Cell perforation mediated by plasmonic bubbles generated by a single near infrared femtosecond laser pulse

We report on transient membrane perforation of living cancer cells using plasmonic gold nanoparticles (AuNPs) enhanced single near infrared (NIR) femtosecond (fs) laser pulse. Under optimized laser energy fluence, single pulse treatment (τ = 45 fs, λ = 800 nm) resulted in 77% cell perforation efficiency and 90% cell viability. Using dark field and ultrafast imaging, we demonstrated that the generation of submicron bubbles around the AuNPs is the necessary condition for the cell membrane perforation. AuNP clustering increased drastically the bubble generation efficiency, thus enabling an effective laser treatment using low energy dose in the NIR optical therapeutical window.

Schematic representation of single femtosecond laser pulse plasmonic bubble generation in the vicinity of a cell.     

Investigating the effects of wettability and gaseous nanobubbles on roughened wall–fluid interface using molecular dynamics simulation

This paper reports on the use of molecular dynamics (MD) simulation to investigate the coupling effects of wettability, surface roughness and interfacial nanobubbles (INBs) on wall–fluid interfaces. The fluid properties close to the wall–fluid interface, such as potential energy, density, diffusion coefficients of fluid molecules and effective slip length are simulated. In the cases without surface nanobubbles, regions with lower potential energy have a higher probability of hosting water molecules. The local translational and rotational diffusion coefficients of water within the cavities are strongly influenced by wettability but largely unaffected by hydrodynamic effects. In cases where INBs exist, variations in wettability result in distinctly different argon morphologies. Argon nanobubbles form a convex shape on Wenzel-like interfaces but a shallow concave shape on Cassie-like interfaces. The phenomenon of water molecules invading grooves tends to occur on Wenzel-like interfaces; however, this depends largely on the morphology of the grooves. The high mobility and high density of argon molecules indicate that the state of the argon molecules within the grooves may require further investigation. Our results also show that the effective slip length is significantly influenced by wall–fluid wettability as well as the morphology of INBs.     

Evaluation of antitumor effect of oxygen nanobubble water on breast cancer-bearing BALB/c mice

Hypoxia is a condition of low oxygen level which poses a common feature of most cancers. In the current study, we investigated effect of water containing oxygen nanobubble (ONB) on tumor growth in breast cancer 4T1-bearing mice during 14-day treatment period. Tumor-bearing mice were randomly divided into three groups (six mice per group), including the ONB group drinking water containing ONB, the air nanobubble (ANB) group drinking water containing ANB, and control group drinking normal water. Tumor weight and size were measured in 2-day interval during 14-day treatment. mRNA expression of p53, vascular endothelial growth factor (VEGF), hypoxia-inducible factor (HIF), and cyclin D/Cdk2 genes were measured in the treated and control mice. After 8, 12, and 14 days of treatment, tumor size in ONB group was significantly decreased by 40.5%, 32.8%, and 28%, respectively, when compared with the control group. In addition, ANB group showed a significant reduction in tumor burden as well. The messenger RNA (mRNA) level of p53 in tumor cells of ONB and ANB group was found to be 36-fold (P = 0.0001) and 33-fold (P = 0.0001) higher than that in the control group, respectively. There was a ninefold increase in mRNA expression of VEGF gene in tumor cells of ANB mice than that in control mice; however, there was no significant changes in ONB group. Expression of HIF gene was significantly lower in tumor cells of ONB and ANB group than in the control group. It is concluded that drinking ONB water has potential to inhibit tumor growth, however more preclinical and proof-of-concept studies are needed to confirm its safety and therapeutic effect.     

Defouling and cleaning using nanobubbles on stainless steel

The present work demonstrates that nanobubbles can be used as cleaning agents on stainless steel (SS) surfaces. Cleaning efficiency has been quantified. Using an Atomic Force Microscope (AFM), it was demonstrated that nanobubbles can be produced by electrochemical treatment on a SS surface either with or without adsorbed bovine serum albumin (BSA). After allowing adsorption on SS overnight, radio-labeled BSA was removed by electrochemically generated nanobubbles, and then the remaining BSA on the surface was quantified by radioactivity measurement. The results indicate that nanobubbles can remove >10% of the protein in each 3-min electrochemical treatment while in a control group, washing with water and electrolyte resulted in no more than 3% of the protein being removed each time. Cleaning of conducting surfaces by nanobubbles is promising in any system where fouling occurs in biomedia.