Hydrogel Films Research Articles

Electrically Powered Dissipative Hydrogel Networks Reveal Transient Stiffness Properties for Out-of-Equilibrium Operations.

Living systems use dissipative processes to enable precise spatiotemporal control over various functions, including the transient modulation of the stiffness of tissues, which, however, is challenging to achieve in soft materials. Here, we report a new platform to program hydrogel films with tunable, time-dependent mechanical properties under out-of-equilibrium conditions, powered by electricity. We show that the lifetime of the transient network of a surface-confined hydrogel film can be effectively controlled by programming the generation of an electrochemically oxidized mediator in the presence of a chemical or photoreducing agent in solution. It is, therefore, electrically possible to direct the transient stiffening or softening of the hydrogel film, enabling high modularity of the material functions with precise spatiotemporal control. Temporally controlled operations of the hydrogel films are demonstrated for the on-demand, dose-controlled release of multiple model protein payloads from electrode arrays using the present electrically powered dissipative system. This demonstration of electrically driven transient modulation of the stiffness properties of hydrogel films represents an important step toward the engineering of dissipative materials for developing future biomedical applications that can harness the temporal, adaptive properties of this new class of materials.

Fluorescent carbon dots in situ polymerized biodegradable semi-interpenetrating tough hydrogel films with antioxidant and antibacterial activity for applications in food industry

A flexible, antioxidant, biodegradable, and UV-resistant polymeric nanocomposite hydrogel with heteroatom-doped carbon dots (CDs) has been fabricated using a simple one-step in situ free radical gelation process. The hydrogel formation and their physico-mehcanical characteristics have been assessed by rheology, uniaxial tensile and compression testing. The water uptake behaviour of the hydrogels is controlled by the CDs by manipulating their internal morphology and porosity. The porous nature of the hydrogels has been found from their scanning electron microscopic images which are also supported by their anomalous diffusion-based transport mechanism. The rheological signatures of the hydrogels show delayed network rupturing due to the secondary physical crosslinking alleviated by CDs. Moreover, CDs are directly influencing the permeabilites (oxygen and moisture) by lowering the values compared to their neat hydrogel films which are essential for a packing material. The biodegradability of the hydrogel films showed gradual weight loss (<75 %) within 3 weeks. The hydrogel films also have been qualified to be acted as antibacterial and antioxidant material. The shelf-life and non-leaching of CDs from gel matrices are also performed which shows its excellent capability to be used as a potential antibacterial, biodegradable, antioxidant alternative packaging material in food sectors.

Theoretical analysis of the enzyme reaction processes within the multiscale porous biocatalytic electrodes: Akbari–Ganji's and Taylor’s series method

We discuss a theoretical model that describes glucose oxidation in a multiscale porous biocatalytic electrode. The model under consideration consists of two nonlinear differential equations that describe diffusion and reaction in the hydrogel film. The Akbari–Ganji's and Taylor series methods have been used in this communication to obtain the analytical expressions for the concentrations of the oxidized mediator, Glucose, and current. Additionally, the optimal electrode thickness of the film is calculated analytically. The impact of parameters on current is also explored. The parameter with the most significant effect on the current is the ratio of the oxidized mediator's diffusion to the enzymatic process occurring within the film. The numerical solution (Matlab) validates our analytical results.

In situ fabricated ZnO nanostructures within carboxymethyl cellulose-based ternary hydrogels for wound healing applications

