Effect of crosslinking concentration on properties of 3-(trimethoxysilyl) propyl methacrylate/N-vinyl pyrrolidone gels

Gold nanostructures on polyelectrolyte-brush-modified cellulose membranes as a synergistic platform for uric acid detection

In this study, we present a convenient approach utilizing gold nanostructures coated cellulose membrane for the quantification of uric acid in an aqueous solution. The synthesis of system was achieved by functionalizing cellulose membrane with poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride (PMETAC) and cross-linked with ethylene glycol dimethacrylate (EGDMA). FT-IR and XPS confirm the formation of PMETAC and PMETAC/EGDMA on the cellulose. The fabricated substrates were exposed to tetrachloroaurate solution, then reduced by NaBH4. We have systematically investigated the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2) in various pH conditions, absent uric acid, using the fabricated substrates. The colorimetric response-observed through UV-Vis spectroscopy-revealed significant shifts in absorbance at 660 nm, correlating with uric acid concentrations across a range of pH levels. The films exhibited a pronounced color change from green to light yellow in basic to neutral environments and from yellow to dark green under more acidic conditions, demonstrating their potential for high-sensitivity uric acid detection. The assessment of the catalytic films' reusability and stability revealed insights into their enduring performance, identifying opportunities for enhancing material design and functionality for extended applications. This study not only underscores the films' versatile detection capabilities but also emphasizes the importance of pH in tuning the assay's sensitivity and specificity.

Biocide physically cross-linked hydrogels based on carrageenan and guanidinium polyampholytes for wound healing applications

Over last years, hydrogels based on natural polymers have attracted considerable interest as materials for wound healing. Herein, hydrogel films based on kappa-carrageenan and guanidinium polyampholytes were prepared by the in situ physical cross-linking with potassium chloride and borax, respectively. The polyampholytes were obtained by a free radical copolymerization of 2,2-diallyl-1,1,3,3-tetraethylguanidinium chloride and unsaturated acids. To characterize the composite films, NMR, FTIR, SEM, TGA, XRD, element analysis and tensile test were used. Ampicillin was incorporated into the hydrogels to enhance wound healing potential. The healing-related characteristics, including swelling ratio, drug release and antimicrobial activity, were assessed. The equilibrium swelling ratios were in the range of 3.9-6.5 depending on the polyampholyte composition. According to the in vitro ampicillin release studies, 30-43 % of ampicillin was released from the hydrogels after 5 h at 37 °C and pH 7.4, with drug release being temperature and pH dependent. The ampicillin-loaded films showed a remarkable antimicrobial effect. The inhibition sizes for Escherichia coli and Staphylococcus aureus were 1.10-1.85 and 1.95-2.60 cm, respectively. Although the bi-polymeric hydrogels were thoroughly characterized, with the in vitro study of their biocidal effects carried out in this work, the in vivo drug release assessment needs to be further explored.

Highly swellable, cytocompatible and biodegradeable guar gum-based hydrogel system for controlled release of bioactive components of liquorice (Glycyrrhiza glabra L.): Synthesis and evaluation

Glycyrrhiza glabra Linn (liquorice) has been widely used for therapeutic purposes to treat digestive disorders, immunomodulatory disorders, inflammatory disorders, diabetes, viral infections, and cancer. Liquorice contains a wide variety of bioactive compounds, including glycyrrhizin, flavonoids, and terpenoids. Several factors compromise their therapeutic efficacy, such as poor pharmacokinetic profiles and physicochemical properties. Therefore, to improve its overall effectiveness, liquorice solid dispersion (LSD) was incorporated into biopolymer-based guar gum-grafted-2-acrylamido-2-methylpropane sulfonic acid (Guar gum-g-AMPS) hydrogels designed for controlled delivery via the oral route and characterized. The qualitative analysis of LSD revealed 51 compounds. Hydrogel structural properties were assessed for their effect on swelling and release. The highest swelling ratio (6413 %) and drug release (84.12 %) occurred at pH 1.2 compared to pH 7.4 (swelling ratio of 2721 % and drug release of 79.36 %) in 48 h. The hydrogels exhibited high porosity (84.23 %) and biodegradation (9.30 % in 7 days). In vitro hemolysis tests have demonstrated the compatibility of the hydrogel with blood. CCK-8 assay confirmed the biocompatibility of the synthesized hydrogel using osteoblasts and RIN-m5f cells. LSD exhibited good anti-inflammatory activity when loaded into hydrogels after being subjected to protein denaturation experiments. Moreover, LSD-loaded hydrogels have good antioxidant and antibacterial properties.

