One-Step Synthesis of Polypyrrole-Coated Gold Nanoparticles for Use as a Photothermally Active Nano-System

Abstract

Maha Fadel,1 Doaa Abdel Fadeel,1 Moustafa Ibrahim,2 Rania M Hathout,3 Abdullah I El-Kholy1 1Department of Medical Applications of Laser, Pharmaceutical Technology Unit, National Institute of Laser Enhanced Sciences (NILES), Cairo University, Giza, Egypt; 2Physics Department, Faculty of Science, Banha University, Banha, Egypt; 3Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Ain Shams University, Cairo, EgyptCorrespondence: Maha FadelNational Institute of Laser Enhanced Sciences (NILES), Cairo University, Giza 12613, EgyptTel [phone]Fax [phone]Email [email protected]: This paper introduces a simple one-step and ultra-fast method for synthesis of highly photothermally active polypyrrole-coated gold nanoparticles. The synthesis process is so simple that the reaction is very fast without the need for any additives or complicated steps.Methodology: Polypyrrole-coated gold nanoparticles (AuPpy NPs) were synthesized by reacting chloroauric acid (HAuCl4) with pyrrole (monomer) in aqueous medium at room temperature. These nanoparticles were characterized by UV–visible–NIR spectrometry, transmission electron microscopy (TEM), AC conductivity, zeta sizer and were evaluated for dark cytotoxicity and photocytotoxicity using human hepatocellular carcinoma (HepG2) cell line as a model for cancer cells.Results: The synthesized AuPpy NPs showed a peak characteristic for gold nanoparticles (530– 600 nm, molar ratio dependent) and a wide absorption band along the visible–NIR region with intensity about triple or even quadruple that of polypyrrole synthesized by the conventional FeCl3 method at the same concentration and under the same conditions. TEM imaging showed that the synthesized AuPpy NPs were composed of spherical or semi-spherical gold core(s) of about 4– 10 nm coated with distinct layer(s) of polypyrrole seen either loosely or in clusters. Mean sizes of the synthesized nanoparticles range between ∼ 25 and  220 nm (molar ratio dependent). Zeta potentials of the AuPpy NPs preparations indicate their good colloidal stability. AC conductivity values of AuPpy NPs highly surpass that of Ppy prepared by the conventional FeCl3 method. AuPpy NPs were non-toxic even at high concentrations (up to 1000 μM pyrrole monomer equivalent) under dark conditions. Unlikely, light activated the photothermal activity of AuPpy NPs in a dose-dependent manner.Conclusion: This method simply and successfully synthesized AuPpy NPs nanoparticles that represent a safe alternative photothermally active multifunctional tool instead of highly toxic and non-biodegradable gold nanorods.Keywords: polypyrrole, gold nanoparticles, ultra-fast synthesis, AuPpy NPs, photothermal activity

Keywords

• polypyrrole
• gold nanoparticles
• ultra-fast synthesis
• auppy nps
• photothermal activity.