Bio-inspired self-healing structural color hydrogel

Biologically inspired self-healing structural color hydrogels were developed by adding a glucose oxidase (GOX)- and catalase (CAT)-filled glutaraldehyde cross-linked BSA hydrogel into methacrylated gelatin (GelMA) inverse opal scaffolds. The composite hydrogel materials with the polymerized GelMA scaffold could maintain the stability of an inverse opal structure and its resultant structural colors, whereas the protein hydrogel filler could impart self-healing capability through the reversible covalent attachment of glutaraldehyde to lysine residues of BSA and enzyme additives. A series of unprecedented structural color materials could be created by assembling and healing the elements of the composite hydrogel. In addition, as both the GelMA and the protein hydrogels were derived from organisms, the composite materials presented high biocompatibility and plasticity. These features of self-healing structural color hydrogels make them excellent functional materials for different applications.

A Topical Hydrogel with Deferiprone and Gallium-Protoporphyrin Targets Bacterial Iron Metabolism and Has Antibiofilm Activity

Many infectious diseases are associated with multidrug-resistant (MDR) bacteria residing in biofilms that require high antibiotic concentrations. While oral drug delivery is frequently ineffective, topical treatments have the potential to deliver higher drug concentrations to the infection site while reducing systemic side effects. This study determined the antibiofilm activity of a surgical wound gel loaded with the iron chelator deferiprone (Def) and the heme analogue gallium-protoporphyrin (GaPP), alone and in combination with ciprofloxacin. Activity against MDR Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Acinetobacter johnsonii biofilms was assessed in the colony biofilm and artificial wound model by enumeration of CFU and correlative light/electron microscopy. While Staphylococcus biofilms were equally susceptible to GaPP and Def-GaPP gels (log10 reduction of 3.8 and 3.7, respectively), the Def-GaPP combination was crucial for significant activity against P. aeruginosa biofilms (log10 reduction of 1.3 for GaPP and 3.3 for Def-GaPP). When Def-GaPP gel was combined with ciprofloxacin, the efficacy exceeded the activity of the individual compounds. Def-GaPP delivered in a surgical wound gel showed significant antibiofilm activity against different MDR strains and could enhance the gel's wound-healing properties. Moreover, Def-GaPP indicated a potentiation of ciprofloxacin. This antibiofilm strategy has potential for clinical utilization as a therapy for topical biofilm-related infections.

Development and characterization of nanostructured lipid carriers based chitosan thermosensitive hydrogel for delivery of dexamethasone

This study aims to explore a novel composite thermosensitive in situ gelling formulation which the nanostructured lipid carriers (NLC) was incorporated into hydroxypropyltrimethyl ammonium chloride chitosan (HACC)-based hydrogels, and the resulting formulation investigated for its potential to act as a potential sustained ocular delivery system. NLC formulation loaded with dexamethasone (DXM) were prepared using the melt-emulsification method. The particle size, zeta potential, encapsulation efficiency, and morphological properties of the NLC were characterized. The HACC was synthesized and structure was analyzed by FT-IR and ¹H NMR. A thermosensitive hydrogel was designed and prepared by simply mixing HACC and β-glycerophosphate (β-GP). The obtained formulation showed a rapid solution-to-gel transition at 35°C. The NLC were then incorporated in HACC/β-GP hydrogel to form a NLC-loaded hydrogel carrier. In vitro release studies, 88.65% of total DXM was released from the NLC-HACC/GP gel within 3days, indicating DXM-based NLC-gel could release drug sustainably. Taken together, DXM-based NLC-HACC/GP gel is a promising drug delivery system.

