Laser-Carbon Combo Opens Cells

Carbon black nanoparticles activated by femtosecond laser pulses can help deliver molecules across cell membranes, researchers at Georgia Institute of Technology report (Nat. Nanotechnol., DOI: 10.1038/nnano.2010.126). By irradiating a suspension of carbon black nanoparticles and cells with ultrafast laser pulses, Mark R. Prausnitz, Mostafa A. El-Sayed, and coworkers create transient openings in cell membranes through which a variety of small molecules, proteins, and DNA can enter the cells. The team speculates that the carbon black reacts with water when irradiated, generating photoacoustic shock waves that form transient holes in cell membranes. The researchers demonstrated the effect in multiple cell types by exposing the cells to calcein, the protein bovine serum albumin, or plasmid DNA with and without carbon black and laser activation. With carbon black or laser pulses alone, the cells take up very little of any of the compounds, but when exposed to both carbon black and laser irradiation, the cells take up significant amounts of all three. Under similar conditions using multiwalled carbon nanotubes instead of carbon black, the researchers also see much less uptake. They attribute the performance difference to carbon black’s more reactive surface.