Polyelectrolyte Complex Hydrogel Research Articles

Sustained release of MAPK14-targeting siRNA from polyelectrolyte complex hydrogels mitigates MSC osteogenesis in vitro with potential application in growth plate injury.

The growth plate is a cartilage structure at the end of long bones which mediates growth in children. When fractured, the formation of bony repair tissue known as a "bony bar" can occur and cause limb deformities. There are currently no effective clinical solutions for the prevention of the bony bar formation or regeneration of healthy growth plate cartilage after a fracture. This study employs previously developed alginate/chitosan polyelectrolyte complex (PEC) hydrogels as a sustained release vehicle for the delivery of short-interfering RNA (siRNA). Specifically, the siRNA targets the p38-MAPK pathway in mesenchymal stem cells (MSCs) to prevent their osteogenic differentiation. In vitro experimental findings show sustained release of siRNA from the hydrogels for 6 months. Flow cytometry and confocal imaging indicate that the hydrogels release siRNA to effectively knockdown GFP expression over a sustained period. MAPK-14 targeting siRNA was used to knockdown the expression of MAPK-14 and correspondingly decrease the expression of other osteogenic genes in MSCs in vitro over the span of 21 days. These hydrogels were used in a rat model of growth plate injury to determine whether siMAPK-14 released from the gels could inhibit bony bar formation. No significant reduction of bony bar formation was seen in vivo at the one concentration of siRNA examined. This PEC hydrogel represents a significant advancement for siRNA sustained delivery, and presents an interesting potential therapeutic delivery system for growth plate injuries and other regenerative medicine applications.

Lidocaine HCl-Loaded Polyelectrolyte Complex -Poloxamer Thermoresponsive Hydrogel: In Vitro- In Vivo Anesthetic Evaluations for Tooth Socket Wound Delivery.

Local anesthesia is essential in dental practices, particularly for managing pain in tooth socket wounds, yet improving drug delivery systems remains a significant challenge. This study explored the physicochemical characteristics of lidocaine hydrochloride (LH) incorporated into a polyelectrolyte complex and poloxamer thermosensitivity hydrogel, assessing its local anesthetic efficacy in mouse models and its onset and duration of action as topical anesthetics in clinical trials. The thermoresponsive hydrogel exhibited a rapid phase transition within 1-3minutes and demonstrated pseudo-plastic flow behavior. Its release kinetics followed Korsmeyer-Peppas, with 50% of biodegradation occurring over 48h. In mouse models, certain thermogels showed superior anesthetic effects, with rapid onset and prolonged action, as evidenced by heat tolerance in tail-flick and hot plate models. In clinical trials, the LH-loaded thermoresponsive hydrogel provided rapid numbness onset, with anesthesia (Ton) beginning at an average of 46.5 ± 22.5seconds and lasting effectively (Teff) for 202.5 ± 41.0seconds, ranging from 120 to 240seconds, indicating sustained release. These results highlight the promising properties of these formulations: rapid onset, prolonged duration, mucoadhesion, biodegradability, and high anesthesia effectiveness. This study demonstrates the potential for advancing local anesthesia across various medical fields, emphasizing the synergy between material science and clinical applications to improve patient care and safety.

Chitosan-Polyethylene Glycol Inspired Polyelectrolyte Complex Hydrogel Templates Favoring NEO-Tissue Formation for Cardiac Tissue Engineering.