Effects of Gelatin Hydrogel Containing Anti-Transforming Growth Factor-β Antibody in a Canine Filtration Surgery Model

In this present study, we investigated the effect of a controlled release of anti-transforming growth factor β (TGF-β) antibody on intraocular pressure (IOP), bleb formation, and conjunctival scarring in a canine glaucoma filtration surgery model using gelatin hydrogel (GH). Glaucoma surgery models were made in 14 eyes of 14 beagles and divided into the following two groups: (1) subconjunctival implantation of anti-TGF-β antibody-loaded GH (GH-TGF-β group, n = 7), and (2) subconjunctival implantation of GH alone (GH group, n = 7). IOP and bleb features were then assessed in each eye at 2- and 4-weeks postoperative, followed by histological evaluation. We found that IOP was significantly reduced at 4-weeks postoperative in the two groups (p < 0.05) and that IOP in the GH-TGF-β-group eyes was significantly lower than that in the GH-group eyes (p = 0.006). In addition, the bleb score at 4-weeks postoperative was significantly higher in the GH-TGF-β group than in the GH group (p < 0.05), and the densities of fibroblasts, proliferative-cell nuclear antigen (PCNA)-positive cells, mast cells, and TGF-β-positive cells were significantly lower in the GH-TGF-β group than in the GH group. The findings of this study suggest that, compared with the GH-group eyes, implantation of anti-TGF-β antibody-loaded GH maintains IOP reduction and bleb formation by suppressing conjunctival scarring due to the proliferation of fibroblasts for a longer time period via a sustained release of anti-TGF-β antibody from GH.

Formation of novel hydrogel bio-anode by immobilization of biocatalyst in alginate/polyaniline/titanium-dioxide/graphite composites and its electrical performance

A new bio-anode containing gel-entrapped bacteria in alginate/polyaniline/TiO₂/graphite composites was constructed and electrically investigated. Alginate as dopant and template as well as entrapped gel was used for immobilization of microorganism cells. Increase of polyaniline concentration resulted an increase in the conductivity in gels. Addition of 0.01 and 0.02 g/mL polyaniline caused 6-fold and 10-fold higher conductivity, respectively. Furthermore, addition of 0.05 g/mL graphite powder caused 10-fold higher conductivity and 4-fold higher power density, respectively. The combination of polyaniline and graphite resulted 105-fold higher conductivity and 7-fold higher power-density output. Optimized concentrations of polyaniline and graphite powder were determined to be 0.02 g/mL and 0.05 g/mL, respectively. Modified hydrogel anode was successfully used in microbial fuel cell systems both in semi- and continuous operations modes. In semi-continuous mode, about 7.88 W/m³ power density was obtained after 13 h of fermentation. The glucose consumption rate was calculated to be about 7 mg glucose/h/1.2·10⁷ CFU immobilized cells. Similar power density was observed in the continuous operation mode of the microbial fuel cell, and it was operated stably for more than 7 days. Our results are very promising for development of an improved microbial fuel cell with new type of bio-anode that have higher power density and can operate for long term.

Natural healing-inspired collagen-targeting surgical protein glue for accelerated scarless skin regeneration

Skin scarring after deep dermal injuries is a major clinical problem due to the current therapies limited to established scars with poor understanding of healing mechanisms. From investigation of aberrations within the extracellular matrix involved in pathophysiologic scarring, it was revealed that one of the main factors responsible for impaired healing is abnormal collagen reorganization. Here, inspired by the fundamental roles of decorin, a collagen-targeting proteoglycan, in collagen remodeling, we created a scar-preventive collagen-targeting glue consisting of a newly designed collagen-binding mussel adhesive protein and a specific glycosaminoglycan. The collagen-targeting glue specifically bound to type I collagen in a dose-dependent manner and regulated the rate and the degree of fibrillogenesis. In a rat skin excisional model, the collagen-targeting glue successfully accelerated initial wound regeneration as defined by effective reepithelialization, neovascularization, and rapid collagen synthesis. Moreover, the improved dermal collagen architecture was demonstrated by uniform size of collagen fibrils, their regular packing, and a restoration of healthy tissue component. Collectively, our natural healing-inspired collagen-targeting glue may be a promising therapeutic option for improving the healing rate with high-quality and effective scar inhibition.

