Semi-interpenetrating Hydrogels Research Articles

Synthesis of sodium alginate / polyvinyl alcohol / polyethylene glycol semi-interpenetrating hydrogel as a draw agent for forward osmosis desalination

Typically, hydrogels are described as three-dimensional networks of hydrophilic polymers that are able to capture a certain mass of water within their structure. Recently, hydrogels have been widely used as drawing agents in forward osmosis (FO) desalination processes. The major aim of this study is to prepare a novel semi-interpenetrating hydrogel by crosslinking sodium alginate (SA) and polyvinyl alcohol (PVA) by using the epichlorohydrin (ECH) crosslinker and polyethylene glycol (PEG) interpenetrated within the hydrogel’s network as a linear polymer. Based on the optimum composition of SA/PVA composite hydrogel obtained from our earlier research, the effect of various percentages of PEG on the response of the hydrogel was investigated. The optimal composition of SA/PVA/PEG hydrogel was characterized by scanning electron microscopy (SEM), compression strength testing, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The morphological and mechanical properties of the SA/PVA/PEG semi-interpenetrating hydrogel were also compared to those of the SA/PVA composite hydrogel. Moreover, the performance of the optimal SA/PVA/PEG hydrogel in a FO batch unit as a drawing agent was investigated based on the optimal operation conditions from our previous experiments. The results showed that the optimal PEG/polymer blend mass ratio was 0.25, which increased the swelling ratio (SR) (%) of the hydrogel from 645.42 (of the neat SA/PVA hydrogel) to 2683. The SA/PVA/PEG semi-interpenetrating hydrogel was superior to the SA/PVA copolymer hydrogel in pore structure and mechanical properties. Additionally, in terms of FO desalination, the achieved water flux by SA/PVA/PEG hydrogel is higher than that accomplished by SA/PVA hydrogel.

A carboxymethyl-resistant starch/polyacrylic acid semi-IPN hydrogel with excellent adhesive and antibacterial properties for peri-implantitis prevention

Hydrogels possess inherent characteristics that render them promising for the prevention of peri-implantitis. Nonetheless, hydrogels with singular network structures are incapable of concurrently achieving the desired adhesion and mechanical properties. In this work, a carboxymethyl resistant starch/polyacrylic acid semi-interpenetrating (CMRS/PAA semi-IPN) hydrogel was successfully prepared in one step. Its morphology, structure, mechanical properties, and adhesion properties were systematically assessed, which revealed a homogeneously porous structure with a commendable mechanical strength of 67.317 kPa and an adhesion strength of 63 kPa. Ciprofloxacin (Cip) was loaded in the CMRS/PAA hydrogel via in situ compounding. The in vitro kinetic study of drug release shows that the slow drug release efficiency exceeds 90 % in the weakly acidic microenvironment at the infection site after 72 h, indicating enhanced antimicrobial properties. The Cip-loaded hydrogel also exhibits a remarkable bacterial inhibition rate exceeding 99 % against the pathogenic bacterium P. gingivalis and good cytocompatibility and hemocompatibility in vitro. In summary, the current work explored a novel solution and direction for the development of anti-infective medical materials applicable to dental implants.

Preparation of CMC-poly(N-isopropylacrylamide) semi-interpenetrating hydrogel with temperature-sensitivity for water retention

The CMC-PNIPAM hydrogel with semi-interpenetrating structure and temperature-sensitivity was prepared by in-situ polymerization of N-isopropylacrylamide (NIPAM) in sodium carboxymethylcellulose (CMC) solution at room temperature. The mass ratio of CMC to NIPAM was a key factor influencing the network structure and property of CMC-PNIPAM hydrogel. The low critical phase transition temperature (LCST) of CMC-PNIPAM hydrogels increased from 34.4 °C to 35.8 °C with the mass ratio of CMC to NIPAM rising from 0 to 1.2. The maximum compressive stress of CMC-PNIPAM hydrogel reached to 26.7 kPa and the relaxation elasticity was 52 % at strain of 60 %. The viscoelasticity of CMC-PNIPAM hydrogel was consistent with the generalized Maxwell model. The maximum swelling ratio in deionized water was 170.25 g·g−1 (dried hydrogel) with swelling rate of 2.57 g·g−1·min−1 at 25 °C. CMC-PNIPAM hydrogel hardly absorbed water above LCST, but the swollen hydrogel could release water at the rate of 0.36 g·g−1·min−1 once exceeding LCST. The test of water retention showed that soil mixed with 2 wt% dried CMC-PNIPAM hydrogel could retain 13.08 wt% water after 30 days at 25 °C that was 4.4 times than that of controlled soil without CMC-PNIPAM hydrogel. The semi-interpenetrating CMC-PNIPAM hydrogel showed a potential to conserve water responding to temperature.

