Tough,stretchable and compressive alginate-based hydrogels achieved by non-covalent interactions

In this study, two alginate-based hydrogels with good mechanical strength, toughness and resilience were synthesized by hydrophobic interaction and coordination bonding. Sodium alginate/poly(acrylamide) semi-interpenetrating network (NaAlg/PAM semi-IPN) hydrogels were first synthesized through the micelle copolymerization of acrylamide and stearyl methacrylate in the presence of sodium alginate, then calcium alginate/poly(acrylamide) double network (CaAlg/PAM DN) hydrogels were prepared by immersing the as-prepared NaAlg/PAM semi-IPN hydrogels in a CaCl₂ solution. FT-IR and XPS results revealed NaAlg/PAM semi-IPN hydrogels and CaAlg/PAM DN hydrogels were successfully synthesized through non-covalent interactions. The tensile strength of CaAlg/PAM DN hydrogels could reach 733.6 kPa, and their compressive strengths at 80% strain are significantly higher than those of the corresponding NaAlg/PAM semi-IPN hydrogels, which is attributed to the alginate network crosslinked by Ca²⁺. The dual physically crosslinked CaAlg/PAM DN hydrogels can achieve fast self-recovery, and good fatigue resistance, which is mainly assigned to energy dissipation through dynamic reversible non-covalent interactions in both networks. The self-healing ability, swelling behavior and morphology of the synthesized alginate-based hydrogels were also evaluated. This study offers a new avenue to design and construct hydrogels with high mechanical strength, high toughness and fast self-recovery properties, which broadens the current research and application of hydrogels.

Alginate-based hydrogels based on non-covalent interactions were synthesized, and exhibited good mechanical strength, toughness and resilience.     

Anisotropic tough poly(vinyl alcohol)/graphene oxide nanocomposite hydrogels for potential biomedical applications

Hydrogels, one of the most important bioinspired materials, are receiving increasing attention because of their potential applications as scaffolds for artificial tissue engineering and vehicles for drug delivery, etc. However, these applications are always severely limited by their microstructure and mechanical behavior. Here we report the fabrication of a tough polyvinyl alcohol/graphene oxide (PVA/GO) nanocomposite hydrogel through a simple and effective directional freezing–thawing (DFT) technique. The resulting hydrogels show well-developed anisotropic microstructure and excellent mechanical properties with the assistance of DFT method and lamellar graphene. The hydrogels with anisotropic porous structures that consisted of micro-sized fibers and lamellas exhibit high tensile strengths, up to 1.85 MPa with a water content of 90%. More interestingly, the PVA/GO composite hydrogels exhibit the better thermostability, which can maintain the original shape when swollen in hot water (65 °C). In addition, the hydrogels with biocompatibility show good drug release efficiency due to the unique hierarchical structure. The successful synthesis of such hydrogel materials might pave the way to explore applications in biomedical and soft robotics fields.

Tough PVA/GO nanocomposite hydrogel with well-developed anisotropic microstructure and excellent mechanical properties.     

Rapid preparation of PAM/N-CNT nanocomposite hydrogels by DEM frontal polymerization and its performance study

In this study, a simple and eco-friendly method was proposed to efficiently prepare nanocomposite hydrogels with excellent mechanical properties and satisfactory pH response behaviour by frontal polymerization (FP) of DEM in close to 4 minutes. Acrylamide (AM) and choline chloride (ChCl) were used as raw materials to synthesize deep eutectic monomers (DEMs). Nitrogen-doped carbon nanotubes were dispersed in DEMs as fillers, and poly(acrylamide)/nitrogen-doped carbon nanotube (PAM/N-CNT) nanocomposite hydrogels were prepared by FP. The non-covalent interactions between PAM hydrogels and N-CNTs was verified by Fourier infrared spectroscopy. The mechanical properties of PAM/N-CNT nanocomposite hydrogels were investigated, as well as the swelling and pH response properties. The results showed that the compressive strength of PAM hydrogels was significantly enhanced by the addition of N-CNTs due to the hydrophobic interaction of N-CNTs, which also causes sensitive response properties of the PAM hydrogels in acid solution.

