Effect of degree of cross-linking on swelling and on drug release of low viscous chitosan/poly(vinyl alcohol) hydrogels

Synergistic effects of starch and carrageenan from Kappaphycus alvarezii in composite film formation: Physicochemical and degradable properties

Rising concerns around plastic pollution from single-use plastic (SUPs), especially food packaging, have driven interest in sustainable alternatives. As such, algae biomass has gained attention for bioplastic production due to algae's rapid growth and abundant polysaccharides. This research focuses on extracting carrageenan from Kappaphycus alvarezii, extensively cultivated in Sabah, Malaysia, and utilizing it in combination with starch and glycerol to develop algae-based films. The physicochemical properties and degradation rate of these films were evaluated, revealing that the addition of carrageenan enhanced overall thermal stability meanwhile increasing water solubility, water content but reducing the degradation rate and swelling degree. This is primarily due to the crystalline structures of carrageenan, which provide a more rigid arrangement compared to the network of starch polymers. However, the incorporation of starch into the blends has enhanced the elongation and surface morphology, resulting in more balanced properties. Overall, these carrageenan films displayed impressive thermal, mechanical, and biodegradability characteristics, establishing their viability as substitutes for conventional plastics.

Doxorubicin-loaded liposome-like particles embedded in chitosan/hyaluronic acid-based hydrogels as a controlled drug release model for local treatment of glioblastoma

Glioblastoma (GBM) resection and medication treatment are limited, and local drug therapies are required. This study aims to create a hybrid system comprising liposome-like particles (LLP-DOX) encapsulated in chitosan/hyaluronic acid/polyethyleneimine (CHI/HA/PEI) hydrogels, enabling controlled local delivery of doxorubicin (DOX) into the resection cavity for treating GBM. CHI/HA/PEI hydrogels were characterized morphologically, physically, chemically, mechanically, and thermally. Findings revealed a high network and compact micro-network structure, along with enhanced physical and thermal stability compared to CHI/HA hydrogels. Simultaneously, drug release from CHI/HA/PEI/LLP-DOX hydrogels was assessed, revealing continuous and controlled release up to the 148th hour, with no significant burst release. Cell studies showed that CHI/HA/PEI hydrogels are biocompatible with low genotoxicity. Additionally, LLP-DOX-loaded CHI/HA/PEI hydrogels significantly decreased cell viability and gene expression levels compared to LLP-DOX alone. It was also observed that the viability of GBM spheroids decreased over time when interacting with CHI/HA/PEI/LLP-DOX hydrogels, accompanied by a reduction in total surface area and an increase in apoptotic tendencies. In this study, we hypothesized that creating a hybrid drug delivery system by encapsulating DOX-loaded LLPs within a CHI/HA/PEI hydrogel matrix could achieve sustained drug release, improve anticancer efficacy via localized treatment, and effectively mitigate GBM progression for 3D microtissues.

Electron beam irradiation developed cinnamon oil- (polyvinyl alcohol/gum tragacanth)/graphene oxide dressing hydrogels: Antimicrobial and healing assessments

This study aimed to develop hydrogel dressings for wound healing composed of gum tragacanth (TG) and polyvinyl alcohol (PVA) loaded with Graphene oxide (GO) and Cinnamon oil (CMO) using electron beam irradiation. The impact of the preparation conditions and the incorporation of GO and CMO on the characteristic properties of the prepared CMO-(PVA/TG)-GO wound dressings was evaluated. The healing-related characteristics were assessed, including fluid absorption and retention, water vapor transmission rate (WVTR), hemolytic assay, and antimicrobial potential. Wound healing efficacy was evaluated using a scratch wound healing assay. FTIR analysis verified the chemical structure, whereas scanning electron microscopy demonstrated an appropriate porosity structure necessary for optimal wound healing. The gel content increases with the initial total polymer concentration and the irradiation dose increases. Higher GO and CMO content improve the gel content and decreases swelling. WVTR decreases with the rise in CMO content. In vitro, cytotoxicity and hemolytic potency assessments confirmed their biocompatibility. The incorporation of GO and CMO enhances the antimicrobial activity and wound-healing capability. Based on the above findings, CMO-(PVA/TG)-GO dressings show promising potential as candidates for wound care.

Transdermal drug delivery of rizatriptan using microneedles array patch: preparation, characterization and ex-vivo/in-vivo study

Given the extensive first pass metabolism of rizatriptan in oral administration and its delayed absorption during a migraine attack as a result of gastric stasis, focus has been on transdermal delivery. The main purpose of this study is to prepare and assess transdermal formulation of rizatriptan, loaded on hydrogel microneedles delivery system, to avoid first pass metabolism and also improve its percutaneous permeation rate. Rizatriptan hydrogel microneedles were prepared using micromolding method and evaluated in terms of mechanical strength, encapsulation efficiency, permeation and in-vivo skin absorption. Different formulations of rizatriptan microneedles (F1-F5) were successfully prepared using different concentrations of carboxymethyl cellulose and gelatin type A. Rizatriptan hydrogel microneedles demonstrated favorable mechanical properties, including withstanding insertion forces, thereby enhancing its skin insertion ability. In permeation study, the percent cumulative drug released after 24 h ranged between 93.1-100% which means that microneedles were able to deliver the drug effectively. For in-vivo study, F3 formulation was selected due to its superior characteristics over other formulations as it exhibited the highest swelling capacity, and demonstrated favorable mechanical properties. Furthermore, F3 showcased the most controlled drug release over a 24-hour period. Relative bioavailability of F3 microneedles was 179.59% compared to oral administration based on the AUC0-24. The observed AUC0-24 in F3 microneedles was statistically significant and 1.80 times greater than that in oral administration. The higher rizatriptan level in the microneedle demonstrated adequate drug permeability through the rat skin, suggesting the potential of microneedles for enhanced therapeutic effectiveness.

Fabrication of 3D printed mutable drug delivery devices: a comparative study of volumetric and digital light processing printing

Mutable devices and dosage forms have the capacity to dynamically transform dimensionally, morphologically and mechanically upon exposure to non-mechanical external triggers. By leveraging these controllable transformations, these systems can be used as minimally invasive alternatives to implants and residence devices, foregoing the need for complex surgeries or endoscopies. 4D printing, the fabrication of 3D-printed structures that evolve their shape, properties, or functionality in response to stimuli over time, allows the production of such devices. This study explores the potential of volumetric printing, a novel vat photopolymerisation technology capable of ultra-rapid printing speeds, by comparing its performance against established digital light processing (DLP) printing in fabricating hydrogel-based drug-eluting devices. Six hydrogel formulations consisting of 2-(acryloyloxy)ethyl]trimethylammonium chloride solution, lithium phenyl-2,4,6-trimethylbenzoylphosphinate, varying molecular weights of the crosslinking monomer, poly(ethylene glycol) diacrylate, and paracetamol as a model drug were prepared for both vat photopolymerisation technologies. Comprehensive studies were conducted to investigate the swelling and water sorption profiles, drug release kinetics, and physicochemical properties of each formulation. Expandable drug-eluting 4D devices were successfully fabricated within 7.5 s using volumetric printing and were shown to display equivalent drug release kinetics to prints created using DLP printing, demonstrating drug release, swelling, and water sorption properties equivalent to or better than those of DLP-printed devices. The reported findings shed light on the advantages and limitations of each technology for creating these dynamic drug delivery systems and provides a direct comparison between the two technologies, while highlighting the promising potential of volumetric printing and further expanding the growing repertoire of pharmaceutical printing.