Zinc oxide nanostructures (ZnO NS) were fabricated in situ within a ternary hydrogel system composed of carboxymethyl cellulose-agarose-polyvinylpyrrolidone (CAP@ZnO TNCHs) by a one-pot method employing moist-heat solution casting. The percentages of CMC and ZnO NS were varied in the CAP hydrogel films and then they were investigated by different techniques, such as ATR/FTIR, TGA, XRD, XPS, and FE-SEM analysis. Furthermore, the mechanical properties, hydrophilicity, swelling, porosity, and antibacterial activity of the CAP@ZnO TNCHs were studied. In-vitro biocompatibility assays were performed with skin fibroblast (CCD-986sk) cells. In-vitro culture of CCD-986sk fibroblasts showed that the ZnO NS facilitated cell adhesion and proliferation. Furthermore, the application of CAP@ZnO TNCHs enhanced cellular interactions and physico-chemical, antibacterial bacterial, and biological performance relative to unmodified CAP hydrogels. Also, an in vivo wound healing study verified that the CAP@ZnO TNCHs promoted wound healing significantly within 18 days, an effect superior to that of unmodified CAP hydrogels. Hence, these newly developed cellulose-based ZnO TNCHs are promising materials for wound healing applications.

A novel HEMA-based copolymer hydrogel film with excellent ultraviolet/high-energy short-wavelength blue light shielding

A novel HEMA-based copolymer hydrogel film with excellent ultraviolet/high-energy short-wavelength blue light shielding

Flexible SERS substrate with tunable gap based on laser-induced reduction

Flexible SERS substrate with tunable gap based on laser-induced reduction

UiO-66-NH2 initiated cascade reaction: Constructing a ratiometric fluorescence sensor for ultrasensitive detection of nerve agent simulant

BackgroundHighly toxic organophosphorus nerve agents often exist in the form of gas in the environment and can damage human neuroregulatory system by inhibiting the activity of acetylcholinesterase (AChE). However, fluorescent probes based on small organic molecules bring a secondary burden to environment, and their sensitivity and specificity for sarin simulant diethyl chlorophosphate (DCP) detection are unsatisfactory. Nanozyme cascade systems with signal amplification can be used for highly sensitive identification of analytes, but are rarely used in ratiometric analysis of DCP. Combination of enzyme cascades and ratiometric fluorescence ensures the accuracy and sensitivity of the output signal. ResultsWe prepared a self-assembled nanohybrid (Ag–AuNCs@UiO-66-NH2) by metal-organic framework material and gold nanoclusters. On the one hand, UiO-66-NH2 with enzyme-like activity was used to hydrolyze DCP into diethyl phosphate (DEP) and chloridion (Cl−). Cl− hindered aggregation-induced enhanced emission (AIEE) of AuNCs by binding with Ag+ and decreased the fluorescence of AuNCs. On the other hand, ligand metal charge transfer effect (LMCT) of UiO-66-NH2 was blocked by DCP to enhance the fluorescence of UiO-66-NH2. Combining ratiometric analysis and nanozyme cascade reaction, an ultra-sensitive fluorescence sensor for detecting DCP was constructed, and ensured the accuracy of experimental results. In addition, Ag–AuNCs@UiO-66-NH2 was embedded into the agarose hydrogel substrate, the resulting agarose hydrogel film allowed quantitative assessment of DCP vapor and high sensitivity was demonstrated (detection limit as low as 1.02 ppb). SignificanceA strategy combining enzyme cascade with ratiometric fluorescence was proposed, which improved the accuracy and sensitivity of the analysis results. The soft-solid platform based on agarose hydrogel film was constructed to realize the quantitative monitoring of sarin simulant gas. The LOD value obtained in this work is much lower than the immediately life-threatening or health threatening concentration of sarin.

Self-regulated reversal deformation and locomotion of structurally homogenous hydrogels subjected to constant light illumination

Environmentally adaptive hydrogels that are capable of reconfiguration in response to external stimuli have shown great potential toward bioinspired actuation and soft robotics. Previous efforts have focused mainly on either the sophisticated design of heterogeneously structured hydrogels or the complex manipulation of external stimuli, and achieving self-regulated reversal shape deformation in homogenous hydrogels under a constant stimulus has been challenging. Here, we report the molecular design of structurally homogenous hydrogels containing simultaneously two spiropyrans that exhibit self-regulated transient deformation reversal when subjected to constant illumination. The deformation reversal mechanism originates from the molecular sequential descending-ascending charge variation of two coexisting spiropyrans upon irradiation, resulting in a macroscale volumetric contraction-expansion of the hydrogels. Hydrogel film actuators were developed to display complex temporary bidirectional shape transformations and self-regulated reversal rolling under constant illumination. Our work represents an innovative strategy for programming complex shape transformations of homogeneous hydrogels using a single constant stimulus.

