Efficient Quantification by X-ray Photoelectron Spectroscopy and Thermogravimetric Analyses of the One-Pot Grafting of Two Molecules on the Surface of Iron Oxide Nanoparticles

Abstract

Superparamagnetic iron oxide nanoparticles (SPION) can be developed for biomedical applications but need to be functionalized before use to avoid agglomeration in biological media. In this study, SPION were functionalized in one step with two organic molecules. Firstly, polyethylene glycol (PEG) was mixed for 46 hours to improve steric stability and then, two hours before the end of the reaction, dimercaptosuccinic acid (DMSA) was added to provide negative charges and thiol groups. Three different molecular weights of PEG were used (550, 2000 and 5000 g.mol-1). We demonstrated that by coupling thermogravimetric to X-Ray photoelectron spectrometry analyses it was possible to quantify accurately the covering of SPION's surface. We also showed that the length of the PEG influenced the quantity of DMSA adsorbed. With the smallest PEG (550 g.mol-1) the presence of DMSA is almost ten times higher than with the two other PEG used proving that long polymers prevent the adsorption of small molecules on the surface of SPION.