Linseed hydrogel-mediated green synthesis of silver nanoparticles for antimicrobial and wound-dressing applications

Polysaccharides are being extensively employed for the synthesis of silver nanoparticles (Ag NPs) having diverse morphology and applications. Herein, we present a novel and green synthesis of Ag NPs without using any physical reaction conditions. Linseed hydrogel (LSH) was used as a template to reduce Ag+ to Ag0. AgNO3 (10, 20, and 30 mmol) solutions were mixed with LSH suspension in deionized water and exposed to diffused sunlight. Reaction was monitored by noting the change in the color of reaction mixture up to 10 h. Ag NPs showed characteristic ultraviolet-visible (UV/Vis) absorptions from 410 to 437 nm in the case of sunlight and 397-410 nm in the case of temperature study. Transmission electron microscopy images revealed the formation of spherical Ag NPs in the range of 10-35 nm. Face-centered cubic array of Ag NPs was confirmed by characteristic diffraction peaks in powder X-ray diffraction spectrum. Ag NPs were stored in LSH thin films, and UV/Vis spectra recorded after 6 months indicated that Ag NPs retained their texture over the storage period. Significant antimicrobial activity was observed when microbial cultures (bacteria and fungi) were exposed to the synthesized Ag NPs. Wound-healing studies revealed that Ag NP-impregnated LSH thin films could have potential applications as an antimicrobial dressing in wound management procedures.

A Moldable Nanocomposite Hydrogel Composed of a Mussel-Inspired Polymer and a Nanosilicate as a Fit-to-Shape Tissue Sealant

The engineering of bioadhesives to bind and conform to the complex contour of tissue surfaces remains a challenge. We have developed a novel moldable nanocomposite hydrogel by combining dopamine-modified poly(ethylene glycol) and the nanosilicate Laponite, without the use of cytotoxic oxidants. The hydrogel transitioned from a reversibly cross-linked network formed by dopamine-Laponite interfacial interactions to a covalently cross-linked network through the slow autoxidation and cross-linking of catechol moieties. Initially, the hydrogel could be remolded to different shapes, could recover from large strain deformation, and could be injected through a syringe to adhere to the convex contour of a tissue surface. With time, the hydrogel solidified to adopt the new shape and sealed defects on the tissue. This fit-to-shape sealant has potential in sealing tissues with non-flat geometries, such as a sutured anastomosis.

Preparation of Quantum Dots Hydrogel Nanocomposites with Improved Cytotoxicity

Nanocomposites are materials with unique properties and a wide range of applications. The combination of different nanostructures with traditional materials gives a variety of possibilities that should be analyzed. Especially, functional fluorescent semiconductor quantum dots (QDs) embedded in polymeric matrices have shown promising fluorescence and biocompatibility properties. These hybrid materials can be used in medical applications such as biodiagnostic and bioimaging. In this study, two hydrogels, one of polyethylene glycol diacrylate (PEGDA) and other of polyacrylamide (PAAm), were prepared with quantum dots of CdTe (4 nm of diameter) and characterized. The aim of this research was to analyze the optical properties of the nanocomposites and their cell viability. QDs nanocomposites were fabricated by a free radical polymerization process. The optical studies showed that the nanocomposites have well defined properties of fluorescence. To study the biocompatibility of the nanocomposites, metastatic B16f10 cell line were used and MTT assay was performed. The nanocomposites had a significant improved cell viability compared with QDs solutions.

Nanoemulsion-Based Hydrogel for Topical Delivery of Highly Skin-Permeable Growth Factor Combinations: Preparation and In Vitro Evaluation

