Doxorubicin‐Loaded Single Wall Nanotube Thermo‐Sensitive Hydrogel for Gastric Cancer Chemo‐Photothermal Therapy

Single wall carbon nanotube (SWNT) based thermo‐sensitive hydrogel (SWNT‐GEL) is reported, which provides an injectable drug delivery system as well as a medium for photothermal transduction. SWNT‐hydrogel alone appears to be nontoxic on gastric cancer cells (BGC‐823 cell line) but leads to cell death with NIR radiation through a hyperthermia proapoptosis mechanism. By incorporating hyperthermia therapy and controlled in situ doxorubicin (DOX) release, DOX‐loaded SWNT‐hydrogel with NIR radiation proves higher tumor suppression rate on mice xenograft gastric tumor models compared to free DOX without detectable organ toxicity. The developed system demonstrates improved efficacy of chemotherapeutic drugs which overcomes systemic adverse reactions and presents immense potential for gastric cancer treatment.     

Aligned Carbon Nanotube–Based Flexible Gel Substrates for Engineering Biohybrid Tissue Actuators

Muscle‐based biohybrid actuators have generated significant interest as the future of biorobotics but so far they move without having much control over their actuation behavior. Integration of microelectrodes into the backbone of these systems may enable guidance during their motion and allow precise control over these actuators with specific activation patterns. Here, this challenge is addressed by developing aligned carbon nanotube (CNT) forest microelectrode arrays and incorporating them into scaffolds for cell stimulation. Aligned CNTs are successfully embedded into flexible and biocompatible hydrogels exhibiting excellent anisotropic electrical conductivity. Bioactuators are then engineered by culturing cardiomyocytes on the CNT microelectrode‐integrated hydrogel constructs. The resulting cardiac tissue shows homogeneous cell organization with improved cell‐to‐cell coupling and maturation, which is directly related to the contractile force of muscle tissue. This centimeter‐scale bioactuator has excellent mechanical integrity, embedded microelectrodes, and is capable of spontaneous actuation behavior. Furthermore, it is demonstrated that a biohybrid machine can be controlled by an external electrical field provided by the integrated CNT microelectrode arrays. In addition, due to the anisotropic electrical conductivity of the electrodes provided by aligned CNTs, significantly different excitation thresholds are observed in different configurations such as the ones with electrical fields applied in directions parallel versus perpendicular to the CNT alignment.     

A Universal and Facile Approach for the Formation of a Protein Hydrogel for 3D Cell Encapsulation

A universal and facile approach to modifying proteins so that they can rapidly form hydrogel upon mixing with crosslinkers is presented. The concept of it is to introduce maleimide, which is highly reactive with dithiol‐containing crosslinkers via thiol‐ene click chemistry, onto proteins. Bovine serum albumin (BSA) is used as a model protein due to its good stability and low cost. The results here show that a protein hydrogel can be readily formed by blending modified BSA and resilin‐related peptide crosslinker solutions at a proper ratio. The hydrogel exhibits good elasticity and tunable mechanical as well as biochemical properties. Moreover, it allows convenient 3D cell encapsulation and shows good biocompatibility. Muscle cells embedded in the hydrogel are promoted to spread by incorporating arginyl‐glycyl‐aspartic acid (RGD)‐containing peptide into the system, thus warranting a bright future of it in regenerative medicine.     

Graphene‐Directed Supramolecular Assembly of Multifunctional Polymer Hydrogel Membranes

Polymer‐based nanoporous hydrogel membranes hold great potential for a range of applications including molecular filtration/separation, controlled drug release, and as sensors and actuators. However, to be of practical utility, polymer membranes generally need to be fabricated as ultrathin yet mechanically robust, have a large‐area yet be defect‐free and in some cases, their structure needs the capability to adapt to certain stimuli. These stringent and sometimes self‐conflicting requirements make it very challenging to manufacture such bulk nanostructures in a controllable, scalable and cost‐effective manner. Here, a versatile approach to the fabrication of multifunctional polymer‐based hydrogel membranes is demonstrated by a single step involving filtration of an aqueous dispersion containing chemically converted graphene (CCG) and a polymer. With CCG uniquely serving as a membrane‐ and pore‐forming directing agent and as a physical cross‐linker, a range of water soluble polymers can be readily processed into nanoporous hydrogel membranes through supramolecular interactions. With the interconnected CCG network as a robust and porous scaffold, the membrane nanostructure can easily be fine‐tuned to suit different applications simply by controlling the chemistry and concentration of the incorporated polymer. This work provides a simple and versatile platform for the design and fabrication of new adaptive supramolecular membranes for a variety of applications.     