Sodium alginate/polyvinyl alcohol semi-interpenetrating hydrogels reinforced with PEG-grafted-graphene oxide

Semi-interpenetrating polymer network (SIPN) hydrogels composed of sodium alginate/poly (vinyl alcohol), reinforced by PEG-grafted-graphene oxide (GO-g-PEG) were prepared by ionic crosslinking of sodium alginate. The impact of grafted PEG molecular weight with two molecular weights, i.e. 400 and 2000 g/mol, and component composition were studied on the morphology, swelling behavior, mechanical and dynamic properties. SEM observation showed fine dispersion and distribution of GO-g-PEG throughout the hydrogel indicating a good interaction of particles with the components. Our results revealed that although incorporating GO-g-PEG increases the water content, it significantly enhances the mechanical properties, i.e. tensile modulus, elongation at break, and fracture toughness with a more pronounced impact at higher PEG molecular weight. As a result, the tensile modulus and the elongation at break increased by 270 % and 28 %, respectively. The SA/PVA SIPN hydrogels reinforced with the GO-g-PEG exhibit a non-linear elastic behavior with a toe at low strains. This behavior is attributed to the unique structural features of SIPN hydrogels and the orientation of GO-g-PEG particles with proper interaction with the components. The small amplitude oscillatory shear was also performed to further study the impact of SA, PVA, and GO-g-PEG compositions on the microstructure of hydrogels.

High stretchable and tough xylan-g-gelatin hydrogel via the synergy of chemical cross-linking and salting out for strain sensors

Stretchable and tough hydrogels have been extensively used in tissue engineering scaffolds and flexible electronics. However, it is still a significant challenge to prepare hydrogels with both tensile strength and toughness by utilizing xylan, which is abundant in nature. Herein, we present a novel hydrogel of carboxymethyl xylan(CMX) graft gelatin (G) and doped with conductive hydroxyl carbon nanotubes (OCNT). CMX and G are combined through amide bonding as well as intermolecular hydrogen bonding to form a semi-interpenetrating hydrogel network. The hydrogel was further subjected to salting-out treatment, which induced the aggregation of the CMX-g-G molecular chain and the formation of chain bundles to toughen the hydrogel, the tensile strain, tensile stress, and toughness of CMX-g-G hydrogels were 1.547 MPa, 324 %, and 2.31 MJ m−3, respectively. In addition, OCNT was used as a conductive filler to impart electrical conductivity and further improve the mechanical properties of CMX-g-G/OCNT hydrogel, and a tensile strength of 1.62 MPa was obtained. Thus, the synthesized CMX-g-G/OCNT hydrogel can be used as a reliable and sensitive strain sensor for monitoring human activity. This study opens up new horizons for the preparation of xylan-based high-performance hydrogels.