Conjugated Polymer-Based Hydrogel Film for a Fast and Sensitive Detection of Fe(Ⅲ) in Vegetables.

Fluorescent film sensors are ideal for the real-time outdoor detection of heavy metal ions of Fe3+, but they are limited because of their low sensitivity and long response time due to their special structure. In this work, we constructed a fluorescent hydrogel for the specific detection of Fe3+, utilizing poly(9-fluorenecarboxylic acid) (PFCA) as the sensing moiety and sodium alginate (SA) as the cross-linking substrate, which exhibited a rapid and selective recognition of Fe3+ among a panel of 16 anions and 21 cations. It can sense Fe3+ at 0.1 nM immediately owing to the porous network structure of the PFCA-SA film that provided enhanced ion transport channels and active sites, and the "molecular line effect" of polymer PFCA. Moreover, we successfully applied this platform to detect Fe3+ in four different vegetable samples. This work provides an innovative and effective strategy for fabricating green and sustainable fluorescent sensors.

α-Mangostin hydrogel film with chitosan alginate base for recurrent aphthous stomatitis (RAS) treatment: study protocol for double-blind randomized controlled trial.

Background: Recurrent Aphthous Stomatitis (RAS) is a common ulcerative disease of the oral mucosa which is characterized by pain, and recurrent lesions in the oral cavity. This condition is quite painful, causing difficulty in eating, speaking and swallowing. Topical medications have been used for this condition, but the obstacle in using topical medications is the difficulty of achieving drug effects due to saliva wash out. This problem can be overcome by film hydrogel formulation which can protect the ulcer and reduce the pain to some extent. α-mangostin is a xanthone isolated from the rind of the mangosteen fruit. One of the activities of α-mangostin is anti-inflammatory effects, which operate through the characteristic mechanism of inhibiting the inflammatory response. This protocol study aims to investigate the efficacy of an α-mangostin hydrogel film with a chitosan alginate base for recurrent aphthous stomatitis (RAS) in comparison with a placebo over a period of 7days. Study design: This is a two-arm, double blinding, randomized controlled trial enrolling patients with RAS. The efficacy test of α-mangostin Hydrogel Film will be tested against the placebo. Patients with RAS will be allocated randomly into the two arms and the hydrogel film will be administered for 7days. The diameter of ulcer and visual analog scale (VAS) score will be used as the primary efficacy endpoint. The outcome measure will be compared between the two arms at the baseline, day 3, day 5, and at the end of 7days. Discussion: The purpose of this clinical research is to provide scientific evidence on the efficacy of α-mangostin hydrogel film with a chitosan alginate basis in treating recurrent aphthous stomatitis. The trial is expected to improve our capacity to scientifically confirm the anti-inflammatory effectiveness of α-mangostin compounds in a final formulation that is ready to use. Trial registration: NCT06039774 (14 September 2023).

In Situ Fabrication of Photoluminescent Hydrogen-Bonded Organic Framework-Functionalized Ca (II) Hydrogel Film for the Tetracyclines Visual Sensor and Information Security.