In this study, a simple and eco-friendly method was proposed to efficiently prepare nanocomposite hydrogels with excellent mechanical properties and satisfactory pH response behaviour by frontal polymerization of DEM in close to 4 minutes.     

The surface chemical composition effect of a polyacrylic acid/polyvinyl alcohol nanofiber/quartz crystal microbalance sensor on ammonia sensing behavior

Polyacrylic acid (PAA)/polyvinyl alcohol (PVA)-based quartz crystal microbalance (QCM) ammonia sensors were fabricated by depositing composite PAA/PVA nanofibrous substrates onto QCM gold electrodes. Morphological analysis of the PAA/PVA substrates revealed a homogenous smooth surface and similar specific surface areas. X-ray photoelectron spectroscopy results indicated their distinct chemical properties with different carboxyl group contents on the surface. The ammonia sensing tests demonstrated the significant effect of the surface chemical characteristics on ammonia-sensing sensitivity, and the sensing process was proven to be derive from a monolayer adsorption mechanism. Because of the inherent high specific surface areas (SSAs) and three-dimensional porous architecture, the prepared PAA/PVA nanofiber-based QCM sensors exhibited ultrahigh sensitivity (100 ppb) and rapid response (several seconds) with good selectivity and repeatability in terms of ammonia detection.

Polyacrylic acid (PAA)/polyvinyl alcohol (PVA)-based quartz crystal microbalance (QCM) ammonia sensors were fabricated by depositing composite PAA/PVA nanofibrous substrates onto QCM gold electrodes.     

Synthesis of physically crosslinked PAM/CNT flakes nanocomposite hydrogel films via a destructive approach

Carbon nanotube (CNT)-based hydrogels have recently found a wide variety of applications due to the unique physical and chemical properties of CNTs. CNTs can be used as a nanofiller and/or crosslinker to produce nanocomposite hydrogels with good mechanical and structural properties. In this research, a novel method was reported for producing polyacrylamide (PAM)/oxidized-multiwalled carbon nanotube (O-MWCNT) flakes nanocomposite hydrogel films without using any organic cross-linker or surfactant. Through a mechanism dependent on the reactive oxygen species (ROS), some O-MWCNTs were broken down in situ into small flakes in the aqueous solutions containing acrylamide (AM) and sodium persulfate (NaPS) at the temperature range of 85–90 °C. Simultaneously, in situ polymerization of the AM monomers occurred using free radicals, which resulted in the formation of PAM chains. The flakes acted as crosslinkers by forming hydrogen bonds with PAM chains and formed a hydrogel network after 48 h at room temperature. The hydrogels were characterized by different techniques (FT-IR, Raman, FE-SEM, TEM, TGA, tensile test). The porous structure of the hydrogel films as well as micro-network structures with unique morphologies were observed by SEM. The O-MWCNT flakes and some undegraded O-MWCNTs in the hydrogel network were also observed by TEM. The results showed that PC₂I₂H hydrogel film, as an evolved hydrogel, has excellent swelling performance in aqueous solutions at different pH and temperatures. In addition, this hydrogel showed a tensile strength of 103 MPa in the dry state and an elongation of 703% in the swollen state.

Novel PAM/CNT flakes nanocomposite hydrogel films were synthesized by in situ degradation of the oxidized-MWCNTs into flakes using persulfate activation. The flakes crosslinked the PAM chains via hydrogen bonding to form a hydrogel network.     

Design and performance of a poly(vinyl alcohol)/silk fibroin enzymatically crosslinked semi-interpenetrating hydrogel for a potential hydrophobic drug delivery

