Design and characterization of lisinopril-loaded superparamagnetic nanoparticles as a new contrast agent for in vitro, in vivo MRI imaging, diagnose the tumors and drug delivery system.

Superparamagnetic γ-Fe2 O3 @SiO2 @lisinopril (MNPs-Lisinopril) nanoparticles are T2 and T2* negative contrast agents for magnetic resonance imaging. In this work, we report the preparation of lisinopril-coated MNPs for the first time as new T2 and T2* negative contrast agent for in vitro and in vivo MRI imaging and demonstrate the potential it simultaneously for drug delivery system, diagnose the tumors and MRI contrast agent. Measurements on the relaxivities (r1 , r2 and r2 *) of the MNPs-Lisinopril were determined in deionized water (in vitro). Furthermore, after subcutaneous injection of the MNPs-Lisinopril into 4T1 (ATCC® CRL2539™) tumor in BALB/c mice, the relaxivities were determined by a 1.5 T MRI apparatus (in vivo). T2- and T2*-weighted MRI images of MNPs-Lisinopril showed that the MR signal intensity decreased significantly with increasing nanoparticle concentration in water. With measured r2 values up to 236.66 mM-1 s -1 , our MNPs-Lisinopril show better performance than commercial alternatives. Also we tested drug release of Lisinopril coated MNPs at two different pHs. The MNPs- Lisinopril is a pH-sensitive drug delivery system and releases different amounts of lisinopril from MNPs-Captopril in different pHs.