Topical administration of growth factors has been suggested as a promising strategy for promoting the healing process and skin regeneration in wound management. However, several restrictions hinder their successful clinical use; specifically, limited percutaneous absorption causes inconsistent efficacy, and various growth factors with specific functionalities are required at different stages of healing. To overcome these shortcomings, previously we have constructed highly skin-permeable analogues of epidermal growth factor (EGF), insulin-like growth factor-I (IGF-I), and platelet-derived growth factor-A (PDGF-A) (LMWP-EGF, LMWP-IGF-I and LMWP-PDGF-A) by genetically conjugating the low-molecular-weight protamine (LMWP) to their N-terminus. In the present study, we determined the optimal concentration ratio of these growth factors by investigating In Vitro cell proliferation and the scratch wound repairing assay. After confirming synergetic effects of growth factors in combinations, we developed a topical delivery system consisting of a nanoemulsion (NE)-dispersed polyvinylpyrrolidone hydrogel loaded with all three growth factors. In Vitro permeability studies were also performed to assess whether the LMWP-conjugated growth factors in the formulation enhanced their skin permeation compared to native growth factors. Combinations of native or LMWP-fused growth factors significantly promoted fibroblast proliferation and scratch wound recovery, and the synergy of LMWP-EGF, LMWP-IGF-I and LMWP-PDGF-A was optimal at a ratio of 100:100:10 by concentration. The growth factor combination-loaded NE appeared to be spherical under cryo-transmission electron microscopy and the average droplet diameter was 127±4.30 nm. The LMWP-conjugated growth factors allowed significantly higher skin permeation than native growth factors from the NE-dispersed hydrogel. Thus, the LMWP-conjugated growth factor combination-loaded NE-dispersed hydrogel is expected to induce more rapid and prolonged wound healing.

Morphological Properties of Siloxane-Hydrogel Contact Lens Surfaces

PURPOSE

The aim of this study was to quantitatively characterize the micromorphology of contact lens (CL) surfaces using atomic force microscopy (AFM) and multifractal analysis.

MATERIALS AND METHODS

AFM and multifractal analysis were used to characterize the topography of new and worn siloxane-hydrogel CLs made of Filcon V (I FDA group). CL surface roughness was studied by AFM in intermittent-contact mode, in air, on square areas of 25 and 100 μm², by using a Nanoscope V MultiMode (Bruker). Detailed surface characterization of the surface topography was obtained using statistical parameters of 3-D (three-dimensional) surface roughness, in accordance with ISO 25178-2: 2012.

RESULTS

Before wear, the surface was found to be characterized by out-of-plane and sharp structures, whilst after a wear of 8 h, two typical morphologies were observed. One morphology (sharp type) has a similar aspect as the unworn CLs and the other morphology (smooth type) is characterized by troughs and bumpy structures. The analysis of the AFM images revealed a multifractal geometry. The generalized dimension D_q and the singularity spectrum f(α) provided quantitative values that characterize the local scale properties of CL surface geometry at nanometer scale.

CONCLUSIONS

Surface statistical parameters deduced by multifractal analysis can be used to assess the CL micromorphology and can be used by manufacturers in developing CLs with improved surface characteristics. These parameters can also be used in understanding the tribological interactions of the back surface of the CL with the corneal surface and the front surface of the CL with the under-surface of the eyelid (friction, wear, and micro-elastohydrodynamic lubrication at a nanometer scale).

Boron removal by a composite sorbent: Polyethylenimine/tannic acid derivative immobilized in alginate hydrogel beads

A novel composite material was prepared by the grafting of tannic acid on polyethylenimine (PEI), which allows an efficient sorption of boron (sorption capacity close to 0.89 mmol B g^-1). The encapsulation of this chelating sorbent (finely crushed) facilitates its use (readily solid/liquid separation, use in fixed-bed columns) at the expense of a loss in sorption capacity (proportionally decreased by the introduction of alginate having poor efficiency for boron uptake). Sorption isotherms are modeled using the Langmuir equation, while the kinetic profiles are presented a good fit by pseudo-second order rate equation. In addition, the encapsulating matrix introduces supplementary resistance to intraparticle diffusion, especially when the resin is dried without control: freeze-drying partially limits this effect. The stability (at long-term storage) of the sorbent is improved when the sorbent is stored under nitrogen atmosphere. The presence of an excess of NaCl was investigated. The degradation of the hydrogel (by ion-exchange of Ca(II) with Na(I)) leads to a decrease in the sorption performance of composite material but the action of Ca(II) ions in the solutions re-stabilizes the hydrogel.