In this study, in order to obtain hydrogels with good properties for sustained release of hydrophobic drugs or for tissue engineering, poly(vinyl alcohol) (PVA)/silk fibroin (SF) semi-interpenetrating (semi-IPN) hydrogels with varied ratios of PVA/SF were enzymatically cross-linked using horseradish peroxidase. A vial inversion test determined approximate gelation times of PVA/SF hydrogels ranging from 5 to 10 min. The hydrogels with varied ratios showed differences in pore size and morphology. Mass loss rate of hydrogels increased from 15% to 58% with increasing PVA concentration. Stable hydrogels with PVA/SF at 0.5 : 1 w/w showed the best swelling ratio values in distilled water (7.36). FTIR analysis revealed that silk fibroin in these hydrogels exhibited the coexistence of amorphous and silk I crystalline structures and the SF and PVA molecules interacted with each other well. The mechanical properties of the composite hydrogels were controlled by the SF content. From the cell viability results, it was found that the hydrogels exerted very low cytotoxicity. Paeonol was chosen as the hydrophobic drug model for release studies from the hydrogels. Paeonol can be uniformly loaded into the composite hydrogels using the emulsifying property of PVA and paeonol release from the hydrogels was dependent on the PVA/SF ratio. This study applied a novel type of enzymatically crosslinked semi-IPN hydrogel that may have potential applications in drug delivery.

Enzymatically cross-linked PVA/SF semi-IPN hydrogels with tunable pore structure have potential applications in sustained release of hydrophobic drug.     

Ag-exchanged NaY zeolite introduced polyvinyl alcohol/polyacrylic acid mixed matrix membrane for pervaporation separation of water/isopropanol mixture

Ag-exchanged NaY zeolite (Ag-NaZ) particles were prepared by ion exchange and introduced to a polyvinyl alcohol (PVA) membrane cross-linked with polyacrylic acid (PAA) for the pervaporation dehydration of an isopropanol (IPA) aqueous mixture. The Ag-exchanged NaY zeolite particles were characterized by FE-SEM, EDS, BET, and XRD studies. The prepared Ag-NaZ-loaded PVA/PAA composite membrane was characterized by FE-SEM, XRD, a swelling study, and contact angle measurements. Pervaporation characteristics were investigated in terms of Ag-NaZ concentrations within PVA/PAA membranes using diverse feed solution conditions. The preferential sorption of IPA/water mixtures for Ag-NaZ-introduced membranes were also determined by calculating the apparent activation energies of IPA and water permeation, respectively. As a result, flux and selectivity increased with the Ag-NaZ concentration to 5 wt% in the membrane. Optimum pervaporation performance was observed in a 5 wt% Ag-NaZ-incorporated membrane with a flux equal to 0.084 kg m⁻² h⁻¹ and a separation factor of 2717.9 at 40 °C from an 80 wt% IPA aqueous feed solution.

Ag-exchanged NaY zeolite (Ag-NaZ) particles were prepared by ion exchange and introduced to a polyvinyl alcohol (PVA) membrane cross-linked with polyacrylic acid (PAA) for the pervaporation dehydration of an isopropanol (IPA) aqueous mixture.     

Nature-inspired preparation of self-adhesive,frost-resistant,and ion-conductive hydrogels for flexible strain sensors

A nature-inspired strategy has been developed to prepare polyvinyl alcohol (PVA)/catechol-modified quaternized chitosan (QCS-C)/MXene hydrogels with good self-adhesion, frost-resistance, and high ion-conductivity. The PVA/QCS-C/MXene hydrogel shows an ionic conductivity of 8.82 S m⁻¹ and a gauge factor of 33.53 at low strain (0–10%), and remains flexible and conductive at −47 °C. The PVA/QCS-C₁₅/MXene hydrogel displays promising potential as an ionically conductive hydrogel sensor for applications in flexible electronic devices.

A nature-inspired strategy is developed to prepare polyvinyl alcohol/catechol-modified quaternized chitosan/MXene hydrogels with good self-adhesion, frost-resistance, water retention capacity, and high ion-conductivity.     

The use of fractionated Kraft lignin to improve the mechanical and biological properties of PVA-based scaffolds

The mechanical properties of poly(vinyl alcohol) (PVA)-based scaffolds were successfully improved. The improvements in mechanical properties correlated with the amount of Kraft lignin in PVA matrices. The critical property for any scaffold is its capacity to allow cells to ingrow and survive within its internal structure. The ingrowth of cells was tested using bioreactors creating simulated in vivo conditions. In the context of all the mentioned parameters, the most advantageous properties were exhibited by the scaffold containing 99 wt% PVA and 1 wt% Kraft lignin. The composites with 1 wt% Kraft lignin exhibited sufficient mechanical stability, a lack of cytotoxicity, and mainly the ability to allow the ingrowth of cells into the scaffold in a rotation bioreactor.

