Sonochemically Prepared Polydopamine Nanospheres Doped with Metal Oxides

Gil Yeroslavsky, Chemistry, Bar Ilan University, Ramat Gan, Israel
Shai Rahimipour, Chemistry, Bar Ilan University, Ramat Gan, Israel

The use of polydopamine (PDA) for the facile generation of nanospheres (NS) is reported. The generation of NS was achieved by a sonochemical method using a two phase solvent system and was largely enhanced by the presence of various metal ions. Particles were characterized for their morphology, size, and entrapment efficacy, using light and electron microscopy (SEM and TEM), dynamic light scattering (DLS). While X-ray diffraction, X-ray photoelectron spectroscopy, thermal gravimetric analysis (XRD, XPS, TGA) and Raman scattering were use to analyze the particles in the molecular level.

Additionally, different metal salts were incorporated to the sonication process to afford new properties to the NS. We have demonstrated that particles containing Ag+ or Cu2+ exhibit potent anti-bacterial and anti-biofilm activity against a large variety of gram positive and gram negative bacteria, while showing no toxicity towards mammalian cells. Electron paramagnetic resonance (EPR) and fluorometric studies suggested that the particles generate reactive oxygen species (ROS), which may contribute to antibacterial activity. We have also utilized the adhesive property of PDA to immobilize Ag-PDA-NS onto different surfaces and convert them to antibacterial. Gd+2 was added to generate particles with magnetic properties that are highly bright in Magnetic Resonance Imaging (MRI). Ni2+ was used to prepare particles doped with NiO that easily attach peptides synthesized with a His-tag and later can be removed by wash with imidazole solution, as determined by Fluorescence-activated cell sorting (FACS) . Finally, NS prepared with Tb+3 showed phosphoresence by fluorometry, a property greatly enhanced by doping the particles with Ag nanocrystals. Tb/Ag-doped NS were also visualized using fluoresence microscopy and were shown to enter  living cells.