Ultrafine PEG-capped gadolinia nanoparticles: cytotoxicity and potential biomedical applications for MRI and luminescent imaging

Abstract

Ultrafine PEG-capped gadolinium oxide NPs doped with erbium ions, which could serve as a dual-imaging agent for MRI/optical imaging were synthesized using a simple, green, and quick method.

A simple straightforward thermal decomposition synthesis of PEG-covered Gd 2 O 3 (Gd 2 O 3 @PEG) nanoparticles

“…4. In the IR spec- trum of sample (a), PEG has characteristic vibration bands at 3458 cm À1 corresponding to the ʋ as AOAH stretching band, at 2875, 1342, and 950 cm À1 corresponding to ʋACAH stretching and dACAH bending bands, respectively, and at 1104 cm À1 corresponding to the ʋACAOAC stretching band [12,22,29]. After the thermal decomposition process, three additional vibration bands appeared at around 1542, 1436, and 540 cm À1 .…”

“…The paramagnetic character of these Gd 2 O 3 @PEG nanoparticles is commonly shared by positive contrast agents for magnetic resonance imaging (MRI) [48,49]. The slope of the M-H curve corresponds to a susceptibility, j, of 8.2 Â 10 À5 which is greater than the susceptibility of PEG-coated Gd 2 O 3 :Er 3+ nanoparticles (j = 2.0 Â 10 À5 ) [29]. However, Huang et al [34] who studied magnetic characteristics of hollow Gd 2 O 3 particles, reported that paramagnetism of the particle species turned superparamagnetic in the present of carbon residue.…”

“…In this role PEG serves as a template that both encapsulates the surfaces of the particles and covers the positive ions to prevent aggregation between particles. PEG produces spherical nanoparticles because the particle growth is constrained in all directions resulting in smaller, uniformly shaped, spherical nanoparticles [9,22,28,29]. The molecular weight of PEG required to operate as a non-fouling surface is 500-2000 [30].…”

Fabrication of carbon coated gadolinia particles for dual-mode magnetic resonance and fluorescence imaging

“…Spherical Gd 2 O 3 NPs were fabricated according to the reported protocols [7,10]. First, a sealed beaker with a freshly prepared aqueous solution of gadolinium nitrate (0.001 mol in 40 mL of H 2 O) was placed into an electrical furnace and heated to 90 ℃ for 1.5 h. The dried precipitates were then calcined in air at 800 ℃ for 1 h to produce the gadolinia particles.…”

“…The higher density of magnetic ions is the main advantage of using paramagnetic gadolinium oxide NPs as a "positive" CA [6]. The resulting gadolinia NPs covered with biocompatible polyethylene glycol (PEG) have been used in cell labeling studies [6,7]. In particular, thin PEG layer on the surface of Gd 2 O 3 enhances the steric repulsion between NPs, and prevents protein adhesion that leads no NPs aggregation [8].…”