Chitosan-driven biocompatible hydrogel based on water-soluble polypyrrole for stable human-machine interfaces.

Recently, wearable hydrogel sensors based on polypyrrole have shown considerable promise in the realms of human-machine interfaces. However, because of the water insolubility of pyrrole and polypyrrole, the preparation of polypyrrole conductive hydrogels with comprehensive properties by a simplified method remains a great challenge. Herein, the water-soluble polypyrrole was synthesized and the conformal CxPy conductive hydrogels were fabricated by the strategy of one-pot method of introducing chitosan and water-soluble polypyrrole into acrylamide matrix containing cucurbit[7]uril. The hydrogel exhibited good mechanical strength (215.48 kPa at the fracture strain of 2149.17 %), superior adhesion strength (~51.54 kPa), excellent conductivity (0.534 S m-1) and biocompatibility (The cell viability of NIH3T3 is 98.25 %). As a strain sensor, C10P5 hydrogel exhibited excellent stability during 1000 times cycles, which is suitable for epidermal sensors to monitor body motions and physiological signals. Therefore, the chitosan-driven conductive hydrogel would present prosperous prospects in the fields of human-machine interfaces.

Control Viscoelasticity of Polymer Networks with Crosslinks of Superposed Fast and Slow Dynamics.

Depending on the dynamics of the crosslinks, polymer networks can have distinct bulk mechanical behaviors, from viscous liquids to tough solids. Here, by means of designing a crosslink with variable molecular dynamics, we show the control of viscoelasticity of polymer networks in a broad range quantitatively. The hexanoate-isoquinoline@cucurbit[7]uril (HIQ@CB[7]) crosslink exhibits in a combination of protonated and deprotonated states of similar association affinity but distinct molecular dynamics. The molecular property of this crosslink is contributed by linear combination of the parameters at the two states, which is precisely tuned by pH. Using this crosslink, we achieve the quantitative control of viscoelasticity of quasi-ideal networks in 5 orders of magnitude, and we show the reversible control of mechanical response, such as stiffness, strength and extensibility, of tough random polymer networks. This strategy offers a way to tailor the mechanical properties of polymer networks at the molecular level and paves the way for engineering "smart" responsive materials.

Self-assembly of an alkynylpyrene derivative for multi-responsive fluorescence behavior and photoswitching performance.

Highly emissive fluorophores based on polyaromatic hydrocarbons with tunable emission properties and aggregated structures play a very important role in relevant functional studies. In this study, a novel alkynylpyrene derivative 1 was synthesized, which exhibits unimolecular to excimer emission in methanol with an increasing concentration accompanied by the formation of nanovesicles via the π-π stacking, hydrogen bond and hydrophobic interaction. The self-assembly behavior as well as emission properties of 1 in aprotic polar solvents (ACN, acetone, DMF and DMSO) can also be adjusted by the volume fraction of the poor solvent H2O, which can induce 1 self-assembly to excimer state and could be applied in information transfer. Moreover, upon visible light irradiation, photoswitchable performance of nanovesicles of 1 was observed in which the emission markedly changes from yellow to blue; this is attributed to the cycloaddition reaction of alkynyl groups and singlet oxygen, which can be generated without the addition of external photosensitizers. The multi-responsive and fluorescence behavior of the alkynylpyrene derivative show that the self-assembly can be used to expand the development of this type of fluorophores, and the novel photoinduced tunability of the fluorescence emission provides an effective strategy to obtain high-performance transmitting and sensing materials.

Hexanoate-Cucurbit[7]uril: Highly Soluble with Controlled Release Ability.

Current drug delivery systems gain more functions with increased complexity. With the idea of less is more, we synthesized hexanoate-cucurbit[7]uril (CB[7]C5 COONa) with multiple promising features for drug delivery. The hexanoate group integrates multiple functions. It endows CB[7]C5 COONa extremely high solubility of over 600 mg mL-1 and well-defined pH-controlled release ability without sacrificing on the high binding affinity of CB[7] cavity. Based on the pH-controlled release ability, CB[7]C5 COONa can be used for controlling the bioactivity of drug molecules. We anticipate that the strategy of function integration would be useful for the design of simple yet powerful drug delivery systems.