Highly deformable and strongly magnetic semi-interpenetrating hydrogels based on alginate or cellulose

The effective implementation of many of the applications of magnetic hydrogels requires the development of innovative systems capable of withstanding a substantial load of magnetic particles to ensure exceptional responsiveness, without compromising their reliability and stability. To address this challenge, double-network hydrogels have emerged as a promising foundation, thanks to their extraordinary mechanical deformability and toughness. Here, we report a semi-interpenetrating polymer networks (SIPNs) approach to create diverse magnetic SIPNs hydrogels based on alginate or cellulose, exhibiting remarkable deformability under certain stresses. Achieving strong responsiveness to magnetic fields is a key objective, and this characteristic is realized by the incorporation of highly magnetic iron microparticles at moderately large concentrations into the polymer network. Remarkably, the SIPNs hydrogels developed in this research accommodate high loadings of magnetic particles without significantly compromising their physical properties. This feature is essential for their use in applications that demand robust responsiveness to applied magnetic fields and overall stability, such as a hydrogel luminescent oxygen sensor controlled by magnetic fields that we designed and tested as proof-of-concept. These findings underscore the potential and versatility of magnetic SIPNs hydrogels based on carbohydrate biopolymers as fundamental components in driving the progress of advanced hydrogels for diverse practical implementations.

An anti-fouling wearable molecular imprinting sensor based on semi-interpenetrating network hydrogel for the detection of tryptophan in sweat

The challenge of heavy biofouling in complex sweat environments limits the potential of electrochemical sweat sensors for noninvasive physiological assessment. In this study, a novel semi-interpenetrating hydrogel of PSBMA/PEDOT:PSS was engineered by interlacing PEDOT:PSS conductive polymer with zwitterionic PSBMA network. This versatile hydrogel served as the foundation for developing an anti-fouling wearable molecular imprinting sensor capable of sensitive and robust detection of tryptophan (Trp) in complex sweat. The incorporation of PEDOT:PSS conductive polymer into the semi-interpenetrating hydrogel introduced diverse physical crosslinks, including hydrogen bonding, electrostatic interactions, and chain entanglement. This incorporation considerably boosted the hydrogel's mechanical robustness and imparted commendable self-healing property. At the same time, the synergistic coupling between the well-balanced charge of the zwitterionic network and the high conductivity of the PEDOT:PSS polymer facilitated efficient charge transfer. The formation of the desired molecular imprinting membrane of semi-interpenetrating hydrogel was triggered by self-polymerization of dopamine (DA) in the presence of Trp. The designed biosensor demonstrated good sensitivity, selectivity and stability in detecting the target Trp. Notably, it also exhibited exceptional anti-fouling abilities, allowing for accurate Trp detection in complex real sweat samples, yielding results comparable to commercial enzyme-linked immunoassay (ELISA).

Eco-Friendly Semi-Interpenetrating Polymer Network Hydrogels of Sodium Carboxymethyl Cellulose/Gelatin for Methylene Blue Removal.

The present work describes the potential application of environmentally friendly sodium carboxymethylcellulose/gelatin (CMC/Gel) semi-interpenetrating hydrogels prepared by citric acid as a nontoxic cross-linking agent to adsorb dyes. The prepared hydrogels were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA/DTG), and swelling study. The adsorption performance of CMC/Gel2 (C/G2) hydrogel on methylene blue (MB) was investigated. The results showed the better adsorption conditions: adsorption time of 300 min, initial MB concentration of 500 mg/L, adsorbent dosage of 1.2 g/L, solution pH of 7, and temperature of 30 °C. The adsorption kinetics fit the pseudo-second order kinetics model, and the adsorption isotherm fit the Langmuir isotherm model. The maximum adsorption capacity reached 943.40 mg/g. The adsorption process is a spontaneous exothermic process. After three adsorption-desorption cycles, the removal rate of MB by hydrogel still reached 85%, with good reusability. Consequently, the hydrogel can be used as an environmentally friendly, stable, and efficient adsorbent for dyes in wastewater treatment.

