Firooz Salehpour Professor Department of Neurosurgery, Tabriz University of Medical Sciences, Tabriz, Iran e-mail: firoozsalehpour@hotmail.com Ainaz Khorramdin Department of Material Sciences and Engineering, Shiraz University of Technology, Shiraz, Iran e-mail: a.khorramdin@sutech.ac.ir Hooman Shokrollahi Assistant Professor Department of Material Sciences and Engineering, Shiraz University of Technology, Shiraz, Iran e-mail: shokrollahi@sutech.ac.ir Arastoo Pezeshki Department of Material Sciences and Engineering, Shiraz University of Technology, Shiraz, Iran e-mail: Draraspz@yahoo.com Farhad Mirzaei Department of Neurosurgery, Tabriz University of Medical Sciences, Tabriz, Iran Nader D. Nader 1 Professor Department of Anesthesiology, University at Buffalo 252 Farber Hall, South Campus, Buffalo, NY 14214 e-mail: nnader@buffalo.edu Synthesis of Zn-Doped Manganese Ferrite Nanoparticles Via Coprecipitation Method for Magnetic Resonance Imaging Contrast Agent Two different preparations of biocompatible magnetic nanoparticles (MNPs), both (MnFe 2 O 4 and Mn0.91Zn0.09Fe 2 O 4 ) coated with methoxy polyethylene glycol aldehyde (m-PEG-CHO) were prepared through coprecipitation method. The prepared powder was reanalyzed for material structure with an X-ray diffractometer (XRD) and for parti- cle size using a transition electron microscope (TEM). Magnetic saturation (MS) and coercivity (HC) of the formed particles were examined by a vibrating sample magnetome- ter (VSM). Surface structure of the samples was characterized by Fourier transform infrared spectroscopy (FTIR). Biocompatible ferrofluids were intravenously injected into four rabbits. Then the magnetic resonance (MR) images of brain were obtained by mag- netic resonance imaging (MRI) experiments before and after intravenous injection of fer- rofluids. The MNPs demonstrate super paramagnetic behavior with a spinel structure measuring 30–40 nm in size. Doping of these magnetite nanoparticles with zinc resulted in decreases in crystallite size from 24.23 nm to 21.15 nm, the lattice parameter from 8.45 A ˚ to 8.43 A ˚ and the coercivity from 41.20 Oe to 13.07 Oe. On the other hand, satura- tion magnetization increased from 50.12 emu/g to 57.36 emu/g following zinc doping. Image exposure analysis revealed that the reduction of MR signal intensity for zinc- doped magnetite nanoparticles was more than nondoped nanoparticles (shorter T 2 relaxation time) thereby making the images darker. [DOI: 10.1115/1.4029855] Introduction Mn–Zn ferrites MNPs have been formally described in 1947 and gained more interest over the past few years for their use in magnetic data storage technology as well as their biomedical utili- zation [1,2]. Early investigators predicted a bright future for Mn–Zn in electronic industry because of their superior electrical and magnetic properties [3]. Mn–Zn ferrites belong to a class of soft magnetic materials with a great ability for magnetic penetra- tion. Main characteristics of these nanoparticles are their high electrical resistance and saturation magnetization [4,5]. Saturation magnetization of these ferrite particles increases by addition of zinc (doping) to the ferrite nucleus [6]. MNPs are widely used in the field of electronics and electrics such as deflection yoke rings, computer memory chips, magnetic recording heads, microwave devices, transducers, and transformers [7–10]. Apart from these applications, nanosized Mn–Zn ferrites have potential usage in ferrofluid technology, enzyme and protein immobilization, and magnetically guided drug delivery [11–13]. Gadolinium is commonly used in its ionized form as a commer- cially available contrast medium. This is a heavy metal and easily filtered by the kidneys due to its smaller size. Free gadolinium ions toxicity in both human and different animal models is medi- ated through interfering with calcium-ion channels. Nephrogenic systemic fibrosis has been reported following clinical uses of gad- olinium ions for MRI [14]. Additionally, gadolinium image enhancement is mainly useful for T 1 phase of MRI. Since brain tissue enhancement is more prominent during T 2 phase, therefore synthesis of a magnetic particle with this property is advanta- geous. Additionally, polyglycation and coating these particles will theoretically decrease the ability of the particle to freely pass into the nephron and therefore may reduce their nephrotoxicity. Superparamagnetic characteristics of Mn–Zn ferrite nanopar- ticles are responsible for proton relaxation in tissues and therefore make these particles suitable for MRI contrast enhancement [15]. These nanoparticles induce large magnetic moments altering the magnetic field in a tissue over time and space, thus creating a large magnetic heterogeneity through which water molecules 1 Corresponding author. Manuscript received August 1, 2014; final manuscript received February 13, 2015; published online March 11, 2015. Assoc. Editor: Roger Narayan. Journal of Nanotechnology in Engineering and Medicine NOVEMBER 2014, Vol. 5 / 041002-1 Copyright V C 2014 by ASME Downloaded From: http://nanoengineeringmedical.asmedigitalcollection.asme.org/ on 03/11/2015 Terms of Use: http://asme.org/terms