Ultra-Large Stress and Strain Polymer Nanocomposite Actuators Incorporating a Mutually-Interpenetrated, Collective-Deformation Carbon Nanotube Network.

Stimulus-responsive polymer-based actuators are extensively studied, with the challenging goal of achieving comprehensive performance metrics that include large output stress and strain, fast response, and versatile actuation modes. The design and fabrication of nanocomposites offer a promising route to integrate the advantages of both polymers and nanoscale fillers, thus ensuring superior performance. Here, it is started from a three-dimensional (3D) porous sponge to fabricate a mutually interpenetrated nanocomposite, in which the embedded carbon nanotube (CNT) network undergoes collective deformation with the shape memory polymer (SMP) matrix during large-degree stretching and releasing, increases junction density with polymer chains and enhances molecular orientation. These features result in substantial improvement of the overall mechanical properties and during thermally actuated contraction, the bulk SMP/CNT composites exhibit output stresses up to 19.5 ± 0.97 MPa and strains up to 69%, accompanied by a rapid response and high energy density, exceeding the majority of recent reports. Furthermore, electrical actuation is also demonstrated via uniform Joule heating across the self-percolated CNT network. Applications such as low-temperature thermal actuated vascular stent and wound dressing are explored. These findings lay out a universal blueprint for developing robust and highly deformable SMP/CNT nanocomposite actuators with broad potential applications.

Functional Materials Made by Combining Hydrogels (Cross-Linked Polyacrylamides) and Conducting Polymers (Polyanilines)-A Critical Review.

Hydrogels made of cross-linked polyacrlyamides (cPAM) and conducting materials made of polyanilines (PANIs) are both the most widely used materials in each category. This is due to their accessible monomers, easy synthesis and excellent properties. Therefore, the combination of these materials produces composites which show enhanced properties and also synergy between the cPAM properties (e.g., elasticity) and those of PANIs (e.g., conductivity). The most common way to produce the composites is to form the gel by radical polymerization (usually by redox initiators) then incorporate the PANIs into the network by oxidative polymerization of anilines. It is often claimed that the product is a semi-interpenetrated network (s-IPN) made of linear PANIs penetrating the cPAM network. However, there is evidence that the nanopores of the hydrogel become filled with PANIs nanoparticles, producing a composite. On the other hand, swelling the cPAM in true solutions of PANIs macromolecules renders s-IPN with different properties. Technological applications of the composites have been developed, such as photothermal (PTA)/electromechanical actuators, supercapacitors, movement/pressure sensors, etc. PTA devices rely on the absorption of electromagnetic radiation (light, microwaves, radiofrequency) by PANIs, which heats up the composite, triggering the phase transition of a thermosensitive cPAM. Therefore, the synergy of properties of both polymers is beneficial.

BMSCs-Seeded Interpenetrating Network GelMA/SF Composite Hydrogel for Articular Cartilage Repair.

Because of limited self-healing ability, the treatment of articular cartilage defects is still an important clinical challenge. Hydrogel-based biomaterials have broad application prospects in articular cartilage repair. In this study, gelatin methacrylate (GelMA)and silk fibroin (SF) were combined to form a composite hydrogel with an interpenetrating network (IPN) structure under ultraviolet irradiation and ethanol treatment. Introducing silk fibroin into GelMA hydrogel significantly increased mechanical strength as compressive modulus reached 300 kPa in a GelMA/SF-5 (50 mg/mL silk fibroin) group. Moreover, composite IPN hydrogels demonstrated reduced swelling ratios and favorable biocompatibility and supported chondrogenesis of bone mesenchymal stem cells (BMSCs) at day 7 and day 14. Additionally, significantly higher gene expressions of Col-2, Acan, and Sox-9 (p < 0.01) were found in IPN hydrogel groups when compared with the GelMA group. An in vivo study was performed to confirm that the GelMA-SF IPN hydrogel could promote cartilage regeneration. The results showed partial regeneration of cartilage in groups treated with hydrogels only and satisfactory cartilage repair in groups of cell-seeded hydrogels, indicating the necessity of additional seeding cells in hydro-gel-based cartilage treatment. Therefore, our results suggest that the GelMA/SF IPN hydrogels may be a potential functional material in cartilage repair and regeneration.

A novel hydrogel based on Bletilla striata polysaccharide for rapid hemostasis: Synthesis, characterization and evaluation.

The purpose of this study is to develop a new polysaccharide-based hydrogel. The Box-Behnken design was used to optimize the optimal synthesis conditions of the hydrogel, with the swelling parameters as indicators. The findings of rheologic tests confirm that free radical polymerization and the introduction of linear polymers improved the mechanical strength of the hydrogel. Combined with the characterization results, the gel mechanism of BSP-g-PAA/PVA DN hydrogel was proposed. The intermolecular association and entanglement increase, which effectively dissipates energy, thereby enhancing the mechanical properties of the hydrogel. In vitro blood compatibility experiments show that DN hydrogel has a low hemolysis rate and a good coagulation effect. The material is non-cytotoxic to L929 cells. The hepatic haemorrhage and mouse-tail amputation models of rats and mice were used to further evaluate the in vivo wound sealing and hemostatic properties of the hydrogel. The blood loss and hemostatic time were significantly lower than those of the control group, indicating that the hydrogel has excellent hemostatic effects. Therefore, the obtained BSP-g-PAA/PVA DN network hydrogel has good comprehensive properties and is expected to be used as a hemostatic material or a precursor of a drug carrier and a tissue engineering scaffold.

Amphipathic Substrates Based on Crosslinker-Free Poly(ε-Caprolactone):Poly(2-Hydroxyethyl Methacrylate) Semi-Interpenetrated Networks Promote Serum Protein Adsorption.