Fabrication, optimization, and in vitro validation of penicillin-loaded hydrogels for controlled drug delivery

Bacterial infections present a major global challenge. Penicillin, a widely used antibiotic known for its effectiveness and safety, is frequently prescribed. However, its short half-life necessitates multiple high-dose daily administrations, leading to severe side-effects. Therefore, this study aims to address these issues by developing hydrogels which control the release of penicillin and alleviate its adverse effects. Various combinations of aspartic acid and acrylamide were crosslinked by N', N'-methylene bisacrylamide through a free radical polymerization process to prepare aspartic acid/acrylamide (Asp/Am) hydrogels. The fabricated hydrogels underwent comprehensive characterization to assess physical properties and thermal stability. The soluble and insoluble fractions and porosity of the synthesized matrix were evaluated by sol-gel and porosity studies. Gel fraction was estimated at 88-96%, whereas sol fraction was found 12-4% and porosity found within the 63-78% range for fabricated hydrogel formulations. Maximum swelling and drug release were seen at pH 7.4, demonstrating a controlled drug release from hydrogel networks. The results showed that swelling, porosity, gel fraction, and drug release increased with higher concentrations of aspartic acid and acrylamide. However, integration of N', N'-methylene bisacrylamide exhibited the opposite effect on swelling and porosity, while increasing gel fraction. All formulations followed the Korsymer-Peppas model of kinetics with 'r' values within the range of 0.9740-0.9980. Furthermore, the cytotoxicity study indicated an effective and safe use of hydrogel because the cell viability was higher than 70%. Therefore, these prepared hydrogels show promise candidates for controlled release of Penicillin and are anticipated to be valuable in clinical applications.

Development and characterization of curcumin nanosuspension-embedded genipin-crosslinked chitosan/polyvinylpyrrolidone hydrogel patch for effective wound healing

This study investigated the development of a genipin-crosslinked chitosan (CS)-based polyvinylpyrrolidone (PVP) hydrogel containing curcumin nanosuspensions (Cur-NSs) to promote wound healing in an excisional wound model. Cur-NSs were prepared, and a simplex centroid mixture design was employed to optimize hydrogel properties for high water absorption, degree of crosslinking, and sufficient toughness. The in vivo wound healing effect was tested in Wistar rats. The optimized hydrogel consisted of a 70:30 ratio of CS:PVP, crosslinked with a 2 % w/w genipin solution. It exhibited high swelling capability (486 %) while maintaining solidity, robustness, and durability. Incorporating 5 % w/w Cur-NSs resulted in a more compact structure, although with a reduction in swelling properties. The release kinetics of Cur from the hydrogel followed the Korsmeyer-Peppas Fickian diffusion model. In vitro biocompatibility studies demonstrated that the hydrogel was non-toxic to skin fibroblast cells. The in vivo experiment revealed a desirable wound healing rate with over 80 % recovery by day 7. Cur-NSs likely aided wound healing by reducing the inflammatory response and stimulating fibroblast proliferation. Additionally, the CS-based hydrogel provided a moist wound environment with hydration and gas transfer, further accelerating wound closure. These findings suggest that the Cur-NS-embedded hydrogel shows promise as a wound dressing material.

Design of gelatin cryogel scaffolds with the ability to release simvastatin for potential bone tissue engineering applications

Tissue engineering aims to improve or restore damaged tissues by using scaffolds, cells and bioactive agents. In tissue engineering, one of the most important concepts is the scaffold because it has a key role in keeping up and promoting the growth of the cells. It is also desirable to be able to load these scaffolds with drugs that induce tissue regeneration/formation. Based on this, in our study, gelatin cryogel scaffolds were developed for potential bone tissue engineering applications and simvastatin loading and release studies were performed. Simvastatin is lipoliphic in nature and this form is called inactive simvastatin (SV). It is modified to be in hydrophilic form and converted to the active form (SVA). For our study's drug loading and release process, simvastatin was used in both inactive and active forms. The blank cryogels and drug-loaded cryogels were prepared at different glutaraldehyde concentrations (1, 2, and 3%). The effect of the crosslinking agent and the amount of drug loaded were discussed with morphological and physicochemical analysis. As the glutaraldehyde concentration increased gradually, the pores size of the cryogels decreased and the swelling ratio decreased. For the release profile of simvastatin in both forms, we can say that it depended on the form (lipophilic and hydrophilic) of the loaded simvastatin.

Construction of Dome-Shaped 3D Corneal Epithelial Tissue Models Based on Eyeball-Shaped Gel Microspheres

By overcoming interspecies differences and mimicking the in vivo microenvironment, three-dimensional (3D) in vitro corneal models have become a significant novel tool in contemporary ophthalmic disease research. However, existing 3D corneal models struggle to replicate the actual human corneal environment, especially the dome-shaped physiological structure with adjustable curvature. Addressing these challenges, this study introduces a straightforward method for fabricating collagen/chitosan-alginate eyeball-shaped gel microspheres with a Janus structure via a two-phase aqueous system, used subsequently to construct in vitro 3D corneal epithelial tissue models. By adjusting the diameter ratio of collagen/chitosan to alginate droplets, we can create eyeball-shaped gel microspheres with varying curvatures. Human corneal epithelial cells were seeded on the surfaces of these microspheres, leading to the formation of in vitro 3D corneal epithelial tissues characterized by dome-like multilayers and tight junctions. Additionally, the model demonstrated responsiveness to UVB exposure through the secretion of reactive oxygen species (ROS) and proinflammatory factors. Therefore, we believe that in vitro 3D corneal epithelial tissue models with dome-shaped structures hold significant potential for advancing ophthalmic research.

Photocrosslinked gelatin/chondroitin sulfate/chitosan-based composites with tunable multifunctionality for bone tissue regeneration

Novel hydrogel-based multifunctional systems prepared utilizing photocrosslinking and freeze-drying processes (PhotoCross/Freeze-dried) dedicated for bone tissue regeneration are presented. Fabricated materials, composed of methacrylated gelatin, chitosan, and chondroitin sulfate, possess interesting features including bioactivity, biocompatibility, as well as antibacterial activity. Importantly, their degradation and swellability might be easily tuned by playing with the biopolymeric content in the photocrosllinked systems. To broaden the potential application and deliver the therapeutic features, mesoporous silica particles functionalized with methacrylate moieties decorated with hydroxyapatite and loaded with the antiosteoporotic drug, alendronate, (MSP-MA-HAp-ALN) were dispersed within the biopolymeric sol and photocrosslinked. It was demonstrated that the obtained composites are characterized by a significantly extended degradation time, ensuring optimal conditions for balancing hybrids removal with the deposition of fresh bone. We have shown that attachment of MSP-MA-HAp-ALN to the polymeric matrix minimizes the initial burst effect and provides a prolonged release of ALN (up to 22 days). Moreover, the biological evaluation in vitro suggested the capability of the resulted systems to promote bone remodeling. Developed materials might potentially serve as scaffolds that after implantation will fill up bone defects of various origin (osteoporosis, tumour resection, accidents) providing the favourable conditions for bone regeneration and supporting the infections' treatment.

Formulation and In Vitro Assessment of Polymeric pH-Responsive Nanogels of Chitosan for Sustained Delivery of Madecassoside

Madecassoside, a triterpenoid saponin compound mainly isolated from the gotu kola herb (Centella asiatica), shows an extensive range of biological activities, including antiapoptotic, antioxidant, anti-inflammatory, moisturizing, neuroprotective, and wound healing effects. It has been highly used in the management of eczema, skin wounds, and other diseases. Due to poor oral bioavailability, membrane permeability, and intestinal absorption, the clinical application of the madecassoside is limited. Hence, a drug carrier system is needed that not only sustains the release of the madecassoside but also overcomes the drawbacks associated with its administration. Therefore, the authors prepared novel pH-responsive chitosan-based nanogels for the sustained release of madecassoside. Free radical polymerization technique was used for cross-linking of polymer chitosan and monomer methacrylic acid in the presence of cross-linker N',N'-methylene bis(acrylamide). The decrease in polymer crystallinity after polymerization and development of nanogels was demonstrated by XRD and FTIR analysis. The effects of nanogel contents on polymer volume, sol-gel analysis, swelling, drug loading, and release were investigated. Results indicated that high swelling and maximum release of the drug occurred at pH 7.4 compared to pH 1.2 and 4.6, indicating the excellent pH-sensitive nature of the engineered nanogels. High swelling and drug release were perceived with the integration of a high quantity of chitosan, while a decline was observed with the high integration of N',N'-methylene bis(acrylamide) and methacrylic acid contents. The same effects of nanogel contents were shown for drug loading too. Sol fraction was reduced, while gel fraction was enhanced by increasing the chitosan load, N',N'-methylene bis(acrylamide), and methacrylic acid. The Korsmeyer-Peppas model of kinetics was trailed by all nanogel formulations with non-Fickian diffusion. The results demonstrated that prepared nanogels can be employed for sustained release of the madecassoside.

