Swelling Of Hydrogels Research Articles

Inclusion of konjac glucomannan in pea protein hydrogels improved the rheological and in vitro release properties of the composite hydrogels

In this study, a composite hydrogel consisting of pea protein and konjac glucomannan (KG) was fabricated using three approaches, namely neutral, salt-set, and alkaline gelation. Hydrogels made from pea protein were brittle and weak. The addition of KG improved the elasticity and water holding capacity of the pea protein hydrogels. Concomitantly, a decrease in syneresis rate and swelling of the composite hydrogels was observed. The alkaline-set hydrogels exhibited the highest resilience to strain. Thixotropicity was found to be less pronounced for salt-set hydrogels. Sulphate had a greater positive effect on the structural recovery and negative effect on hysteresis area than chloride due to the greater salting-out effect of the sulphates. The addition of KG facilitated the formation of an interconnected structure with limited mobility of biopolymer chains. A sharp increase in G' and G" during the temperature ramp indicated the predominance of hydrophobic interactions towards the aggregation of biopolymers. The infrared spectra of the hydrogels revealed a change in secondary structure of proteins on addition of KG. A controlled in vitro release of riboflavin was observed in neutral and salt-set hydrogels. The alkaline-set hydrogels exhibited a prolonged gastric retention time, thereby establishing in vitro antacid activity in the gastric environment.

A Janus hydrogel sealant with instant wet adhesion and anti-swelling behavior for gastric perforation repair

Achieving instant adhesion on wet tissues and preventing the concurrently occurred postoperative tissue adhesion remain tough challenges but urgently demanded. And the deteriorated cohesion and adhesion caused by undesired swelling of hydrogel could not be ignored. Herein, we developed a Janus hydrogel with instant wet adhesion and anti-swelling behavior, based on poly (acrylic acid) (PAA), gelatin (GT) and hyperbranched polymers modified with catechol (HBPC). The asymmetric structure is achieved through complexed one-side of the hydrogel with cationic polymers. The strong physical interaction between PAA and GT formed during immersing in water enhanced the mechanical strength of the gels. And the hydrogel exhibits good anti-swelling behavior, which circumvents the limitations of conventional hydrogel caused by swelling. Water drainage induced by hydrophobic component and the following removal of water residuals achieved by hydrophilic PAA synergistically enhanced the instant wet adhesion of the hydrogel. Besides, pH-responsive protonation of carboxyl groups in PAA equipped the adhesive with extreme acid-tolerance. The in vivo evaluation results demonstrated that the asymmetric adhesive hydrogel could promote the repair of gastric perforation while reducing the risk of postoperative tissue adhesion. The hydrogel with asymmetric wet adhesion might provide valuable insights into the establishment of bioadhesives for gastric sealing and repair.

ROS-responsive hydrogels with spatiotemporally sequential delivery of antibacterial and anti-inflammatory drugs for the repair of MRSA-infected wounds.

For the treatment of MRSA-infected wounds, the spatiotemporally sequential delivery of antibacterial and anti-inflammatory drugs is a promising strategy. In this study, ROS-responsive HA-PBA/PVA (HPA) hydrogel was prepared by phenylborate ester bond cross-linking between hyaluronic acid-grafted 3-amino phenylboronic acid (HA-PBA) and polyvinyl alcohol (PVA) to achieve spatiotemporally controlled release of two kinds of drug to treat MRSA-infected wound. The hydrophilic antibiotic moxifloxacin (M) was directly loaded in the hydrogel. And hydrophobic curcumin (Cur) with anti-inflammatory function was first mixed with Pluronic F127 (PF) to form Cur-encapsulated PF micelles (Cur-PF), and then loaded into the HPA hydrogel. Due to the different hydrophilic and hydrophobic nature of moxifloxacin and Cur and their different existing forms in the HPA hydrogel, the final HPA/M&Cur-PF hydrogel can achieve different spatiotemporally sequential delivery of the two drugs. In addition, the swelling, degradation, self-healing, antibacterial, anti-inflammatory, antioxidant property, and biocompatibility of hydrogels were tested. Finally, in the MRSA-infected mouse skin wound, the hydrogel-treated group showed faster wound closure, less inflammation and more collagen deposition. Immunofluorescence experiments further confirmed that the hydrogel promoted better repair by reducing inflammation (TNF-α) and promoting vascular (VEGF) regeneration. In conclusion, this HPA/M&Cur-PF hydrogel that can spatiotemporally sequential deliver antibacterial and anti-inflammatory drugs showed great potential for the repair of MRSA-infected skin wounds.