Characterization of semi-interpenetrating hydrogel based on Artemisia sphaerocephala Krasch Polysaccharide and cellulose nanocrystals crosslinked by ferric ions

Hydrogels are important bionic materials that can be used in a wide variety of biomedical applications. Artemisia sphaerocephala Krasch polysaccharide (ASKP) has been demonstrated to be crosslinked by ferric ions to form three-dimensional network. Here, a semi-interpenetrating network (semi-IPN) hydrogel based on ASKP and cellulose nanocrystals (CNC) crosslinked by ferric ions was fabricated and the effect of specific rod-like CNC was evaluated. It was found that the network of ASKP-Fe3+ hydrogel incorporated by CNC became denser along with the decreased pore diameter and the thickened pore wall. ASKP/CNC-Fe3+ hydrogel displayed an enhanced gel strength and water holding capacity. The dominant interaction of ASKP and CNC was hydrogen bonds proved by FTIR and QCM-D. Additionally, the elasticity of the semi-IPN hydrogel significantly increased along with the decrease of platform height in MSD curves based on particles tracking. These results may be caused by the fact that the rod-shaped CNC can be entangled with ASKP and prone to induce the orderly extension of ASKP chains, resulting in more hydroxyl and carboxyl groups exposed to be crosslinked with ferric ions. What's more, the stiff CNC located on the pore wall of ASKP-Fe3+ hydrogel can also strengthen the rigidity of network. Thus, this study suggests a new strategy to improve the properties of ASKP based hydrogel, and can be developed as a carrier to deliver iron ions.

Chitosan-coated and thymol-loaded polymeric semi-interpenetrating hydrogels: An effective platform for bioactive molecule delivery and bone regeneration in vivo

Thymol (2-isopropyl-5-methylphenol; Thy) is a monoterpene phenolic phytocompound with medicinal properties; however, its impact on osteogenesis is yet to be thoroughly investigated. Its distribution is often hampered because of its intricate hydrophobic structure, which reduces its bioavailability. In this study, we synthesized a drug delivery vehicle using semi-interpenetrating polymer network (SIPN) hydrogels containing sodium alginate and poly(2-ethyl-2-oxazoline) (SA/Pox) loaded with Thy at varying concentrations (100, 150, and 200 μM). Subsequently, they were coated with chitosan (CS) to increase bioactivity and for sustained and prolonged release of Thy. Thy-loaded CS-coated SIPN hydrogels (SA/Pox/CS-Thy) were developed using ionic gelation and polyelectrolyte-complexation techniques. The addition of CS to hydrogels enhanced their physicochemical and material properties. These hydrogels were cytofriendly toward mouse mesenchymal stem cells (mMSCs). When mMSCs were cultured on hydrogels, Thy stimulated osteoblastic differentiation, as evidenced by calcium deposits at the cellular level. The expression of RUNX2, a key bone transcriptional factor, and other differentiation biomarkers was significantly enhanced in mMSCs cultured on SA/Pox/CS-Thy hydrogels. Notably, Thy in the SA/Pox/CS hydrogels significantly activated the TGF-β/BMP signaling pathway, which is involved in osteogenesis. A rat tibial bone defect model system revealed that the incorporation of Thy into SA/Pox/CS hydrogels augmented bone regeneration. Thus, sustained and prolonged release of Thy from the SA/Pox/CS hydrogels promoted osteoblast differentiation in vitro and bone formation in vivo. These findings shed light on the effect of Thy bioavailability in fostering osteoblast differentiation and its prospective application in bone rejuvenation.

Silk fibroin based interpenetrating network hydrogel for corneal stromal regeneration

There is a need to develop tissue engineering based approaches to address the shortage of donor corneas worldwide for transplantation. To do this a novel approach to fabricate three-dimensional hydrogels using free-radical polymerization was investigated to generate constructs for corneal stromal tissue regeneration. Different ratios of silk fibroin (SF) to polyacrylamide (PA) were used to fabricate semi-interpenetrating hydrogels. Scanning electron micrograph displayed the interconnectivity of pores within the fabricated hydrogels. Pore sizes ranged from 25 to 66 μm. Scaffolds with increasing concentration of SF had enhanced β-sheet structure (verified by Fourier transform infrared spectroscopy). The biological response of human corneal stromal cells to these hydrogels was examined using cellular adhesion, proliferation, cytoskeleton organization, gene expression and immunocytochemical analysis. The fabricated hydrogels possess rapid gelation (∼3 min) at 37 °C, 84 % porosity facilitating keratocyte migration during healing, improved cellular adhesion and no cytotoxicity, indicating their efficiency for in-situ corneal tissue regeneration. Presence of SF in semi-interpenetrating network hydrogel enhanced cellular proliferation, elevated GAG deposition, and increased expression of keratocyte genes, normally associated with healthy corneal stromal tissue. This study acts as an initial step towards fabricating SF based semi-interpenetrating network hydrogels for developing clinically applicable ocular implants.