Synthesis and characterization of an innovative sodium alginate/polyvinyl alcohol bioartificial hydrogel for forward-osmosis desalination

Recently, hydrogels have been widely applied as draw agents in forward osmosis (FO) desalination. This work aims to synthesize bioartificial hydrogel from a blend of sodium alginate (SA) and polyvinyl alcohol (PVA) using epichlorohydrin (ECH) as a crosslinker. Then this prepared hydrogel was applied as a draw agent with cellulose triacetate membrane in a batch (FO) cell. The effects of the PVA content in the polymer blend and the crosslinker dose on the hydrogel's swelling capacity were investigated to optimize the hydrogel's composition. Furthermore, the water flux and the reverse solute flux of the optimum SA/PVA hydrogel were evaluated in a batch (FO) unit under the effect of the hydrogel's particle size, feed solution (FS) temperature, FS concentration, and membrane orientation. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and compression strength tests were used to characterize the prepared hydrogel. Results revealed that the equilibrium swelling ratio (%) of 5228 was achieved with a hydrogel that had 25% PVA and a crosslinking ratio of 0.8. FO experiments revealed that the maximum water flux of 0.845 LMH achieved, when distilled water was used as FS, average hydrogel's particle size was 60 µm, and the FS temperature was 40 °C.

Smart Free-Standing Bilayer Polyacrylamide/DNA Hybrid Hydrogel Film-Based Sensing System Using Changes in Bending Angles as a Visual Signal Readout

Stimuli-responsive DNA hydrogels have shown great potential in sensing applications due to their attractive properties such as programmable target responsiveness, excellent biocompatibility, and biodegradability. In contrast to the extensively developed DNA hydrogel sensing systems based on the stimuli-responsive hydrogel-to-solution phase transition of the hydrogel matrix, the quantitative sensing application of DNA hydrogels exhibiting smart shape deformations has rarely been explored. Moreover, bulk DNA hydrogel-based sensing systems also suffer from high material cost and slow response. Herein, free-standing bilayer polyacrylamide/DNA hybrid hydrogel films with programmable responsive properties directed by the sequence of functional DNA units have been constructed. Compared with bulk DNA hydrogels, these DNA hydrogel films with a thickness at the micrometer scale not only greatly reduce the consumption of DNA materials but also facilitate the mass transfer of biomacromolecular substances within the hydrogel network, thus favoring their sensing applications. Therefore, a target-responsive smart DNA hydrogel film-based sensor system is further demonstrated based on the large amplitude macroscopic shape deformation of the film as a visual signal readout. As a proof of concept, Pb2+ or UO22+ ion-responsive DNA units were introduced into the active layer of the bilayer hydrogel films. In the presence of Pb2+ or UO22+ ions, the occurrence of a cleavage reaction within the DNA units leads to the release of DNA segments from the hydrogel film, inducing a dramatic shape deformation of the film, and thus sensing of Pb2+ or UO22+ ions with high specificity is achieved based on measuring the bending angle changes of these smart free-standing films. These smart DNA hydrogel film sensors with target-programmable responsiveness, simple operation, and ease of storage may hold promise for future rapid on-site testing applications.

MOF/MXene-loaded PVA/chitosan hydrogel with antimicrobial effect and wound healing promotion under electrical stimulation and improved mechanical properties

Electrical stimulation modulates cell behavior and influences bacterial activity, so highly conductive, antimicrobial hydrogels are suitable for promoting wound healing. In this study, highly conductive and antimicrobial Ti3C2Tx (MXene) hydrogels composed of chitosan and poly(vinyl alcohol) and AgCu- H2PYDC MOF were developed. In PVACS/MOF/MXene (PCMM) hydrogels, the MXene layer acts as an electrical conductor. The electrical conductivity is 0.61 ± 0.01 S·cm-1. PCMM hydrogels modulate cell behavior and provide ES antimicrobial capacity under ES at 1 V. The metal ions of MOF form coordination with chitosan molecules and increase the cross-linking density between chitosan molecules, thus improving the mechanical properties of the hydrogel (tensile strength 0.088 ± 0.04 MPa, elongation at break 233 ± 11 %). The PCMM gels had good biocompatibility. The PCMM hydrogels achieved 100 % antibacterial activity against E. coli and S. aureus for 12 h. 1 V electrical stimulation of PCMM hydrogel accelerated the wound healing process in mice by promoting cell migration and neovascularization, achieving 97 ± 0.4 % wound healing on day 14. The hydrogel dressing PCMM-0.1 with MOF addition of 0.1 % had the best wound healing promoting effect and which is a promising dressing for promoting wound healing and is a therapeutic strategy worth developing.

Rhizobial oxidized 3-hydroxylbutanoyl glycan-based gelatin hydrogels with enhanced physiochemical properties for pH-responsive drug delivery

Rhizobial exopolysaccharide (EPS) is an acidic polysaccharide involved in nitrogen fixation-related signal transduction in the rhizosphere, serving as a structural support for biofilms, and protecting against various external environmental stresses. Rhizobial EPS as a hydrogel biomaterial was used for a pH-responsive drug delivery system combing with gelatins. Pure gelatin (GA) hydrogels have limited practical applications due to their poor mechanical strength and poor thermal stability. We developed new GA hydrogels using oxidized 3-hydroxylbutanoyl glycan (OHbG) as a polymer cross-linking agent to overcome these limitations. OHbG was synthesized from sodium periodate oxidation of 3-hydroxylbutanoyl glycan directly isolated from Rhizobium leguminosarum bv. viciae VF39. The newly fabricated OHbG/GA hydrogels exhibited 21-fold higher compressive stress and 4.7-fold higher storage modulus (G') than GA at the same strain. This result suggested that OHbG provided mechanical improvement. In addition, these OHbG/GA hydrogels showed effective pH-controlled drug release for 5-fluorouracil, self-healable, and self-antioxidant capacity by uronic acids of OHbG. Cell viability tests using HEK-293 cells in vitro also showed that the OHbG/GA hydrogels were non-toxic. This suggests that the new OHbG/GA hydrogels can be used as a potentially novel biomaterial for drug delivery based on its self-healing ability, antioxidant capacity, and pH-responsive drug delivery.

Probing the influence of crosslinkers on the properties, response, and degradation of enzymatic hydrogels for electrochemical glucose biosensing through fluorescence analysis

Drop-cast crosslinked hydrogels are a common platform for enzymatic electrochemical biosensors. Despite the widespread use of these complex systems, there are still several questions about how their physicochemical properties affect their performance, stability, and reproducibility. In this work, first-generation faradaic biosensors composed of glucose oxidase and branched polyethyleneimine (BPEI) are prepared using either glutaraldehyde (GA) or ethylene glycol diglycidyl ether (EGDGE) as crosslinkers. While EGDGE gels present an increasing electrochemical response with increasing crosslinker concentration, the current of GA gels decreases at high crosslinker concentration probably due to the hampered diffusion on tightly networked gels. We compared different strategies to use fluorescence microscopy to gain insight into the gel structure either by labeling the gel components with fluorophores or taking advantage of the intrinsic fluorescence of the imines formed upon crosslinking with GA. By monitoring the fluorescence of the crosslinking bonds and the electrochemical response, we demonstrate that hydrolysis, a common hydrogel degradation mechanism, is not responsible for the loss of electrical current over time in gels prepared with glutaraldehyde. Most hydrogel-based electrochemical biosensor studies do not perform specific experiments to determine the cause of the degradation and instead just infer it from the dependence of the current on the preparation conditions (most commonly concentrations). We show that, by taking advantage of several analytical techniques, it is possible to gain more knowledge about the degradation mechanisms and design better enzymatic biosensors.

