Branched PEI Capped Gold Nanoparticles in Water for siRNA Delivery to Cancer Cells

K. Rahme, J. Guo, S. Biswas, C.M. O’Driscoll, J.D. Holmes
Notre Dame University-Louaize,

Keywords: gold nanoparticles, polymers, siRNA delivery, cancer


Herein we describe a simple method for the synthesis of different sizes of polyethylenimine-capped gold nanoparticles (AuNPs-PEI) in water and assess their potential to deliver siRNA or other therapeutic agents to cancer cells. AuNP-PEI with diameters ranging between 25-150 nm have been synthesised in aqueous solutions using PEI (25 KD and 2KD) as capping ligands and using hydroxylamine-O-sulfonic acid or ascorbic acid as reducing agents. Different parameters were found to affect the final size of nanoparticles core (i.e. gold salt concentrations, PEI molecular weight/concentrations, and temperature). The obtained AuNP-PEIs were fully characterized using UV-visible spectroscopy, Electron Microscopy (EM), and Dynamic Light Scattering (DLS). UV-visible spectra clearly showed that the synthesized particles have size dependent optical properties with a plasmon band shift to longer wavelengths, as the size of the AuNP core was increased. In addition, DLS analysis indicated that all samples were nearly monodisperse with one size distribution and a polydispersity index (PDI) of about 0.15 (Std 0.03). EM analysis indicated that AuNPs-PEI were nearly spherical in shape. Zeta (ζ) potential measurements showed that all AuNPs-PEI samples were positively charged with a ζ-potential in the range of 38 (Std 5 mV), leading to a very high stability of the colloidal solution for several months when stocked at 4 C. Furthermore, the potential application of AuNP-PEIs in siRNA delivery to PC-3 prostate cancer cells was investigated. The ability of AuNP-PEIs to complex siRNA was analysed by gel electrophoresis. Results indicated that AuNP-PEI 2KD and AuNP-PEI 25KD could complex siRNA at MR0.5 and MR0.25 onwards, respectively, suggesting that AuNP-PEI 25KD has a better siRNA binding capacity than AuNP-PEI 2KD. Cellular uptakes were also performed using PC-3 cancer cells. Results following 24 h incubation indicated that AuNP-PEI 25KD achieved significantly higher fluorescein-positive cells (~ 98%) relative to that of AuNP-PEI 2KD (~ 5%), suggesting that AuNP-PEI 25KD, but not AuNP-PEI 2KD, could deliver siRNA into cells. Finally, we have also demonstrated that the surface of AuNPs-PEI can be further conjugated with thiolated polyethylene glycol (SH-PEG) onto AuNPs surface. Moreover, we have previously showed that covalently bonded targeting ligand (such as Anisic Acid or Folic acid) could be also chemically grafted on PEI, leading therefore to a multifunctional nanoparticle that may be promising in the field of Nanobiotechnology and Nanomedicine. Acknowledgments: We acknowledge financial support from the National Council for Scientific Research Lebanon (CNRS-L-GRP2015-3538), and Science Foundation Ireland and AMBER (Grant 12/RC/2278).