Structuring of composite hydrogel bioadhesives and its effect on properties and bonding mechanism

Bioadhesives are polymeric hydrogels that can adhere to a tissue after crosslinking and are an essential element in nearly all surgeries worldwide. Several bioadhesives are commercially available. However, none of them are ideal. The main limitation of current tissue adhesives is the tradeoff between biocompatibility and mechanical strength, especially in wet hemorrhagic environments. Our novel bioadhesives are based on the natural polymers gelatin (coldwater fish) and alginate, crosslinked by carbodiimide (EDC). Two types of hemostatic agents with a layered silicate structure, montmorillonite (MMT) and kaolin, were loaded in order to improve the sealing ability in a hemorrhagic environment. The effect of the adhesive's components on its mechanical strength was studied by three different methods - burst strength, lap shear and compression. The viscosity, gelation time and structural features of the adhesive were also studied. A qualitative model that describes the effect of the bioadhesive's parameters on the cohesive and adhesive strength was developed. A formulation based on 400mg/mL gelatin, 10mg/mL alginate and 20mg/mL EDC was found as optimal, enabling a burst strength of 387mmHg. Incorporation of kaolin increased the burst strength by 25% due to microcomposite structuring, whereas MMT increased the burst strength by 50% although loaded in a smaller concentration, due to nano-structuring effects. This research clearly shows that the incorporation of kaolin and MMT in gelatin-alginate surgical sealants is a very promising novel approach for improving the bonding strength and physical properties of surgical sealants for use in hemorrhagic environments.

STATEMENT OF SIGNIFICANCE

The current manuscript focuses on novel bioadhesives, based on natural polymers and loaded with hemostatic agents with a layered silicate structure, in order to improve the sealing ability in hemorrhagic environment. Such composite bioadhesives have not been developed and studied before. The effect of the adhesive's components on its mechanical strength was studied by three different methods, as well as the physical properties and structural features. Thorough understanding of these unique biomaterials resulted in a qualitative model which describes the effect of the bioadhesive's parameters on the cohesive and adhesive strength. Thus, structure-property-function relationships are presented. Structuring of the composite bioadhesives and its effect of the properties and bonding mechanism, are expected to be of high interest to Acta readership.

pH-sensitive peptide hydrogel for glucose-responsive insulin delivery

Glucose-responsive system is one of important options for self-regulated insulin delivery to treat diabetes, which has become an issue of great public health concern in the world. In this study, we developed a novel and biocompatible glucose-responsive insulin delivery system using a pH-sensitive peptide hydrogel as a carrier loaded with glucose oxidase, catalase and insulin. The peptide could self-assemble into hydrogel under physiological conditions. When hypoglycemia is encountered, neighboring alkaline amino acid side chains are significantly repulsed due to reduced local pH by the enzymatic conversion of glucose into gluconic acid. This is followed by unfolding of individual hairpins, disassembly and release of insulin. The glucose-responsive hydrogel system was characterized on the basis of structure, conformation, rheology, morphology, acid-sensitivity and the amount of consistent release of insulin in vitro and vivo. The results illustrated that our system can not only regulate the blood glucose levels in vitro but also in mice models having STZ-induced diabetes.

STATEMENT OF SIGNIFICANCE

In this report, we have shown the following significance supported by the experimental results. 1. We successfully developed, characterized and screened a novel pH-responsive peptide. 2. We successfully developed a novel and biocompatible pH-sensitive peptide hydrogel as glucose-responsive insulin delivery system loaded with glucose oxidase, catalase and insulin. 3. We successfully confirmed that the hydrogel platform could regulate the blood glucose level in vitro and in vivo. Overall, we have shown enough significance and novelty with this smart hydrogel platform in terms of biomaterials, peptide chemistry, self-assembly, hydrogel and drug delivery. So we believe this manuscript is suitable for Acta Biomaterialia.

Assessing the Potential of Folded Globular Polyproteins As Hydrogel Building Blocks

The native states of proteins generally have stable well-defined folded structures endowing these biomolecules with specific functionality and molecular recognition abilities. Here we explore the potential of using folded globular polyproteins as building blocks for hydrogels. Photochemically cross-linked hydrogels were produced from polyproteins containing either five domains of I27 ((I27)5), protein L ((pL)5), or a 1:1 blend of these proteins. SAXS analysis showed that (I27)5 exists as a single rod-like structure, while (pL)5 shows signatures of self-aggregation in solution. SANS measurements showed that both polyprotein hydrogels have a similar nanoscopic structure, with protein L hydrogels being formed from smaller and more compact clusters. The polyprotein hydrogels showed small energy dissipation in a load/unload cycle, which significantly increased when the hydrogels were formed in the unfolded state. This study demonstrates the use of folded proteins as building blocks in hydrogels, and highlights the potential versatility that can be offered in tuning the mechanical, structural, and functional properties of polyproteins.

