Structure-Property Relationships Governing Membrane-Penetrating Behaviour of Complex Coacervates.

Complex coacervates are phase-separated liquid droplets composed of oppositely charged multivalent molecules. The unique material properties of the complex coacervate interior favours the sequestration of biomolecules and facilitates reactions. Recently, it is shown that coacervates can be used for direct cytosolic delivery of sequestered biomolecules in living cells. Here, it is studied that the physical properties required for complex coacervates composed of oligo-arginine and RNA to cross phospholipid bilayers and enter liposomes penetration depends on two main parameters: the difference in ζ-potential between the complex coacervates and the liposomes, and the partitioning coefficient (Kp ) of lipids into the complex coacervates. Following these guidelines, a range of complex coacervates is found that is able to penetrate the membrane of living cells, thus paving the way for further development of coacervates as delivery vehicles of therapeutic agents.

Hybrid artificial muscle: enhanced actuation and load-bearing performance via an origami metamaterial endoskeleton.

Owing to their compliance, soft robots demonstrate enhanced compatibility with humans and the environment compared with traditional rigid robots. However, ensuring the working effectiveness of artificial muscles that actuate soft robots in confined spaces or under loaded conditions remains a challenge. Drawing inspiration from avian pneumatic bones, we propose the incorporation of a lightweight endoskeleton into artificial muscles to augment the mechanical integrity and tackle load-bearing environmental difficulties. We present a soft origami hybrid artificial muscle that features a hollow origami metamaterial interior with a rolled dielectric elastomer exterior. The programmable nonlinear origami metamaterial endoskeleton significantly improves the blocked force and load-bearing capability of the dielectric elastomer artificial muscle and an increased actuation strain. The origami hybrid artificial muscle demonstrates a maximum strain of 8.5% and a maximum actuating stress of 12.2 mN mm-2 at 30 V µm-1 while preserving its actuating ability, even under a 450 mN load, which is equivalent to 155 times its own weight. We further investigate the dynamic responses and demonstrate the potential use of the hybrid artificial muscle in flapping-wing actuation applications.

Recent Advances in Polysaccharide-Based Physical Hydrogels and Their Potential Applications for Biomedical and Wastewater Treatment.

Polysaccharides are widely employed to fabricate hydrogels owing to their intrinsic properties including biocompatibility, biodegradability, sustainability, and easy modification. However, a considerable amount of polysaccharide-based hydrogels are prepared by chemical crosslinking method using organic solvents or toxic crosslinkers. The presence of reaction by-products and residual toxic substances in the obtained materials causes a potential secondary pollution risk and thus severely limits their practical applications. In contrast, polysaccharide-based physical hydrogels are preferred over chemically derived hydrogels and can be used to address existing drawbacks of chemical hydrogels. The polysaccharide chains of such hydrogel are typically crosslinked by dynamic noncovalent bonds, and the co-existence of multiple physical interactions stabilizes the hydrogel network. This review focuses on providing a detailed outlook for the design strategies and formation mechanisms of polysaccharide-based physical hydrogels as well as their specific applications in tissue engineering, drug delivery, wound healing, and wastewater treatment. The main preparation principles, future challenges, and potential improvements are also outlined. It is hoped that this review can provide valuable information for the rational fabrication of polysaccharide-based physical hydrogel. The specific research works listed in the review can provide a systematic and solid research basis for the reliable development of polysaccharide-based physical hydrogel.

Simple ultrasonic-assisted approach to prepare polysaccharide-based aerogel for cell research and histocompatibility study.

Salecan, a water-soluble microbial polysaccharide with attractive biocompatible characteristics, is very suitable for aerogel fabrication. However, the practical application of salecan-based aerogels for cell culture was limited by complicated preparation method, lack of cell anchorage signals, and the ability to modulate this properly. Here, a smart aerogel was designed by ultrasonic-assisted self-assembly of salecan and cationic starch (CAS) without any organic and toxic crosslinkers. The ultrasound waves generated a marked impact on self-assemble process by means of ultrasonic cavitation. Aerogel network was produced by strong electrostatic attractions between the polysaccharides. Especially, salecan/CAS ratio can be precisely modulated to tailor the hydrophilicity, mechanical stiffness, and morphologic property. The specific surface area of the aerogels gradually increased with the increase in salecan/CAS ratio. These aerogels were non-cytotoxic, and the incorporation of salecan into them promoted cell-matrix interactions by directionally supporting cell adhesion and proliferation. Most strikingly, in vivo experiment revealed that the histological features in the main organs of the mice were similar to those observed in the PBS-treated control group, and no sign of the histopathological abnormality or tissue destruction was observed, indicating the excellent histocompatibility of the aerogels. This study offered a new and powerful avenue to fabricate functional biomaterial.