Fluorescent Composite Cotton Fabric Modified with Crosslinked Chitosan for Theranostic Applications

Developing multifunctional textile material for wound dressing is challenging due to the variety of wounds and their differing healing stages. Therefore, theranostics replaces the traditional approach to provide patient comfort and accelerated healing. In this study, we developed and compared three different materials. For this purpose, for the first time, chitosan was modified with 4-nitro-1,8-naphthalic anhydride in N,N-dimethylformamide (DMF) suspension, and subsequent nucleophilic substitution of the nitro group with N,N-dimethylamino group, whereby chitosan with a yellow color and fluorescence was obtained. Cotton fabric was impregnated successively with a citric acid solution and solution from chitosan and chitosan modified with 1,8-naphthalimide fluorophore (CN material). The same experimental protocol was applied for the second material, but indomethacin was added to the chitosan solution (CNI material). The third material was prepared similarly to the second but was immersed in an alginate solution as a last step (CNIA material). The obtained materials have been characterized by optical and scanning electron microscopy and thermal analysis (TG-DTA-DTG). Indomethacin release from composite materials and hydrogel swelling and erosion in phosphate buffer pH 7.4 at 37 °C was examined using gravimetric analysis, UV-vis absorption, and fluorescence spectroscopy. The antimicrobial activity of the cotton samples has been evaluated against B. cereus and P. aeruginosa as model bacterial strains. The analysis showed that CN material inhibited about 98.8% of the growth of P. aeruginosa and about 95.5% of the growth of B. cereus. Other composite materials combine antimicrobial properties with a sustained release of biologically active substances that can observed visually.

Multifunctional hydrogel for synergistic reoxygenation and chemo/photothermal therapy in metastatic breast cancer recurrence and wound infection

Metastatic recurrence and postoperative wound infection are two major challenges for breast cancer patients. In this study, a multifunctional responsive hydrogel system was developed for synergistic reoxygenation and chemo/photothermal therapy in metastatic breast cancer and wound infection. The hydrogel system was obtained by cross-linking Prussian blue-modified N-carboxyethyl chitosan (PBCEC) and oxidized sodium alginate using the amino and aldehyde groups on the polysaccharides, resulting in the formation of responsive dynamic imine bonds. Conditioned stimulation (e.g., acid microenvironment) enabled the controlled swelling of hydrogels as well as subsequent slow release of loaded doxorubicin (DOX). Additionally, this hydrogel system decomposed endogenous reactive oxygen species into oxygen to relieve the hypoxic tumor microenvironment and promote the healing of infected-wounds. Both in vitro and in vivo experiments demonstrated the synergistic reoxygenation and chemo/photothermal effects of the PB/DOX hydrogel system against metastatic breast cancer and its recurrence, as well as postoperative wound infection. Thus, the combination of reoxygenation and chemo/photothermal therapy represents a novel strategy for treating and preventing tumor recurrence and associated wound infection.

Poromechanical modeling of fluid penetration in chemo-responsive gels: Parameter optimization and applications

As an important category of smart materials, stimuli-responsive hydrogels are highly concerned due to their extensive application possibilities and their outstanding biocompatibilities. The ability of responsive hydrogels about significant volume change by external stimuli inspires the design of electronic devices, for example, as sensors and actuators. The modeling of the hydrogel behavior enables the optimization of corresponding applications. In the present research, on the basis of the experimentally determined material parameters, a chemo-poromechanical model was implemented in COMSOL Multiphysics® to investigate the constricted swelling of hydrogels. The swelling kinetics affected by the diffusion coefficient is discussed in detail with numerical simulations.

Multifunctional Hydrogels Based on Cellulose and Modified Lignin for Advanced Wounds Management.