A facilely in situ fabricated hydrogen-bonded organic framework (HOF) hydrogel film with perfect photoluminescent performance was designed for visual sensing of tetracycline antibiotics (TCs) and information security. Luminescent HOF (MA-IPA) was combined with sodium alginate (SA) through hydrogen bonding actions and electrostatic interactions, then cross-linked with Ca2+ ions to form HOF hydrogel film (Ca@MA-IPA@SA). The HOF hydrogel film exhibited exceptional mechanical robustness along with stable blue fluorescence and ultralong green phosphorescence. After exposure to TCs, Ca2+ was combined with TCs to generate a new green fluorescence exciplex (TC-Ca2+) in hydrogel films. Due to fluorescence resonance energy transfer, the fluorescence of MA-IPA was quenched, and the fluorescent color of the HOF hydrogel film was changed from blue to green. This dichromatic fluorescent response is convenient for the visual and rapid detection of TCs. The detection limits of tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC) were 5.1, 7.7, and 32.7 ng mL-1, respectively. Importantly, this hydrogel sensing platform was free of tedious operation and enabled the ultrasensitive and selective detection of TCs within 6 min. It has been successfully applied to TC detection in pork and milk samples. Based on the stable photoluminescence performance of HOF hydrogel films and fluorescent-responsive properties to TCs, two types of anticounterfeiting arrays were fabricated for information encryption and decryption. This work provides a novel approach for on-site detection of TCs and offers valuable insights into information security.

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.

High‐Strength Self‐Healable Supercapacitor Based on Supramolecular Polymer Hydrogel with Upper Critical Solubility Temperature

AbstractHere, poly(N‐acryloylglycinamide‐co‐vinyltriazole) p(NAGA‐co‐VTZ) supramolecular polymer hydrogel doped with carbonized and activated polypyrrole nanotubes as a high‐strength self‐healable material is presented for supercapacitors. Initially, the p(NAGA‐co‐VTZ) hydrogel films are synthesized by photopolymerization of N‐acryloylglycinamide and 1‐vinyl‐1,2,4‐triazole without the use of any cross‐linkers. The hydrogels demonstrated remarkable self‐healing ability via hydrogen bonding at temperatures above upper critical solubility temperature, excellent mechanical properties (0.86 MPa), large stretchability (1300%) and cut resistance. Subsequently, carbonized and ethanol/KOH‐activated polypyrrole nanotubes (acNTs) are prepared as the active material for electrochemical double‐layer capacitors (EDLC). Then, a symmetric self‐healable supercapacitor employing p(NAGA‐co‐VTZ) hydrogel, acNTs and aqueous 3 m KCl solution is assembled. Cyclic voltammetry and galvanostatic charge–discharge measurements show that the prepared device gives a specific capacitance of 282.62 F g−1 at 0.2 A g−1 and a high areal capacitance of 316.86 mF cm−2 at a scan rate of 10 mV s−1. Importantly, the supercapacitor operates over a wide voltage window (0–1.2 V) and provides excellent cyclic performance with capacitance retention of 97% after 10 000 cycles and 94% after self‐healing. In summary, the developed self‐healable supercapacitor exhibits considerable potential as a high‐performance energy storage device.

Electrochemically Enhanced Antimicrobial Action of Plasma‐Activated Poly(Vinyl Alcohol) Hydrogel Dressings

AbstractThis paper presents and explains the principle behind anelectrochemical method to enhance the antimicrobial action of plasma‐activated hydrogel therapy (PAHT) in the context of wound decontamination. The process involves grounding and hydratingpoly(vinyl alcohol) (PVA) hydrogel films during treatment with a helium (He) plasma jet. This electrochemically enhances production of hydrogen peroxide (H2O2), which is amajor antibacterial agent produced in the PVA hydrogel. Production of H2O2 is shownto be electrically enhanced through electron dissociation reactions, and through reactions associated with excited state species, metastables and ultra‐violet (UV) photolysis. H2O2 production is chemically enhanced through the He flow of the plasma jet dehydrating the PVA hydrogel, which fuels the electrochemical dependent reactions associated with H2O2 production. The electrochemical process produces an unprecedented 3.4 mM of H2O2 in the PVA hydrogel. Production of other molecules such as reactive nitrogen species (RNS) are also enhanced by the same method. The electrochemically enhanced PAHT is highly effective ateradicating common wound pathogens Escherichia coli and Pseudomonas aeruginosa and mildly effective against Staphylococcus aureus. Overall, this study shows that the new PAHT dressing offers a promising alternative to antibiotics and silver‐based dressings for controlling infection and stimulating healing in wounds.

