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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.

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The conjunction of low intensity ultrasound and encapsulated microbubbles can alter the permeability of cell membrane, offering a promising theranostic technique for non-invasive gene/drug delivery. Despite its great potential, the biophysical mechanisms of the delivery at the cellular level remains poorly understood. Here, the first direct high-speed micro-photographic images of human lymphoma cell and microbubble interaction dynamics are provided in a completely free suspension environment without any boundary parameter defect. Our real-time images and theoretical analyses prove that the negative divergence side of the microbubble's dipole microstreaming locally pulls the cell membrane, causing transient local protrusion of 2.5 µm in the cell membrane. The linear oscillation of microbubble caused microstreaming well below the inertial cavitation threshold, and imposed 35.3 Pa shear stress on the membrane, promoting an area strain of 0.12%, less than the membrane critical areal strain to cause cell rupture. Positive transfected cells with pEGFP-N1 confirm that the interaction causes membrane poration without cell disruption. The results show that the overstretched cell membrane causes reparable submicron pore formation, providing primary evidence of low amplitude (0.12 MPa at 0.834 MHz) ultrasound sonoporation mechanism.

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