Considering the complex process of wound healing, it is expected that an optimal wound dressing should be able to overcome the multiple obstacles that can be encountered in the wound healing process. An ideal dressing should be biocompatible, biodegradable and able to maintain moisture, as well as allow the removal of exudate, have antibacterial properties, protect the wound from pathogens and promote wound healing. Starting from this desideratum, we intended to design a multifunctional hydrogel that would present good biocompatibility, the ability to provide a favorable environment for wound healing, antibacterial properties, and also, the capacity to release drugs in a controlled manner. In the preparation of hydrogels, two natural polymers were used, cellulose (C) and chemically modified lignin (LE), which were chemically cross-linked in the presence of epichlorohydrin. The structural and morphological characterization of CLE hydrogels was performed by ATR-FTIR spectroscopy and scanning electron microscopy (SEM), respectively. In addition, the degree of swelling of CLE hydrogels, the incorporation/release kinetics of procaine hydrochloride (PrHy), and their cytotoxicity and antibacterial properties were investigated. The rheological characterization, mechanical properties and mucoadhesion assessment completed the study of CLE hydrogels. The obtained results show that CLE hydrogels have an increased degree of swelling compared to cellulose-based hydrogel, a better capacity to encapsulate PrHy and to control the release of the drug, as well as antibacterial properties and improved mucoadhesion. All these characteristics highlight that the addition of LE to the cellulose matrix has a positive impact on the properties of CLE hydrogels, confirming that these hydrogels can be considered as potential candidates for applications as oral wound dressings.

Imperfect cross-linking of xanthan for pH-responsive bio-based composite moist wound dressings by stencil printing.

The work addresses the use of bio-based and -degradable materials for the production of a moist, adaptive and anti-microbial wound dressing. The dressing is targeted to exhibit a pH-dependent active agent release. Xanthan hydrogel structures are coated on cellulose fabrics via stencil printing and subsequently cross-linked using glyoxal. By alteration of the cross-linker content from 1 to 6% by mass, the hydrogel elasticity can be tuned within a range of 2-16kPa storage modulus. Increasing initial glyoxal concentrations also result in higher amounts of glyoxal release. Glyoxal, an anti-microbial agent with approval in veterinary medicine, is mostly released upon wound application supporting infection management. As wound simulation, normal saline, as pH 5 and pH 8 buffer solutions, were used. The release profile and magnitude of approx. 65%-90% glyoxal is pH-dependent. Increased release rates of glyoxal are present in pH 8 fluids, which mostly base on faster hydrogel swelling. Higher total glyoxal release is present in pH 5 fluid and normal saline after 3days. Accordingly, a pH-dependent release profile was encountered. As glyoxal attacks any cell unselectively, it is expected to be effective against antibiotic resistant bacteria. By stencil printing the dressing size can be adjusted to minimize healthy glyoxal tissue exposure.

Development of Poly(vinyl alcohol) Grafted Glycidyl Methacrylate/Cellulose Nanofiber Injectable Hydrogels for Meniscus Tissue Engineering.

This study aimed to develop poly (vinyl alcohol) grafted glycidyl methacrylate/cellulose nanofiber (PVA-g-GMA/CNF) injectable hydrogels for meniscus tissue engineering. PVA-g-GMA is an interesting polymer for preparing cross-linking injectable hydrogels with UV radiation, but it has poor mechanical properties and low cell proliferation. In this study, CNF as a reinforcing agent was selected to improve mechanical properties and cell proliferation in PVA-g-GMA injectable hydro-gels. The effect of CNF concentration on hydrogel properties was investigated. Both PVA-g-GMA and PVA-g-GMA hydrogels incorporating 0.3, 0.5, and 0.7% (w/v) CNF can be formed by UV curing at a wavelength of 365 nm, 6 mW/cm2 for 10 min. All hydrogels showed substantial microporosity with interconnected tunnels, and a pore size diameter range of 3-68 µm. In addition, all hydrogels also showed high physicochemical properties, a gel fraction of 81-82%, porosity of 83-94%, water content of 73-87%, and water swelling of 272-652%. The water content and swelling of hydrogels were increased when CNF concentration increased. It is worth noting that the reduction of porosity in the hydrogels occurred with increasing CNF concentration. With increasing CNF concentration from 0.3% to 0.7% (w/v), the compressive strength and compressive modulus of the hydrogels significantly increased from 23 kPa to 127 kPa and 27 kPa to 130 kPa, respectively. All of the hydrogels were seeded with human cartilage stem/progenitor cells (CSPCs) and cultured for 14 days. PVA-g-GMA hydrogels incorporating 0.5% and 0.7% (w/v) CNF demonstrated a higher cell proliferation rate than PVA-g-GMA and PVA-g-GMA hydrogels incorporating 0.3% (w/v) CNF, as confirmed by MTT assay. At optimum formulation, 10%PVA-g-GMA/0.7%CNF injectable hydrogel met tissue engineering requirements, which showed excellent properties and significantly promoted cell proliferation, and has a great potential for meniscus tissue engineering application.

