Mono and dialkoxysilane surface modification of superparamagnetic iron oxide nanoparticles for application as magnetic resonance imaging contrast agents

In this study, we have developed and characterized two previously unstudied alkoxysilane surface chemistries for use with superparamagnetic iron oxide (SPIO) nanoparticles as a magnetic resonance imaging contrast agent. We modified superparamagnetic iron oxide nanoparticles (SPIO) using aminopropyl triethoxysilane and two analogous alkoxysilanes, aminopropyl dimethylethoxysilane and aminopropyl methyldiethoxysilane, to compare a mono- and dialkoxysilane, respectively, to a more commonly used trialkoxysilane as two new SPIO surface chemistries capable of forming ultrathin functional surface coatings. The ligand densities of the mono- and dialkoxysilane-modified SPIO produced in this study are consistent with near monolayers of ligands on the SPIO surface. We studied the chemical stability of the mono-, di-, and trialkoxysilane-modified SPIO in neutral and acidic media to evaluate the viability of these surface chemistries for use in long-term intracellular applications. The mono- and dialkoxysilane-modified SPIO demonstrate comparable chemical stability to the trialkoxysilane-modified SPIO, indicating that the mono- and dialkoxysilane are both viable new SPIO surface chemistries for future applications requiring minimally thick alkoxysilane surface coatings.