Doubly Dynamic Hydrogel Formed by Combining Boronate Ester and Acylhydrazone Bonds.

The incorporation of double dynamic bonds into hydrogels provides an effective strategy to engineer their performance on demand. Herein, novel hydrogels were PREPARED by combining two kinetically distinct dynamic covalent bonds, boronate ester and acylhydrazone bonds, and the synergistic properties of the hydrogels were studied comprehensively. The functional diblock copolymers P(N-isopropyl acrylamide-co-N-acryloyl-3-aminophenylboronic acid)-b-(N-isopropyl acrylamide-co-diacetone acrylamide) (PAD) were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. The hydrogel was constructed by exploiting dynamic reaction of phenyboronic acid moieties with polyvinyl alcohol (PVA) and ketone moieties with adipic dihydrazide (ADH) without any catalyst. The active boronate ester linkage endows the hydrogel with fast gelation kinetics and self-healing ability, and the stable acylhydrazone linkage can enhance the mechanical property of the hydrogel. The difference in kinetics endows that the contribution of each linkage to mechanical strength of the hydrogel can be accurately estimated. Moreover, the mechanical property of the hydrogel can be readily engineered by changing the composition and solid content, as well as by controlling the formation or dissociation of the dynamic linkages. Thus, we provide a promising strategy to design and prepare multi-responsive hydrogels with tunable properties.

Practical Modification of Tannic Acid Polyether Demulsifier and Its Highly Efficient Demulsification for Water-in-Aging Crude Oil Emulsions.

In order to break the aging crude oil (WACO) emulsion of the offshore platform more effectively, a highly active isocyanate, polyaryl polymethylene isocyanate (PAPI), was selected to modify the pilot-scale tannic acid demulsifier. In the addition of PAPI, its molecular weight and viscosity dramatically increased, while its relative solubility, hydroxyl number, and cloud point exhibited an opposite direction, showing an increase in hydrophobicity. After adding the above modified demulsifier, a remarkably improved water removal of WACO emulsion accompanied by a notable reduction of the water content in the oil phase monitored by the Karl Fischer method was observed. Demulsification on the offshore platform demonstrated that the best water removal was achieved when the proportion of PAPI is 1.5 wt %. Its demulsification efficiency reached 95.7%, which was 25.6% higher than the 76.2% of unmodified demulsifier. In addition, a positive correlation between viscoelasticity of emulsion and demulsification performance was found by only adjusting the parameters of the rheometer. This method may be utilized to characterize the demulsification performance by any rotary rheometer. The pilot-scale demulsification experiment demonstrated that the water removal can reach 98.14 vol % and residual water content was only 0.55 vol %. These results further confirmed the excellent demulsification performance of the modified demulsifier toward the WACO emulsion in production.

Dual-cross-linked dynamic hydrogels with cucurbit[8]uril and imine linkages.

The strategy of dual cross-linking was investigated by enhancing the performance of dynamic hydrogels. To this end, phenylalanine modified ε-polylysine was synthesized and employed as the polymer backbone of hydrogels. The phenylalanine moieties and amine groups of the polymer could be cross-linked with cucurbit[8]uril (CB[8]) and the dialdehyde cross-linker, respectively. Single CB[8] linkage with fast dynamics led to an increase in the viscosity of the polymer solution, and single imine linkage with slow dynamics led to the formation of weak and brittle hydrogels. However, the two linkages were combined together to form a dual-cross-linked hydrogel and the performance of the hydrogel could be well enhanced. Compared with the single imine cross-linked hydrogel, the dual-cross-linked hydrogel demonstrated a higher mechanical strength, better extensibility and faster self-healing rate. It is anticipated that this line of research could provide a useful method to enhance the performance of dynamic hydrogels.

Tunable Fluorescence-Responsive Double Hydrophilic Block Polymers Induced by the Formation of Pseudopolyrotaxanes with Cucurbit[7]Uril.