Chitosan Poly(vinyl alcohol) Methacrylate Hydrogels for Tissue Engineering Scaffolds

A major challenge in tissue engineering scaffolds is controlling scaffold degradation rates during healing while maintaining mechanical properties to support tissue formation. Hydrogels are three-dimensional matrices that are widely applied as tissue scaffolds based on their unique properties that can mimic the extracellular matrix. In this study, we develop a hybrid natural/synthetic hydrogel platform to tune the properties for tissue engineering scaffold applications. We modified chitosan and poly(vinyl alcohol) (PVA) with photo-cross-linkable methacrylate functional groups and then synthesized a library of chitosan PVA methacrylate hydrogels (ChiPVAMA) with two different photoinitiators, Irgacure 2959 (I2959) and lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP). ChiPVAMA hydrogels showed tunability in degradation rates and mechanical properties based on both the polymer content and photoinitiator type. This tunability could enable their application in a range of tissue scaffold applications. In a 2D scratch wound healing assay, all hydrogel samples induced faster wound closure compared to a gauze clinical wound dressing control. NIH/3T3 cells encapsulated in hydrogels showed a high viability (∼92%) over 14 days, demonstrating the capacity of this system as a supportive cell scaffold. In addition, hydrogels containing a higher chitosan content demonstrated a high antibacterial capacity. Overall, ChiPVAMA hydrogels provide a potential tissue engineering scaffold that is tunable, degradable, and suitable for cell growth.

Ibuprofen-Loaded Silver Nanoparticle-Doped PVA Gels: Green Synthesis, In Vitro Cytotoxicity, and Antibacterial Analyses

In contrast to conventional drug delivery systems, controlled drug release systems employ distinct methodologies. These systems facilitate the release of active substances in predetermined quantities and for specified durations. Polymer hydrogels have gained prominence in controlled drug delivery because of their unique swelling-shrinkage behavior and ability to regulate drug release. In this investigation, films with a hydrogel structure were crafted using polyvinyl alcohol, a biocompatible polymer, and silver nanoparticles. Following characterization, ibuprofen was loaded into the hydrogels to evaluate their drug release capacity. The particle sizes of silver nanoparticles synthesized using a green approach were determined. This study comprehensively examined the structural properties, morphological features, mechanical strength, and cumulative release patterns of the prepared films. In vitro cytotoxicity analysis was employed to assess the cell viability of drug-loaded hydrogel films, and their antibacterial effects were examined. The results indicated that hydrogel films containing 5% and 10% polyvinyl alcohol released 89% and 97% of the loaded drug, respectively, by day 14. The release kinetics fits the Korsmeyer-Peppas model. This study, which describes nanoparticle-enhanced polyvinyl alcohol hydrogel systems prepared through a cost-effective and environmentally friendly approach, is anticipated to contribute to the existing literature and serve as a foundational study for future research.

Preparation, Swelling, and Drug Release Studies of Chitosan-based Hydrogels for Controlled Delivery of Buspirone Hydrochloride

BACKGROUND

Buspirone is used for the management of depression and anxiety disorders. Due to its short half-life and low bioavailability, it requires multiple daily doses and is associated with some side effects.

AIM

This study aimed to develop chitosan-based hydrogels as drug-controlled release carriers.

OBJECTIVE

The objective of this study is to prepare chitosan-based hydrogels as controlled release carriers in order to overcome the side effects of buspirone HCl and improve patients' compliance and their life quality.

METHODS

Polymer chitosan was polymerized with two monomers, acrylic acid and itaconic acid, to synthesize pH-sensitive hydrogel. The Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis were performed to confirm the structure formation and thermal stability. Water penetration capability and loading of the drug were performed by porosity and drug loading studies. The swelling and dissolution tests were performed to analyze the pH-sensitive nature of the developed hydrogels.

RESULTS

FTIR, TGA, and DSC demonstrated that the chitosan-based hydrogels were successfully prepared. An increase in water penetration and drug loading into the hydrogel network was seen with the high incorporation of chitosan, acrylic acid, and itaconic acid. The swelling and dissolution studies revealed that prepared hydrogel offered the greatest swelling and drug release at a high pH of 7.4. The swelling and drug release from the hydrogel were affected by the concentrations of the incorporated contents. A controlled release of the drug was achieved by using chitosan-based hydrogel as a delivery carrier compared to commercial tablets of buspirone.

CONCLUSION

The results showed that the developed chitosan-based hydrogel can be considered one of the most suitable drug carrier systems for the controlled delivery of buspirone.

Nano-residronate loaded κ-carrageenan-based injectable hydrogels for bone tissue regeneration

Bone tissue possesses intrinsic regenerative capabilities to address deformities; however, its ability to repair defects caused by severe fractures, tumor resections, osteoporosis, joint arthroplasties, and surgical reconsiderations can be hindered. To address this limitation, bone tissue engineering has emerged as a promising approach for bone repair and regeneration, particularly for large-scale bone defects. In this study, an injectable hydrogel based on kappa-carrageenan-co-N-isopropyl acrylamide (κC-co-NIPAAM) was synthesized using free radical polymerization and the antisolvent evaporation technique. The κC-co-NIPAAM hydrogel's cross-linked structure was confirmed using Fourier transform infrared spectra (FTIR) and nuclear magnetic resonance (1H NMR). The hydrogel's thermal stability and morphological behavior were assessed using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM), respectively. Swelling and in vitro drug release studies were conducted at varying pH and temperatures, with minimal swelling and release observed at low pH (1.2) and 25 °C, while maximum swelling and release occurred at pH 7.4 and 37oC. Cytocompatibility analysis revealed that the κC-co-NIPAAM hydrogels were biocompatible, and hematoxylin and eosin (H&E) staining demonstrated their potential for tissue regeneration and enhanced bone repair compared to other experimental groups. Notably, digital x-ray examination using an in vivo bone defect model showed that the κC-co-NIPAAM hydrogel significantly improved bone regeneration, making it a promising candidate for bone defects.

Mevacor/Poly(vinyl acetate/2-hydroxyethyl methacrylate) as Solid Solution: Preparation, Solubility Enhancement and Drug Delivery

Mevacor/Poly(vinyl acetate-co-2-hydroxyethyl methacrylate) drug carrier systems (MVR/VAC-HEMA) containing different Mevacor (MVR) contents were prepared in one pot by free radical copolymerization of vinyl acetate with 2-hydroxyethyl methacrylate using an LED lamp light in the presence of camphorquinone as a photoinitiator and Mevacor as a drug filler. The prepared material was characterized by FTIR, 1H NMR, DSC, SEM and XRD methods. Different parameters influencing the efficiency in the Mecvacor-water solubility and the drug delivery of this system, such as the swelling capacity of the carrier, the amount of Mevacor loaded and the pH medium have been widely investigated. The results obtained revealed that the Mevacor particles were uniformly dispersed in their molecular state in the copolymer matrix forming a solid solution; the cell toxicity of the virgin poly(vinyl acetate-co-2-hydroxy ethyl methacrylate) (VAC-HEMA) and MVR/VAC-HEMA drug carrier system exhibited no significant effect on their viability when between 0.25 and 2.00 wt% was loaded in these materials; the average swelling capacity of VAC-HEMA material in water was found to be 45.16 wt%, which was practically unaffected by the pH medium and the solubility of MVR deduced from the release process reached more than 22 and 37 times that of the powder dissolved directly in pH 1 and 7 media, respectively. The in vitro MVR release kinetic study revealed that the MVR/VAC-HEMA system containing 0.5 wt% MVR exhibited the best performance in the short gastrointestinal transit (GITT), while that containing 2.0 wt% is for the long transit as they were able to considerably reduce the minimum release of this drug in the stomach (pH1).

Fibrin-Dextran Hydrogels with Tunable Porosity and Mechanical Properties

Hydrogels as scaffolds in tissue engineering have gained increasing attention in recent years. Natural hydrogels, e.g., collagen or fibrin, are limited by their weak mechanical properties and fast degradation, whereas synthetic hydrogels face issues with biocompatibility and biodegradation. Therefore, combining natural and synthetic polymers to design hydrogels with tunable mechanical stability and cell affinity for biomedical applications is of interest. By using fibrin with its excellent cell compatibility and dextran with controllable mechanical properties, a novel bio-based hydrogel can be formed. Here, we synthesized fibrin and dextran-methacrylate (MA)-based hydrogels with tailorable mechanical properties, controllable degradation, variable pore sizes, and ability to support cell proliferation. The hydrogels are formed through in situ gelation of fibrinogen and dextran-MA with thrombin and dithiothreitol. Swelling and nuclear magnetic resonance diffusometry measurements showed that the water uptake and mesh sizes of fabricated hydrogels decrease with increasing dextran-MA concentrations. Cell viability tests confirm that these hydrogels exhibit no cytotoxic effect.