A Flexible and Free‐Standing Photonic Crystal‐Hydrogel Film for Enhanced Fluorescence from Nitrogen Doped Carbon Dots

AbstractEnhancement of fluorescence emission in a flexible and free‐standing fluorescing film is a key requirement for sensing platforms with augmented sensitivity. In this context, a study on the enhanced fluorescence emission from nitrogen‐doped carbon dots (NCDs) embedded on a flexible free‐standing photonic crystal hydrogel film prepared via photopolymerization, is presented. The composite structure utilizes the photonic crystal enhanced fluorescence (PCEF) technique and incorporates a self‐assembled 3D photonic crystal (3D PC) onto a photopolymerizable hydrogel matrix containing the NCDs. The 3D PC template is prepared through vertical deposition self‐assembly using monodisperse polystyrene (PS) spheres. By leveraging the enhanced excitation and extraction effect in a PC‐fluorophore composite, the authors’ structure exhibits a fourfold enhancement in fluorescence emission compared to the control sample. The relative positioning of the photonic stopband with the excitation and emission spectra of the fluorophore (NCDs) is thoroughly studied by selecting four different 3D PCs with varied lattice parameters. In addition, the hydrogel matrix offers improved photostability and enhanced lifetime for the NCDs. This structure can be further modified into an efficient sensor through appropriate functionalization.

Model-based design of continuous biotransformation in a microscale bioreactor with yeast cells immobilized in a hydrogel film

Miniaturized flow reactors with immobilized biocatalysts offer enormous potential for process intensification. They enable long-term use of biocatalysts, continuous operation that significantly outperforms batch processes, and efficient mass and heat transfer that results in highly controlled reaction conditions. Despite their increasing use in biocatalytic processes, optimization of reactor design and operating conditions based on mathematical description is very rare. This work aims to fill this gap by developing and validating a mathematical model for the continuous biotransformation process in a microreactor between two plates with immobilized whole cells in hydrogel layers on the bottom and top of the reactor. A biocatalytic production of l-malic acid by fumaric acid hydration using permeabilized Saccharomyces cerevisiae whole cells was used as a model reaction. The diffusivity of substrate and product in a liquid phase and in a copolymeric hydrogel layer and the reaction kinetic parameters considering the Michaelis-Menten kinetics of the reversible enzymatic reaction were estimated in initial batch experiments. The results obtained in a continuously operated microbioreactor with immobilized whole cells at different fumaric acid concentrations and flow rates were in excellent agreement with the predictions of the developed mathematical model comprising transport phenomena and reaction kinetics. Based on the validated model and using time-scale analysis with characteristic times, the optimal process and operating conditions for the developed microbioreactor system were determined. The model predicts an equilibrium conversion of fumaric acid at the highest inlet concentration tested when using a liquid height of 200 μm and a hydrogel thickness on both sides of the channel of 400 μm at a residence time of 30 min.

Gelatin/Polyacrylamide-Based Antimicrobial and Self-Healing Hydrogel Film for Wound Healing Application.

In this study, a self-healing, adhesive, and superabsorbent film made of gelatin, poly(acrylamide), and boric acid (GelAA) was successfully synthesized using a free radical reaction mechanism. The optimized film showed a remarkable 2865 ± 42% water absorptivity and also exhibited excellent self-healing behavior. The GelAA films were further loaded with silver nanoclusters (AgNCs) and ursodeoxycholic acid (UDC) (loading efficiency = 10%) to develop UDC/Ag/GelAA films. The loading of AgNCs in UDC/Ag/GelAA films helped in exhibiting 99.99 ± 0.01% antibacterial activity against both Gram-positive and Gram-negative bacteria, making them very effective against bacterial infections. Additionally, UDC/Ag/GelAA films had 77.19 ± 0.52% porosity and showed 90% of UDC release in 30 h, which helps in improving the cell proliferation. Our research provides an easy but highly effective process for synthesizing a hydrogel film, which is an intriguing choice for wound healing applications without the use of antibiotics.

