Emergence of PEI as a Valuable Reducing Agent and Cationic Coating in the Production of Gold Nanoparticles as Transfection Vectors

Introduction Gold nanoparticles (GNPs) attract researchers from both fundamental and applied sciences. Due to inert and nontoxic nature, they are very valuable nanomaterials for in vivo biomedical applications including... [ view full abstract ]

Introduction

Gold nanoparticles (GNPs) attract researchers from both fundamental and applied sciences. Due to inert and nontoxic nature, they are very valuable nanomaterials for in vivo biomedical applications including imaging and therapy. One attractive composition would be GNPs coated with polyethyleneimine (PEI), which is the golden standard for non-viral gene delivery. Here, we aimed to study the one step, aqueous synthesis of gold nanoparticles by using branched polyethyleneimine (bPEI). The influence of PEI protonation on particle size and stability is investigated for the first time. Impact of the molecular weight was also studied in detail. High gene transfection efficiency coupled with simple one pot synthesis make this process a valuable alternative for the generation of new GNP based transfection agents.

Methods

GNPs were synthesized by thermal reduction of HAuCl₄ with bPEI as capping and reduction agent. Molecular weight of the PEI (25, 10, 1.8, 0.6 kDa), reaction time and pH  of the solution were changed systematically. MTT assay was used to analyze cytotoxicity of particles in HEK-293T cells. For the transfection analysis GNPs were loaded with pMax-GFP.

Results and Discussion

The surface plasmon band (SPB) of GNPs was observed at around 520 nm. At longer reaction times, peak maxima shifted to 530-540 nm due to particle growth. The influence of reaction pH and PEI molecular weight influenced particle size and aggregation dramatically. Best synthetic and storage pH will be discussed.

These PEI coated gold nanoparticles are cationic and they successfully condensed and transfected pMax-GFP to HEK-293T.  Toxicity and transfection potential will be discussed in detail.