Xanthan-Gum/Pluronic-F-127-Based-Drug-Loaded Polymeric Hydrogels Synthesized by Free Radical Polymerization Technique for Management of Attention-Deficit/Hyperactivity Disorder

Smart and intelligent xanthan gum/pluronic F-127 hydrogels were fabricated for the controlled delivery of atomoxetine HCl. Different parameters such as DSC, TGA, FTIR, XRD, SEM, drug loading, porosity, swelling index, drug release, and kinetics modeling were appraised for the prepared matrices of hydrogels. FTIR confirmed the successful synthesis of the hydrogel, while TGA and DSC analysis indicated that the thermal stability of the reagents was improved after the polymerization technique. SEM revealed the hard surface of the hydrogel, while XRD indicated a reduction in crystallinity of the reagents. High gel fraction was achieved with high incorporated contents of the polymers and the monomer. An increase in porosity, drug loading, swelling, and drug release was observed with the increase in the concentrations of xanthan gum and acrylic acid, whereas Pluronic F-127 showed the opposite effect. A negligible swelling index was shown at pH 1.2 and 4.6 while greater swelling was observed at pH 7.4, indicating a pH-responsive nature of the designed hydrogels. Furthermore, a higher drug release was found at pH 7.4 compared to pH 1.2 and 4.6, respectively. The first kinetics order was followed by the prepared hydrogel formulations. Thus, it is signified from the discussion that smart xanthan gum/pluronic F-127 hydrogels have the potential to control the release of the atomoxetine HCl in the colon for an extended period of time.

Synthesis and Evaluation of Alginate-Based Nanogels as Sustained Drug Carriers for Caffeine

The objective of this study is to design a polymeric network of nanogels for sustained release of caffeine. Therefore, alginate-based nanogels were fabricated by a free-radical polymerization technique for the sustained delivery of caffeine. Polymer alginate was crosslinked with monomer 2-acrylamido-2-methylpropanesulfonic acid by crosslinker N',N'-methylene bisacrylamide. The prepared nanogels were subjected to sol-gel fraction, polymer volume fraction, swelling, drug loading, and drug release studies. A high gel fraction was seen with the increasing feed ratio of polymer, monomer, and crosslinker. Greater swelling and drug release were observed at pH 4.6 and 7.4 as compared to pH 1.2 due to the deprotonation and protonation of functional groups of alginate and 2-acrylamido-2-methylpropanesulfonic acid. An increase was observed in swelling, loading, and release of the drug with the incorporation of a high feed ratio of polymer and monomer, while a reduction was seen with the increase in crosslinker feed ratio. Similarly, an HET-CAM test was used to evaluate the safety of the prepared nanogels, which showed that the prepared nanogels have no toxic effect on the chorioallantoic membrane of fertilized chicken eggs. Similarly, different characterizations techniques such as FTIR, DSC, SEM, and particle size analysis were carried out to determine the development, thermal stability, surface morphology, and particle size of the synthesized nanogels, respectively. Thus, we can conclude that the prepared nanogels can be used as a suitable agent for the sustained release of caffeine.

Prevention of marine biofouling in the aquaculture industry by a coating based on polydimethylsiloxane-chitosan and sodium polyacrylate

In this study, a series of novel hydrophobic/hydrophilic hybrid (HHH) coatings with the feature of preventing the fouling phenomenon was fabricated based on polydimethylsiloxane (PDMS), as matrix and two hydrophilic polymers: chitosan and sodium polyacrylate, as dispersed phases. Antibacterial activity, pseudo-barnacle adhesion strength, surface free energy, water contact angle, and water absorption were performed for all samples. Evaluating field immersion of the samples was performed in the natural seawater. The results showed that the dispersed phase containing PDMS coatings showed simultaneously both of antibacterial activity and foul release behavior. Among the samples, the PCs4 coating containing 4 wt% Cs indicated the lowest pseudo barnacle adhesion strength (0.04 MPa), the lowest surface free energy (18.94 mN/m), the highest water contact angle (116.05°), and the percentage of fouling organisms 9.8 % after 30 days immersion. The HHH coatings can be considered as novel eco-friendly antifouling/foul release coatings for aquaculture applications.

Nafcillin-Loaded Photocrosslinkable Nanocomposite Hydrogels for Biomedical Applications

Skin infections are frequently treated via intravenous or oral administration of antibiotics, which can lead to serious adverse effects and may sometimes contribute to the proliferation of resistant bacterial strains. Skin represents a convenient pathway for delivering therapeutic compounds, ensured by the high number of blood vessels and amount of lymphatic fluids in the cutaneous tissues, which are systematically connected to the rest of the body. This study provides a novel, straightforward method to obtain nafcillin-loaded photocrosslinkable nanocomposite hydrogels and demonstrates their performance as drug carriers and antimicrobial efficacy against Gram-positive bacteria. The novel formulations obtained, based on polyvinylpyrrolidone, tri(ethylene glycol) divinyl ether crosslinker, hydrophilic bentonite nanoclay, and/or two types of photoactive (TiO₂ and ZnO) nanofillers, were characterized using various analytical methods (transmission electron microscopy (TEM), scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDX), mechanical tests (tension, compression, and shear), ultraviolet-visible spectroscopy (UV-Vis), swelling investigations, and via specific microbiological assays ("agar disc diffusion method" and "time-kill test"). The results reveal that the nanocomposite hydrogel possessed high mechanical resistance, good swelling abilities, and good antimicrobial activity, demonstrating a decrease in the bacteria growth between 3log₁₀ and 2log₁₀ after one hour of direct contact with S. aureus.

Hydrophobic modified agar: Structural characterization and application in encapsulation and release of curcumin

In this study, three kinds of anhydrides with different structures were introduced into agar molecules to study the effects of varying degrees of substitution (DS) and anhydride structures on the physicochemical properties and curcumin (CUR) loading capacity. Increasing the carbon chain length and saturation of the anhydride affects the hydrophobic interaction and hydrogen bonding of the esterified agar, thereby changing the stable structure of the agar. Although the gel performance declined, the hydrophilic carboxyl group and the loose porous structure provide more binding sites for the adsorption of water molecules, hence providing excellent water retention (1700 %). Next, CUR was used as a hydrophobic active ingredient to study agar microspheres' drug encapsulation and in vitro release ability. Results showed that the excellent swelling and hydrophobic structure of esterified agar could promote the encapsulation of CUR (70.3 %). The release process is controlled by pH, and the release of CUR under weak alkaline conditions is significant, which can be explained by the pore structure, swelling characteristics, and carboxyl binding of agar. Therefore, this study shows the application potential of hydrogel microspheres in loading hydrophobic active ingredients and sustained release and provides the possibility for the application of agar in drug delivery systems.

CO2-responsive gels

CO₂-responsive materials undergo a change in chemical or physical properties in response to the introduction or removal of CO₂. The use of CO₂ as a stimulus is advantageous as it is abundant, benign, inexpensive, and it does not accumulate in a system. Many CO₂-responsive materials have already been explored including polymers, latexes, surfactants, and catalysts. As a sub-set of CO₂-responsive polymers, the study of CO₂-responsive gels (insoluble, cross-linked polymers) is a unique discipline due to the unique set of changes in the gels brought about by CO₂ such as swelling or a transformed morphology. In the past 15 years, CO₂-responsive gels and self-assembled gels have been investigated for a variety of emerging potential applications, reported in 90 peer-reviewed publications. The two most widely exploited properties include the control of flow (fluids) via CO₂-triggered aggregation and their capacity for reversible CO₂ absorption-desorption, leading to applications in Enhanced Oil Recovery (EOR) and CO₂ sequestration, respectively. In this paper, we review the preparation, properties, and applications of these CO₂-responsive gels, broadly classified by particle size as nanogels, microgels, aerogels, and macrogels. We have included a section on CO₂-induced self-assembled gels (including poly(ionic liquid) gels).

