Zhen Zheng

Facile Preparation of Mussel-Inspired Polyurethane Hydrogel and Its Rapid Curing Behavior

A facile method was found to incorporate a mussel-inspired adhesive moiety into synthetic polymers, and mussel mimetic polyurethanes were developed as adhesive hydrogels. In these polymers, a urethane backbone was substituted for the polyamide chain of mussel adhesive proteins, and dopamine was appended to mimic the adhesive moiety of adhesive proteins. A series of mussel mimetic polyurethanes were created through a step-growth polymerization based on hexamethylene diisocyanate as a hard segment, PEG having different molecular weights as a soft segment, and lysine-dopamine as a chain extender. Upon a treatment with Fe(3+), the aqueous mussel mimetic polyurethane solutions can be triggered by pH adjustment to form adhesive hydrogels instantaneously; these materials can be used as injectable adhesive hydrogels. Upon a treatment with NaIO4, the mussel mimetic polyurethane solutions can be cured in a controllable period of time. The successful combination of the unique mussel-inspired adhesive moiety with a tunable polyurethane structure can result in a new kind of mussel-inspired adhesive polymers.

Facile functionalization of a tetrahedron-like PEG macromonomer-based fluorescent hydrogel with high strength and its heavy metal ion detection

A tetrahedron-like PEG macromonomer-based fluorescent hydrogel was fabricated by a facile method. The functional hydrogel shows comparable high strength, up to megapascals, and sensitivity to heavy metal ions, such as Cu2+, Zn2+, Pb2+, Co2+, Hg2+ and Ni2+, which allow a potentially rapid visual response, trace analysis and one-step recyclable sensing for metal ion detection.

Self-assembly of pH-responsive biodegradable mixed micelles based on anionic and cationic polycarbonates for doxorubicin delivery.

Poly(5-propyl-1,3-dioxan-2-one)-b-dimethylamine modified polycarbonate (PC(MPpC-MMA)) and poly(ethylene glycol)-b-carboxylated polycarbonate (PEG-PCCOOH) diblock copolymers were prepared to construct a pH responsive, highly stable and biodegradable mixed micelle. The two copolymers self-assembled into the mixed micelle in pH 7.4 PBS driven by electrostatic and hydrophobic interactions. PC(MPpC-MMA) with hydrophobic inner core was used for carrying drug and the dimethylamine part was designed as a trigger to disassemble the mixed micelle. PEG-PCCOOH could shield the positive character of the micelle which might show disadvantage to normal tissue. In addition, the free carboxyl groups could further increase the loading efficiency of positive charged drugs. The size and zeta potential of the micelle gradually decreased with increasing the molar ratio of PEG-PCCOOH to PC(MPpC-MMA). These mixed micelles could withstand high ionic strength of plasma and were rather stable for long time storage. However, via decrease of pH value from 7.4 to 5.0, they could undergo dissociation into smaller nanoparticles which were in a diameter of 20nm and showed positive surface nature. In vitro drug delivery studies showed a faster release rate at pH 5.0 than that at pH 7.4. The MTT assays demonstrated potent cytotoxic activity against HepG2 cells. All these results indicate that the newly mixed polycarbonate micelle can show great potential in biomedical field.

Synthesis and properties of tunable thermoresponsive aliphatic polycarbonate copolymers with oligo ethylene glycol containing thioether and/or sulphone groups

A series of novel thermoresponsive copolycarbonates were constructed by cyclic trimethylene carbonate (MTC) monomers bearing oligo ethylene glycol (OEG) and with thioether or/and sulphone linkages. They were initiated by 1,4-benzenedimethanol with N-(3,5-trifluoromethyl)phenyl-N′-cyclohexylthiourea (TU)/1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) as the organic catalyst. The lower critical solution temperature (LCST) properties of the polycarbonates with thioether or sulphone linkage were studied and discussed with regard to molecular weight, salt concentration and polymer concentration. By using monomers of different OEG chain lengths and thioether and/or sulphone linkages, the LCSTs of biodegradable and thermoresponsive polycarbonate copolymers can be easily tuned within a wide temperature window from 0 °C to 46 °C (3 g L−1 in aqueous solution). In addition, block polycarbonates with two tunable LCSTs were further synthesized and investigated. Results showed that LCST1 was constructed by polycarbonate with a hydrophobic thioether linkage, while the LCST2 was achieved by a polycarbonate containing hydrophilic sulphone linkage.