Comparison of two starch-based flocculants with polyacrylamide for the simultaneous removal of phosphorus and turbidity from simulated and actual wastewater samples in combination with FeCl3.

Two laboratory-made cationic starch-based flocculants (St-CTA and St-AD) with different chain architectures were used to simultaneously remove phosphorus and turbidity from two simulated wastewaters and one actual wastewater with laboratory and pilot scales, respectively, in conjunction with FeCl3. A commercial polyacrylamide (PAM) has been also tried and compared with aforementioned starch-based flocculants. The removal extents of phosphorus and turbidity increased, the required dosages of FeCl3 decreased, and floc properties improved after dosing each polymeric flocculant after FeCl3 in all tested wastewaters due to their synergistic effects. However, the three flocculants exhibited different improvement efficiencies on the treated wastewaters containing different forms of phosphorus and showed various synergistic mechanisms owing to their distinct structural features. In inorganic-phosphorus-simulated wastewater, the linear nonionic PAM with a high molecular weight had a more notable contribution than the two starch-based flocculants due to its efficient bridging flocculation effect. Given the branched-chain structure and high positive charge density of St-AD, it had a higher efficiency in treating real wastewater and organic-phosphorus-simulated wastewater than PAM and linear cationic St-CTA. These results may serve as references for the design and selection of a suitable flocculant in treating target wastewaters.

Femtosecond laser programmed artificial musculoskeletal systems.

Natural musculoskeletal systems have been widely recognized as an advanced robotic model for designing robust yet flexible microbots. However, the development of artificial musculoskeletal systems at micro-nanoscale currently remains a big challenge, since it requires precise assembly of two or more materials of distinct properties into complex 3D micro/nanostructures. In this study, we report femtosecond laser programmed artificial musculoskeletal systems for prototyping 3D microbots, using relatively stiff SU-8 as the skeleton and pH-responsive protein (bovine serum albumin, BSA) as the smart muscle. To realize the programmable integration of the two materials into a 3D configuration, a successive on-chip two-photon polymerization (TPP) strategy that enables structuring two photosensitive materials sequentially within a predesigned configuration was proposed. As a proof-of-concept, we demonstrate a pH-responsive spider microbot and a 3D smart micro-gripper that enables controllable grabbing and releasing. Our strategy provides a universal protocol for directly printing 3D microbots composed of multiple materials.

Development of photocrosslinked salecan composite hydrogel embedding titanium carbide nanoparticles as cell scaffold.

Salecan is a water-soluble extracellular ß­glucan and appropriate for preparing hydrogels applicable in biomedical field. Herein, an innovative photocrosslinked composite hydrogel composed of salecan/poly(hydroxypropyl methacrylate (PHPMA) network and titanium carbide (TiC) nanoparticles was successfully prepared. XRD patterns clearly showed the crystal planes of Ti. More importantly, the introduction of TiC nanoparticles into the hydrogel network provided structural reinforcement, and thereby synergistically enhanced the mechanical strength and thermal stability of the hydrogels. The change of salecan content markedly affected the swelling behavior and morphology of the composite hydrogels. Cytotoxicity results revealed that the composite hydrogels were non-toxic to L929 and 3T3L1 cells. Cell proliferation and Live/Dead assay further demonstrated excellent cytocompatibility of the cells within the composite hydrogels, which highlights the value of this system for potential application as soft tissue engineering scaffold.

Magnetic field-driven drug release from modified iron oxide-integrated polysaccharide hydrogel.