Characterization of materials used for 3D printing dental crowns and hybrid prostheses

OBJECTIVES

To compare the filler weight percentage (wt%), filler and resin composition, flexural strength, modulus, and hardness of several 3D-printed resins to direct and indirect restorative materials.

MATERIALS AND METHODS

Four 3D-printed resins (C&B MFH, Ceramic Crown, OnX, and OnX Tough), one milled resin composite (Lava Ultimate), one conventional composite (Filtek Supreme), and one ceramic (IPS e.max CAD) were evaluated. Filler wt% was determined by the burned ash technique, and filler particle morphology and composition were analyzed by scanning electron microscopy and energy-dispersive spectroscopy, respectively. Organic resin composition was analyzed by Fourier transform infrared spectroscopy. Three-point bend flexural strength and modulus of the materials were determined by ISO 4049 or ISO 6872. Vickers microhardness was measured. Data were compared with a one-way analysis of variance (ANOVA) and Tukey post hoc analysis. Linear regression analysis was performed for filler wt% versus flexural strength, modulus, and hardness.

RESULTS

3D-printed resins were composed of various sized and shaped silica fillers and various types of methacrylate resins. Significant differences were found among filler wt% with some materials around 3% (C&B MFH), others between 33% and 38% (OnX Tough and OnX), others around 50% (Ceramic Crown), and some around 72% (Filtek Supreme and Lava Ultimate). All 3D-printed resins had significantly lower flexural strength, modulus, and hardness than the conventional and milled resin composites and ceramic material (p < 0.001). Filler wt% demonstrated a linear relationship with modulus (p = 0.013, R2  = 0.821) and hardness (p = 0.018, R2  = 0.787) but not flexural strength (p = 0.056, R2  = 0.551).

CONCLUSIONS

3D-printed resins contain from 3% to 50% filler content. Filler wt% alone does not affect flexural strength, but strength may be affected by resin composition as well. Although the 3D-printed resins had lower flexural strength, modulus, and hardness than milled and conventional composite and ceramic, they demonstrated nonbrittle plastic behavior.

CLINICAL SIGNIFICANCE

The properties of 3D-printed resins vary based on their composition, which affects their clinical applications.

Development and optimisation of hydroxyapatite-polyethylene glycol diacrylate hydrogel inks for 3D printing of bone tissue engineered scaffolds

In the event of excessive damage to bone tissue, the self-healing process alone is not sufficient to restore bone integrity. Three-dimensional (3D) printing, as an advanced additive manufacturing technology, can create implantable bone scaffolds with accurate geometry and internal architecture, facilitating bone regeneration. This study aims to develop and optimise hydroxyapatite-polyethylene glycol diacrylate (HA-PEGDA) hydrogel inks for extrusion 3D printing of bone tissue scaffolds. Different concentrations of HA were mixed with PEGDA, and further incorporated with pluronic F127 (PF127) as a sacrificial carrier. PF127 provided good distribution of HA nanoparticle within the scaffolds and improved the rheological requirements of HA-PEGDA inks for extrusion 3D printing without significant reduction in the HA content after its removal. Higher printing pressures and printing rates were needed to generate the same strand diameter when using a higher HA content compared to a lower HA content. Scaffolds with excellent shape fidelity up to 75-layers and high resolution (∼200 µm) with uniform strands were fabricated. Increasing the HA content enhanced the compression strength and decreased the swelling degree and degradation rate of 3D printed HA-PEGDA scaffolds. In addition, the incorporation of HA improved the adhesion and proliferation of human bone mesenchymal stem cells (hBMSCs) onto the scaffolds. 3D printed scaffolds with 2 wt% HA promoted osteogenic differentiation of hBMSCs as confirmed by the expression of alkaline phosphatase activity and calcium deposition. Altogether, the developed HA-PEGDA hydrogel ink has promising potential as a scaffold material for bone tissue regeneration, with excellent shape fidelity and the ability to promote osteogenic differentiation of hBMSCs.