The mechanical properties of poly(vinyl alcohol) (PVA)-based scaffolds were successfully improved.     

3D printable SiO2 nanoparticle ink for patient specific bone regeneration

Sodium alginate and gelatin are biocompatible & biodegradable natural polymer hydrogels, which are widely investigated for application in tissue engineering using 3D printing and 3D bioprinting fabrication techniques. The major challenge of using hydrogels for tissue fabrication is their lack of regeneration ability, uncontrolled swelling, degradation and inability to hold 3D structure on their own. Free hydroxyl groups on the surface of SiO₂ nanoparticles have the ability to chemically interact with alginate–gelatin polymer network, which can be explored to achieve the above parameters. Hence validating the incorporation of SiO₂ nanoparticles in a 3D printable hydrogel polymer network, according to the patient''s critical defects has immense scope in bone tissue engineering. In this study, SiO₂ nanoparticles are loaded into alginate–gelatin composite hydrogels and chemically crosslinked with CaCl₂ solution. The effect of SiO₂ nanoparticles on the viscosity, swelling, degradation, compressive modulus (MPa), biocompatibility and osteogenic ability were evaluated on lyophilized scaffolds and found to be desirable for bone tissue engineering. A complex irregular patient-specific virtual defect was created and the 3D printing process to fabricate such structures was evaluated. The 3D printing of SiO₂ nanoparticle hydrogel composite ink to fabricate a bone graft using a patient-specific virtual defect was successfully validated. Hence this type of hydrogel composite ink has huge potential and scope for its application in tissue engineering and nanomedicine.

3D printing of a complex and irregular virtual defect using SiO₂ nanoparticle and hydrogel composite ink for patient specific defect fabrication.     

Bacterial cellulose-poly(acrylic acid-co-N,N′-methylene-bis-acrylamide) interpenetrated networks for the controlled release of fertilizers

In this study, composite hydrogels with interpenetrated polymer networks (IPNs), based on bacterial cellulose (BC) and poly(acrylic acid-co-N,N′-methylene-bis-acrylamide) (PAA), were synthesized by radical polymerization and characterized herein for the first time. Liquid fertilizer (LF) formulations, containing potassium, phosphorus, ammonium oxides and micronutrients, were encapsulated directly into the IPNs of the composite hydrogels during synthesis. Thermal analyses and scanning electron microscopy of control and composite xerogels highlighted the formation of IPNs between BC and PAA. Swelling determinations confirmed the influence of the crosslinker and of the liquid fertilizer concentration upon the density of the IPNs. Further rheology studies and release profiles indicated how the presence of BC and the increase of the crosslinking density of IPNs improved the mechanical strength and the release profile of LF for the innovative composite BC-PAA hydrogels. Results regarding the fertilizer release indicated that the presence of the BC led to a more controlled liberation of the fertilizer proving that this new formulation is potentially viable for application in agricultural practices.

In this study, composite hydrogels with interpenetrated polymer networks (IPNs), based on bacterial cellulose (BC) and poly(acrylic acid-co-N,N′-methylene-bis-acrylamide) (PAA) were synthesized by radical polymerization.     

A simple one-pot fabrication of silver loaded semi-interpenetrating polymer network (IPN) hydrogels with self-healing and bactericidal abilities