There is an urgent need for new strategies that allow the simultaneous detection and control of drug delivery. By making use of supramolecular host-guest interactions, a kind of pseudopolyrotaxanes, as a visualizable nanoscale drug carrier has been constructed by self-assembly of cucurbit[7]uril (CB[7]) with methoxy poly(ethylene glycol)-block-quaternized poly(4-vinyl pyridine) (mPEG-b-QP4VP) using 4-(chloromethyl)benzonitrile. Simple addition of CB[7] into an aqueous solution of mPEG-b-QP4VP resulted in noncovalent attachment of CB[7] to 4-cyanobenzyl-containing polymers, transforming the nonemissive mPEG-b-QP4VP micelles into highly fluorescent micelles. These pseudopolyrotaxanes micelles exhibited remarkable supramolecular assembly-induced emission enhancement and excellent biocompatibility, showing great potential for bioimaging applications. In addition, the efficient cellular uptake of the developed pseudopolyrotaxanes micelles loaded with the anticancer drug doxorubicin was a promising platform for simultaneous cell imaging and drug delivery, thereby widening their application in cancer theranostics.

A facile method to fabricate thermo- and pH-sensitive hydrogels with good mechanical performance based on poly(ethylene glycol) methyl ether methacrylate and acrylic acid as a potential drug carriers.

A thermo- and pH-sensitive hydrogel was prepared by a facile free aqueous radical copolymerization of PEGMA and AAc without any crosslinkers for controlled drug delivery. The successful fabrication of hydrogels was confirmed by Fourier transform infrared spectroscopy (FT-IR) and thermo gravimetric analysis (TGA) measurements. The morphological, mechanical and swelling properties of the obtained hydrogels were studied systematically. The results showed that the morphological and mechanical behaviors of the resultant hydrogels were strongly affected by the content of AAc. Moreover, the obtained hydrogels showed an excellent thermo-, pH- and salinity sensitivities. Release profiles of 5-Fu were studied at different pH (gastric pH 1.2 and intestinal pH 7.4) and temperatures (25 °C and 37 °C). The results showed that the release is very low at pH 1.2/37 °C and high at pH 7.4/25 °C. The cytotoxicity of hydrogels to cells was determined by an MTT assay. The result demonstrated that the blank hydrogels had negligible toxicity to cells, whereas the 5-Fu-loaded hydrogels remained high in cytotoxicity for LO2 and HepG-2 cells. Results of the present investigation exemplify the potential of this novel thermo- and pH-sensitive hydrogel for the controlled and targeted delivery of the anti cancer drug 5-Fu.

Self-Assembly of Europium-Containing Polyoxometalates/Tetra-n-alkyl Ammonium with Enhanced Emission for Cu2+ Detection.

Lanthanide-containing polyoxometalates (POMs) can be used to detect various materials, but their luminescence in water has suffered enormous limitations due to the strong fluorescence quenching. Herein, to resolve this problem, three-dimensional nanoparticles built by mixed Weakley-type europium-containing POMs (Na9[EuW10O36]·32H2O, abbreviated to EuW10) and tetra-n-alkyl ammonium (TA) with enhanced fluorescent properties have been designed in aqueous solution using an ionic self-assembly (ISA) technique, which is mainly driven by the electrostatic interaction between EuW10 and TA. The morphology and fluorescent properties of the system as well as some influencing factors (alkyl chain length, amino group, and inorganic salt concentration) were systematically investigated. The results indicated that the fluorescent intensity of EuW10/tetramethylammonium bromide (TMAB) composite increased about 14 times, whereas the extent of increase of fluorescence for EuW10/tetraethylammonium bromide (TEAB) and EuW10/tetrabutylammonium bromide (TMAB) composites gradually decrease due to the bulkier steric hindrance of the longer alkyl chain. Besides, the luminescence of EuW10/TMAB nanoparticles is pH responsive, and the reversibility of their structures and luminescence can be realized upon the addition of NaOH/HCl. Moreover, the EuW10/TMAB system also shows great fluorescence-sensing behavior, which could detect Cu2+ with a detection limit of 0.15 µM. Our work provides a facile construction strategy for a functional fluorescent complex via POMs-based supramolecular self-assembly in aqueous solution, which will be further used in biomarkers and sensors.