Neo-tissue formation and host tissue regeneration determine the success of cardiac tissue engineering where functional hydrogel scaffolds act as cardiac (extracellular matrix) ECM mimic. Translationally, the hydrogel templates promoting neo-cardiac tissue formation are currently limited; however, they are highly demanding in cardiac tissue engineering. The current study focused on the development of a panel of four chitosan-based polyelectrolyte hydrogels as cardiac scaffolds facilitating neo-cardiac tissue formation to promote cardiac regeneration. Chitosan-PEG (CP), gelatin-chitosan-PEG (GCP), hyaluronic acid-chitosan-PEG (HACP), and combined CP (CoCP) polyelectrolyte hydrogels were engineered by solvent casting and assessed for physiochemical, thermal, electrical, biodegradable, mechanical, and biological properties. The CP, GCP, HACP, and CoCP hydrogels exhibited excellent porosity (4.24 ± 0.18, 13.089 ± 1.13, 12.53 ± 1.30 and 15.88 ± 1.10 for CP, GCP, HACP and CoCP, respectively), water profile, mechanical strength, and amphiphilicity suitable for cardiac tissue engineering. The hydrogels were hemocompatible as evident from the negligible hemolysis and RBC aggregation and increased adsorption of plasma albumin. The hydrogels were cytocompatible as evident from the increased viability by MTT (>94% for all the four hydrogels) assay and direct contact assay. Also, the hydrogels supported the adhesion, growth, spreading, and proliferation of H9c2 cells as unveiled by rhodamine staining. The hydrogels promoted neo-tissue formation that was proven using rat and swine myocardial tissue explant culture. Compared to GCP and CoCP, CP and HACP were superior owing to the cell viability, hemocompatibility, and conductance, resulting in the highest degree of cytoskeletal organization and neo-tissue formation. The physiochemical and biological performance of these hydrogels supported neo-cardiac tissue formation. Overall, the CP, GCP, HACP, and CoCP hydrogel systems promise novel translational opportunities in regenerative cardiology.

K-Carrageenan based magnetic@polyelectrolyte complex composite hydrogel for pH and temperature-responsive curcumin delivery

The dual stimuli-responsive drug delivery system has attracted a lot of interest in controlled drug delivery to specific sites. The magnetic iron oxide nanoparticles integrated polyelectrolyte complex-based hydrogel (MPEC HG) system was developed in this work. First, magnetic nanoparticles were produced in situ in the synthetic polymer polyhexamethylene guanidine (PHMG). Furthermore, the natural biopolymer k-carrageenan (kCG) was employed to form the polyelectrolyte complex (PEC) through charge-balancing interaction between positively charged guanidine units and negatively charged sulfonate groups. Various characterization approaches were used to characterize the developed magnetic polyelectrolyte complex hydrogel (MPEC HG) system. Curcumin (Cur) was employed as a model bioactive agent to examine the drug loading and stimuli-responsive drug release efficiency of the MPEC HG system. Under the combined pH and temperature stimuli conditions (pH 5.0/42 °C), the developed hydrogel system demonstrated great drug loading efficiency (∼ 68 %) and enhanced drug release. Furthermore, the MPEC HG system's in vitro cytotoxicity behavior was investigated on a human liver cancer (HepG2) cell line, and the results revealed that the MPEC HG system is biocompatible. As a result, the MPEC HG system might be used for dual pH and temperature stimuli-responsive drug delivery applications in cancer therapy.

Preparation and Characterizations of PSS/PDADMAC Polyelectrolyte Complex Hydrogel.

Polyelectrolyte complex (PEC) hydrogel, formed via physically electrostatic crosslinks between polyanion and polycation, is an interesting hydrogel in terms of its nontoxicity and solvent-free technique. In this work, poly (sodium 4-styrenesulfonate) (PSS)/poly (diallyl dimethyl ammonium chloride) (PDADMAC) complex hydrogels were prepared. Firstly, the PSS/PDADMAC complex aggregates using various PSS/PDADMAC mole fractions that were prepared in the presence of NaCl solution. Then, the aggregates were resolubilized under stirring at 70 °C for 2 h to obtain a homogeneous PEC solution. Finally, the PEC solution was dialyzed using a dialysis membrane with 3500 molecular cut-off for 1 day. The dialysis bath was changed every interval period of 2 h to control the rate of reversible electrostatic interaction, resulting in the homogenous PEC hydrogel with porous morphology as revealed by SEM and BET investigations. The dimensional stability and viscoelasticity of the PEC hydrogel was studied by DMA experiment, which showed the viscoelastic behavior at a compressive force ranging from 0 to 0.1 N. Finally, PSS/PDADMAC hydrogels showed a high water absorbency property and excellent affinity to textile anionic dyes.

