A study on the Concentration‐dependent Relaxometric Transition in Manganese Oxide Nanocolloid as MRI Contrast Agent

Abstract

A green precipitation method has been used for the synthesis of ultra-small APTMS-mPEG conjugated Mn 3 O 4 nanoparticles. Spherical cores in the uniform size of 4 � 1 nm were characterized by HRTEM. Zeta potential of À 45 mV and the invariant turbidimetry results during the time, confirmed super-stability of the colloids. MRI relaxometry by 1.5 T scanner represented two values of r 1 = 8.23 s À 1 mM À 1 and r 1 = 7.3 s À 1 mM À 1 for diluted and concentrated samples. The r 2 /r 1 ratio was also decreased from 11.86 to 6.9 by dilution of colloids. Particle aggregation and motional narrowing phenomena led to a dual T 1 /T 2 contrast agent in the Mn ion concentrations of more than 0.2 mM. The optimum concentration of Mn ion for maximum dual signal intensity was estimated about 0.4 mM which is two times less than commercial Gd-DTPA. Cytotoxicity was examined through MTT assay and respectively, showed high cell viability at 48 h incubation. Overall, a potential dual T 1 /T 2 contrast agent was developed for early-stage detection.

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