Vapor nanobubble is the more reliable photothermal mechanism for inducing endosomal escape of siRNA without disturbing cell homeostasis

Abstract

Strategies for controlled delivery of therapeutic siRNA into living cells are in high demand as endosomal escape remains the most prominent bottleneck at the intracellular level. Photothermal properties of gold nanoparticles (AuNP) can be used to overcome the endosomal membrane barrier upon laser irradiation by two mechanisms: endosomal rupture by mechanical energy from water vapor nanobubbles (VNBs), or permeabilization of the endosomal membrane by heat diffusion. Here we evaluated how both mechanisms influence cargo release, transfection efficiency, acute cytotoxicity and cell homeostasis. Using a siRNA/AuNP drug delivery system we found that the in vitro release of siRNA from the AuNP carrier occurs equally efficiently by VNB formation or heat generation. Heat-mediated endosomal escape happened more efficiently in cells that had more particles per endosome, resulting in variable siRNA-induced downregulation (20-50%). VNB-mediated endosomal escape did not dependent on the number of AuNP per endosome, yielding high downregulations (50-60%) independent of the cell type. Effects on cell homeostasis by whole transcriptome analysis, showed a quick recover after 24 h or 48 h for either of both photothermal mechanisms. We conclude that VNBs are more consistent to induce efficient endosomal escape and gene silencing independent of the cell type without long lasting effects on cell homeostasis.

Keywords: Endosomal escape; Gold nanoparticles; Intracellular delivery; Photoporation; Transcriptomics; Transfection; Vapor nanobubbles; siRNA.