Salecan is a novel water-soluble extracellular ß-glucan and suitable for the hydrogel preparation due to its excellent physicochemical and biological properties. The present article describes the fabrication and characterization of a pH/magnetic field-driven hydrogel based on salecan-g-poly(vinylacetic acid-co-2-hydroxyethyl acrylate) [poly(VA-co-HEA)] copolymer and Fe3O4@Agarose nanoparticles for drug release testing. Vibrating sample magnetometer characterization verified that integration of Fe3O4@Agarose nanoparticles in the copolymer provided the sensitivity to magnetic fields. The doxorubicin hydrochloride (DOX) release test showed a pH/magnetic field-triggered and sustained release property, and the release could be accelerated under mildly acidic conditions or the presence of an external magnetic field. Meanwhile, the increase in salecan content could also enhance the release rate. Cytotoxicity assays revealed that the released DOX maintained relatively high killing efficacy of A549 cells. In sum, these salecan-g-poly(VA-co-HEA)/Fe3O4@Agarose hydrogels were well-suited for magnetically targeted drug delivery systems.

Design of a pH-sensitive magnetic composite hydrogel based on salecan graft copolymer and Fe3O4@SiO2 nanoparticles as drug carrier.

Salecan, a novel water-soluble extracellular ß-glucan, is very suitable for the hydrogel preparation. Here, pH-sensitive magnetic composite hydrogel was fabricated by the graft copolymerization of crotonic acid (CA) and N-(hydroxymethyl) acrylamide (HMAA) onto salecan in the presence of Fe3O4@SiO2 nanoparticles for doxorubicin (DOX) delivery. The embedment of Fe3O4@SiO2 nanoparticles into salecan-g-poly(CA-co-HMAA) hydrogel network endowed the material with magnetic property. In addition, DOX not only achieved effectively bound to the composite hydrogel, but also released in a controlled and pH-dependent manner. The application of an external magnetic field could significantly enhance the drug release rate. More importantly, the released DOX preserved its bioavailability. Taken together, these hydrogel drug carriers provide a promising platform for magnetically targeted drug delivery.

Dual-pH/Magnetic-Field-Controlled Drug Delivery Systems Based on Fe3 O4 @SiO2 -Incorporated Salecan Graft Copolymer Composite Hydrogels.

Salecan is a water-soluble extracellular ß-glucan and has excellent physicochemical and biological properties for hydrogel preparation. In this study, a new pH/magnetic field dual-responsive hydrogel was prepared by the graft copolymerization of salecan with 4-pentenoic acid (PA) and N-hydroxyethylacrylamide (HEAA) in the presence of Fe3 O4 @SiO2 nanoparticles for doxorubicin hydrochloride (DOX) release. Integration of Fe3 O4 @SiO2 nanoparticles in salecan-g-poly(PA-co-HEAA) copolymers afforded magnetic sensitivity to the original material. DOX-loaded hydrogels exhibited a clear capacity for pH/magnetic field dual-responsive controlled drug release. Lowering the pH to acidic conditions or introducing an external magnetic field caused an enhancement in DOX release. This salecan-g-poly(PA-co-HEAA)/Fe3 O4 @SiO2 composite hydrogel is a promising drug carrier for magnetically targeted drug delivery with enhanced DOX cytotoxicity against A549 cells.

Phenylene vinylene macrocycles as artificial transmembrane transporters.

A series of rigid phenylene vinylene macrocycles and phenylene ethynylene macrocycles with various substituents have been investigated as transmembrane ion channels. The length and polarity of the substituents have a significant effect on the ion channel formation and the mass transport efficiency. Macrocycles with strong aggregation facilitate ion passage across lipid bilayers.

Synthesis and characterization of a novel pH-thermo dual responsive hydrogel based on salecan and poly(N,N-diethylacrylamide-co-methacrylic acid).

Salecan is a water-soluble microbial polysaccharide produced by Agrobacterium sp. ZX09, a salt-tolerant strain isolated from a soil sample in our laboratory. Previous work inspired us salecan is a good candidate to fabricate hydrogels. Poly(N,N-diethylacrylamide) is one type of thermo sensitive polymer which is not investigated extremely as poly(N-isopropylacrylamide). Here, we report a novel pH-thermo dual responsive hydrogel based on salecan and poly(N,N-diethylacrylamide-co-methacrylic acid) semi-interpenetrating polymer networks (semi-IPNs). The physicochemical property of this hydrogel was investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analyses (TGA), rheological test and Scanning Electron Microscopy (SEM). It was interesting that the storage modulus (G') and pore size of the hydrogel could be tuned by adjusting the content of salecan and crosslinker. The pH-thermo dual responsive property was demonstrated by swelling behavior test: the swelling ratio of the hydrogel decreased continuously as the temperature increased from 25 °C to 37 °C, while it was pH-dependent as well. Especially, when exposed to a higher temperature (37 °C) and acidic environment (pH 4.0), drug-loaded hydrogel would have a quick release. Finally, the cytotoxicity of drug-free hydrogels was investigated on A549 and HepG2 cells, results showed that it was non-toxic while the DOX released from hydrogels had comparable cytotoxicity with respect to free DOX. In conclusion, the novel salecan/poly(N,N-diethylacrylamide-co-methacrylic acid) semi-interpenetrating polymer network hydrogels were pH-thermo dual responsive and may be a promising candidate for drug delivery system.