Preparation and Characterization of Poly(vinyl Acetate-co-2-hydroxyethyl Methacrylate) and In Vitro Application as Contact Lens for Acyclovir Delivery

A series of poly(vinyl acetate-co-2-hydroxyethylmethacrylate)/acyclovir drug carrier systems (HEMAVAC) containing different acyclovir contents was prepared through bulk free radical polymerization of 2-hydroxyethyl methacrylate with vinyl acetate (VAc) in presence of acyclovir (ACVR) as the drug using a LED lamp in presence of camphorquinone as the photoinitiator. The structure of the drug carrier system was confirmed by FTIR and 1HNMR analysis, and the uniform dispersion of the drug particles in the carrier was proved by DSC and XRD analysis. The study of the physico-chemical properties of the prepared materials, such as the transparency, swelling capacity, wettability and optical refraction, was carried out by UV–visible analysis, a swelling test and measurement of the contact angle and the refractive index, respectively. The elastic modulus and the yield strength of the wet prepared materials were examined by dynamic mechanical analysis. The cytotoxicity of the prepared materials and cell adhesion on these systems were studied by LDH assay and the MTT test, respectively. The results obtained were comparable to those of standard lenses with a transparency of 76.90–89.51%, a swelling capacity of 42.23–81.80% by weight, a wettability of 75.95–89.04 o, a refractive index of 1.4301–1.4526 and a modulus of elasticity of 0.67–1.50 MPa, depending on the ACVR content. It was also shown that these materials exhibit no significant cytotoxicity; on the other hand, they show significant cell adhesion. The in vitro dynamic release of ACVR in water revealed that the HEMAVAC drug carrier can consistently deliver uniformly adequate amounts of ACVR (5.04–36 wt%) over a long period (7 days) in two steps. It was also found that the solubility of ACVR obtained from the release process was improved by 1.4 times that obtained by direct solubility of the drug in powder form at the same temperature.

A comprehensive review on hydrogel materials in urology: Problems, methods, and new opportunities

Hydrogel materials provide an extremely promising group of materials that can find an increasingly wide range of use in treating urinary system conditions due to their unique properties. The present review describes achievements to date in terms of the use and development prospects of hydrogel materials applications in the treatment and reconstruction of the urinary system organs, which among others include: hydrogel systems of intravesical drug delivery, ureteral stents design, treatment of vesicoureteral reflux, urinary bladder and urethral defects reconstruction, design of modern urinary catheters and also solutions applied in urinary incontinence therapy (Figure 4). In addition, hydrogel materials find increasingly growing applications in the construction of educational simulation models of organs and specific conditions of the urinary system, which enable the education of medical personnel. Numerous research efforts are underway to expand the existing treatment methods and reconstruction of the urinary system based on hydrogel materials. After conducting the further necessary research, many of the innovative solutions developed to date have high application potential.

Preparation and optimization of tetraethyl orthosilicate cross-linked chitosan-guar gum-poly(vinyl alcohol) composites reinforced with montmorillonite for sustained release of sitagliptin

Development of efficient drug carriers has become an integral part of advanced drug delivery systems. This work aims at developing composites by adopting an economically viable method for sustained release of anti-diabetic drug sitagliptin - a potent and selective dipeptidyl peptidase-IV inhibitor. To combat the harsh environment of gastrointestinal tract, the composite (F13) was prepared using biodegradable polymers namely chitosan, guar gum and poly(vinyl alcohol) with montmorillonite clay as nano-filler and tetraethyl orthosilicate as the cross linker. The composites were characterized using FT-IR, XRD, DSC and SEM techniques. Physical properties such as thickness, swelling capacity, folding endurance and water solubility were studied. In vitro analysis of composites (F17, F19 and F20) in simulated gastric medium showed <14 % cumulative release in 2 h while a sustained release was observed in simulated intestinal medium. Drug release kinetics was investigated using five mathematical models namely zero order, first order, Higuchi, Hixon-Crowell and Korsemeyer-Peppas wherein the latter was the best fit model (R², 0.969). Antimicrobial studies of drug free composite (F13) revealed good activity against bacteria as well as fungi. The results implied that the composites were pH sensitive and could serve as a potential choice for sustained release of drugs.

Solvent types used for the preparation of hydrogels determine their mechanical properties and influence cell viability through gelatine and calcium ions release

Alginate-gelatin hydrogels are the most commonly used materials for 3D bioprinting. Their printability depends on their properties, and these derive from the way they are prepared and their very composition. Therefore, the aim of the study was to investigate the type of solvent (deionized water, phosphate buffer, and culture medium) and contents of gelatin in the composition of hydrogel (2% wt/vol alginate, 6% and 9% wt/vol of gelatin) on their biological, physicochemical, and mechanical properties, as well as printability and the ability of cells to proliferate in the printed structures. The results obtained revealed that all the manufactured hydrogel materials are biocompatible. The use of deionized water as a solvent results in the highest degree of cross-linking of hydrogels, thus obtaining a polymer with the highest rigidity. Moreover, an increase in gelatin content leads to an increase in the Young's modulus value, irrespectively of the solvent in which the hydrogels were prepared. Based on the chemical structure, it is more reasonable to use a culture medium for bioink preparation due to free NH and NH₂ groups being present, which are ligands for cell attachment and their proliferation. For the selected material (2A9GM), the printability and high viability of the cells after printing were confirmed. In this case, the concentration of the cross-linking agent influences gelatin amount release and calcium ions release, and these two processes determine the change in the viability of the cells encapsulated in the bioink.

Polymeric hydrogel forming microneedle-mediated transdermal delivery of sildenafil citrate from direct-compressed tablet reservoir for potential improvement of pulmonary hypertension therapy

Pulmonary hypertension (PH) is a cardiovascular disease affecting patient's life. Sildenafil citrate (SC), the first-line treatment, is present in oral and injectable forms with some drawbacks, primarily poor patient's comfort and low oral bioavailability. To counter these limitations, stratum corneum-penetrating hydrogel-forming microneedles (HFM) was created, making it easier to distribute SC transdermally. HFM was fabricated using polyvinyl alcohol (PVA) and two variations of polyvinyl pyrrolidone's (PVP) concentration as polymers and citric acid (CA) as crosslinking agent. The crosslinking time was also variated. The assessment of swelling, insertion characteristics, and mechanical resistance revealed that it possessed swelling capacities up to 470 % and strong insertion capabilities. This HFM was integrated with a tablet reservoir prepared using several concentrations of sodium starch glycolate (SSG) as super disintegrant. The tablet reservoir's hardness, dissolution rate, XRD, and FTIR profiles were evaluated and the results showed that 4 % of SSG was the option for enhancing SC's solubility. According to ex vivo study, this system released 24.12 ± 0.92 % of SC. For the first time, SC was successfully incorporated into a system of HFM and tablet reservoir and was non-toxic, showing promise in terms of improving PAH therapy's efficacy following comprehensive in vivo studies in the future.

Development and Evaluation of Sodium Alginate/Carbopol 934P-Co-Poly (Methacrylate) Hydrogels for Localized Drug Delivery

This research was carried out to create a pH-responsive polymeric system for the targeted drug delivery of Diloxanide furoate. It relied on sodium alginate (Na-Alg) and Carbopol 934P as building blocks. Using an aqueous free radical polymerization method, SCH1-SCH12 was created with varying polymer, MAA, and MBA input ratios. Positive outcomes were seen in the swelling and release profiles at higher pH levels. Hydrogel formation, as well as component compatibility, thermal stability, and Diloxanide furoate loading, were all validated by instrumental characterization. A drug loading percentage of 83.56% was determined, with the swelling reaching 743.19%. For the formulation with MBA, the gel fraction was 94.58%. The release of diloxanide furoate increased to 91.77% at neutral pH. The formulation containing Carbopol 934P provided the highest mucoadhesion force (3993.42 dynes/cm²). The created hydrogel has been shown to be biocompatible by toxicological testing of the network. Based on the findings, the created polymeric nexus proved promising for pH-dependent localized and regulated delivery of Diloxanide furoate.

Update on Chitosan-Based Hydrogels: Preparation, Characterization, and Its Antimicrobial and Antibiofilm Applications

Chitosan is a prominent biopolymer in research for of its physicochemical properties and uses. Each year, the number of publications based on chitosan and its derivatives increases. Because of its comprehensive biological properties, including antibacterial, antioxidant, and tissue regeneration activities, chitosan and its derivatives can be used to prevent and treat soft tissue diseases. Furthermore, chitosan can be employed as a nanocarrier for therapeutic drug delivery. In this review, we will first discuss chitosan and chitosan-based hydrogel polymers. The structure, functionality, and physicochemical characteristics of chitosan-based hydrogels are addressed. Second, a variety of characterization approaches were used to analyze and validate the physicochemical characteristics of chitosan-based hydrogel materials. Finally, we discuss the antibacterial, antibiofilm, and antifungal uses of supramolecular chitosan-based hydrogels. This review study can be used as a base for future research into the production of various types of chitosan-based hydrogels in the antibacterial and antifungal fields.

