Speaker
Description
Magnetic resonance imaging (MRI) is a non-invasive diagnostic technique that provides high-resolution images of internal tissues based on nuclear magnetic resonance. It relies on the interaction between hydrogen nuclei and an external magnetic field to generate contrast between different biological structures. Contrast agents are often used in MRI to enhance image quality and improve diagnostic accuracy. Among these agents, iron oxide nanoparticles, specifically magnetite (Fe3O4) and maghemite (γ-Fe2O3), are used to shorten mainly the transverse relaxation time (T₂), significantly enhancing image contrast.
BSA-coated magnetite nanoparticles were synthesized and stabilized with HClO4; subsequently, betulinic acid (BA) was conjugated to the resulting carrier. Physicochemical characterization revealed that the hydrodynamic diameter increased from 34.0 nm for the magnetic fluid (MF) to 52.1 nm after BSA coating (MFBSA), and further increased to 89.9 nm following BA binding (MFBSA-BA). Additionally, the observed decrease in zeta potential from +31.0 mV (MF) to +19.8 mV (MFBSA) confirms the successful coating of the positively charged maghemite core with amphiphilic BSA molecules. The MF sample exhibited the highest longitudinal relaxivity (r1 = 6.49 mM-1s-1) together with high transverse relaxivity (r2 = 389 mM-1s-1). Conjugation with BSA resulted in a substantial decrease in r1 (1.72 mM-1s-1), while r2 remained relatively high (370 mM-1s-1). Further functionalization with betulinic acid (BA) led to a slight additional decrease in both r1 (1.51 mM-1s-1) and r2 (273 mM-1s-1). Overall, surface modification reduced both the longitudinal and transverse relaxivities, while significantly increasing the r2/r1 ratio (60→215→181), indicating predominantly T2-type contrast behavior.