Injectable supramolecular hydrogel formed from α-cyclodextrin and PEGylated arginine-functionalized poly(l-lysine) dendron for sustained MMP-9 shRNA plasmid delivery

Hydrogels have attracted much attention in cancer therapy and tissue engineering due to their sustained gene delivery ability. To obtain an injectable and high-efficiency gene delivery hydrogel, methoxypolyethylene glycol (MPEG) was used to conjugate with the arginine-functionalized poly(l-lysine) dendron (PLLD-Arg) by click reaction, and then the synthesized MPEG-PLLD-Arg interacted with α-cyclodextrin (α-CD) to form the supramolecular hydrogel by the host-guest interaction. The gelation dynamics, hydrogel strength and shear viscosity could be modulated by α-CD content in the hydrogel. MPEG-PLLD-Arg was confirmed to bind and deliver gene effectively, and its gene transfection efficiency was significantly higher than PEI-25k under its optimized condition. After gelation, MMP-9 shRNA plasmid (pMMP-9) could be encapsulated into the hydrogel matrix in situ and be released from the hydrogels sustainedly, as the release rate was dependent on α-CD content. The released MPEG-PLLD-Arg/pMMP-9 complex still showed better transfection efficiency than PEI-25k and induced sustained tumor cell apoptosis. Also, in vivo assays indicated that this pMMP-9-loaded supramolecular hydrogel could result in the sustained tumor growth inhibition meanwhile showed good biocompatibility. As an injectable, sustained and high-efficiency gene delivery system, this supramolecular hydrogel is a promising candidate for long-term gene therapy.

STATEMENT OF SIGNIFICANCE

To realize the sustained gene delivery for gene therapy, a supramolecular hydrogel with high-efficiency gene delivery ability was prepared through the host-guest interaction between α-cyclodextrin and PEGylated arginine-functionalized poly(l-lysine) dendron. The obtained hydrogel was injectable and biocompatible with adjustable physicochemical property. More importantly, the hydrogel showed the high-efficiency and sustained gene transfection to our used cells, better than PEI-25k. The supramolecular hydrogel resulted in the sustained tumor growth inhibition meanwhile keep good biocompatibility. As an injectable, sustained and high-efficiency gene delivery system, this supramolecular hydrogel is a promising candidate in long-term gene therapy and tissue engineering.

Enhanced Swelling and Responsive Properties of Pineapple Peel Carboxymethyl Cellulose-g-poly(acrylic acid-co-acrylamide) Superabsorbent Hydrogel by the Introduction of Carclazyte

The superabsorbent hydrogels were synthesized by grafting acrylic acid and acrylamide onto pineapple peel carboxymethyl cellulose and effect of carclazyte introduction was compared. The structure and morphology of the superabsorbents were investigated by Fourier transform infrared spectroscopy, X-ray diffraction, and field emission scanning electron microscopy. Swelling behaviors of the superabsorbents were investigated in distilled water, 0.9% NaCl solution, various salt and pH solutions, as well as surfactant solutions and simulated physiological fluids. The swelling dynamic mechanism of the superabsorbents was explained well by Fickian diffusion and Schott's pseudo-second-order models. The introduction of carclazyte effectively improved the swelling capacity of the superabsorbents in various solutions as well as its salt- and pH-sensitivity. The prepared superabsorbents also exhibited excellent sensitivities to various surfactant solutions and simulated physiological fluids, showing potential applications in the biomaterials field.

