Effect of gold nanoparticle shapes for phototherapy and drug delivery

In this study, we compared three different hybrid gold nanoparticle shapes (spherical, rod and star) for photothermal therapy and the delivery of doxorubicin. Diblock copolymers (P(OEGMA)-b-P(VBA)) containing aldehyde groups for the conjugation of doxorubicin via a Schiff base linkage were grafted onto gold nanoparticles by utilizing the thiol moiety present on the polymer chain end. The resulting grafting density was compared between the three different gold nanoparticle morphologies. Spherical nanoparticles exhibited the highest grafting density (24.3 w/w%) of the drug conjugated polymer on the gold nanoparticles. The localization of these nanoparticles and quantitative drug release was monitored in live cells using fluorescence lifetime imaging (FLIM) microscopy. These nanoparticles were then tested in vitro for the delivery of doxorubicin as well as their potential application in photothermal therapy under near infrared (NIR) light. For photothermal therapy, star nanoparticles exhibited the highest toxicity to cancer cells, while spherical nanoparticles have a very low efficiency under NIR light exposure. Spherical nanoparticles also showed the least efficient for drug delivery purposes. FLIM showed a rapid accumulation of star nanoparticles in the nucleus, while the other nanoparticle shapes stayed in the cytoplasm. Although the highest grafting density was achieved with spherical gold nanoparticles, photothermal therapy and drug delivery performance of the nanorods and nanostars were found to be far superior. These findings yield valuable insights into the effect of different gold nanoparticle shapes for anticancer drug delivery and photothermal therapy, which can be useful for the evaluation and optimization of the formulation using gold nanoparticles.