High-strength, strong-adhesion, and antibacterial polyelectrolyte complex hydrogel films from natural polysaccharides

Naturally occurring polysaccharide-based polyelectrolyte complex (PEC) physical hydrogels have broad applications in biomedicine. Yet, obtaining high-strength, strong-adhesion, and antibacterial PEC hydrogels via physically crosslinking of natural polysaccharides still remains a challenge. In this work, a chitosan (CS)/sodium alginate (SA) PEC physical hydrogel film was developed by using two oppositely charged natural polysaccharides, CS and SA, of equivalently high molecular weight (Mw, approx. 105 Da), the tensile stress of which was achieved as high as 12.3 MPa due to CS-CS intermolecular hydrogen bonding and CS-SA electrostatic interaction. In addition, the hydrogel films, upon protonation at acidic conditions (e.g. pH 2.6), exhibited excellent antibacterial activity against Escherichia coli (E. coli) and the CS/SA hydrogel films also demonstrated strong adhesion to biological tissue. The high Mw-matching, two-component natural polysaccharide approach presented in this work to preparing high-strength, strong-adhesion, and antibacterial PEC hydrogels may shed some lights on converting renewable biomass to value-added biomaterials.

Controllable fabrication of alginate/poly-L-ornithine polyelectrolyte complex hydrogel networks as therapeutic drug and cell carriers

Polyelectrolyte complex (PEC) hydrogels are advantageous as therapeutic agent and cell carriers. However, due to the weak nature of physical crosslinking, PEC swelling and cargo burst release are easily initiated. Also, most current cell-laden PEC hydrogels are limited to fibers and microcapsules with unfavorable dimensions and structures for practical implantations. To overcome these drawbacks, alginate (Alg)/poly-L-ornithine (PLO) PEC hydrogels are fabricated into microcapsules, fibers, and bulk scaffolds to explore their feasibility as drug and cell carriers. Stable Alg/PLO microcapsules with controllable shapes are obtained through aqueous electrospraying technique, which avoids osmotic shock and prolongs the release time. Model enzyme and nanosized cargos are successfully encapsulated and continuously released for more than 21 days. Alg/PLO PEC fibers are then prepared to encapsulate brown adipose progenitors (BAPs) and Jurkat T cells. The electrostatic interactions between Alg and PLO are found to facilitate the printability and self-support ability of Alg/PLO bioinks. Alg/PLO PEC fibers and scaffolds support cell proliferation, differentiation, and functionalization. These results demonstrate new options for biocompatible PEC hydrogel preparation and improve the understanding of PEC hydrogels as drug and cell carriers. Statement of significanceIn this study, the concept of polyelectrolyte complex hydrogel networks as drug and cell carriers has been demonstrated. Their feasibility to achieve sustained drug release and cell functionality was explored, from microcapsules to fibers to three-dimension printed scaffolds. PEC microcapsules with controllable shapes were obtained. Therapeutic drugs can be encapsulated and continuously release for more than 21 days. Benefiting from the dynamic interactions of physically crosslinked PEC, self-healing fibers were achieved. Besides, the electrostatic interactions between polyelectrolytes were found to facilitate the printability and self-support ability of PEC bioinks. The PEC fibers and scaffolds with controllable structure supported cell proliferation, differentiation, and function. The outcome of current research promotes design of new biocompatible PEC hydrogels and potential drug and cell carriers.

Antibacterial reduced graphene oxide reinforces polyelectrolyte hydrogels with polysaccharides via a green method

A green and straightforward method has been employed for the preparation of graphene oxide (GO) and reduced graphene oxide (rGO) in nanocomposite polyelectrolyte complex (NC-PEC) hydrogel made of xanthan gum (XG) and chitosan (CS). In this study, glucuronic acid δ-galactone (GDL) was used as an acidifying agent for the formation of PEC between XG and CS, and fenugreek seed extract was used to reduce GO to rGO. Reduction of GO to rGO was confirmed by FTIR, XRD, UV–visible spectra, and TEM. FTIR characterized the reinforcement of GO and rGO into PEC hydrogels. XRD techniques were performed to verify the formation and structural interactions between rGO with PEC hydrogels. SEM confirmed the microstructure of NC-PEC hydrogels. Furthermore, rGO in NC-PEC hydrogel exhibited improved antibacterial properties against gram-positive and -negative bacteria compared to GO-reinforced PEC hydrogel. Moreover, the presence of rGO in PEC hydrogel did not have any cytotoxic effects against skin fibroblasts. Furthermore, NC-PEC hydrogels showed good hemocompatability. Hence, the developed NC-PEC hydrogels have potential in wound dressing applications.