Differences between the Interactions of Linear and Tetrahedron-like Ditopic Guests with Cucurbit[8]uril: Steric Hindrance and Molecular Structure Play Dominant Roles.

A tetrahedron-like guest molecule (THV) with four ditopic arms, consisting of viologen (V) and hexylene moieties, was synthesized, and its interaction with cucurbit[8]uril (CB[8]) was investigated. As a reference, the interaction between CB[8] and an analogue of the arm of the linear ditopic guest (LHV) was first explored by 1 H NMR and UV/Vis spectroscopy. In this case, CB[8] was located on the hexylene moiety and resulted in the formation of a binary complex. However, when THV interacted with CB[8], despite having four arms with four hexylene moieties, only two CB[8] molecules were identified as located on the hexylene moieties; the other two CB[8] molecules resided on the V moieties. Great steric hindrance among the arms played a dominant role in the interaction between THV and CB[8]. Regardless of whether the guest molecule was THV or LHV, CB[8] moved to its V moiety (electron-deficient part) to form the charge-transfer complex upon the addition of a stopper containing a naphthol residue (electron-rich part). Guests LHV and THV were reduced to LHV+(+.) and THV+4(+.) upon the addition of sodium dithionite. Dimerization of LHV+(+.) was enhanced when CB[8] was present in less than 0.5 equivalents. In contrast, dimerization was suppressed when CB[8] was present in more than 0.5 equivalents. However, the V+. units of THV+4(+.) stacked intramolecularly because of the tetrahedron-like molecular structure of THV. The influence of CB[8] on the dimerization of THV+4(+.) was weaker than that on LHV+(+.) .

Controlled gelation kinetics of cucurbit[7]uril-adamantane cross-linked supramolecular hydrogels with competing guest molecules.

Gelation kinetics of hydrogels is closely linked to many applications such as the development of injectable and printable hydrogels. However, the control of gelation kinetics without compromising the structure and other properties of the hydrogels, remains a challenge. Here, we demonstrate a method to control the gelation kinetics of cucurbit[7]uril-adamantane (CB[7]-AD) cross-linked supramolecular hydrogels by using competing guest molecules. The association between CB[7] and AD moieties on the polymer backbone was impeded by pre-occupying the CB[7] cavity with competing guest molecules. By using various guest molecules and concentrations, the gelation of the hydrogels could be varied from seconds to hours. The strong interaction of CB[7]-AD pair endue the hydrogels good mechanical properties and stability. Moreover, the binding of functionalized guest molecules of CB[7] moieties offers a facile approach for tailoring of the hydrogels' scaffold. Combined with hydrogel injection and printing technology, this method offers an approach for the development of hydrogels with advanced temporal and spatial complexity.

Preparation and characterisation of multilayer films and microcapsules containing poly(N-isopropylacrylamide-co-sodium vinylsulphonate) and applicability on controlled release.

The copolymers of N-isopropylacrylamide and sodium vinylsulphonate were synthesised by free radical polymerisation. The layer-by-layer self-assembly of the copolymers with poly(allylamine) hydrochloride was performed through assembling onto silicon wafer to form multilayer films and onto CaCO3 microparticles doped with poly(styrene sulphonate) as well as deltamethrin microcrystals to form microcapsules. The multilayer films and microcapsules were characterised by atomic force microscopy, transmission electron microscopy and scanning electron microscopy. The release behaviour of deltamethrin in the microcapsules under different conditions was also investigated by high performance liquid chromatography. Results show that these deltamethrin microcapsules have good thermo-sensitive properties and deltamethrin release can be controlled via changing temperature or self-assembly layers.

Comparisons of simple and complex coacervations for preparation of sprayable insect sex pheromone microcapsules and release control of the encapsulated pheromone molecule.

With dodecanol (C12OH) as a model molecule of insect sex pheromone as core material, natural polymers gelatin (GE) and acacia gum (AG) as wall materials, microcapsules aiming to be a sprayable environment-friendly pesticide were prepared via GE simple coacervation and complex coacervation of GE and AG. C12OH encapsulation in complex coacervation was higher than those in simple coacervation. Its encapsulation was enhanced with increase in wall material cross-linking. C12OH release revealed that samples from simple coacervation reached their end in 7 days, whereas those from complex coacervation manifested a quick release followed by a constant release. With increase in wall material cross-linking, the release was slowed down. SEM observation confirmed that core-shell morphology existed in the capsules.