Cysteine–Ag Cluster Hydrogel Confirmed by Experimental and Numerical Studies

The native cysteine (Cys)‐Ag₃ cluster hydrogel is approved for the first time by both experimental and theoretical studies. From the detailed molecular structure and energy information, three factors are found to ensure the self‐assembly of Cys and Ag₃, and result in the hydrogel. First, the Ag–S bonds make Cys and Ag₃ form Cys‐Ag₃‐Cys monomer. Second, intermolecular hydrogen bonds between carboxyl groups of adjacent monomer push them self‐assembled. Third, more monomer precisely self‐assemble to produce the –[Cys‐Ag₃‐Cys]_n multimer, e.g., a single molecular chain with the left‐handed helix conformation, via a benign thermodynamic process. These multimers entangle together to form micro‐network to trap water and produce hydorgel in situ. The hydrogen bonds of hydrogel are sensitive to thermal and proton stimuli, and the hydrogel presents lysosome targeting properties via fluorescent imaging with biocompatibility.     

Preparation and characterization of PAM/SA tough hydrogels reinforced by IPN technique based on covalent/ionic crosslinking

In order to fabricate tough hydrogels with superior formability, polyacrylamide/sodium alginate (PAM/SA) interpenetrating polymer network (IPN) hydrogels were produced with ionically crosslinked SA interpenetrated in covalently crosslinked PAM. TGA results show that the heat resistance of PAM/SA IPN hydrogel is improved as compared to that of the individual component. Swelling studies indicate that increasing either chemical crosslinker content or ionic crosslinking via adding more N,N′‐methylenebisacrylamide (MBA) or SA results in lower ESR. It is concluded by tensile test that loosely crosslinked PAM coupled with tightly crosslinked SA improve mechanical strength for hydrogels based on covalent/ionic crosslinking. PAM/SA hydrogels via “one‐pot” method can form different complex shapes with mechanical properties comparable to conventional double network (DN) gels. The fracture strength of PAM_0.05/SA₂₀ reaches level of MPa, approaching 2.0 MPa. The work strives to provide method to tune mechanical and physical properties for hydrogels, which is hopefully to guide the design of hydrogel material with desirable properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41342.     

A Novel Wound Dressing Based on Ag/Graphene Polymer Hydrogel: Effectively Kill Bacteria and Accelerate Wound Healing

Avoiding wound infection and retaining an appropriate level of moisture around woundz are major challenges in wound care management. Therefore, designing hydrogels with desired antibacterial performance and good water‐maintaining ability is of particular significance to promote the development of wound dressing. Thus a series of hydrogels are prepared by crosslinking of Ag/graphene composites with acrylic acid and N,N′‐methylene bisacrylamide at different mass ratios. The antibacterial performance and accelerated wound‐healing ability of hydrogel are systematically evaluated with the aim of attaining a novel and effective wound dressing. The as‐prepared hydrogel with the optimal Ag to graphene mass ratio of 5:1 (Ag5G1) exhibits stronger antibacterial abilities than other hydrogels. Meanwhile, Ag5G1 hydrogel exhibits excellent biocompatibility, high swelling ratio, and good extensibility. More importantly, in vivo experiments indicate that Ag5G1 hydrogel can significantly accelerate the healing rate of artificial wounds in rats, and histological examination reveals that it helps to successfully reconstruct intact and thickened epidermis during 15 day of healing of impaired wounds. In one word, the present approach can shed new light on designing of antibacterial material like Ag/graphene composite hydrogel with promising applications in wound dressing.