Tang Shao Qiang, Moon Seung Je, Park Ki Ho, Paek Sun Ha, Chung Kyung-Won, Bae Seongtae
Biomagnetics Laboratory (BML), Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore.
J Nanosci Nanotechnol. 2011 Jan;11(1):82-9. doi: 10.1166/jnn.2011.3043.
Magnetic properties of 200 nm ferrimagnetic CoFe2O4 nanoparticles before and after coating with TEOS were explored and compared to soft ferrimagnetic MgFe2O4 nanoparticles (200 nm) to evaluate the feasibility as an in-vitro GMR SV (giant magnetoresistance spin-valve) biosensor agent for single molecular detection (SMD). It was found that the magnetic degradation (or variation) of TEOS coated CoFe2O4 and MgFe2O4 nanoparticles are dominantly affected by the chemical dispersion process, which is carried out in the oleic acid (OA), oleylamine (OL), or OA+OL surfactant, before starting major coating process. In addition, the TEOS coating thickness controlled by TEOS concentration and pH level in the buffer solution prominently influenced on the magnetic degradation of TEOS coated nanoparticles. According to the experimental analysis results, the magnetic degradation of TEOS coated nanoparticles is mainly attributed to the variation of particle dipole interaction caused by the degree of particle aggregation depending on TEOS coating process conditions. The TEOS coated CoFe2O4 nanoparticles exhibited a higher magnetic stability for a GMR biosensor agent, e.g., small variation of remnant magnetization, saturation magnetization and magnetic coercivity, than that of MgFe2O4 nanoparticles at the different coating process conditions. The physical and chemical analysis confirmed that this is primarily due to its higher magnetic anisotropy. The experimentally verified high biocompatibility as well as the stably maintained magnetic properties of TEOS coated CoFe2O4 nanoparticles demonstrate that CoFe2O4 nanoparticles can be considered as one of the promising ferrimagnetic nanoparticle sensor agent for an SMD GMR SV biosensor.
研究并比较了200纳米亚铁磁性CoFe2O4纳米颗粒在涂覆TEOS前后的磁性，并与软亚铁磁性MgFe2O4纳米颗粒（200纳米）进行比较，以评估其作为用于单分子检测（SMD）的体外巨磁电阻自旋阀（GMR SV）生物传感器试剂的可行性。研究发现，TEOS包覆的CoFe2O4和MgFe2O4纳米颗粒的磁降解（或变化）主要受化学分散过程的影响，该过程在开始主要包覆过程之前，在油酸（OA）、油胺（OL）或OA + OL表面活性剂中进行。此外，缓冲溶液中由TEOS浓度和pH值控制的TEOS包覆厚度对TEOS包覆纳米颗粒的磁降解有显著影响。根据实验分析结果，TEOS包覆纳米颗粒的磁降解主要归因于取决于TEOS包覆工艺条件的颗粒聚集程度所引起的颗粒偶极相互作用的变化。在不同的包覆工艺条件下，TEOS包覆的CoFe2O4纳米颗粒作为GMR生物传感器试剂表现出更高的磁稳定性，例如剩余磁化强度、饱和磁化强度和矫顽力的变化较小。物理和化学分析证实，这主要是由于其较高的磁各向异性。TEOS包覆的CoFe2O4纳米颗粒经实验验证具有高生物相容性以及稳定保持的磁性，这表明CoFe2O4纳米颗粒可被视为用于SMD GMR SV生物传感器的有前景的亚铁磁性纳米颗粒传感器试剂之一。