Novel sulfonated poly (vinyl alcohol)/carboxy methyl cellulose/acrylamide-based hybrid polyelectrolyte membranes

Novel polyelectrolytic hybrid membranes are prepared by blending carboxy methyl cellulose (CMC)-polyvinyl alcohol (PVA)-acrylamide (AA). Succinic acid and chlorosulfonic acid (CSA) are employed as crosslinkers and modifiers, respectively. Additionally, carboxylated carbon nanotube (CCNT) and sulfonated activated carbon (SAC) as fillers are used to attain appropriate chemical and mechanical stability for use as polyelectrolyte membranes (PEM). CMC, PVA, and AA are mixed and treated with CSA, CCNT, and SAC in different concentrations. First, CMC/PVA/AA solution is modified using CSA to produce a sulfonated polymeric matrix. Second, a different amount of CCNT or SAC was added as a filler to enhance the ion exchange capacity (IEC), ionic conductivity, and chemical stability. Third, the solution is cast as polyelectrolytic membranes. Chemical interactions between CMC, PVA, AA and other membrane components were confirmed using various characterization techniques such as Raman scattering spectroscopy and Fourier Transform Infrared (FTIR). Furthermore, mechanical strength, methanol uptake, gel fraction, ion exchange capacity (IEC), proton conductivity (PC), chemical and thermal stability were determined as functions of varied membrane modification components. Results reveal that the increase of CSA, CCNT and SAC is leading to increase the IEC values reaching 1.54 mmol/g for (CMC/PVA-4% CSA), 1.74 mmol/g for (CMC/PVA-4%CSA-2%CCNT) and 2.31 mmol/g for (CMC/PVA-4% CSA-2% SAC) comparing to 0.11 mmol/g for non-modified CMC/PVA/AA membrane. Sequentially, the proton conductivity value is changed from 1 × 10^-3 S/cm in non-modified CMC/PVA/AA membrane to 0.082 S/cm for (CMC/PVA-4% CSA), 0.0984 S/cm for (CMC/PVA-4%CSA-2%CCNT) and 0.1050 S/cm for (CMC/PVA-4% CSA-2% SAC). Such results enhance the potential feasibility of modified CMC/PVA/AA hybrid as polyelectrolytic membranes.

Fabrication and characterization of electrospun GelMA/PCL/CS nanofiber composites for wound dressing applications

In the present study, the effect of different ratios of GelMA concentration has been exhibited for wound dressing implementation by the electrospinning method using a new polymer combination of Gelatin methacrylate (GelMA)/Polycaprolactone (PCL)/Chitosan (CS). The nanofiber composites were fabricated due to their biocompatible, biodegradable, improved mechanical strength, low degradation rate, and hydrophilic nature to develop cell-mimicking, cell adhesion, proliferation, and differentiation. Different concentrations of GelMA were added to the PCL/CS solution as 5, 10, and 20 wt%, respectively, in the formic acid/acetic acid (7:3) solution. A photoinitiator was added to the solution for photo-crosslinking of GelMA. The influence of different solution concentrations (5, 10, and 20 wt%) on the structure’s nanofiber production and fiber morphology was examined. SEM micrographs revealed that varied GelMA concentrations resulted in suitable and stable nanofiber composites. The average diameter of nanofiber composites grows as the GelMA concentration rises. FTIR, DSC, tensile test, degradation, and swelling test were evaluated. The results demonstrated that high mechanical strength, hydrophilic properties, and a slow degradation rate were observed with the presence and increment of GelMA concentration within the nanofiber composites. The antibacterial potential of GelMA/PCL/CS nanofiber composites was evaluated against P. aeruginosa and S. aureus using a disc diffusion assay. In vitro cell culture research was conducted by seeding NIH 3T3 fibroblast cells on nanofiber composites, proving these cells’ high cell proliferation rate, viability, and adhesion. 10 wt% GelMA-based nanofiber composites were found to have great potential for wound dressing applications.

pH Responsive Hydrogels for the Delivery of Capecitabine: Development, Optimization and Pharmacokinetic Studies

The objective of the current study was to achieve a sustained release profile of capecitabine (CAP), an anticancer agent frequently administered in conventional dosage form due to its short plasma half-life. A drug-loaded smart pH responsive chitosan/fenugreek-g-poly (MAA) hydrogel was synthesized by an aqueous free radical polymerization technique. The developed network was evaluated for capecitabine loading %, swelling response, morphology, structural and compositional characteristics, and drug release behavior. Significantly higher swelling and in vitro drug release rate were exhibited by formulations at pH 7.4 than at pH 1.2, demonstrating the pH responsive character of hydrogels. Swelling percentage and CAP loading ranged within 74.45-83.54% and 50.13-72.43%, respectively. Maximum release, up to 93%, was demonstrated over 30 h, evidencing the controlled release pattern of CAP from hydrogels. The optimized formulation was further screened for acute oral toxicity studies. No signs of oral, dermal, or ocular toxicities were noticed, confirming safety evidence of the network. Furthermore, pharmacokinetic analysis demonstrated the sustained release response of CAP from hydrogels as confirmed by a significant increase in plasma half-life (t_1/2) (13 h) and AUC (42.88 µg h/mL) of CAP. Based on these findings, fabricated hydrogels are strongly recommended as a biocompatible carrier for colorectal delivery of active agents.

Determination of reducing carbohydrates in natural honey samples by optical micrometry method

The present article deals with the determination of the total amount of glucose and fructose in natural honey samples by the optical micrometry (OM) method. (Poly)vinyl alcohol spherical granules impregnated with a 0.05 mol/l borax solution were chosen as a sensitive element. It was shown that the formation of chelate esters of boron with polymer and carbohydrates is a pH-dependent process, and that the pH range 8.5–10.0 is the most appropriate for quantifying the total amount of reducing carbohydrates because glucose and fructose are undiscriminated. The impregnated polymer is not sensitive to the sucrose presence in the solution due to the absence of cis-diol fragments in it. Subsequently, the OM method was tested in the analysis of natural honey samples. The relative standart deviation in the case of OM method is less than 6%, and the results are similar to those obtained by the iodometric titration method. This makes the OM method suitable for laboratory-scale applications.

In-vitro and in-vivo evaluation of biocompatible polymeric microgels for pH- driven delivery of Ketorolac tromethamine

The aim of the current study was to prepare glutamic acid crosslinked poly(itaconic acid/methacrylic acid) microgels for pH-responsive delivery of ketorolac tromethamine, using aqueous free radical polymerization technique. The polymerization of polymer with monomers was carried out by a crosslinking agent N', N'-methylene bisacrylamide in the presence of initiator ammonium persulfate. The prepared microgels were characterized for structure, surface morphology, thermal stability, and crystallinity. Similarly, studies such as sol-gel analysis, drug loading, and polymer volume fraction were performed for the fabricated microgels. The pH-sensitivity of the developed microgels was investigated at three different pH values i.e., pH 1.2, 4.6, and 7.4 by swelling and in-vitro drug release studies. Maximum swelling and drug release were found at pH 7.4 as compared to pH 1.2 and 4.6, which indicated the pH-sensitive nature of the prepared microgels. The toxicity of the prepared microgels was evaluated by cell line and HET-CAM test, which demonstrated no toxic effect of the prepared microgels. In-vivo study was carried out on rabbits and high plasma concentration was reported for the drug loaded microgels as compared to drug solution and commercial product Keten. Hence, the prepared microgel system could be employed as an excellent carrier for the controlled drug delivery system.