Hydrogen-bonded network enables polyelectrolyte complex hydrogels with high stretchability, excellent fatigue resistance and self-healability for human motion detection

Polyelectrolyte complex hydrogel (PECH) is an emerging ion conductive hydrogel made from non-covalent interacted oppositely charged polyelectrolytes in water. However, the construction of PECH with high stretchability, excellent fatigue resistance and self-healability is heavily demanded while remaining a profound challenge. Herein, a hydrogen-bonded network densification strategy is presented for preparing a highly stretchable and deformation-tolerant PECH hydrogel (Fe/CS/PAA), which is composed of an anionic Fe3+-coordinated polyacrylic acid network (Fe-PAA) and cationic Fe3+-coordinated chitosan network (Fe-CS). Benefiting from the formation of dense hydrogen-bonded network between the Fe-PAA and Fe-CS networks activated by salt impregnation, the resultant densified hydrogen-bonded Fe/CS/PAA hydrogel (DHB-Fe/CS/PAA) exhibits large tensile strength (~0.34 MPa), high stretchability (~1370%), low-temperature resistance to −25 °C, and heat-accelerated self-healability. Due to its high stretchability, excellent fatigue resistance and high ionic conductivity, the DHB-Fe/CS/PAA can readily work as a stretchable ionic conductor for skin-inspired ionic strain sensor, displaying high sensitivity in a wide strain range (0.5%–500%), fast response time (<180 ms) and excellent durability for 500 cycles at a 100% strain. Besides, the as-assembled ionic sensor is capable of maintaining high ionic conductivity and mechanical robustness at a sub-zero temperature of −25 °C ascribing to the presence of high-concentration charged functional groups and impregnated salts. As a demonstration, a wearable DHB-Fe/CS/PAA ionic sensor in a resistive mode is assembled, demonstrating high sensitivity, wide response range and excellent cyclability in detecting and distinguishing complex human motions rapidly and in real-time.

New κ-Carrageenan-montmorillonite Polyelectrolyte Complex used as a Polymer for the Extended Release Circular Pellets Containing Tapentadol Hydrochloride: Statistical optimization

ABSTRACT The present investigation aims at development of extended release (ER) pellets using κ-carrageenan-montmorillonite (κ-Carr-MMT) polyelectrolyte complex (PEC) hydrogel. The PEC was used as binder and ER polymer, whereas tapentadol was a model drug. The hydrogels were optimised using 32 full factorial design and characterised by FTIR, DSC, XRPD, and SEM analyses. The pelletisation was done using extrusion-spheronization procedure. The prepared pellets were further characterised for yield, FTIR, DSC, XRPD, pellet morphology, flow characteristics, mucoadhesion, and in vitro drug release studies.The interactions between the cationic silicate hydroxylated edge groups of MMT with the anionic sulphate group of κ-carrageenan leads to the formation of κ-Carr-MMT PEC hydrogel and these interactions were confirmed by FTIR analysis. The optimised pellet formulation containing 2.25:1.00 ratio of κ-Carr and MMT exhibited sustained drug release upto 12 h, in vitro. Present ER pellet formulation could be a best alternative to the conventional formulations for pain management.