In the last decade, there has been a significant increase in the development of self-healing hydrogels. However, in most cases, the synthesized self-healing hydrogels possess no antibacterial properties. Further, the preparation of self-healing hydrogels usually requires sophisticated processes and also involves multiple steps. Herein, we proposed a simple one-pot synthesis of silver loaded semi-IPN hydrogels with self-healing and antibacterial properties. The hydrogels were prepared by physical cross-linking between polyacrylic acid (PAA) and ferric ions (Fe³⁺) and further modified by the interpenetration of gelatin-silver in the networks. In addition, the effect by varying the gelatin concentration was also studied. The mechanical properties of the as-prepared hydrogels reached 0.79 MPa in stress and 920% in strain with the self-healing efficiency of 87.5% (healed at 70 °C for 2 h). As displayed by the SEM images, the incorporated silver chloride nanoparticles (AgCl NPs) in gelatin-free hydrogels were agglomerated. Meanwhile, well-distributed AgCl NPs in the hydrogels were obtained in the presence of gelatin which acts as a stabilizer. Moreover, due to Fe³⁺ and AgCl NPs, the hydrogels were able to inhibit the growth of bacteria indicated by an inhibition zone (9–9.6 mm) which was examined toward Escherichia coli via the disk-diffusion method.

The semi-interpenetrating polymer network hydrogel possesses self-healing ability due to the dynamic ionic interactions between polyacrylic acid and Fe³⁺. The antibacterial properties are due to embedded silver chloride nanoparticles well-distributed in the hydrogel.     

Mechanical behaviors and probabilistic multiphase network model of polyvinyl alcohol hydrogel after being immersed in sodium hydroxide solution

Because of the advantages of a uniform distribution of reinforcing particles and in situ preparation, in situ precipitation has become an important way to prepare magnetic and other smart hydrogels. An important step in this process is to immerse hydrogels in alkaline solution to implant magnetic particles. Previous studies generally have ignored the effect of this process on the network structure and mechanical properties of hydrogels. In this study, we immersed polyvinyl alcohol (PVA) hydrogel samples in sodium hydroxide solutions of different concentrations to study changes in mechanical properties, such as stress–strain relationship, self-recovery, and fracture failure. The results showed that after the immersion process, the hydrogel''s tensile and compressive properties changed significantly, and the failure behavior changed from brittle fracture to ductile fracture. Through a microscopic mechanism, the alkaline solution caused a high degree of phase separation and crystallization within the polymer network, thereby changing the PVA hydrogel network from a single phase to a multiphase. Hence, we used a continuous multiphase network model with a certain probability distribution to describe this tensile behavior. This model well described the stress–strain relationship of the hydrogel from stretching to fracture and revealed that the macroscopic failure corresponded to the peak of fracture distribution. Studies have shown that attention should be paid to the influence of the in situ precipitation on the mechanical properties, and the probabilistic multiphase network model can be used to predict the mechanical behavior of hydrogels with multiple phase separation.

Phase separation occurs in polyvinyl alcohol hydrogel after being immersed in sodium hydroxide solution. The change of the network structure leads to significant changes in the mechanical behaviors.     

Poly(N,N-dimethylacrylamide-octadecyl acrylate)-clay hydrogels with high mechanical properties and shape memory ability

As a type of important intelligent materials, shape memory hydrogels (SMHs) have gathered a lot of interest due to their promising applications. However, preparing SMHs with excellent mechanical properties still remains a big challenge. In this study, a new type of SMHs with excellent mechanical strength is created. The SMHs were prepared by free radical micellar polymerization of hydrophobic monomer (octadecyl acrylate) with gelatin as emulsifier in a aqueous system containing hydrophilic monomer (N,N-dimethylacrylamide, DMA) and clay as reinforcing filler. The polymerization provided physically cross-linked network structures constructed by two non-covalent interactions, i.e. hydrophobic association formed by monomer units and multiple H-bonds among inorganic clay, gelatin and DMA. A judicious combination of the two physically cross-linked networks significantly improved the mechanical strength of hydrogels. More interestingly, the hydrogels demonstrated shape memory behavior due to the hydrophobic poly(octadecyl acrylate) domains. The novel SMHs are expected to find practical applications as biomaterials.

As a type of important intelligent materials, shape memory hydrogels (SMHs) have gathered a lot of interest due to their promising applications.     