Mechanically Enhanced Soft Contact Lenses from Photodimerization Cross-Linking

In this study, we synthesized three novel acrylic monomers with a cinnamate group. We then mixed each monomer with 2-hydroxyethyl methacrylate (HEMA) to prepare soft contact lenses through bulk polymerization. Fourier transform infrared (FT-IR) and UV spectral analyses confirmed that the cinnamate group in the polymer undergoes a photodimerization reaction via UV irradiation. After UV curing, the present lenses stably maintained their shapes even in a water-swollen state and showed significantly improved mechanical properties compared to conventional lenses manufactured using a cross-linking agent. These lenses showed slightly lower water contact angles than the conventional lenses, although the water content was slightly reduced. The present photodimerization cross-linking method was found to be useful in reducing the tearability of soft lenses.

Development of Composite Sponge Scaffolds Based on Carrageenan (CRG) and Cerium Oxide Nanoparticles (CeO2 NPs) for Hemostatic Applications

In this study, a novel absorbable hemostatic agent was developed using carrageenan (CRG) as a natural polymer and cerium oxide nanoparticles (CeO2 NPs). CRG-CeO2-0.5 and CRG-CeO2-1 composites were prepared by compositing CeO2 to CRG + CeO2 at a weight ratio of 0.5:100 and 1:100, respectively. The physicochemical and structural properties of these compounds were studied and compared with pristine CRG. Upon incorporation of CeO2 nanoparticles into the CRG matrix, significant reductions in hydrogel degradation were observed. In addition, it was noted that CRG-CeO2 exhibited better antibacterial and hemostatic properties than CRG hydrogel without CeO2 NPs. The biocompatibility of the materials was tested using the NIH 3T3 cell line, and all samples were found to be nontoxic. Particularly, CRG-CeO2-1 demonstrated superior hemostatic effects, biocompatibility, and a lower degradation rate since more CeO2 NPs were present in the CRG matrix. Therefore, CRG-CeO2-1 has the potential to be used as a hemostatic agent and wound dressing.

Dual Dynamic Covalently Crosslinked Alginate Hydrogels with Tunable Properties and Multiple Stimuli-Responsiveness

Alginate is a biopolymer that can be crosslinked with calcium ions to fabricate cytocompatible hydrogels. However, using calcium ions to crosslink alginate provides limited properties and functions to alginate hydrogels, restricting their biomedical applications. Here, phenylboronic acid-functionalized polyethyleneimine (PBA-PEI) was developed to introduce two orthogonal dynamic covalent crosslinks in the alginate hydrogels, where PBA-PEI was used to crosslink alginate dialdehyde (ADA) through imine bonds and boronate ester bonds. The grafting degree of PBA in the PEI structure was applied to fine-tune the properties of PBA-PEI/ADA hydrogels, including the rheological property, mechanical strength, swelling behavior, and antibacterial activity. In particular, the highly sensitive boronate ester bonds in the network enabled PBA-PEI/ADA hydrogels to be responsive to several stimuli, such as glucose, fructose, and hydrogen peroxide. Taken together, PBA-PEI/ADA hydrogels with tunable properties and multiple stimuli-responsiveness have been demonstrated as smart biomaterials for advanced biomedical applications.