Effect of noncovalent interaction on the self-assembly of a designed peptide and its potential use as a carrier for controlled bFGF release

Peptide self-assembly is one of the promising bottom-up approaches for creating synthetic supermolecular architectures. Noncovalent interactions such as hydrophobic packing, electrostatic interaction, and polypeptide chain entropy (ΔSC) are the most relevant factors that affect the folding and self-assembly of peptides and the stability of supermolecular structures. The GVGV tetrapeptide is an abundant repeat in elastin, an extracellular matrix protein. In this study, four GVGV-containing peptides were designed with the aim of understanding the effects of these weak interactions on peptide self-assembly. Transmission electron microscopy, circular dichroism spectroscopy, dynamic light scattering measurements, and rheometry assays were used to study the structural features of the peptides. Because self-assembling peptides with different amino acid sequences may significantly affect protein release, basic fibroblast growth factor (bFGF) was used as a model molecule and encapsulated within the P2 (RLDLGVGVRLDLGVGV) hydrogel to study the release kinetics. The results showed that the balance among hydrophobic effects, electrostatic interactions, and chain entropy determined the molecular state and self-assembly of the peptide. Moreover, encapsulation of bFGF within the P2 hydrogel allowed its sustained release without causing changes in the secondary structure. The release profiles could be tuned by adjusting the P2 hydrogel concentration. Cell Counting Kit-8 and Western blot assays demonstrated that the encapsulated and released bFGFs were biologically active and capable of promoting the proliferation of murine fibroblast NIH-3T3 cells, most likely due to the activation of downstream signaling pathways.

Self-Healing Hydrogel Pore-Filled Water Filtration Membranes

Damages to water filtration membranes during installation and operation are known to cause detrimental loss of the product water quality. Membranes that have the ability to self-heal would recover their original rejection levels autonomously, bypassing the need for costly integrity monitoring and membrane replacement practices. Herein, we fabricated hydrogel pore-filled membranes via in situ graft polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) onto microporous poly(ether sulfone) (PES) substrates and successfully demonstrated their self-healing ability. Covalent attachment of the hydrogel to the substrate was essential for stable membrane performance. The membranes autonomously restore their particle rejection up to 99% from rejection levels as low as 30% after being physically damaged. We attribute the observed self-healing property to swelling of the pore-filling hydrogel into the damage site, strong hydrogen bonding, and molecular interdiffusion. The results of this study show that hydrogel pore-filled membranes are a promising new class of materials for fabricating self-healing membranes.

Injectable, Guest-Host Assembled Polyethylenimine Hydrogel for siRNA Delivery

While siRNA has tremendous potential for therapeutic applications, advancement is limited by poor delivery systems. Systemically, siRNAs are rapidly degraded, may have off-target silencing, and necessitate high working concentrations. To overcome this, we developed an injectable, guest-host assembled hydrogel between polyethylenimine (PEI) and polyethylene glycol (PEG) for local siRNA delivery. Guest-host modified polymers assembled with siRNAs to form polyplexes that had improved transfection and viability compared to PEI. At higher concentrations, these polymers assembled into shear-thinning hydrogels that rapidly self-healed. With siRNA encapsulation, the assemblies eroded as polyplexes which were active and transfected cells, observed by Cy3-siRNA uptake or GFP silencing in vitro. When injected into rat myocardium, the hydrogels localized polyplex release, observed by uptake of Cy5.5-siRNA and silencing of GFP for 1 week in a GFP-expressing rat. These results illustrate the potential for this system to be applied for therapeutic siRNA delivery, such as in cardiac pathologies.

A Mussel-Inspired Conductive, Self-Adhesive, and Self-Healable Tough Hydrogel as Cell Stimulators and Implantable Bioelectronics

A graphene oxide conductive hydrogel is reported that simultaneously possesses high toughness, self-healability, and self-adhesiveness. Inspired by the adhesion behaviors of mussels, our conductive hydrogel shows self-adhesiveness on various surfaces and soft tissues. The hydrogel can be used as self-adhesive bioelectronics, such as electrical stimulators to regulate cell activity and implantable electrodes for recording in vivo signals.

