Nina Kostevšek

Abstract:

The majority of the iron oxide-based clinically approved contrast agents for magnetic resonance imaging (MRI) have been withdrawn from the market either due to safety concerns or lack of profits.[1] Therefore, there is a need for novel imaging agents with high safety margins and superior MRI properties. Several factors influence the relaxation of water molecules in the vicinity of the magnetic centres, such as NP's magnetization and surface coatings.[2], [3] The latter can affect the relaxation of water molecules in various forms, such as diffusion, retention, hydration, and hydrogen bonding.[3], [4] In the first part, it will be demonstrated how size and clustering influence nanoparticles’ magnetic properties and consequently relaxivity r2 values. In the second part, the focus will be on coating optimization with a description of all the parameters that influence r2 values and thus the performance of NPs as T2 MRI contrast agents. [2], [3] Proper surface coating endows NPs with good colloidal stability and protects them from undesired degradation or aggregation. The effect of different coating material and thickness on the r2 values will be discussed. Moreover, a surface that favors diffusion and retention of water molecules within the second sphere is preferred. Taking all these parameters into account, the case study made on different phospholipids as optimal coating material will be presented. In conclusion, the in vitro MRI measurements revealed that use of magneto liposomes as contrast agents leads to an improvement in the contrast and an easier distinction between the healthy and the cancerous tissues. This proves that the developed liposomes have a high potential to be used as MRI contrast agents, even at very low concentration.

[1] S. M. Dadfar et al., Adv. Drug Deliv. Rev.138 (2019) 302–325.
[2] Y. Lin et al., J. Mater. Chem. B 5702 (2015) 5702–5710.
[3] W. Zhang et al., Theranostics 8 (2018) 2521–2548.
[4] J. Huang et al. Theranostics 2 (2012) 86–102.