Improving Longitudinal Transversal Relaxation Of Gadolinium Chelate Using Silica Coating Magnetite Nanoparticles

Abstract

Kai Xu,1,2 Heng Liu,3 Junfeng Zhang,1,2 Haipeng Tong,1,2 Zhenghuan Zhao,4 Weiguo Zhang1,2 1Department of Radiology, Daping Hospital, Army Medical Center of PLA, Army Medical University, Chongqing 400042, People’s Republic of China; 2Chongqing Clinical Research Center for Imaging and Nuclear Medicine, Chongqing 400042, People’s Republic of China; 3Department of Radiology, PLA Rocket Force Characteristic Medical Center, Beijing 100088, People’s Republic of China; 4Department of Pharmaceutical Engineering, College of Pharmaceutical Sciences, Southwest University, Chongqing 400716, People’s Republic of ChinaCorrespondence: Zhenghuan ZhaoDepartment of Pharmaceutical Engineering, College of Pharmaceutical Sciences, Southwest University, No. 2 Tiansheng Road, Beibei District, Chongqing 400715, People’s Republic of ChinaTel [phone]Fax [phone]Email [email protected] ZhangDepartment of Radiology, Daping Hospital, 10th Changjiang Road, Yuzhong District, Chongqing 400042, People’s Republic of ChinaTel [phone]Fax [phone]Email [email protected] and objective: Precisely and sensitively diagnosing diseases especially early and accurate tumor diagnosis in clinical magnetic resonance (MR) scanner is a highly demanding but challenging task. Gadolinium (Gd) chelate is the most common T1 magnetic resonance imaging (MRI) contrast agent at present. However, traditional Gd-chelates are suffering from low relaxivity, which hampers its application in clinical diagnosis. Currently, the development of nano-sized Gd based T1 contrast agent, such as incorporating gadolinium chelate into nanocarriers, is an attractive and feasible strategy to enhance the T1 contrast capacity of Gd chelate. The objective of this study is to improve the T1 contrast ability of Gd-chelate by synthesizing nanoparticles (NPs) for accurate and early diagnosis in clinical diseases.Methods: Reverse microemulsion method was used to coat iron oxide (IO) with tunable silica shell and form cores of NPs IO@SiO2 at step one, then Gd-chelate was loaded on the surface of silica-coated iron oxide NPs. Finally, Gd-based silica coating magnetite NPs IO@SiO2-DTPA-Gd was developed and tested the ability to detect tumor cells on the cellular and in vivo level.Results: The r1 value of IO@SiO2-DTPA-Gd NPs with the silica shell thickness of 12 nm was about 33.6 mM−1s−1, which was approximately 6 times higher than Gd-DTPA, and based on its high T1 contrast ability, IO@SiO2-DTPA-Gd NPs could effectively detect tumor cells on the cellular and in vivo level.Conclusion: Our findings revealed the improvement of T1 relaxation was not only because of the increase of molecular tumbling time caused by the IO@SiO2 nanocarrier but also the generated magnetic field caused by the IO core. This nanostructure with high T1 contrast ability may open a new approach to construct high-performance T1 contrast agent.Keywords: gadolinium chelate, silica, iron oxide, nanoparticles, T1 relaxivity, tumbling time

Keywords

• gadolinium chelate
• silica
• iron oxide
• nanoparticles
• T1 relaxivity
• tumbling time