Nanoscale Res Lett (2009) 4:70–77 the same structure and size distribution. The synthesized MNPs also show a superparamagnetic behavior, as evi- denced by zero coercivity and remanance on the magnetization loops. Cellular Uptake of MNPs The cellular uptake amount is counted based on the Fe2O3 per milligram protein that released from the cells. For the DMSA-MNPs, the cellular uptake of MNPs by SMC increases with increasing concentration from 0.001 to 0.5 mg/mL in DMEM, as shown in Fig. 6a. The uptake also shows the same behavior with increasing of incubation time from 24 to 72 h when the concentration of DMSA- MNPs is 0.1 mg/mL (Fig. 6b). Brieﬂy, the cellular uptake shows a clear dose and incubation time dependent patterns under the experiment conditions. The cellular uptake indicates a function of surface properties of MNPs. From Fig. 6c, there is obvious dif- ference among the three types of MNPs at the same concentration (0.1 mg/mL) for the same incubation time (24 h). The uptake amount of APTS-MNPs, GLU-MNPs, and DMSA-MNPs are 3.72, 4.60, and 8.98 lg per milli- gram protein, respectively. We infer that the different surface properties, such as charges of surface molecules, result in the different afﬁnity with SMC [27, 29–32]. According to the results, it is promising to facilitate or alter uptake of SMC by altering the surface properties of MNPs. Endocytosis of DMSA-MNPs by SMC The thin section TEM images indicate that the DMSA- MNPs are incorporated into SMC after 24 h of incubation at 0.1 mg/mL of concentration. As shown in Fig. 7, the MNPs are clearly visible and distinct from the cellular matter because of their high electron density. The particles or their aggregates are distributed outside, on the surface of Fig. 7 The thin-section TEM images of SMC incubated with 0.1 mg/mL of DMSA-MNPs for 24 h. a Control SMC 9 10 K, b SMC incubated with DMSA- MNPs 9 10 K, and c SMC incubated with DMSA- MNPs 9 35 K. Arrows denote the MNPs or their aggregates 75 Fig. 8 The TNF-a level in the supernate of SMC incubated with DMSA-MNPs. The level is expressed with optical density of ELISA results. a SMC was incubated with DMEM containing the indicated concentration of DMSA-MNPs for 24 h. b SMC was incubated with DMEM containing 0.1 mg/mL DMSA-MNPs for the indicated incubation time 123