Development of a novel Z-scheme CoxNi1-xTiO3/CdS (x = 0.5) photocatalyst for the efficient degradation of organic pollutants via a visible-light-driven photocatalytic process.

Herein, for the first time, we reported the synthesis of a novel Z-scheme CoxNi1-xTiO3/CdS (x = 0.5) heterojunction photocatalyst and the investigation of its visible-light-driven photocatalytic performance toward degradation of methylene blue (MB). The developed photocatalyst was structurally characterized by applying X-Ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), differential reflectance spectroscopy (DRS), and photoluminescence (PL) techniques. The results indicated the formation of a highly porous structure with improved visible light adsorption capacity, favorable for the catalytic activity. At an optimum condition of 10 mg/L of MB and 300 mg/L of catalyst, the ternary photocatalyst demonstrated a MB removal efficiency of 99 % after 75 min of the treatment process. The radical trapping experiments unveiled that hydroxyl and superoxide radicals were two main reactive species formed under visible light, while the valance holes possessed an insignificant role. The synergetic impact of the CoxNi1-xTiO3 (x = 0.5) and CdS on the photodegradation of MB over the as-prepared CoxNi1-xTiO3/CdS (x = 0.5) photocatalyst through Z-scheme photocatalysis was indicated by the results of the mechanism studies. The percentage impact of the treatment time, MB concentration, the ratio of CoxNi1-xTiO3/CdS (x = 0.5), and the dosage of catalyst using analysis of the CCD modeling was obtained as 47.04, 16.67, 7.22 and 0.87 %, respectively. Furthermore, the as-synthesized photocatalyst possessed high recyclability and photostability with only a 3 % decline in activity after four repetitive cycles.

Graphene-MoS2 polyfunctional hybrid hydrogels for the healing of transected Achilles tendon.

Healing of injured tendon is a major clinical challenge in orthopaedic medicine, due to the poor regenerative potential of this tissue. Two-dimensional nanomaterials, as versatile scaffolds, have shown a great potential to support, trigger and accelerate the tendon regeneration. However, weak mechanical properties, poor functionality and low biocompatibility of these scaffolds as well as post-surgery infections are main drawbacks that limit their development in the higher clinical phases. In this work, a series of hydrogels consisting polyglycerol functionalized reduced graphene oxide (PG), polyglycerol-functionalized molybdenum disulfide (PMoS2) and PG/PMoS2 hybrid within the gelatin matrix are formulated in new scaffolds and their ability for the healing of injured Achilles tendon, due to their high mechanical properties, low toxicity, cell proliferation enhancement, and antibacterial activities is investigated. While scaffolds containing PG and PMoS2 showed a moderate tendon regeneration and anti-inflammatory effect, respectively, their hybridization into PG/PMoS2 demonstrated a synergistic healing efficiency. Along the same line, an accelerated return of tendon function with low peritendinous adhesion and low cross-sectional area in animal group treated with scaffold containing PG/PMoS2 was observed. Taking advantage of the high biocompatibility, high strength, straightforward construction and fast tendon regeneration, PG/PMoS2 can be used as a new scaffold for the future tissue engineering.

Functionalized Graphene Platforms for Anticancer Drug Delivery.

Two-dimensional nanomaterials are emerging as promising candidates for a wide range of biomedical applications including tissue engineering, biosensing, pathogen incapacitation, wound healing, and gene and drug delivery. Graphene, due to its high surface area, photothermal property, high loading capacity, and efficient cellular uptake, is at the forefront of these materials and plays a key role in this multidisciplinary research field. Poor water dispersibility and low functionality of graphene, however, hamper its hybridization into new nanostructures for future nanomedicine. Functionalization of graphene, either by covalent or non-covalent methods, is the most useful strategy to improve its dispersion in water and functionality as well as processability into new materials and devices. In this review, recent advances in functionalization of graphene derivatives by different (macro)molecules for future biomedical applications are reported and explained. In particular, hydrophilic functionalization of graphene and graphene oxide (GO) to improve their water dispersibility and physicochemical properties is discussed. We have focused on the anticancer drug delivery of polyfunctional graphene sheets.

Covalent Decoration of MoS2 Platforms by Silver Nanoparticles through the Reversible Addition-Fragmentation Chain Transfer Reaction.

Two-dimensional nanomaterials decorated by metal nanoparticles have gained great interest, due to their potential applications in different areas ranging from electrochemical sensing to photothermal therapy. However, metal nanoparticles that are noncovalently immobilized on the surface of two-dimensional nanomaterials can be dissociated from their surface in the complex mediums. This challenge can be overcome by covalent attachment of nanoparticles to the surface of these platforms. In this work, MoS2 sheets are decorated by silver nanoparticles (AgNPs) through a reversible addition-fragmentation chain transfer (RAFT) reaction. Reactive centers were created on the surface of freshly exfoliated MoS2 and a two-dimensional platform with the ability of initiating the RAFT reaction was obtained. Afterwards, silver nanoparticles with acrylamide functionality were synthesized and attached on the surface of MoS2 sheets by the RAFT reaction. MoS2-AgNPs hybrids were characterized by different spectroscopy and microscopy methods as well as thermal and elemental analyses, and then they were used for the electrochemical determination of dipyridamole in aqueous solution. Taking advantage of the straightforward synthesis and the possible MoS2-AgNPs distance adjustment, a variety of hybrid systems with unique physicochemical and optoelectronic properties can be constructed by using this method.

