Measurement of the magnetite nanoparticles' relaxivity during encapsulation into polylactide carriers

Polylactide (PLA)-based carriers are currently widely employed in biomedical applications, where imaging modalities are in high demand; however, information regarding the contrast properties of the PLA-based magnetic carriers in MRI applications is lacking. Therefore, we measured the MRI parameters of the magnetite nanoparticles with different encapsulation rates in PLA spheres. The MRI measurements were performed at the 4.7 T and 0.178 T systems, where the relative contrast, transversal relaxation time (T2), and transversal relaxivity (r2) were evaluated and compared. The results reveal that these parameters can be used in order to determine the magnetic nanoparticles' encapsulation into PLA carriers, as well as in the quantification of the particles' loading rate. Such an approach can be utilised in biomedical applications to determine the rate of drugs' encapsulation into the PLA carrier system, for example, as well as for drug release tracking from the carriers.