Smart and functional polyelectrolyte complex hydrogel composed of salecan and chitosan lactate as superadsorbent for decontamination of nickel ions

Green and functional bio based adsorbents based on naturally derived polysaccharides have attracted considerable interest owing to their non-toxicity, biodegradability, flexible design, and wide origins. Here, smart polyelectrolyte complex (PEC SC1-SC4) hydrogels were developed by self-assembling of different ratios of salecan and chitosan lactate (CL) for clean-up of nickel ion (Ni2+) from wastewater. Preparation process was rapid and eco-friendly, without any toxic cross-linkers. The electrostatic attractions between polysaccharides were studied by FT-IR, XRD, XPS, and TGA. Particularly, the content of salecan and CL could be precisely modulated to tailor the swelling ability, micromorphology, and stiffness of the hydrogels. Ni2+ adsorption onto the hydrogels was dependent on salecan/CL ratio, pH, initial ion concentration, and contact time. SC4 showed the highest Ni2+ uptake, but it was too brittle. SC3 was selected for absorption studies. The equilibrium adsorption data commendably matched the pseudo-second-order and Langmuir models, demonstrating monolayer chemical adsorption mechanisms. The maximum Ni2+ adsorption derived from Langmuir model was 414.9 mg/g, superior to many reported Ni2+ adsorbents. Most strikingly, SC3 performed good recyclability, and the adsorption capacity still kept 95.3% even after five adsorption/desorption cycles. Hopefully, the prepared SC3 hydrogel is a potential agent for treatment of wastewater contaminated with Ni2+ ion.

Structure, Morphology, and Rheology of Polyelectrolyte Complex Hydrogels Formed by Self-Assembly of Oppositely Charged Triblock Polyelectrolytes

We present scattering and rheology studies on model polyelectrolyte complex (PEC) hydrogels that form upon self-assembly of symmetric oppositely charged triblock polyelectrolytes in aqueous media. The hydrogel assembly is driven by associative phase separation of charged end-blocks to form PECs while the neutral mid-blocks restrict bulk phase separation of the PECs, leading to three-dimensional networks with PEC domains surrounded by neutral polymer coronae at sufficiently high polymer concentrations. Comprehensive characterization of the hydrogel structure (PEC domain size, morphology, spacing, and ordering) was enabled by a series of triblock polyelectrolytes with independently varying block lengths, facilitating the construction of morphology maps that offered direct comparisons with earlier theoretical predictions and highlighted the contributions of the charged and neutral blocks in directing PEC morphologies and hydrogel microstructures. Comparisons between the microstructure and shear rheology response emphasize the interplay between PEC domain morphologies and hydrogel flow behaviors. Furthermore, by drawing parallels with rheological models for associating polymer networks, we present preliminary insights into the role of chain-exchange dynamics between the PEC domains and cooperative electrostatic interactions in influencing the hydrogel flow properties.

Role of salt ions and molecular weights on the formation of Mesona chinensis polysaccharide-chitosan polyelectrolyte complex hydrogel

The effects of the addition of salt ions and molecular weights (Mw) of CH on Mesona chinensis polysaccharide (MCP)-chitosan (CH) hydrogel were investigated. Result indicated both low concentration of monovalent salt ions (Na+ and K+), divalent cations (Ca2+) and oxoanions (SO42−) could promote the gel properties of MCP-CH hydrogel. The Mw of CH has huge impact on the formation and properties of hydrogel. Combining the relationship between rheology and structural, monovalent salt ions such as Na+ and K+ affect gel formation and its properties by influencing electrostatic interaction and chain conformation. Both divalent cations (Ca2+) and oxoanions (SO42−) facilitated the formation of gel networks via electrostatic interaction, coordination bonds and hydrogen bonds. Moreover, Mw of CH influenced formation and texture of MCP-CH hydrogel via affecting the conformation of CH molecular chain. These findings will provide a few theoretical bases to understand the formation mechanism of MCP-CH hydrogel.

Formation of self-assembled polyelectrolyte complex hydrogel derived from salecan and chitosan for sustained release of Vitamin C

Vitamin C (VC) is an indispensable nutrient for human health. However, poor chemical stability in gastric environment restricts its full assimilation by intestine. It is important to construct a safe carrier that can protect VC from the gastric fluid and sustainably release it in intestine. Herein, we designed a novel polyelectrolyte complex (PEC) hydrogel through self-assembly of salecan and chitosan. PEC structure formed by electrostatic interactions was confirmed by FT-IR, XRD, XPS and TGA. Their swelling, morphology, rheology, cytocompatibility and biodegradation were well investigated. In particular, VC released in a controlled and pH-dependent manner. The release amount in simulated intestinal fluid (SIF) was significantly higher than simulated gastric fluid (SGF), and can be maintained at high level in blood after 6 h. Release mechanism agreed well with Ritger-Peppas model. The purpose of this study was to develop a smart nutrient delivery platform for targeted release of VC in intestinal condition.

