Physical mechanisms of laser-activated nanoparticles for intracellular drug delivery

Abstract

Novel intracellular drug delivery techniques are needed to overcome the barrier of the cell’s plasma membrane. In this study, we leveraged a novel, laser-mediated technique known as transient nanoparticle energy transduction (TNET), in which carbon black (CB) nanoparticles in suspension with DU145 cells and small molecules irradiated by nanosecond-pulsed near infrared (NIR) laser energy leads to efficacious delivery and high cell viability. To gain mechanistic insight into TNET, we studied various aspects of this in vitro system, including cellular mechanics, total energy input, and the role of photoacoustics. First, we studied the role of cellular mechanics in TNET by way of the cytoskeleton and plasma membrane fluidity. From these studies, we concluded that cytoskeletal mechanics are integral to resulting bioeffects achieved with TNET, whereas the fluidity of the plasma membrane is not. Next, we studied the effect of energy input into the system, which was increased by increasing laser fluence, CB nanoparticle concentration and number of laser pulses. We found that total energy input strongly correlated with resulting bioeffects. Lastly, we studied the effects of three different carbon-based nanoparticles – CB, multi-walled carbon nanotubes (MWCNT) and single-walled (SWCNT) carbon nanotubes – on cellular bioeffects. In addition to the different bioeffect profiles, CB, MWCNT, and SWCNT also exhibited differences in the intensity of photoacoustic output in the form of a single, mostly positive-pressure pulse of ~100 ns duration. Lack of a universal correlation between peak pressure and cellular bioeffects, suggested that total energy input rather than pressure output was more mechanistically relevant to TNET. Overall, this work provides functional characterization and mechanistic understanding the cellular bioeffects cause by TNET. These studies will contribute to a necessary understanding of TNET that will enable rational design of TNET systems for future applications and possible translation into the clinic.