Multilayer Hydrogel Microcubes: Effects of Templating Particle Morphology on Cubic Hydrogel Properties

AbstractNon‐spherical stimuli‐responsive polymeric particles have shown critical importance in therapeutic delivery. Herein, pH‐responsive poly(methacrylic acid) (PMAA) cubic hydrogel microparticles are synthesized by crosslinking PMAA layers within PMAA/poly(N‐vinylpyrrolidone) hydrogen‐bonded multilayers templated on porous inorganic microparticles. This study investigates the effects of template porosity and surface morphology on the PMAA multilayer hydrogel microcube properties. It is found that the hydrogel structure depends on the template's calcination time and temperature. The pH‐triggered PMAA hydrogel cube swelling depends on the hydrogel's internal architecture, either hollow capsule‐like or non‐hollow continuous hydrogels. The loading efficiency of the doxorubicin (DOX) drug inside the microcubes is analyzed by high‐performance liquid chromatography (HPLC), and shows the dependenceof the drug uptake on the network structure and morphology controlled by the template porosity. Varying the template calcination from low (300 °C) to high (1000 °C) temperature results in a 2.5‐fold greater DOX encapsulation by the hydrogel cubes. The effects of hydrogel surface charge on the DOX loading and release are also studied using zeta‐potential measurements. This work provides insight into the effect of structural composition, network morphology, and pH‐induced swelling of the cubical hydrogels and may advance the development of stimuli‐responsive vehicles for targeted anticancer drug delivery.

Developing a ternary conductive hydrogel of polyacrylamide, polyaniline, and carbon nanotube: A potential chemiresistive gas sensor

Over the past few years, conductive hydrogels have received increasing attention for numerous electronic applications because of the concurrent provision of electrical conductivity, flexibility, and conformability. In the present study, a polyaniline-based conductive hydrogel was synthesized. Carbon nanotubes (CNTs) were associated with the hydrogel to impart higher electrical conductivity to the hydrogel, and ternary composites of polyacrylamide (PAM), polyaniline (PANI), and CNT were developed. To fulfill this, at first, CNT surface was decorated with carboxyl functionalities, and the carboxyl decorated CNT was included into the composition in two manners: firstly, CNTs were included during acrylamide polymerization, whereas in the second manner, CNTs were incorporated during aniline polymerization. The composite hydrogels' chemical, swelling, morphological, and electrical properties were evaluated. The experimental results corroborated that in the latter case, abundant intermolecular interactions were developed between the PANI chains and the CNT surface. Moreover, the swelling value was increased by 9% comapred to the former case. In the former case, a porous microstructure and in the latter case a fibrous microstructure was dominated. And more importantly, the electrical conductivity of the hydrogel in the latter case was 104 folds higher than that in the former case. The ternary composition prepared with the latter manner was employed for sensing the ammonia gas, and the analyses unveiled that the hydrogel represents an appropriate response in the range of 10.43%–16.87% to various concentrations of the target gas and has the potential to be a thriving chemiresistive gas sensor.

Independent characterization of the elastic and the mixing parts of hydrogel osmotic pressure

Osmotic pressure is the driving force for the swelling of hydrogels. The hydrogel osmotic pressure can be decomposed into two parts: the mixing part due to polymer-solvent interaction and the elastic part due to polymer chain stretching. While the two components are distinguished in existing constitutive models, they have not been independently characterized in experiments. This paper reports a novel method to independently measure these two components using a fully constrained swelling test. The test allows the crosslink density to be varied at a fixed polymer content, thus varying the elastic part independently of the mixing part. Our measurement shows that the widely used Flory-Rehner model predicts the mixing part accurately for polyacrylamide hydrogel of a wide range of swelling ratios but predicts the elastic part with one order-of-magnitude error.

Shape-Morphing Photoresponsive Hydrogels Reveal Dynamic Topographical Conditioning of Fibroblasts.