Boronic Acid-Functionalized Two-Dimensional MoS2 at Biointerfaces.

While noncovalent interactions at two-dimensional nanobiointerfaces are extensively investigated, less knowledge about covalent interactions at this interface is available. In this work, boronic acid-functionalized 2D MoS2 was synthesized and its covalent multivalent interactions with bacteria and nematodes were investigated. Polymerization of glycidol by freshly exfoliated MoS2 and condensation of 2,5-thiophenediylbisboronic acid on the produced platform resulted in boronic acid-functionalized 2D MoS2. The destructive interactions between 2D MoS2 and bacteria as well as nematodes were significantly amplified by boronic acid functional groups. Because of the high antibacterial and antinematodal activities of boronic acid-functionalized 2D MoS2, its therapeutic efficacy for diabetic wound healing was investigated. The infected diabetic wounds were completely healed 10 days after treatment with boronic acid-functionalized 2D MoS2, and a normal structure for recovered tissues including different layers of skin, collagen, and blood vessels was detected.

Fabrication of new generation of co-delivery systems based on graphene-g-cyclodextrin/chitosan nanofiber.

Although many techniques have been devoted to promote therapeutic purposes of drug carrier systems, however, there are still many challenges in this area. Here, we designed co-loaded delivery systems, composed of curcumin loaded cyclodextrin-graphene oxide core (Cur@CD-GO) and gallic acid loaded chitosan shell nanofibers (Cur-Ga NF), which can promote the therapeutic efficiency of drugs. The synthesized nanofibres were fabricated by electrospinning technique with the coaxial system. Results showed that co-loaded delivery systems (Cur-Ga NF) provide better performance over single drug-loaded NFs (Cur@CD-GO). It was demonstrated that the nanofibers were successfully prepared, and the drugs in the core and sell of nanofibers were released in a controlled and sustained manner. The produced Cur-Ga NF, providing improved anti-cancer activity, antimicrobial activity, antioxidant activity and anti-inflammatory outcome as compared to single drug-loaded NFs. Our investigations showed that such co-delivery fiber systems could be employed as a promising nanocarrier for therapeutic applications.

Thermoresponsive Amphiphilic Functionalization of Thermally Reduced Graphene Oxide to Study Graphene/Bacteria Hydrophobic Interactions.

An understanding of the interactions of 2D nanomaterials with pathogens is of vital importance to developing and controlling their antimicrobial properties. In this work, the interaction of functionalized graphene with tunable hydrophobicity and bacteria is investigated. Poly(ethylene glycol)- block-(poly- N-isopropylacrylamide) copolymer (PEG- b-PNIPAM) with the triazine joint point was attached to the graphene surface by a nitrene [2 + 1] cycloaddition reaction. By thermally switching between hydrophobic and hydrophilic states, functionalized graphene sheets were able to bind to bacteria. Bacteria were eventually disrupted when the functionality was switched to the hydrophobic state. On the basis of measuring the different microscopy methods and a live/dead viability assay, it was found that Escherichia coli ( E. coli) bacteria are more susceptible to hydrophobic interactions than B. cereus bacteria, under the same conditions. Our investigations confirm that hydrophobic interaction is one of the main driving forces at the presented graphene/bacteria interfaces and promotes the antibacterial activity of graphene derivatives significantly.

Functionalized 2D nanomaterials with switchable binding to investigate graphene-bacteria interactions.

Graphene and its derivatives have recently attracted much attention for sensing and deactivating pathogens. However, the mechanism of multivalent interactions at the graphene-pathogen interface is not fully understood. Since different physicochemical parameters of graphene play a role at this interface, control over graphene's structure is necessary to study the mechanism of these interactions. In this work, different graphene derivatives and also zwitterionic graphene nanomaterials (ZGNMs) were synthesized with defined exposure, in terms of polymer coverage and functionality, and isoelectric points. Then, the switchable interactions of these nanomaterials with E. coli and Bacillus cereus were investigated to study the validity of the generally proposed "trapping" and "nano-knives" mechanisms for inactivating bacteria by graphene derivatives. It was found that the antibacterial activity of graphene derivatives strongly depends on the accessible area, i.e. edges and basal plane of sheets and tightness of their agglomerations. Our data clearly confirm the authenticity of "trapping" and "nano-knives" mechanisms for the antibacterial activity of graphene sheets.

pH-Responsive Hybrid Hydrogels as Antibacterial and Drug Delivery Systems.

This study describes the design and synthesis of organic⁻inorganic hybrid hydrogels based on an interpenetrating polymer network (IPN) composed of polyaspartic acid crosslinked by graphene nanosheets as the primary network and poly(acrylamide-co-acrylic acid) as the secondary network. Silver, copper oxide, and zinc oxide nanoparticles were formed within the gel matrix, and the obtained hydrogel was applied to a load and controlled release of curcumin. The loading of curcumin and the release of this drug from the gels depended on the nanoparticle's (NP's) content of hydrogels as well as the pH of the medium. The synthesized hydrogels showed antibacterial activity against E. coli and S. aureus bacteria. The ability of the synthesized hydrogels to incapacitate bacteria and their loading capacity and controlled release of curcumin qualify them for future therapies such as wound-dressing applications.