Application of the photothermal-responsive gelatin-based microspheres for controlled release of imidacloprid by helix-coil structural transition mechanism

Intelligent controlled release systems (ICRS) are recognized as a feasible and economical way for the highly efficient utilization of agrochemicals. In this work, we developed an intelligent photothermal-responsively controlled-release pesticide particle (IYGCP) based on imidacloprid (IMI, a model pesticide), yeast biochar (YB, adsorbent and photothermal material), gelatin (GE, temperature-responsive polymer), and Ca-alginate (CA, microsphere matrix). Therein, YB with high adsorption property and photothermal conversion capacity was used as a carrier of IMI to avoid the loss of active ingredients, and as an agent to endow the IYGCP platform with unique photothermal-responsive performance. After IMI loading, IMI/YB was scattered and anchored in CA/GE semi-interpenetrating hydrogels by the chelation of sodium alginate and Ca2+. Upon irradiation under simulated sunlight, YB with satisfactory photothermal conversion efficiency can effectively transfer solar energy into thermal energy, induing a free helix-coil structural transition of the un-crossed GE polymers, thereby resulting in changes in microstructure of hydrogel spheres and further enabling a controlled release of IMI encapsulated in the IYGCP. Besides, the composite displayed high control efficacy on corn borers. Consequently, this photothermal-responsive gelatin-based microsphere shows a bright prospect for controlling the release and loss of pesticides.

Subchondral bone-inspired hydrogel scaffold for cartilage regeneration

Promoting the in situ regeneration of cartilage without additional cells or cytokines remains challenging. Here, inspired by the unique microstructures of subchondral bone, a cell and cytokine free hydrogel scaffold for cartilage regeneration was developed via a strategy of directional lyophilization and postcrosslinking. This strategy achieved intersecting microchannels in an orderly arrangement and an aligned ladder-like texture in a semi-interpenetrating hydrogel network. The resulting hydrogel had similar mechanical properties to the native cartilage extracellular matrix. Incorporating chitosan into the rigid network also endowed the hydrogel with excellent hemostatic properties. By delicately tuning the components and postcrosslinking conditions, the hydrogel was further endowed with suitable swelling and degradation properties for cartilage regeneration. In vitro tests showed that the highly biocompatible hydrogel scaffold could facilitate the migration and chondrogenic differentiation of bone marrow mesenchymal stem cells. In vivo results further verified that the hydrogel could promote the in situ regeneration of cartilage in a rat model of osteochondral defects. In summary, the subchondral bone-like hydrogel revealed promising prospects in cartilage regeneration and a variety of bioremediation applications.

Preparation, assessment, and swelling study of amphiphilic acrylic acid/chitosan-based semi-interpenetrating hydrogels

The aim of this study was to synthesize amphiphilic semi-IPN hydrogels based on acrylic acid (AA) and chitosan (CS) using AIBN as an initiator and N,N?methylene bis acrylamide as a crosslinking agent. The swelling behavior of the hydrogels was evaluated at a variety of pH values, temperature, the salinity of media and time, and the swelling mechanism was investigated using Fickian diffusion and Schott's 2nd-order-kinetics models. FTIR spectroscopy was used to confirm the synthesis of AA/CS hydrogel. The swelling results showed that, in the acidic media, as the CS content increase the hydrogel swelling ratio reduces. It was found that the maximum swelling ratio (8550%) is attained for the sample HAC2 with an AA/CS ratio of 1:0.001 in the alkaline Ph value. It also revealed that the absorption capacity is directly dependent on the temperature and inversely related to the salt concentration. Besides, the absorption capacity of the synthesized hydrogels in the saline solution of Na2SO4 was higher than NaCl.

