An oxygen nanoshuttle based on a reduced graphene oxide/copper peroxide (rGO/CuO 2 ) nanocomposite has been presented to deliver in situ oxygen nanobubbles (O 2 NBs) for combating bacterial infections. In the presence of rGO, the solid source of oxygen (i.e., CuO 2 ) was decomposed (in response to environmental conditions such as pH and temperature) into O 2 NBs in a more controllable and long-lasting trend (from 60 to 144 h). In a neutral buffer, the O 2 NBs experienced growth and collapse evolutions, creating a dynamic micro− nanoenvironment around the nanocomposite. In addition to effective battling against methicillin-resistant Staphylococcus aureus bacteria, the O 2 NBs demonstrated superior antibacterial properties on Gram-positive S. aureus to those on Gram-negative Escherichia coli bacteria, especially in the presence of rGO. In fact, the rGO contents could provide synergistic effects through harvesting some respiratory electrons (leading to striking interruption of the bacterial respiratory pathway) in one side and transferring them into the O 2 NBs, resulting in nanoscale reactive oxygen species (ROS) generation in another side. Moreover, nearinfrared laser irradiation induced more damage to the cell membrane due to the synergistic effects of local heat elevation and catalyzing the release/collapse of NBs imposing mechanical disruptions. Our results show that the O 2 -containing nanoshuttles can effectively be used as intelligent and controllable anti-infection nanorobots in upcoming graphene-based nanobiomedical applications.
The aim of this study was to develop novel biomedicated nanofiber electrospun mats for controlled drug release, especially drug release directly to an injury site to accelerate wound healing. Nanofibers of poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), and a 50:50 composite blend, loaded with ciprofloxacin HCl (CipHCl), were successfully prepared by an electrospinning technique for the first time. The morphology and average diameter of the electrospun nanofibers were investigated by scanning electron microscopy. X-ray diffraction studies indicated an amorphous distribution of the drug inside the nanofiber blend. Introducing the drug into polymeric solutions significantly decreased solution viscosities as well as nanofiber diameter. In vitro drug release evaluations showed that both the kind of polymer and the amount of drug loaded greatly affected the degree of swelling, weight loss, and initial burst and rate of drug release. Blending PVA and PVAc exhibited a useful and convenient method for electrospinning in order to control the rate and period of drug release in wound healing applications. Also, the thickness of the blend nanofiber mats strongly influenced the initial release and rate of drug release.
A remote controllable working graphite nanostructured swimmer based on a graphene jet nanomotor has been demonstrated for the first time. Graphite particles with pyramidal-like morphologies were fabricated by the creation of suitable defects in wide high-purity graphite flakes followed by a severe sonication. The particles were able to be self-exfoliated in water after Na intercalation between the graphene constituents. The self-exfoliation resulted in jet ejection of graphene flakes from the end of the swimmers (with speeds as high as ∼7000 m/s), producing a driving force (at least ∼0.7 L (pN) where L (μm) is swimmer size) and consequently the motion of the swimmer (with average speed of ∼17-40 μm/s). The jet ejection of the graphene flakes was assigned to the explosion of H2 nanobubbles produced between the Na intercalated flakes. The direction of motion of the swimmers equipped with TiO2 nanoparticles (NPs) can be controlled by applying a magnetic field in the presence of UV irradiation (higher UV intensity, lower radius of rotation). In fact, the negative surface charge of the graphene flakes of the swimmers increased by UV irradiation due to transferring the photoexcited electrons of TiO2 NPs into the flakes. Because of higher production of H2 nanobubbles under UV irradiation, the speed of swimmers exposed to UV light significantly increased. In contrast, UV irradiation with various intensities could not affect total distance traversed by the self-exfoliated swimmers having the same initial sizes. These confirmed the mass ejection mechanism for motion of the swimmers. The self-exfoliation of swimmers (and so their motion) occurred only in water (and not, e.g., in organic solutions). Such swimmers promise the design of remote controllable nanovehicles with the capability of initiating and/or improving their operations in response to environmental changes in order to realize broad ranges of versatile and fantastic nanotechnology-based applications.
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