The extracellular environment defines a physical boundary condition with which cells interact. However, to date, cell response to geometrical environmental cues is largely studied in static settings, which fails to capture the spatiotemporally varying cues cells receive in native tissues. Here, a photoresponsive spiropyran-based hydrogel is presented as a dynamic, cell-compatible, and reconfigurable substrate. Local stimulation with blue light (455nm) alters hydrogel swelling, resulting in on-demand reversible micrometer-scale changes in surface topography within 15min, allowing investigation into cell response to controlled geometry actuations. At short term (1h after actuation), fibroblasts respond to multiple rounds of recurring topographical changes by reorganizing their nucleus and focal adhesions (FA). FAs form primarily at the dynamic regions of the hydrogel; however, this propensity is abolished when the topography is reconfigured from grooves to pits, demonstrating that topographical changes dynamically condition fibroblasts. Further, this dynamic conditioning is found to be associated with long-term (72h) maintenance of focal adhesions and epigenetic modifications. Overall, this study offers a new approach to dissect the dynamic interplay between cells and their microenvironment and shines a new light on the cell's ability to adapt to topographical changes through FA-based mechanotransduction.

Preparation and antibacterial activity of chitosan grafted cyclodextrin hydrogel loaded berberine hydrochloride using dual gelling agent

In this paper, cyclodextrin-grafted-chitosan (CD-g-CS) with different degrees of substitution (DS) was synthesized successfully by the reaction of O-p-toluenesulfonyl-β-cyclodextrin (TCD) and chitosan (CS), and a novel injectable thermosensitive hydrogel with rapid gelation was developed by physical cross-linking using dual gelling agents of αβ-glycerophosphate-sodium and hydrogen carbonate (GP-SHC). The results of 1H-NMR showed that the DS of CD-g-CS increased with the increase of TCD/CS (w/w). The influence of CD-g-CS with different DS, the concentration of SHC, and the ratio of CD-g-CS/GP-SHC (v/v) on gel time, swelling, drug release, degradation, and antibacterial activity of hydrogels prepared were studied. The results of FTIR indicated that the intermolecular interaction occurred in the hydrogel. And the hydrogel had a three-dimensional porous structure seen from SEM images. Compared with CS/GP hydrogel, the gel time of prepared hydrogel was shorter, which was less than 6 min, and the shortest gel time was 0.5 min. The prepared hydrogels had a good swelling ratio and degradable behavior. Berberine hydrochloride (BBH) was used as a model drug, and the gel showed a sustained drug release profile. In addition, the hydrogel had excellent antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Therefore the BBH@CD-g-CS/GP-SHC hydrogels had great potential in the development of biomedical drug delivery systems and antibacterial materials.

Construction and Evaluation of Alginate Dialdehyde Grafted RGD Derivatives/Polyvinyl Alcohol/Cellulose Nanocrystals IPN Composite Hydrogels.

To enhance the mechanical strength and cell adhesion of alginate hydrogel, making it satisfy the requirements of an ideal tissue engineering scaffold, the grafting of Arg-Gly-Asp (RGD) polypeptide sequence onto the alginate molecular chain was conducted by oxidation of sodium periodate and subsequent reduction amination of 2-methylpyridine borane complex (2-PBC) to synthesize alginate dialdehyde grafted RGD derivatives (ADA-RGD) with good cellular affinity. The interpenetrating network (IPN) composite hydrogels of alginate/polyvinyl alcohol/cellulose nanocrystals (ALG/PVA/CNCs) were fabricated through a physical mixture of ion cross-linking of sodium alginate (SA) with hydroxyapatite/D-glucono-δ-lactone (HAP/GDL), and physical cross-linking of polyvinyl alcohol (PVA) by a freezing/thawing method, using cellulose nanocrystals (CNCs) as the reinforcement agent. The effects of the addition of CNCs and different contents of PVA on the morphology, thermal stability, mechanical properties, swelling, biodegradability, and cell compatibility of the IPN composite hydrogels were investigated, and the effect of RGD grafting on the biological properties of the IPN composite hydrogels was also studied. The resultant IPN ALG/PVA/CNCs composite hydrogels exhibited good pore structure and regular 3D morphology, whose pore size and porosity could be regulated by adjusting PVA content and the addition of CNCs. By increasing the PVA content, the number of physical cross-linking points in PVA increased, resulting in greater stress support for the IPN composite hydrogels of ALG/PVA/CNCs and consequently improving their mechanical characteristics. The creation of the IPN ALG/PVA/CNCs composite hydrogels' physical cross-linking network through intramolecular or intermolecular hydrogen bonding led to improved thermal resistance and reduced swelling and biodegradation rate. Conversely, the ADA-RGD/PVA/CNCs IPN composite hydrogels exhibited a quicker degradation rate, attributed to the elimination of ADA-RGD by alkali. The results of the in vitro cytocompatibility showed that ALG/0.5PVA/0.3%CNCs and ADA-RGD/PVA/0.3%CNCs composite hydrogels showed better proliferative activity in comparison with other composite hydrogels, while ALG/PVA/0.3%CNCs and ADA-RGD/PVA/0.3%CNCs composite hydrogels displayed obvious proliferation effects, indicating that PVA, CNCs, and ADA-RGD with good biocompatibility were conducive to cell proliferation and differentiation for the IPN composite hydrogels.