Hybrid Coatings of SiO2-Recycled PET Unsaturated Polyester Resin by Sol-Gel Process

Hybrid coatings of SiO₂ and recycled unsaturated polyester resin (R-UPR) from recycled polyethylene-terephthalate (PET) were prepared by the sol-gel process on glass substrates. First, SiO₂ was synthesized by the sol-gel process using a tetraethyl orthosilicate (TEOS) solution. Next, bis(2-hydroxypropyl-terephthalate) (BHPT) was synthesized from mechanical and chemical recycling (glycolysis) of post-consumer PET bottles in propylene glycol (PG) using ZnA as catalyst, in a Vessel-type reactor (20–200 °C); maleic anhydride (MA) was added and, following the same procedure, the unsaturated polyester (UP) was synthetized, which was cooled to room temperature. Next, styrene (St) and benzoyl-peroxide (PBO)-initiator were added to obtain R–UPR. TEOS (T) and three hybrid solutions were synthesized, with molar ratios of 0:1:0 (T), 1:2:0.25 (H1), 1:1:0.25 (H2), and 1:0:0.25 (H3) for R–UPR:TEOS:3-trimethoxy-(silyl)-propyl-methacrylate (TMSPM), respectively, with which TC, HC1, HC2, and HC3 coatings were elaborated using the immersion technique and polymerized (120 °C for 24 h). The solutions were characterized by FT–IR and TGA, and the coatings by SEM, nanoindentation, AFM, adhesion, and contact angle. The results showed that SiO₂ enhanced mechanical (hardness and Young’s modulus) and thermal properties of the R-UPR. The coatings adhered perfectly to the substrate, with thicknesses of micrometer units and a flat surface; in addition, hydrophilicity decreased as SiO₂ decreased.

Characterization and analysis of extended-wear silicone hydrogel contact lenses utilizing novel silicone macromers

Contact lenses are one of the most successful biomaterials in history with a global market estimated to be worth over $17 billion in 2025. Silicone hydrogel contact lenses dominate the market and are complex biphasic biomaterials with several critical material properties needed for clinical use. Careful consideration of composition and chemistry is needed to identify formulations of lenses meeting all commercial standards with the potential for improved manufacturability, cost, and/or next generation use. Four silicone macromers were investigated in this work with varying symmetry of siloxane units and macromer structure, number of siloxane groups, branching, length, and concentration. Novel silicone hydrogel lenses were produced and evaluated for optical transmittance, elastic modulus, oxygen transmissibility, water content, and surface wettability. Several lenses met commercial standards and demonstrated an increase in oxygen permeability (Dk) and inverse relationship with elastic modulus and siloxane concentration, respectively. A hydrophobic/hydrophilic ratio below 1.4 was needed for a co‐continuous water phase. Substitution of methoxypropyl groups for butyl groups increased hydrophobic microdomains leading to decreased optical quality and mechanical properties. Generally, fluorine‐containing silicone macromers allowed for a wider range of successful compositions, and above a certain hydrophilic composition, the presence of trifluoropropyl groups resulted in improved solubility and optically clear lenses. Data also showed asymmetric siloxane macromers have potential to meet critical lens properties at lower overall siloxane content. New lens materials with wider composition ranges meeting all clinical lens properties is a significant challenge and may significantly expand the field.

Development and characterization of a dry reservoir-hydrogel-forming microneedles composite for minimally invasive delivery of cefazolin

Cefazolin (CFZ) is one of the most extensively used cephalosporins. This antibiotic exerts its bactericidal activity by interfering with bacterial cell wall formation, leading to bacteriolysis. CFZ is highly polar, resulting in the drug having poor oral bioavailability. Accordingly, the antibiotic is administered via intramuscular or intravenous injections, which are both painful and invasive. Due to these limitations, there is an impetus to explore alternative drug delivery platforms which offer a minimally invasive approach to delivery CFZ into and across the skin. The current work presents the development of a composite pharmaceutical system composed of hydrogel-forming microneedles (MNs) in tandem with CFZ dry reservoirs. The hydrogel system was fabricated from Gantrez® S-97 and Carbopol® 974P NF crosslinked with PEG 10,000. Swelling kinetic studies showed that the hydrogel system developed was capable of achieving 4000% swelling in PBS pH 7.4. In addition, results from a solute diffusion study showed that CFZ was able to achieve ≈100% cumulative permeation across the swollen hydrogel film. When formulated into MNs, the hydrogel system was capable of breaching the stratum corneum, resulting in intradermal insertion of the hydrogel forming MNs into ex vivo neonatal porcine skin, as evidenced from optical coherence tomography. In addition, two different CFZ loaded dry reservoirs consisting of directly compressed tablets (DCT) and lyophilised (LYO) wafers were formulated and characterised. These dry reservoir systems showed fast dissolution, dissolving in phosphate buffer saline pH 7.4 in less than one minute. In vitro permeation studies, using full thickness ex vivo neonatal porcine skin were conducted. HPLC analysis demonstrated the dry reservoir combination consisting of DCT with hydrogel-forming MNs was capable of achieving up to 80 µg CFZ delivery into the epidermis within 2 hours of application. In addition, DCT reservoir coupled with hydrogel-forming MNs were able to deliver CFZ up to 1.8 mg into and across the skin at 24 hours. Should this system be translated into clinical practice, it may provide a minimally invasive strategy to administer CFZ for the treatment of infections such as septic arthritis, osteomyelitis and cellulitis.