The modification mechanism and the effect of magnesium chloride on poly(vinyl alcohol) films

The modification mechanism and the effect of MgCl₂ on poly(vinyl alcohol) and the effect of water in the system were studied in this paper. The effect of MgCl₂ on different fully dried PVA was investigated by Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimeter, thermogravimetric analysis, water content test, dynamic thermomechanical analysis and tensile test, respectively. The results showed that MgCl₂ was an effective strengthening agent, which could crosslink with PVA and then effectively decrease the crystallinity of PVA. With the addition of MgCl₂, the strength and rigidity of PVA increased and the melting temperature decreased. The effect of MgCl₂ on thermal stability of PVA was related to the alcoholysis degree of PVA. The tensile strength of PVA films modified with MgCl₂ were all over 120 MPa. Moreover, the effect of MgCl₂ on the dynamic thermomechanical properties and tensile properties of PVA with various content of water was studied. Water could interact with MgCl₂ to destroy the crosslink between MgCl₂ and PVA. In the presence of water, PVA modified with MgCl₂ became soft, with lower tensile strength and higher elongation at break.

MgCl₂ could crosslink with PVA to increase the strength and rigidity of PVA, while water could decrease the interaction.     

Effect of size of latex particles on the mechanical properties of hydrogels reinforced by latex particles

Herein, cationic latex particles (CL) of different particle sizes were introduced as a cross-linking center to enhance the mechanical properties of the hydrophobically-associated hydrogels (P(AAm-co-HMA)-CL). Firstly, cationic polymethylmethacrylate (PMMA) latex particles were synthesized via soap-free emulsion polymerization. Subsequently, P(AAm-co-HMA)-CL hydrogels with outstanding mechanical properties were prepared using acrylamide as the monomer, hexadecyl methacrylate as the hydrophobic molecule, and CL as the cross-linking center. The size of CL had a significant effect on the mechanical properties and self-recovery properties of the P(AAm-co-HMA)-CL hydrogels. The hydrogel with larger CL size exhibited low mechanical properties due to weak hydrophobic interactions. In contrast, the hydrogel with small CL size displayed excellent mechanical properties due to an effective entanglement of the hydrophobic chains with the smaller size CL, which significantly affects the mechanical properties of the hydrogel. As a result, the maximum fracture stress and fracture strain of the hydrogel were up to 1.47 MPa and 2847%, respectively. This study can have a profound impact on the development of the technology of toughening hydrogels with latex particles.

Herein, cationic latex particles (CL) of different particle sizes were introduced as a cross-linking center to enhance the mechanical properties of the hydrophobically-associated hydrogels (P(AAm-co-HMA)-CL).     

Polyacrylamide crosslinked by bis-vinylimidazolium bromide for high elastic and stable hydrogels

A series of ionic compounds 1,n-dialkyl-3,3′-bis-l-vinylimidazolium bromide (C_nVIM) are prepared and employed to crosslink acrylamide for polyacrylamide (PAAM) hydrogel preparation via in situ solution polymerization. The swelling behavior, mechanical properties and thermal stability of the prepared C_nVIM crosslinked PAAM hydrogels are investigated. C_nVIM effectively crosslink the PAAM networks to form porous structures in the hydrogel, which could stably absorb water as much as 75.9 fold in weight without structural degradation. The prepared hydrogels could endure compressive stress up to 1.95 MPa and compressive deformation more than 90%. Meanwhile, the C_nVIM crosslinked networks show superior thermal stability, and could retain the structural integrity under 150 °C for more than 240 h. The swelling degradation resistance, mechanical strength and thermal stability of C_nVIM crosslinked hydrogels are much better than those of a conventional N,N′-methylenebisacrylamide crosslinked PAAM hydrogel. Using bis-vinylimidazolium bromides as crosslinkers provides an optional strategy for constructing thermally and mechanically robust hydrogel networks.

Polyacrylamide hydrogels crosslinked by bis-vinylimidazolium bromides achieved robust mechanical stability under various conditions, such as equilibrium swelling, compression and high temperatures.     