Self-assembly of binary oppositely charged polysaccharides into polyelectrolyte complex hydrogel film for facile and efficient Pb2+ removal

Herein, a novel polyelectrolyte complex (PEC) hydrogel film has been fabricated through self-assembly of two oppositely charged polysaccharides salecan and carboxymethyl chitosan (CMCS) for Pb2+ removal. The formation of PEC network structure via electrostatic interactions was confirmed by FT-IR, XRD, XPS and TGA. The change of salecan/CMCS ratio had obvious influence on the swelling capacity, morphology and rheological properties of the hydrogel films. The adsorption capacity of Pb2+ was specifically investigated by tuning the salecan/CMCS ratio, other ions, pH, ion concentration and contact time. Furthermore, the equilibrium isotherms were better fitted with Langmuir model, indicating monolayer adsorption behaviour. The maximum adsorption capacity of Pb2+ according to Langmuir model was 418.4 mg/g, higher than that of some other adsorbents. The adsorption kinetics was well modelled by pseudo-second-order and Crank model, suggesting chemisorption and internal diffusion control mechanism. The PEC hydrogel film also exhibited excellent reusability after 5 adsorption/desorption cycles without obvious changes in the adsorption capacity. Overall, these results not only highlight a new idea for the utilization of salecan, but also provide a green method for the rational design of highly efficient adsorbent for Pb2+ removal.

Preparation of chitosan and carboxymethylcellulose‐based polyelectrolyte complex hydrogel via SD‐A‐SGT method and its adsorption of anionic and cationic dye

AbstractThe excellent properties of the polyelectrolyte complex hydrogels (PECHs) prepared with polysaccharides only, including polyampholyte, low toxicity, green, and clean production, have endowed them great application potentials as the adsorbents for dye‐containing wastewater treatments. In the current study, the PECH of chitosan (CTS) and carboxymethylcellulose (CMC) was prepared by semi‐dissolution acidification sol–gel transition (SD‐A‐SGT) method. The hydrogel was formed by the strong electrostatic interaction of cationic NH3+ groups of CTS and the anionic COO− groups of CMC. This simple but efficient means exhibited great potentials in constructing PECHs with uniform composition and controllable sol–gel transitions. Molecular dynamics simulation was first employed to predict the formation process and the microstructure of PECHs prepared by SD‐A‐SGT method. The structure and properties of the CTS‐CMC PECHs were also characterized by Fourier transform infrared spectroscopy, SS 13C‐NMR, scanning electron microscopy, mechanical tests, and rheological measurements, respectively. Taking the advantage of amphoteric polyelectrolyte properties, adsorption properties of anionic and cationic dyes were investigated using sunset yellow FCF and methylene blue as model dyes, respectively. The PECHs prepared in the present work had good adsorption capacity for both cationic and anionic dyes with maximum adsorption capacity of 212.83 mg/g for sunset yellow FCF and 167.35 mg/g for methylene blue. Therefore, this PECH would be a promising environmentally friendly adsorbent for the treatment of functional molecules with different charges.

Construction of self-assembled polyelectrolyte complex hydrogel based on oppositely charged polysaccharides for sustained delivery of green tea polyphenols

In this study, we have developed a novel polyelectrolyte complex (PEC) hydrogel that could be easily prepared by self-assembly of two food-grade polysaccharides salecan and N,N,N-trimethyl chitosan (TMC). The electrostatic interactions between two polysaccharides were driving force in complexation processes and have been demonstrated by FTIR, XRD, XPS and TGA. The swelling capacity, morphology and rheological property of the hydrogels could be well tuned by controlling salecan/TMC ratio. Green tea polyphenols (GTP) was efficiently encapsulated into PEC hydrogels and liberated in a sustained pattern. The amount of GTP released in simulated intestinal fluid (SIF) was significantly higher than simulated gastric fluid (SGF). Increasing salecan/TMC ratio also markedly enhanced GTP release amount. Release exponent n obtained in SGF indicated a Fickian diffusion, while in SIF an anomalous transport occurred. The release mechanism was well-fitted with Ritger-Peppas model. Taken together, these PEC hydrogels could be suitable carriers for intestinal targeted nutrient delivery.