Physicochemical Characteristics of Chitosan-Based Hydrogels Modified with Equisetum arvense L. (Horsetail) Extract in View of Their Usefulness as Innovative Dressing Materials

This work focused on obtaining and characterizing hydrogels with their potential application as dressing materials for chronic wounds. The research included synthesizing chitosan-based hydrogels modified with Equisetum arvense L. (horsetail) extract via photopolymerization, and their characteristics determined with regard to the impact of both the modifier and the amount of crosslinker on their properties. The investigations included determining their sorption properties and tensile strength, evaluating their behavior in simulated physiological liquids, and characterizing their wettability and surface morphology. The release profile of horsetail extract from polymer matrices in acidic and alkaline environments was also verified. It was proved that hydrogels showed swelling ability while the modified hydrogels swelled slightly more. Hydrogels showed hydrophilic nature (all contact angles were <77°). Materials containing horsetail extract exhibited bigger elasticity than unmodified polymers (even by 30%). It was proved that the extract release was twice as effective in an acidic medium. Due to the possibility of preparation of hydrogels with specific mechanical properties (depending on both the modifier and the amount of crosslinker used), wound exudate sorption ability, and possibility of the release of active substance, hydrogels show a great application potential as dressing materials.

PEG-crosslinked-chitosan hydrogel films for in situ delivery of Opuntia ficus-indica extract

In the present study, chitosan-based wound dressings loaded with the extract of Opuntia ficus-indica (OPU) were prepared. OPU is known for its capability to accelerate skin injury repair. Chitosan (Ch) was crosslinked with a low molecular weight diepoxy-poly(ethylene glycol) (diePEG), and hydrogel films with different Ch/PEG composition and OPU content were prepared by casting. The occurrence of crosslinking reaction was confirmed by FTIR spectroscopy. FTIR and DSC analysis suggested that ionic interactions occur between chitosan and OPU. Tensile tests evidenced that the crosslinking caused a decrease of Young's modulus, which approaches the value of the human skin modulus. Swelling characteristics, water vapor transmission rate, and release kinetics demonstrated that these films are adequate for the proposed application. Finally, a scratch test on a keratinocytes monolayer showed that the rate of cell migration in the presence of OPU-loaded samples is about 3-fold higher compared to unloaded films, confirming the repairing activity of OPU.

Double-Crosslinked Polyurethane Acrylate for Highly Conductive and Stable Polymer Electrolyte

High ionic conductivity and good stability are major factors that influence the use of polymer electrolytes in electrochemical storage and conversion devices. In this study, we present polyurethane acrylate (PUA) membranes having enhanced ionic conductivity and swelling stability by double crosslinking the polyurethane (PU) and polyacrylate (PA) compartments. The crosslinking agent concentration was varied to control their mechanical properties, swelling stability, and ionic conductivity. Under optimum conditions, the electrolyte uptake of the double-crosslinked PUA membranes without notable defects was 245%. The maximum ionic conductivity of these membranes reached 9.6 mS/cm, which was higher than those with respect to most of the previously reported PUA- or PU-based polymer electrolytes.