title: Energy Transfer Mechanisms during Molecular Delivery to Cells by Laser-Activated Carbon Nanoparticles.
abstract: Previous studies have shown that exposure of carbon black nanoparticles to nanosecond pulsed near-infrared laser causes intracellular delivery of molecules through hypothesized transient breaks in the cell membrane. The goal of this study is to determine the underlying mechanisms of sequential energy transfer from laser light to nanoparticle to fluid medium to cell. We found that laser pulses on a timescale of 10 ns rapidly heat carbon nanoparticles to temperatures on the order of 1200 K. Heat is transferred from the nanoparticles to the surrounding aqueous medium on a similar timescale, causing vaporization of the surrounding water and generation of acoustic emissions. Nearby cells can be impacted thermally by the hot bubbles and mechanically by fluid mechanical forces to transiently increase cell membrane permeability. The experimental and theoretical results indicate that transfer of momentum and/or heat from the bubbles to the cells are the dominant mechanisms of energy transfer that results in intracellular uptake of molecules. We further conclude that neither thermal expansion of the nanoparticles nor a carbon-steam chemical reaction play a significant role in the observed effects on cells, and that acoustic pressure appears to be concurrent with, but not essential to, the observed bioeffects.
authors.affiliation: School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia.
authors.forename: Aritra
authors.initials: A
authors.lastname: Sengupta
authors.affiliation: George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Gray
authors.affiliation: School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia.
authors.forename: Sean C
authors.initials: SC
authors.lastname: Kelly
authors.affiliation: School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia.
authors.forename: Stefany Y
authors.initials: SY
authors.lastname: Holguin
authors.affiliation: School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia.
authors.forename: Naresh N
authors.initials: NN
authors.lastname: Thadhani
authors.affiliation: School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia. Electronic address: prausnitz@gatech.edu.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Prausnitz
mesh_terms: D001692:Biological Transport; D045744:Cell Line, Tumor; D004735:Energy Transfer; D006358:Hot Temperature; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism*; D007834:Lasers; D053758:Nanoparticles; D011312:Pressure; D053260:Soot / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D053260:Soot