Patterning Electrospun Nanofibers via Agarose Hydrogel Stamps to Spatially Coordinate Cell Orientation in Microfluidic Device

A straightforward, inexpensive, and reliable approach to pattern electrospun nanofibers via solvent-containing agarose hydrogel stamps is reported. Complex hierarchical microstructures can be further constructed via appropriate multistep permutation of microcontact patterning and electrospinning. As a proof-of-concept application, the patterned electrospun nanofibers are employed to spatially coordinate cell orientation in microfluidic devices.

Encapsulation of Pancreatic Lipase in Hydrogel Beads with Self-Regulating Internal pH Microenvironments: Retention of Lipase Activity after Exposure to Gastric Conditions

Oral delivery of lipase is important for individuals with exocrine pancreatic insufficiency; however, lipase loses activity when exposed to the highly acidic gastric environment. In this study, pancreatic lipase was encapsulated in hydrogel beads fabricated from alginate (gel former), calcium chloride (cross-linker), and magnesium hydroxide (buffer). Fluorescence confocal microscopy imaging was used to map the pH microclimate within the hydrogel beads under simulated gastrointestinal tract (GIT) conditions. The pH within buffer-free beads rapidly decreased when they moved from mouth (pH 6.3) to stomach (pH <4), leading to a loss of lipase activity in the small intestine. Conversely, the pH inside buffer-loaded beads remained close to neutral in the mouth (pH 7.33) and stomach (pH 7.39), leading to retention of lipase activity in the small intestine, as shown by pH-stat analysis of lipid digestion. The presence of the encapsulated buffer also reduced bead shrinkage under gastric conditions.

Design, Optimization, and Evaluation of a Novel Metronidazole-Loaded Gastro-Retentive pH-Sensitive Hydrogel

Floating pH-sensitive chitosan hydrogels containing metronidazole were developed for the eradication of Helicobacter pylori from the stomach. Hydrogels were prepared by crosslinking medium or high molecular weight chitosan in lyophilized solutions containing metronidazole using either citrate or tripolyphosphate (TPP) salts at 1% or 2% concentration. A 2³ factorial design was developed to study the influence of formulation parameters on the physical characteristics of the prepared hydrogels. The interaction between hydrogel components was investigated. The morphology of the prepared hydrogels was inspected and their percentage swelling, release pattern, and moisture content were evaluated. The results revealed the absence of interaction between hydrogel components and their highly porous structure. Percentage swelling of the hydrogels was much higher, and drug release was faster in gastric pH compared with intestinal pH. The formula prepared using 2% high molecular weight chitosan and 2% TPP significantly swelled (700%) within the first 4 h and released the loaded drug over a period of 24 h. Its moisture content was not affected by storage at high relative humidity. Therefore, this formula was selected to be tested in dogs for its gastric retention (using X-ray radiography) and efficacy in the eradication of H. pylori (using histopathological and microbiological examination). The results revealed that the prepared hydrogel formula was retained in dog stomach for at least 48 h, and it was more effective against H. pylori than the commercially available oral metronidazole tablets (Flagyl®).

Poly(sodium methacrylate)/eggshell particles hydrogel composites as dye sorbent

Eggshell (ES) particles as an available and low-cost waste material were utilized to prepare novel hydrogel composites for dye adsorbing application. For this purpose, solution polymerization of sodium methacrylate was carried out in the presence of ES particles with various size ranges. Results showed that incorporation of ES particles resulted in heterogeneous pores and cavities in the structure of the poly(sodium methacrylate) (PNaMA) matrix. Hydrogel composites with lower content (20 wt%) and smaller size (<75 μm) of ES particles presented higher water absorption capacity. The equilibrium water absorption values in distilled water were higher than phosphate buffered saline medium. ES particles showed low methylene blue (MB) and crystal violet (CV) adsorption capacities due to electrostatic repulsion of the positively charged species on the surface of ES particles and dye molecules. In contrast, hydrogel composites depicted fast and considerable dye adsorbability. The combination of 60 wt% ES particles within PNaMA provided a cost-effective adsorbent with similar CV adsorption capacity compared with the unfilled matrix, while MB removal was slightly decreased. The dye adsorption by either ES particles or hydrogel composites followed the pseudo-second-order kinetics, indicating that chemical sorption is the rate-limiting step for both of them.