Characterization of a novel semi-interpenetrating hydrogel network fabricated by polyethylene glycol diacrylate/polyvinyl alcohol/tragacanth gum as a wound dressing

In this research, a novel semi-interpenetrating hydrogel network comprised of polyethylene glycol diacrylate (PEGDA)/polyvinyl alcohol (PVA)/tragacanth gum (TG) with adaptable mechanical, biological, and physical characteristics was fabricated for wound healing purposes. The chemical structure of the films and the surface morphology were examined by FTIR and SEM, respectively. In addition, swelling ratio, mechanical characteristics, water vapor transmission rate (WVTR), gel fraction, and degradability of the hydrogels were assessed. To evaluate their cytocompatibility, MTT assay and cell attachment studies were performed. The FTIR results showed that the vinyl peaks were eliminated during crosslinking between PEGDA chains. The results also showed that incorporating PVA into the networks increases the swelling ration and decreases the porosity. Furthermore, as the ratio of PEGDA to PVA increased, WVTR ratio, cell adhesion, and elongation of the networks increased. It was also found that, when the amount of PEGDA reduced, degradation rate of the networks decreased. The results verified the non-toxic nature of PEGDA/PVA/TG hydrogel networks. Finally, the antibacterial results demonstrated that the highest antibacterial activities against bacterial pathogens is related to the TG-containing film. Therefore, PEGDA/PVA/TG hydrogel networks can be favorable wound dressings.

Photo/thermal response of polypyrrole-modified calcium alginate/gelatin microspheres based on helix-coil structural transition and the controlled release of agrochemicals

Responsive controlled-release systems can not only improve the efficiency of agrochemical utilization but also increase crop yield and reduce environmental pollution caused by excessive use of agrochemicals. In this paper, the helix-coil structural transition of gelatin was adopted to construct a novel stimuli-responsive controlled-release system called polypyrrole/Ca-alginate/gelatin (PPy/Ca-alginate/Gel). In PPy/Ca-alginate/Gel, Ca-alginate and gelatin form a semi-interpenetrating network in which uncross-linked gelatin can undergo a free helix-coil structural transition due to the photothermal effect of PPy. The structural transition of gelatin will lead to changes in the functional groups and microstructure of semi-interpenetrating hydrogels and furthermore achieve the release of template agrochemical molecules embedded in hydrogels. By using carbendazim as a template molecule, the photothermal conversion and controlled release of PPy/Ca-alginate/Gel were systematically studied. After 600 s of light irradiation, its temperature could be increased by 17 ℃. The release of carbendazim in microspheres reached 91.8 % after 8 h of light irradiation, while it was only 13.3 % in the dark. The results indicated that PPy/Ca-alginate/Gel have excellent controlled-release and sustained-release properties and broad application potential in agriculture.

Modulating the physico-mechanical properties of polyacrylamide/gelatin hydrogels for tissue engineering application

Along with providing an environment for cell attachment and proliferation, a tissue engineering scaffolds should possess physical and mechanical properties that would fit the target tissue. The present study aimed to manipulate physico-mechanical properties of polyacrylamide/gelatin hydrogels using response surface method-central composite design (RSM-CCD) to reach a scaffold with defined properties. On this demand, mixtures of gelatin and acrylamide (AAm) monomer were used to prepare semi-interpenetrating hydrogels by free radical polymerization of AAm. Selected variables for statistical modeling were chosen to be weight ratios of monomer/crosslinker, monomer/gelatin, and monomer/initiator. The desired responses were compressive modulus, compressive strength, and swelling. Results showed that desired responses could be tailored by varying these parameters with the highest impact for monomer/crosslinker ratio. The swelling ratio of hydrogels was in the range of 947–1654%, while the modulus varied between 5 and 35 kPa. The cyclic compressive test showed the durability of hydrogels under cyclic loadings. Finally, the results of cell attachment and cytocompatibility analyses indicated that the hydrogels were completely biocompatible and enhanced cell attachment. Thus, these hydrogels could potentially be used as tissue engineering scaffolds for load-bearing organs, including muscle and cartilage, or could be used for in vitro differentiation of stem cells using mechanical clues.