PH-Dependent Friction of Polyacrylamide Hydrogels

Polyacrylamide hydrogels are widely used in biomedical applications due to their tunable mechanical properties and charge neutrality. Our recent tribological investigations of polyacrylamide gels have revealed tunable and pH-dependent friction behavior. To determine the origins of this pH-responsiveness, we prepared polyacrylamide hydrogels with two different initiating chemistries: a reduction–oxidation (redox)-initiated system using ammonium persulfate (APS) and N,N,N′N′-tetramethylethylenediamine (TEMED) and a UV-initiated system with 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959). Hydrogel swelling, mechanical properties, and tribological behavior were investigated in response to solution pH (ranging from ≈ 0.34 to 13.5). For polyacrylamide hydrogels in sliding contact with glass hemispherical probes, friction coefficients decreased from µ = 0.07 ± 0.02 to µ = 0.002 ± 0.002 (redox-initiated) and from µ = 0.05 ± 0.03 to µ = 0.003 ± 0.003 (UV-initiated) with increasing solution pH. With hemispherical polytetrafluoroethylene (PTFE) probes, friction coefficients of redox-initiated hydrogels similarly decreased from µ = 0.06 ± 0.01 to µ = 0.002 ± 0.001 with increasing pH. Raman spectroscopy measurements demonstrated hydrolysis and the conversion of amide groups to carboxylic acid in basic conditions. We therefore propose that the mechanism for pH-responsive friction in polyacrylamide hydrogels may be credited to hydrolysis-driven swelling through the conversion of side chain amide groups into carboxylic groups and/or crosslinker degradation. Our results could assist in the rational design of hydrogel-based tribological pairs for biomedical applications from acidic to alkaline conditions.Graphical abstract

A model with contact maps at both polymer chain and network scales for tough hydrogels with chain entanglement, hidden length and unconventional network topology

Tough hydrogels with unconventional polymer network architectures often show superior mechanical properties because of the microstructures at the polymer chain and network scales. In this study, a single-chain based model, or called the network topology with hidden length and entanglement (NeTHE) model for the tough hydrogels with chain entanglement, hidden length and unconventional network topology, is developed by imposing contact maps at both polymer chain and network scales on the Arruda-Boyce model. In particular, the contact map is imposed at the polymer chain scale to characterize both entanglement and hidden length simultaneously, while the contact map is imposed at the polymer network scale to consider different polymeric network topologies. The present NeTHE model is validated well by comparing published experimental results of a highly entangled hydrogel and two soft regular hydrogels with hidden lengths. It is confirmed that the present model is able to characterize the hardening, softening, swelling, and damage of the hydrogels. By simplifications, the NeTHE model is reduced directly to the pseudo-elasticity model [1]. Furthermore, the model is able to cover the exponential or scaling law type of damage behaviors of the hydrogels. Finally, several parameter studies are conducted for the swelling and hysteresis of the hydrogels. It is observed theoretically that the constraints of polymer chains due to entanglements result in the high swelling resistance of highly entangled hydrogels, while the hidden length facilitates the swelling of soft regular hydrogels. It is also found that, regarding the hysteresis of hydrogels with different polymer network topologies, the ideal polymer network possesses the highest damage tolerance when compared with both the random and high-functionality crosslinked polymer networks. Regarding the effects of entanglements and hidden lengths on the hysteresis, the highly entangled hydrogel shows a lower stress–stretch hysteresis due to the energy dissipated partially to harden polymer chains when compared with the soft regular hydrogel of which the energy is dissipated fully to fracture the polymer chains.