Investigation of Salecan/poly(vinyl alcohol) hydrogels prepared by freeze/thaw method.

Salecan is a novel water-soluble extracellular-glucan produced by a new kind of salt-tolerant strain Agrobacterium sp. ZX09 and can be applied in food and medicine industries. In this work, Salecan (Sal) was incorporated into poly(vinyl alcohol) (PVA) to prepare novel Sal/PVA hybrid hydrogels by repeated freeze-thaw processing. Physicochemical and biological characteristics of the hydrogels were investigated to evaluate their potential as cell adhesion materials. By increasing the Salecan content in the hybrid hydrogels, their swelling capacity increased notably, while the compressive modulus decreased. Observed by SEM, Sal/PVA hydrogels had a homogeneous porous structure. The degradation rate of the hydrogels can be controlled by tailoring the composition ratio of Sal/PVA. Furthermore, cells could adhere well on the surface of Sal/PVA hydrogels. In conclusion, these results make Sal/PVA hydrogels attractive materials for biomedical applications.

A novel thermo-responsive hydrogel based on salecan and poly(N-isopropylacrylamide): synthesis and characterization.

Salecan is a novel microbial polysaccharide produced by Agrobacterium sp. ZX09. The salt-tolerant strain was isolated from a soil sample in our laboratory and the 16S rDNA sequence was deposited in the GenBank database under the accession number GU810841. Salecan is suitable to fabricate hydrogel for biomedical applications due to the excellent hydrophilicity and biocompatibility. Here, salecan has been introduced into poly(N-isopropylacrylamide) (PNIPAm) network to form novel thermo-sensitive semi-interpenetrating polymer networks (semi-IPNs). The structure of salecan/PNIPAm semi-IPNs was confirmed by Fourier transformation infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Thermogravimetric analysis (TGA) proved the stability of the semi-IPNs. Rheological and compressive tests revealed an elastic solid-like behavior and good mechanical properties of the hydrogels. Swelling behavior test showed the hydrogels possessed high water content at room temperature. An excellent thermo-sensitive property of fast response rates to temperature had been demonstrated as well. In vitro degradation measurements ensured the semi-IPNs were degradable. Cytotoxicity and cell adhesion study suggested the synthesized salecan/PNIPAm hydrogels were non-toxic and biocompatibility. The results indicated the novel thermo-responsive hydrogels could be a suitable candidate for biomedical applications.

Synthesis and characterization of a novel semi-IPN hydrogel based on Salecan and poly(N,N-dimethylacrylamide-co-2-hydroxyethyl methacrylate).

Salecan is a novel water-soluble, high molecular mass extracellular ß-glucan produced by Agrobacterium sp. ZX09. Salecan has excellent physicochemical and biological properties, making it very suitable for hydrogel preparation. In this study, a series of novel semi-interpenetrating polymer network (semi-IPN) hydrogels containing Salecan and poly(N,N-dimethylacrylamide-co-2-hydroxyethylmethacrylate) (poly(DMAA-co-HEMA)) were synthesized by radical polymerization and semi-IPN technology. Structure and morphology of the hydrogels were characterized by FTIR, XRD, TGA and SEM. The semi-IPNs had a well-interconnected porous structure with tunable pore size ranging from 6 to 41µm. Swelling capability of the hydrogels was improved by introducing the hydrophilic Salecan. Rheological results indicated that the incorporation of poly(DMAA-co-HEMA) into hydrogels enhanced the storage modulus. Compression tests revealed that these semi-IPNs were robust materials with compressive modulus between 13.3 and 90.5kPa, the addition of Salecan increased the fracture strain from 71.1% to 88.8%. Degradation and cytotoxicity tests demonstrated that semi-IPNs were degradable and non-toxic.