Nanoscale Res Lett (2009) 4:70–77 TNF-a Assay After incubation for a period of time, cell culture supernate was collected and centrifuged at 8,0009g for 30 min to remove cell debris and nanoparticles. Tumor necrosis factor a (TNF-a) protein concentrations in the supernate were measured using an ELISA kit (RAT TNF-a, ELISA KIT, BOSTER) according to the manufacturer’s instructions. Cell Viability Assay Viability of SMC was determined by using MTT (3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetra-zolium bromide) assay. After incubation the supernate was removed and 200 lL MTT solution (0.5 mg/mL in DMEM medium) was 73 added at 37 C for 2 h. Then, cells were rinsed two times with PBS and 150 lL extracting solution (0.04 M HCl in isopropanol) was added to each well of 96-well plates. The plates were placed for 15 min at ambient temperature to dissolve the dyes and the dye extract was transferred to 96 well Elisa plates. Absorbance was assayed at 570 nm by Ultra Microplate Reader ELX808 IU (Bio-Tek) and the cell viability was expressed in percent based on the control. Results and Discussion Preparation of the Coated MNPs and Characterization Magnetic nanoparticles were synthesized by chemical coprecipitation and stable magnetic ﬂuid was obtained via coating by DMSA, APTS, and GLU. The morphology and Fig. 2 X-ray powder diffraction of the uncoated MNPs Fig. 4 pH-dependent zeta potential curves of DMSA-MNPs, APTS- MNPs, and GLU-MNPs Fig. 3 FTIR spectra of the uncoated MNPs, DMSA-MNPs, APTS- MNPs, and GLU-MNPs Fig. 5 Magnetization versus applied magnetic ﬁeld for the coated MNPs 123