Novel complex gel beads composed of hydrolyzed polyacrylamide and chitosan: an effective adsorbent for the removal of heavy metal from aqueous solution.

A novel kind of complex gel beads containing HPAM (hydrolyzed polyacrylamide) and chitosan components (HPAM-chitosan gel beads) was prepared and applied in the removal of Cu(2+), Pb(2+), and Hg(2+) ions from aqueous solutions. These gel beads exhibited a good performance for heavy metal removal. Moreover, the average diameter of these gel beads was about 1mm, which could be appropriate for use in column system. The removal order was Pb(2+)>Cu(2+)>Hg(2+) under the same conditions. The effects of different experimental parameters, such as adsorbent dosage, initial pH, temperature, and initial metal concentration, on the adsorption capacities were studied. The Freundlich model gave a better fit to the experimental data than the Langmuir model in adsorption isotherm study. Desorption study indicated that the gel beads were easy to be regenerated.

Preparation, pharmacokinetics and tissue distribution of micelles made of reverse thermo-responsive polymers.

New reverse thermo-responsive polymers, poly(ethylene oxide)-poly(propylene oxide) multiblock copolymers (poly(ether-carbonate)s) were synthesized. The micelles made of new reverse thermo-responsive polymers were also prepared loaded with the poorly soluble anticancer drug, hydroxycamptothecin (HCPT). The structure characterization of poly(ether-carbonate)s was determined by (1)H NMR and FT-IR analysis. The critical micelle concentration (CMC), critical micelle temperature (CMT), size distribution and drug release in vitro were determined. The pharmacokinetics and tissue distribution in vivo for novel copolymer micelles were studied. The experimental results showed that the micelles was spherical in appearance and dispersed well. The process of HCPT release from micelles in vitro was composed of two steps, abrupt release and sustained release. After i.v. administration (2h), the drug concentration of poly(ether-carbonate) micelles group in liver in mice was 3.46microg/g, while that of HCPT injection group was 0.401microg/g. Compared with HCPT injection, the elimination half-life of poly(ether-carbonate) micelles group was prolonged remarkably from 1.3 to 12.5h. The poly(ether-carbonate) micelles showed a combination of liver targeting and sustained drug release in experiments on animals.

[The drug release properties of poly (acrylamide-co-itaconate-vinylbenzylglycosylallylamide) hydrogels].

Sugar-containing monomer vinylbenzylglycosylallyamide (VBG) was synthesized by vinylbenzyl amine and delta-gluconolactone in dimethylformamide(DMF) solution. The sugar-based hydrogel was prepared by free radical crosslinking copolymerization of VBG, itaconic acid (IA) and acrylamide (AM). The release properties of Aspirin from xerogels matrices and from hydrogel in different pH solutions and different concentration NaCl solutions were studied respectively. The release mechanism of Aspirin was further confirmed by evaluating the n value in Peppas equation. The results indicated that the drug release increased with the increase of pH values and with the decrease of NaCl concentration.

[Synthesis and the drug release properties of poly(acrylamide-co-glycosylallylamide) hydrogels].

Sugar-containing monomer glycosylallylamide (AAG) was synthesized by allyl amine and delta-gluconolactone in dimethylformamide (DMF) solution. The sugar-based hydrogels were prepared by free radical crosslinking copolymerization of AAG and acrylamide (AM). The release properties of Aspirin from xerogels matrices were studied and the release mechanism of Aspirin was further identified by evaluating the n value in Peppas equation. The results indicate that the drug release decreases with the increase of the sugar content of hydrogel.

[Two sorts of problems on drug controlled release from swellable polymer].

The mechanism of drug release from swellable polymer was studied. The model which can explain the drug release from glassy polymer was developed by coupling drug diffusion equation and solvent diffusion equation. The effect of viscoelastic stress of polymer was also considered. The Deborah number and swelling interface number were used to describe the mechanism of drug release, especially relax controlled mechanism.