Physicochemical Characteristics of Chitosan–Alginate Scaffold Containing Atorvastatin

In addition to being a lipid-lowering medication, atorvastatin (ATV) is an anti-inflammatory agent. When there is a bone defect or inflammation of adjacent tissues, it aids in bone repair. This study aimed to develop a chitosan–alginate (CS/ALG)–tripolyphosphate (TPP)–ATV hybrid hydrogel as a drug delivery system, using a tissue engineering scaffold for the first time. For this purpose, a CS/ALG hydrogel crosslinked with TPP was developed. The delivery profile of ATV and its physicochemical properties such as particle size and hydrogel swelling percentage were determined. The structure and morphology of the hydrogels were analyzed using Fourier transform infrared spectroscopy and scanning electron microscopy. As a result, an alginate–chitosan hydrogel with a TPP crosslinker was prepared. The results revealed that drug loading was nearly complete, and the first hour revealed a 25% explosive release. The drug was gradually released over 10 hr at approximately 35%. The amount of crosslinker used significantly influenced the encapsulation gain and release profiles. Owing to its high porosity and swelling, the CS/ALG hydrogel crosslinked with PPT is an ideal scaffold for loading drugs, macromolecules, and cells.

Tuning stimuli-responsive properties of alginate hydrogels through layer-by-layer functionalization for dual-responsive dual drug release

This study aimed to understand the effect of layer-by-layer (LbL) modification on the stimuli-responsive properties of physical alginate (ALG) hydrogels and examine the potential of LbL-coated hydrogels as dual responsive, dual drug releasing platforms for antibacterial applications. ALG hydrogels were functionalized through LbL self-assembly using temperature-responsive poly(2-isopropyl-2-oxazoline) (PiPOX) and pH-responsive tannic acid (TA). Ciprofloxacin (CIP) and Curcumin (CUR) were used as model hydrophilic and hydrophobic drugs, respectively. CIP was included in the hydrogel during LbL process, whereas CUR was incorporated into the hydrogel through gelation in the presence of CUR-loaded CaCO3 microparticles. The effect of LbL modification on the stimuli-responsive swelling, stability and drug release properties of hydrogels was examined in comparison with bare hydrogels. We have shown that LbL modification resulted in a partial loss of solid content from the hydrogel, leading to a greater swelling. In addition, LbL modification imparted temperature-responsiveness to ALG hydrogel and provided enhanced CIP release upon increasing the temperature at pH 7.4. On the other hand, LbL-coated hydrogels displayed minimal CIP release at pH 5.5 regardless of the temperature. The antibacterial activity of LbL-coated hydrogels was greater at pH 7.4 than pH 5.5 against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. The combination of CIP and CUR provided enhanced antibacterial effect on the inhibition of E.coli growth at both pH 7.4 and pH 5.5. This effect became more remarkable as the CIP concentration was decreased at a constant CUR concentration in the hydrogels. However, the combinatorial effect of CIP and CUR was not observed with S. aureus. Overall, these results may be promising for wound healing applications where drug release is triggered when the pH becomes alkaline in the presence of bacterial colonization.

Construction of hybridization chain reaction induced optical signal directed change of photonic crystals-DNA hydrogel sensor and its visual determination for aflatoxin B1.

Herein, we have introduced hybridization chain reaction (HCR) into the photonic crystals (PhCs) hydrogel, for the first time, realizing HCR for inducing the change of the optical signal of PhCs hydrogel and using this hydrogel as a sensor for determination of the aflatoxin B1 (AFB1). By using specific sequences as the cross-linker, the extension of the cross-linker by HCR drives the swelling of the hydrogel, and the optical property of 2D PhCs array converts this swelling into a change of the Debye diffraction ring. Moreover, by further selecting the aptamer to construct the cross-linker, the hydrogel is also endowed with a unique capability for AFB1, making the hydrogel a novel sensor based on the signal amplification strategy. The results show that the designed hairpin DNAs can effectively trigger the HCR and cause the swelling of hydrogel, and the hydrogel sensor has a good determination performance and high specific recognition for AFB1.