Ln-MOF-Based Hydrogel Films with Tunable Luminescence and Afterglow Behavior for Visual Detection of Ofloxacin and Anti-Counterfeiting Applications.

Highly selective and sensitive quantitative detection of ofloxacin (OFX) at ultralow concentrations in aqueous media and development of new afterglow materials remains a challenge. Herein, a new 2D water-stable lanthanide metal-organic framework (NIIC-2-Tb) is proposed, which exhibits high selectivity towards OFX through the luminescence quenching with the lowest detection limit (1.1× 10-9 M) reported to date and a fast response within 6 s. In addition, the luminescent detection of OFX by NIIC-2-Tb is not affected by typical components of blood plasma and urine. The excellent sensing effect of NIIC-2-Tb is further utilized to prepare a composite functional sensing carrageenan hydrogel material for the rapid detection of OFX in meat in real time and the first discovery of impressive afterglow in MOF-based hydrogels. This study not only presents novel Ln-MOF materials and Ln-MOF-based hydrogel films for luminescent sensing of OFX, but also demonstrates color-tunable luminescent films with afterglow, which expands the application of composite luminescent materials for detection and anti-counterfeiting.

Enzyme-functionalized hydrogel film for extracorporeal uric acid reduction.

Enzyme replacement therapy for hyperuricemia treatment has been proven effective for critical state hyperuricemia patients. Still, direct administration of recombinant uricase can induce several fatal side effects. To circumvent this drawback, hydrogel protein carriers can be used in platforms for extracorporeal treatment such as microscale-based devices. In this work, calcium alginate and poly-(vinyl alcohol) hydrogel films were studied for their urate oxidase immobilization and uric acid reduction, which could be implemented in microscale-based extracorporeal devices. A mathematical model was developed in conjunction with uric acid reduction experiments to evaluate the influence of mass transfer and reaction parameters in the Michaelis-Menten kinetic expression. Alginate hydrogels prepared with crosslinker 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-(hydroxysuccinimide) offered superior diffusivity of uric acid in the gel matrix at the maximum value of 1.98 × 10-11 m2 /s compared with alginate prepared solely from ionic crosslinking with 5.31 × 10-12 m2 /s at the same alginate concentration. The maximum value of νmax was experimentally determined at 7.78 × 10-5 mol/(m3 s). A 3% sodium alginate hydrogel with crosslinkers yielded the highest reduction of uric acid at 92.70%. The mathematical model demonstrated an excellent prediction of uric acid conversion suggesting potential use of the model for formulation and maximizing the therapeutic performance of functionalized hydrogels.

Magnetic Assembly of Eu-Doped NaYF4 Nanorods for Field-Responsive Linearly and Circularly Polarized Luminescence.

Colloidal assembly has emerged as an effective avenue for achieving polarized light emission. Here, we showcase the efficacy and versatility of the magnetic colloidal assembly in enabling both linearly and circularly polarized luminescence. Colloidal europium-doped NaYF4 nanorods with surface-bound Fe3O4 nanoparticles are magnetically assembled into linear or chiral superstructures using corresponding fields created in permanent magnets. In a uniform magnetic field generated by opposing poles, the assemblies exhibit photoluminescence with intensity tunable in response to the magnetic field direction, which is higher when the nanorods are perpendicular to light propagation than when they are parallel. The obtained superstructures display strong linearly polarized luminescence when the nanorods are aligned vertically, exhibiting a high degree of polarization up to 0.61. In a quadrupole chiral field generated by permanent magnets, the assemblies emit left-handed or right-handed polarized light depending on the position of the sample placement, attaining a g-factor of 0.04. Furthermore, the superstructures immobilized in a hydrogel film are found to retain their chirality, exhibiting opposite chiroptical responses depending on the sample orientation. The magnetic colloidal assembly approach facilitates the convenient and efficient generation of polarized light emissions from nonmagnetic luminescent materials, thus creating opportunities for tailoring light behavior in developing innovative optoelectronic devices.