Antibacterial coordination polymer hydrogels composed of silver(i)-PEGylated bisimidazolylbenzyl alcohol

Herein, antibacterial coordination polymer hydrogels were conveniently fabricated in water via coordination between silver nitrate and PEGylated bisimidazolylbenzyl alcohol (1a–c). These coordination polymer hydrogels exhibit much better antibacterial activity than silver nitrate against both Gram-negative and Gram-positive pathogens including multidrug-resistant pathogens. The coordination polymer Ag/1c with a long PEG chain (PEG1000) was demonstrated to be the most effective antibacterial material, and its minimum inhibition concentrations (MICs) could be as low as 15.2 times for common Staphylococcus aureus and 4.8 times for methicillin-resistant Staphylococcus aureus over that of silver nitrate. With improved antibacterial performance, easy preparation method, improved stability, sustained releasability, outstanding ductility and low cytotoxicity, the as-prepared coordination polymer hydrogels should find various potential applications such as in clinical burn and wound dressings, biofilms, bioadhesives, and coatings of biomedical materials.

Herein, antibacterial coordination polymer hydrogels were conveniently fabricated in water via coordination between silver nitrate and PEGylated bisimidazolylbenzyl alcohol (1a–c).     

Effects of amphiphilic monomers and their hydrophilic spacers on polyacrylamide hydrogels

Hydrogels based on physical interactions have been extensively studied due to their special network structure and excellent mechanical properties. In this paper, a series of hydrogels based on hydrophobic interactions were prepared via the free-radical copolymerization of acrylamide and polymerizable amphiphilic monomers dodecanol polyoxyethylene (n) acrylates (AEO-n-AC, n = 3, 7, 9, 15, 23) by a simple and facile method. The prepared single-network hydrogels cross-linked by the self-assemble AEO-n-AC micelles acting as cross-linkers exhibited great tensile strength of 0.45 MPa and excellent compression strength of 4.5 MPa. Transmission electron microscopy tests reflected that the morphologies of the self-associated micelles were determined by the hydrophilic segment of the amphiphilic monomers, which further affected the mechanical properties of the hydrogel. Amphiphilic monomer with appropriate length of hydrophilic spacers could significantly enhance the tensile strength of the hydrogel. Meanwhile, amphiphilic monomers with long hydrophilic segment were advantageous for the compression properties of the hydrogel. Furthermore, the hydrogels exhibited excellent micro self-repair ability during the cycling tensile and loading-unloading test even at the strain and compression were 400%, 0.95, respectively. This discover of hydrophilic spacer effect is of great significance for the design of physical interaction-based hydrogels with high strength and compression properties.

HA-gels with different hydrophilic spacers were synthesized. These hydrophilic spacers endow the gel with good tensile properties, excellent compression properties and self-recovery. We believe it is a meaningful discovery.     

Design,characterization and evaluation of β-hairpin peptide hydrogels as a support for osteoblast cell growth and bovine lactoferrin delivery

The use of peptide hydrogels is of growing interest in bone regeneration. Self-assembling peptides form hydrogels and can be used as injectable drug delivery matrices. Injected into the defect site, they can gel in situ, and release factors that aid bone growth. We report on the design, synthesis and characterization of three β-hairpin peptide hydrogels, and on their osteoblast cytocompatibility as well as delivery of the lactoferrin glycoprotein, a bone anabolic factor. Osteoblasts cultured in hydrogels of the peptide with sequence NH₂-Leu-His-Leu-His-Leu-Lys-Leu-Lys-Val-dPro-Pro-Thr-Lys-Leu-Lys-Leu-His-Leu-His-Leu-Arg-Gly-Asp-Ser-CONH₂ (H4LMAX-RGDS) increased the osteoblast cell number and the cells appeared healthy after seven days. Furthermore, we showed that H4LMAX-RGDS was capable of releasing up to 60% of lactoferrin (pre-encapsulated in the gel) over five days while retaining the rest of the glycoprotein. Thus, H4LMAX-RGDS hydrogels are cytocompatible with primary osteoblasts and capable of delivering bio-active lactoferrin that increases osteoblast cell number.

Self-assembling peptide H4LMAX-RGDS hydrogels, designed to enhance bone regeneration, are cytocompatible and capable of delivering the bone anabolic factor lactoferrin to increase osteoblast cell number.