Research Institute of Medical & Health Sciences, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates.
Department of Physics, College of Sciences, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates.
Int J Mol Sci. 2022 Nov 26;23(23):14825. doi: 10.3390/ijms232314825.
Magnetically soft-soft MnFeO-FeO core-shell nanoparticles were synthesized through a seed-mediated method using the organometallic decomposition of metal acetyl acetonates. Two sets of core-shell nanoparticles (S1 and S2) of similar core sizes of 5.0 nm and different shell thicknesses (4.1 nm for S1 and 5.7 nm for S2) were obtained by changing the number of nucleating sites. Magnetic measurements were conducted on the nanoparticles at low and room temperatures to study the shell thickness and temperature dependence of the magnetic properties. Interestingly, both core-shell nanoparticles showed similar saturation magnetization, revealing the ineffective role of the shell thickness. In addition, the coercivity in both samples displayed similar temperature dependencies and magnitudes. Signatures of spin glass (SG) like behavior were observed from the field-cooled temperature-dependent magnetization measurements. It was suggested to be due to interface spin freezing. We observed a slight and non-monotonic temperature-dependent exchange bias in both samples with slightly higher values for S2. The effective magnetic anisotropy constant was calculated to be slightly larger in S2 than that in S1. The magnetothermal efficiency of the chitosan-coated nanoparticles was determined by measuring the specific absorption rate (SAR) under an alternating magnetic field (AMF) at 200-350 G field strengths and frequencies (495.25-167.30 kHz). The S2 nanoparticles displayed larger SAR values than the S1 nanoparticles at all field parameters. A maximum SAR value of 356.5 W/g was obtained for S2 at 495.25 kHz and 350 G for the 1 mg/mL nanoparticle concentration of ferrogel. We attributed this behavior to the larger interface SG regions in S2, which mediated the interaction between the core and shell and thus provided indirect exchange coupling between the core and shell phases. The SAR values of the core-shell nanoparticles roughly agreed with the predictions of the linear response theory. The concentration of the nanoparticles was found to affect heat conversion to a great extent. The in vitro treatment of the MDA-MB-231 human breast cancer cell line and HT-29 human colorectal cancer cell was conducted at selected frequencies and field strengths to evaluate the efficiency of the nanoparticles in killing cancer cells. The cellular cytotoxicity was estimated using flow cytometry and an MTT assay at 0 and 24 h after treatment with the AMF. The cells subjected to a 45 min treatment of the AMF (384.50 kHz and 350 G) showed a remarkable decrease in cell viability. The enhanced SAR values of the core-shell nanoparticles compared to the seeds with the most enhancement in S2 is an indication of the potential for tailoring nanoparticle structures and hence their magnetic properties for effective heat generation.
通过使用金属乙酰丙酮盐的有机金属分解，通过种子介导的方法合成了具有软-软 MnFeO-FeO 核壳结构的纳米颗粒。通过改变成核位点的数量，获得了两组具有相似核尺寸（5.0nm）和不同壳厚度（4.1nm 用于 S1 和 5.7nm 用于 S2）的核壳纳米颗粒（S1 和 S2）。在低温和室温下对纳米颗粒进行了磁性测量，以研究壳厚度和磁性能随温度的变化。有趣的是，两种核壳纳米颗粒都表现出相似的饱和磁化强度，表明壳厚度的作用无效。此外，两个样品的矫顽力都表现出相似的温度依赖性和大小。从场冷温度依赖磁化测量中观察到类似自旋玻璃（SG）的行为特征。据推测，这是由于界面自旋冻结。我们观察到两个样品中都存在轻微的非单调的交换偏置温度依赖性，并且 S2 的值略高。在 S2 中计算出的有效磁各向异性能常数略大于 S1。通过在 200-350G 场强和频率（495.25-167.30kHz）下测量交变磁场（AMF）下的比吸收率（SAR），确定了壳聚糖涂覆的纳米颗粒的磁热效率。在所有场参数下，S2 纳米颗粒的 SAR 值均大于 S1 纳米颗粒。对于浓度为 1mg/mL 的 ferrogel，在 495.25kHz 和 350G 下，S2 的最大 SAR 值为 356.5W/g。我们将这种行为归因于 S2 中较大的界面 SG 区域，该区域介导了核心和壳之间的相互作用，从而在核心和壳相之间提供了间接交换耦合。核壳纳米颗粒的 SAR 值与线性响应理论的预测大致相符。纳米颗粒的浓度对热转换有很大的影响。在选定的频率和场强下，对 MDA-MB-231 人乳腺癌细胞系和 HT-29 人结肠直肠癌细胞进行了体外处理，以评估纳米颗粒杀死癌细胞的效率。通过流式细胞术和 MTT 测定法在处理 AMF 后的 0 和 24 小时评估细胞毒性。在用 AMF（384.50kHz 和 350G）处理 45 分钟后，细胞活力明显下降。与种子相比，核壳纳米颗粒的 SAR 值增强，其中 S2 的增强最大，这表明可以调整纳米颗粒的结构，从而调整其磁性能以有效产生热量。