Ultrafast Fabrication of Gradient Nanoporous All‐Polysaccharide Films as Strong, Superfast, and Multiresponsive Actuators

AbstractThe design of smart hydrogel actuators fully constructed from natural polymers for assessing the biomedical applications is important but challenging. Herein, an extremely simple, green, and ultrafast strategy is presented for preparing robust gradient all‐polysaccharide polyelectrolyte complex hydrogel actuators. Driven by diffusing of low molecular weight chitosan into high molecular weight sodium alginate solution, a nanoporous, ultrastrong, and gradient chitosan/sodium alginate complex hydrogel film with adjustable thickness can be directly generated on the interface of two solutions within minutes. The as‐prepared film can provide superfast temperature, ionic strength, and pH‐triggered programmable deformations, and perform a distinct sequential double folding behavior due to the competitive effect between complexed and noncomplexed segments of polyelectrolyte. Besides, patterning Ca2+ to locally crosslink sodium alginate in the film enables various more complex shape transformations. This green and simple diffusion‐driven strategy provides significant guidance for fabricating bio‐friendly actuators with applications in drug delivery, tissue engineering, soft robotics, and active implants.

Electroresponsive Homogeneous Polyelectrolyte Complex Hydrogels from Naturally Derived Polysaccharides

Homogeneous polyelectrolyte complex (PEC) hydrogels made from chitosan and carboxymethylcellulose were prepared in the LiOH/KOH/urea aqueous system through a freeze–thawing method. Following the treatments of sequential chemical and physical cross-linking, the resulting hydrogels with supertough mechanical strength can operate as fast response actuators under electrical stimulus in salt aqueous solutions. The electromechanical behaviors of the hydrogels are strongly dependent on experimental parameters such as electric voltage, solvent constituents, pH, and ionic strength. It is proposed that the electromechanical deformation of hydrogel originates from a dynamic osmotic equilibrium effect taking place at the interface between the hydrogel and the surrounding medium, which is induced by the migration of ions throughout the gel network. In addition, programmable 3D shape transformations were obtained by using the PEC hydrogel with designed 2D geometric patterns. Moreover, the bending actuation behavior of ...

Preparation of the polyelectrolyte complex hydrogel of biopolymers via a semi-dissolution acidification sol-gel transition method and its application in solid-state supercapacitors

Hydrogels have drawn many attentions as the solid-state electrolytes in flexible solid-state supercapacitors (SCs) recently. Among them, the polyelectrolyte complex hydrogel (PECH) electrolytes of natural polymers are more competitive because of their environmentally friendly property and low cost. However, while mixing two biopolymer solutions with opposite charges, the strong electrostatic interactions between the cationic and anionic biopolymers may result in precipitates instead of hydrogels. Here we report a novel method, semi-dissolution acidification sol-gel transition (SD-A-SGT), for the preparation of the PECH of chitosan (CTS) and sodium alginate (SA), with the controllable sol-gel transition and uniform composition and successfully apply it as the hydrogel electrolyte of solid-state supercapacitors (SCs). The CTS-SA PECH exhibits an extremely high ionic conductivity of 0.051 S·cm−1 and reasonable mechanical properties with a tensile strength of 0.29 MPa and elongation at break of 109.5%. The solid-state SC fabricated with the CTS-SA PECH and conventional polyaniline (PANI) nanowire electrodes provided a high specific capacitance of 234.6 F·g−1 at 5 mV·s−1 and exhibited excellent cycling stability with 95.3% capacitance retention after 1000 cycles. Our work may pave a novel avenue to the preparation of biodegradable PECHs of full natural polymers, and promote the development of environmentally friendly electronic devices.