, although this was not found to be significant after 28 days. There were no statistically significant differences between groups with respect to clinical examination, and ocular health scores, electroretinograms, and histology were normal. These results indicate minimal concerns for the hydrogel formulation or high levels of antioxidants. Future research will assess the capability of vitreous substitutes to prolong antioxidant release, with the goal of minimizing cataract after vitrectomy.