A simple procedure has been developed to synthesize uncrosslinked soluble poly(hydroxyethyl methacrylate) (PHEMA) gels, ready for use in a subsequent fabrication stage. The presence of 75 wt % methanol (MetOH) or dimethylformamide (DMF) impedes lateral hydroxyl-hydroxyl hydrogen bonds between PHEMA macromers to form during their solution polymerization at 60 °C, up to 24 h. These gels remain soluble when properly stored in closed containers under cold conditions and, when needed, yield by solvent evaporation spontaneous physically-crosslinked PHEMA adapted to the mould used. Moreover, this two-step procedure allows obtaining multicomponent systems where a stable and water-affine PHEMA network would be of interest. In particular, amphiphilic polycaprolactone (PCL):PHEMA semi-interpenetrated (sIPN) substrates have been developed, from quaternary metastable solutions in chloroform (CHCl3):MetOH 3:1 wt. and PCL ranging from 50 to 90 wt % in the polymer fraction (thus determining the composition of the solution). The coexistence of these countered molecules, uniformly distributed at the nanoscale, has proven to enhance the number and interactions of serum protein adsorbed from the acellular medium as compared to the homopolymers, the sIPN containing 80 wt % PCL showing an outstanding development. In accordance to the quaternary diagram presented, this protocol can be adapted for the development of polymer substrates, coatings or scaffolds for biomedical applications, not relying upon phase separation, such as the electrospun mats here proposed herein (12 wt % polymer solutions were used for this purpose, with PCL ranging from 50% to 100% in the polymer fraction).

Novel pH-sensitive interpenetrated network polyspheres of polyacrylamide-g-locust bean gum and sodium alginate for intestinal targeting of ketoprofen: In vitro and in vivo evaluation.

In this report, novel pH-sensitive interpenetrated network (IPN) polyspheres were developed utilizing polyacrylamide-g-locust bean gum (PAAm-g-LBG) in combination with sodium alginate (SA) to achieve intestinal targeted delivery of ketoprofen. PAAm-g-LBG was synthesized under microwave irradiation wherein ceric ammonium nitrate was used as reaction initiator and then conversion of PAAm-g-LBG as pH-sensitive copolymer was carried out by alkaline hydrolysis. The PAAm-g-LBG copolymer was characterized through 1H-NMR, FTIR and elemental analysis. The IPN polyspheres exhibited pH-depended swelling or de-swelling with the alteration of surrounding pH. The in-vitro release of drug from IPN polyspheres was found to be higher (≈ 90%) in phosphate buffer of pH 7.4 in comparison with that in pH 1.2 buffer (10.6%). The in-vivo pharmacokinetic, anti-inflammatory screening and stomach histopathology studies performed on Wistar rats revealed pH sensitivity of IPN polyspheres where ketoprofen was successfully targeted to small intestine resulting in reduced side effects of ketoprofen like ulcer formation, erosion of gastric mucosa and hemorrhages.

Interpenetrated polymer network with modified chitosan in composition and self-healing properties.

Smart hydrogels endowed with self-healing performance, enhanced stability and unique environmental responsiveness were prepared by interpenetrating the crosslinked poly(2-dimethylaminoethyl methacrylate) between the chains of the water-soluble maleoyl-chitosan. The influence of the ratio between the modified polysaccharide and the homopolymer upon the morphological structure and water uptake behaviour of the hydrogels was put in evidence by Scanning electron microscopy and swelling measurements in simulated body fluids. In addition, the synthesised compounds exhibited responsive properties, self-healing behaviour, and great availability like drug delivery systems. The in vitro study evidenced the dependence of the released procaine on the MAC content in the hydrogels, the release mechanism being controlled mainly by Fickian diffusion. The cytotoxicity assay on fibroblast demonstrated improved viability of cells by increasing the modified polysaccharide ratio into hydrogels. The self-repair capacity along with dual pH/thermo-responsiveness and biocompatibility of the hydrogels demonstrate their viability for various bio-applications.

PVA-Glutaraldehyde as support for lectin immobilization and affinity chromatography / PVA-Glutaraldeído como suporte para imobilização de lectina e cromatografia de afinidade

Immobilized lectins are a powerful biotechnological tool for separation and isolation of glycoconjugates. In the present study, polyvinyl alcohol (PVA) and glutaraldehyde (GA) were used as a support for Concanavalin A (Con A) covalent immobilization and for entrapment of Parkia pendula seed gum (PpeG). Con A immobilization yielded approximately 30% and 0.6 M glucose solution was the minimum concentration able to elute fetuin from column. PVA-GA-PpeG column was efficiently recognized by pure P. pendula lectin (PpeL) . These findings indicate that PVA-GA interpenetrated network showed to be an efficient support for lectin covalent immobilization and as affinity chromatography matrix after trapping of PpeG.

Lectinas imobilizadas são uma poderosa ferramenta biotecnológica para a separação e isolamento de glicoconjugados. No presente trabalho álcool polivinílico (PVA) e glutaraldeído (GA) foram utilizados como um suporte para a imobilização covalente da Concanavalina A (Con A) e para aprisionamento da goma de semente de Parkia pendula (PpeG). A eficiência da imobilização da Con A foi aproximadamente 30 % e a concentração mínima de glucose capaz de eluir a fetuína da coluna foi 0,6 M. Coluna de PVA - GA - PpeG foi eficientemente reconhecida pela lectina de P. pendula (PpeL) pura. Estes resultados indicam que a rede interpenetrada de PVA-GA mostrou-se um suporte eficiente para a imobilização covalente de lectina e como matriz de cromatografia de afinidade após aprisionamento de PpeG.