Preparation of pH-Responsive Hydrogels Based on Chondroitin Sulfate/Alginate for Oral Drug Delivery

This study investigates pH-sensitive hydrogels based on biocompatible, biodegradable polysaccharides and natural polymers such as chondroitin sulfate and alginate in combination with synthetic monomer such as acrylic acid, as controlled drug carriers. Investigations were conducted for chondroitin sulfate/alginate-graft-poly(acrylic acid) hydrogel in various mixing ratios of chondroitin sulfate, alginate and acrylic acid in the presence of ammonium persulfate and N',N'-Methylene bisacrylamide. Crosslinking and loading of drug were confirmed by Fourier transform infrared spectroscopy. Thermal stability of both polymers was enhanced after crosslinking as indicated by thermogravimetric analysis and differential scanning calorimeter thermogram of developed hydrogel. Similarly, surface morphology was evaluated by scanning electron microscopy, whereas crystallinity of the polymers and developed hydrogel was investigated by powder X-ray diffraction. Furthermore, swelling and drug-release studies were investigated in acidic and basic medium of pH 1.2 and 7.4 at 37 °C, respectively. Maximum swelling and drug release were detected at pH 7.4 as compared to pH 1.2. Increased incorporation of hydrogel contents led to an increase in porosity, drug loading, and gel fraction while a reduction in sol fraction was seen. The polymer volume fraction was found to be low at pH 7.4 compared to pH 1.2, indicating a prominent and greater swelling of the prepared hydrogels at pH 7.4. Likewise, a biodegradation study revealed a slow degradation rate of the developed hydrogel. Hence, we can conclude from the results that a fabricated system of hydrogel could be used as a suitable carrier for the controlled delivery of ketorolac tromethamine.

Analysis of the Influence of Both the Average Molecular Weight and the Content of Crosslinking Agent on Physicochemical Properties of PVP-Based Hydrogels Developed as Innovative Dressings

Hydrogels belong to the group of polymers with a three-dimensional crosslinked structure, and their crosslinking density strongly affects their physicochemical properties. Here, we verified the impact of both the average molecular weight of crosslinking agents used during the photopolymerization of hydrogels and that of their content on selected properties of these materials. First, PVP-based hydrogels modified with Aloe vera juice and L-ascorbic acid were prepared using UV radiation. Next, their surface morphology was characterized via optical scanning electron microscopy, whereas their chemical structure was investigated by FT-IR spectroscopy. Moreover, we verified the tendency of the hydrogels to degrade in selected physiological liquids, as well as their tensile strength, percentage of elongation, and swelling capability. We found that the more crosslinking agent in the hydrogel matrix, the higher its tensile strength and the less elongation. The hydrogels showed the highest stability during incubation in SBF and 2% hemoglobin solution. A sharp decrease in the pH of distilled water observed during the incubation of the hydrogels was probably due to the release of Aloe vera juice from the hydrogel matrices. This was additionally confirmed by the decrease in the intensity of the absorption band derived from the polysaccharides included in this additive and by the decrease in the swelling ratio after 48 h. Importantly, all hydrogels demonstrated swelling properties, and it was proven that the higher content of the crosslinking agent in hydrogels, the lower their swelling ability.

Preparation, In Vitro Characterization, and Cytotoxicity Evaluation of Polymeric pH-Responsive Hydrogels for Controlled Drug Release

The aim of the current investigation was based on the development of pH-responsive hydrogels of chondroitin sulfate, carbopol, and polyvinyl alcohol polymerized with acrylic acid in the presence of ammonium persulfate and ethylene glycol dimethylacrylate for controlled drug delivery. A free radical polymerization technique was used for the preparation of these pH-responsive hydrogels. The gel fraction of the prepared hydrogels was increased with the increase in the chondroitin sulfate, carbopol, polyvinyl alcohol, and acrylic acid content, while the sol-fraction was decreased. Swelling and drug release studies were performed in various pH conditions. Greater swelling and drug release were observed at high pH values (pH 4.6 and 7.4) as compared to low pH value (pH 1.2), representing the pH-responsive nature of the synthesized hydrogels. Porosity and drug loading were increased with the incorporation of high concentrations of hydrogel contents except polyvinyl alcohol, which showed reverse effects. Similarly, biodegradation study reported a slow degradation rate of the prepared hydrogels with the increase in hydrogel constituents. Cytotoxicity study proved the safe use of developed hydrogels as no toxic effect was shown on T84 human colon cancer cells. Similarly, various characterizations, including Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy, were performed for prepared hydrogels. Hence, we could demonstrate that the prepared hydrogels can be used as a promising drug carrier for the controlled delivery of drugs.

Improving Mechanical Properties of Starch-Based Hydrogels Using Double Network Strategy

This work aims to improve the mechanical properties of starch-based hydrogels using a double-network (DN) strategy. The single network (SN) starch hydrogel was first prepared using glutaraldehyde as a crosslinker. The compressive properties of the SN hydrogels were influenced by both crosslinker content and crosslinking time. The SN starch hydrogel possessing the best mechanical properties was then fabricated into DN hydrogels. Polyvinyl alcohol (PVA) and borax were used as a secondary polymer and a crosslinker, respectively. The PVA–borax complexation partly enhanced the DN hydrogel’s compressive modulus by 30% and its toughness by 39%. DN hydrogels were found to have denser microstructures than SN hydrogels. To be specific, their walls thickened and grew more continuous while their pores shrank. The increased crosslinking density resulted in changes to the microstructure, which were well correlated with their porosity and water uptake capacity. An in vitro cytotoxicity test of the DN hydrogels revealed that they were non-toxic to chondrocytes. This work demonstrated that double networking is a simple but effective strategy for improving mechanical properties of starch-based hydrogels without sacrificing their biocompatibility. This approach can be used to tailor hydrogel properties to fulfill requirements for biomedical applications, such as tissue engineering and other related fields.

Designing and In Vitro Characterization of pH-Sensitive Aspartic Acid-Graft-Poly(Acrylic Acid) Hydrogels as Controlled Drug Carriers

Acetaminophen is an odorless and white crystalline powder drug, used in the management of fever, pain, and headache. The half-life of acetaminophen is very short; thus, multiple intakes of acetaminophen are needed in a day to maintain a constant pharmacological action for an extended period of time. Certain severe adverse effects are produced due to the frequent intake of acetaminophen, especially hepatotoxicity and skin rashes. Therefore, a drug carrier system is needed which not only prolongs the release of acetaminophen, but also enhances the patient compliance. Therefore, the authors prepared novel aspartic acid-graft-poly(acrylic acid) hydrogels for the controlled release of acetaminophen. The novelty of the prepared hydrogels is based on the incorporation of pH-sensitive monomer acrylic acid with polymer aspartic acid in the presence of ethylene glycol dimethacrylate. Due to the pH-sensitive nature, the release of acetaminophen was prolonged for an extended period of time by the developed hydrogels. Hence, a series of studies was carried out for the formulated hydrogels including sol-gel fraction, FTIR, dynamic swelling, polymer volume analysis, thermal analysis, percent porosity, SEM, in vitro drug release studies, and PXRD analysis. FTIR analysis confirmed the grafting of acrylic acid onto the backbone of aspartic acid and revealed the development of hydrogels. The thermal studies revealed the high thermal stability of the fabricated hydrogels as compared to pure aspartic acid. An irregular surface with a few pores was indicated by SEM. PXRD revealed the amorphous state of the developed hydrogels and confirmed the reduction in the crystallinity of the unreacted aspartic acid by the formulated hydrogels. An increase in gel fraction was observed with the increasing concentration of aspartic acid, acrylic acid, and ethylene glycol dimethacrylate due to the availability of a high amount of free radicals. The porosity study was influenced by the various compositions of developed hydrogels. Porosity was increased due to the enhancement in the concentrations of aspartic acid and acrylic acid, whereas it decreased with the increase in ethylene glycol dimethacrylate concentration. Similarly, the pH-responsive properties of hydrogels were evaluated by dynamic swelling and in vitro drug release studies at two different pH levels (1.2 and 7.4), and a greater dynamic swelling and acetaminophen release were exhibited at pH 7.4 as compared to pH 1.2. An increase in swelling, drug loading, and drug release was seen with the increased incorporation of aspartic acid and acrylic acid, whereas a decrease was detected with the increase in the concentration of ethylene glycol dimethacrylate. Conclusively, the formulated aspartic acid-based hydrogels could be employed as a suitable nonactive pharmaceutical ingredient for the controlled delivery of acetaminophen.