A precise control of the particle size of dextran-coated magnetite nanoparticles (Dex-M NPs) was successfully performed by combination of co-precipitation and hydrothermal synthesis methods. The Dex-M NPs, in the size range 3.1–18.9 nm, were used to fabricate biocompatible magnetic fluids for application in magnetic hyperthermia therapy (MHT). The effects of the carrier fluid viscosity, particle size, and applied magnetic field strength (H_appl) on the specific loss power (SLP) of the Dex-M NPs were investigated at a fixed magnetic field frequency (f). The experimental results show that SLP of the larger Dex-M NPs significantly decreases for a highly viscous carrier fluid. Moreover, regardless of the carrier fluid viscosity, the particle size strongly affects the heating efficiency of the Dex-M NPs. SLP ranges from zero for the smallest Dex-M NPs (with particle size d = 3.1 nm) to 55.21 W/g for the largest ones (d = 18.9 nm) at H_appl = 28 kA/m and f = 120 kHz. The most important finding in our research is that, at a fixed frequency, the optimal size of the Dex-M NPs (the size that maximizes SLP) shows a rising trend by enhancing H_appl. In fact, the highest values of SLP at H_appl = 11 kA/m, 13 − 17.5 kA/m, and 19 − 28 kA/m are obtained for the Dex-M NPs with d = 11.5 nm, 15 nm, and 18.9 nm, respectively. The shift of optimal size to the higher values by increasing H_appl could shed light on the correlated effects of the particle size and H_appl on the heating efficiency of magnetic nanoparticles (MNPs) and pave a new way toward the better tuning of them for an effective and biologically safe treatment.

通过共沉淀和水热合成方法相结合，成功地精确控制了葡聚糖包被的磁铁矿纳米颗粒（Dex-M NPs）的粒径。Dex-M NP的尺寸范围为3.1-18.9 nm，用于制造生物相容性磁流体，用于磁热疗（MHT）。载液粘度，粒径和施加的磁场强度的影响（H _appl）在固定磁场频率（f）下研究了Dex-M NP的比损耗功率（SLP）。实验结果表明，对于高粘性载液，较大的Dex-M NP的SLP显着降低。此外，无论载液粘度如何，粒径都会严重影响Dex-M NP的加热效率。在H _appl  = 28 kA / m和f = 120 kHz的情况下，最小Dex-M NP（粒径d = 3.1 nm）的SLP范围从零到最大（d = 18.9 nm）的SLP范围为55.21 W / g 。我们研究中最重要的发现是，在固定频率下，Dex-M NP的最佳大小（使SLP最大化的大小）通过增强H _appl而呈上升趋势。实际上，在H _appl时SLP的_最大值 对于d分别为d = 11.5 nm，15 nm和18.9 nm的Dex-M NPs，分别获得了11 kA / m，13-17.5 kA / m和19-28 kA / m。通过增加H _appl将最佳尺寸转变为更高的值，可能会揭示粒径和H _appl对磁性纳米粒子（MNP）加热效率的相关影响，并为更好地调整它们的磁性开辟了一条新途径。有效且生物学上安全的治疗。