The effect of grafting method on the colloidal stability and in vitro cytotoxicity of carboxymethyl dextran coated magnetic nanoparticles

The colloidal stability and cytotoxicity of iron oxide nanoparticles coated with adsorbed or covalently-bound carboxymethyl dextran (CMDx) was studied in biologically relevant buffers and in MCF-7 cell culture. Comparisons were also made with aminopropylsilane coated nanopartciles which are an intermediate step in obtaining the particles with covalently bound CMDx. Particles with covalentlybound CMDx were colloidally stable in all the buffers and in cell culture. Conversely, particles with aminopropylsilane and adsorbed CMDx precipitated under the conditions tested. Aminopropylsilane coated nanoparticles were only stable in deionized water and pH < 5. Nanoparticles with adsorbed CMDx precipitate due to desorption of CMDx in the presence of phosphates. Nanoparticles with aminopropylsilane and adsorbed CMDx were significantly more cytotoxic in the absence of magnetic field than nanoparticles with covalently-bound CMDx, which correlates with their poor colloidal stability. Both CMDx coated nanoparticles were equally effective in decreasing MCF-7 cancer cell viability by magnetic fluid hyperthermia (MFH), to levels of around 4-6%, compared to untreated samples. This study illustrates the importance of grafting method on obtaining nanoparticles suitable for biomedical applications.