Facile construction of near-monodisperse and dual responsive polycarbonate mixed micelles with the ability of pH-induced charge reversal for intracellular delivery of antitumor drugs

A mixed strategy was used to construct size-adjustable, pH and redox dual-responsive, near-monodisperse and charge-conversional core-shell polycarbonate carriers. First, two kinds of random polycarbonates (PC(Arss-N2CH3)) with different ratios of hydrophobic disulfide (Arss) and hydrophilic dimethylamine functional groups (N2CH3) (relatively hydrophobic polycarbonate (BPC) with more disulfide groups and relatively hydrophilic polycarbonate (LPC) with more dimethylamine groups) were used to construct near-monodisperse core micelles in pH 7.4 PBS. Then, a negatively charged shell polymer, poly(ethylene glycol)-b-1,2-dicarboxylic-cyclohexene anhydride modified amino polycarbonate (PEG-PCDCA), bearing acid-labile β-carboxylic amides, was added to the core micelle solution to get the desired mixed micelle. The assembly process, pH induced charge-reversal, and dual-response abilities of the resultant mixed micelles were thoroughly studied using zeta potential and dynamic light scattering (DLS). Two model drugs, Nile red (NR) and doxorubicin (DOX), were successfully loaded into the micelle and could be released in response to dithiothreitol (DTT) and acidic conditions. Confocal microscopy indicated that the micelle system could achieve effective cellular uptake and DOX release in Hela cells. Moreover, the blank micelle and the drug-loaded mixed micelle showed slight and great cytotoxicity against Hela cells, respectively, indicating their significant potential in cancer therapy.

One-pot synthesis of highly mechanical and redox-degradable polyurethane hydrogels based on tetra-PEG and disulfide/thiol chemistry

Highly mechanical hydrogels with stimuli degradability are promising scaffold materials for tissue engineering, due to their unique advantage of retaining mechanical strength in use, while being able to be readily removed by external stimuli after use. However, it has always been a big challenge to integrate both good mechanical properties and stimuli degradability into one single hydrogel. In this work, a series of tetra-PEG polyurethane hydrogels with tunable redox-degradability and a high compressive fracture strength has been synthesized by a one-pot method. The good mechanical properties are owed to an extremely uniform network of tetra-PEG, and the redox-degradability is realized using cystamine, which contains a highly DTT-sensitive disulfide bond. The mechanical strength of the as-prepared hydrogels reaches a megapascal range, and their complete degradation time can be flexibly adjusted from 4 to 22 days by controlling the proportion of cystamine. With the above properties, these hydrogels are believed to have potential bio-applications.

Bilayered polyurethane/dipole–dipole and H-bonding interaction reinforced hydrogels as thermo-responsive soft manipulators

Dipole-dipole and hydrogen-bonding interaction reinforced (DHIR) hydrogels that demonstrate both excellent thermo-responsive volume change and high mechanical strength have been developed. Their thermo-responsive volume change originates from the balance between the temperature-sensitive reversible dipole-dipole and H-bonding interaction and an embedded super-hydrophilic component. By integrating these thermal responsive DHIR hydrogels with non-swelling polyurethane (PU) hydrogels, bilayered (DHIR-PU) thermomorphic actuators capable of shape transformation have been fabricated. The hybrid DHIR-PU hydrogels have a wide temperature window allowing dual-responsive actuations to be achieved. The new hydrogel-based actuators are highly attractive materials for a range of transformative applications in soft robotics, medical devices and advanced manufacturing.