Preparation, assessment, and swelling study of amphiphilic acrylic acid/chitosan-based semi-interpenetrating hydrogels.

The aim of this study was to synthesize amphiphilic semi-IPN hydrogels based on acrylic acid (AA) and chitosan (CS) using AIBN as an initiator and N,N'methylene bis acrylamide as a crosslinking agent. The swelling behavior of the hydrogels was evaluated at a variety of pH values, temperature, the salinity of media and time, and the swelling mechanism was investigated using Fickian diffusion and Schott's 2nd-order-kinetics models. FTIR spectroscopy was used to confirm the synthesis of AA/CS hydrogel. The swelling results showed that, in the acidic media, as the CS content increase the hydrogel swelling ratio reduces. It was found that the maximum swelling ratio (8550%) is attained for the sample HAC2 with an AA/CS ratio of 1:0.001 in the alkaline Ph value. It also revealed that the absorption capacity is directly dependent on the temperature and inversely related to the salt concentration. Besides, the absorption capacity of the synthesized hydrogels in the saline solution of Na2SO4 was higher than NaCl.

Amalgamated fiber/hydrogel composites based on semi-interpenetrating polymer networks and electrospun nanocomposite fibrous mats

Amalgamated 3D fiber/hydrogel composites were successfully synthesized based on double-hydrophilic semi-interpenetrating (semi-IPN) hydrogel matrices consisting of 1,2-bis-(2-iodoethoxy)ethane (BIEE)-crosslinked poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA) chains and linear polyvinylpyrrolidone (PVP), and prefabricated PVP/Ag nanocomposite electrospun fibrous mats. The latter were incorporated within the semi-IPN hydrogels by following 2 unique ways of dispersion, i.e. the “laminated” and the “homogeneous” dispersion mode. In the “laminated” dispersion mode, the prefabricated electrospun fibrous mat was placed in the circumference of the fiber/hydrogel composite, while in the “homogeneous” dispersion mode, 2D circular fibrous mats were homogeneously encapsulated within the 3D hydrogel matrix.Among others, the effect of fiber inclusion as well as of the fiber dispersion mode within the hydrogel matrix on the materials’ mechanical properties was investigated. The obtained results clearly demonstrated that the dispersion mode of electrospun fibrous mats within the hydrogel influences significantly the mechanical performance of the resulting composites. Moreover, the influence of the presented structure-defined 3D fiber/hydrogel composites on the viability of human pancreatic fibroblasts was investigated in vitro. Consequently, these fiber/hydrogel composites exhibiting enhanced mechanical performance and biocompatibility could be potentially used as tissue engineering scaffolds with controllable mechanical properties and multi-functionalities.

A mechanically strong polyvinyl alcohol/poly(2-(N,N′-dimethyl amino) ethyl methacrylate)-poly (acrylic acid) hydrogel with pH-responsiveness

Fabrication of a pH-responsive hydrogel with good mechanical strength is highly desirable in applications such as sensors and tissue engineering. In this work, a polyvinyl alcohol (PVA)/poly(2-(N,N′-dimethyl amino) ethyl methacrylate) (PDMAEMA)-poly (acrylic acid) (PAAc) hydrogel was produced via a double-network (DN) protocol, in which PDMAEMA-PVA semi-interpenetrating hydrogel was constructed as the first network by the polymerization and crosslinking of PDMAEMA, and then AAc was polymerized in presence of the first network to form a polyion complexation as the second network. The DN PVA/PDMAEMA-PAAc hydrogel exhibited satisfactory mechanical strength which depended significantly on the crosslinking density of the first layer of the network. An optimal tensile strength of 0.45 MPa and compressive strength of 1.2 MPa can be obtained for DN hydrogel, and the compressive strength was 480% higher than that of the single-network hydrogel. The DN hydrogel also showed a pH-responsive swelling behavior and the equilibrium swelling ratio was controlled by both of the DMAEMA and AAc moieties in the network. Considering the wide potential applications of stimuli-responsive hydrogels, the present strategy is of highly practical value for broadening the application scope of the hydrogels.