Magnetic Nanobeads as Potential Contrast Agents for Magnetic Resonance Imaging

Abstract

Metal-oxo clusters have been used as building blocks to form hybrid nanomaterials and evaluated as potential MRI contrast agents. We have synthesized a biocompatible copolymer based on a water stable, nontoxic, mixed-metal-oxo cluster, Mn8Fe4O12(L)16(H2O)4, where L is acetate or vinyl benzoic acid, and styrene. The cluster alone was screened by NMR for relaxivity and was found to be a promising T2 contrast agent, with r1 = 2.3 mM(-1) s(-1) and r2 = 29.5 mM(-1) s(-1). Initial cell studies on two human prostate cancer cell lines, DU-145 and LNCap, reveal that the cluster has low cytotoxicity and may be potentially used in vivo. The metal-oxo cluster Mn8Fe4(VBA)16 (VBA = vinyl benzoic acid) can be copolymerized with styrene under miniemulsion conditions. Miniemulsion allows for the formation of nanometer-sized paramagnetic beads (~80 nm diameter), which were also evaluated as a contrast agent for MRI. These highly monodispersed, hybrid nanoparticles have enhanced properties, with the option for surface functionalization, making them a promising tool for biomedicine. Interestingly, both relaxivity measurements and MRI studies show that embedding the Mn8Fe4 core within a polymer matrix decreases r2 effects with little effect on r1, resulting in a positive T1 contrast enhancement.

Structural and magnetic properties of Mn 12 -Stearate nanomagnets

“…Below their blocking temperature, SMMs exhibit magnetization hysteresis, quantum tunnelling of magnetization and quantum phase interference paving the way for realization of quantum computing and new avenues in molecular spintronics [6e10]. SMMs have been considered as potential candidates for high density storage devices, quantum computing, magnetic refrigeration [3,4] and also have promising future in the field of biomedical applications [11,12].…”

Magnetic nanoformulations for prostate cancer

“…In a single step, magnetic nanoparticles decorated by albumin, which is cross-linked using glutaraldehyde, were suitable for providing a uniform nanoparticle system for prostate cancer [24,30]. Similarly, liposome [15,31,32], hybrid [33], and dual/multilayer can serve as layers for stable nanoformulations. Stimuli responsive polymer coating on magnetic nanoparticles can also induce controlled drug release characteristics [34,35].…”

Hybrid Materials Based on the Embedding of Organically Modified Transition Metal Oxoclusters or Polyoxometalates into Polymers for Functional Applications: A Review

“…In particular, either a manganese-oxo or manganese-iron-oxo cluster Mn 12 O 12 (VBA) 16 (H 2 O) 4 and Mn 8 Fe 4 O 12 (VBA) 16 (H 2 O) 4 (where VBA = 4-vinylbenzoate), were prepared and characterized. Polymerization of the functionalized metal oxoclusters with styrene, under miniemulsion conditions [200,201], produced monodispersed polymer nanoparticles endowed with magnetic properties for potential magnetic imaging applications [202,203]. …”