Synthesis, characterization, in vitro phantom imaging, and cytotoxicity of a novel graphene-based multimodal magnetic resonance imaging-X-ray computed tomography contrast agent

Abstract

Graphene nanoplatelets (GNPs), synthesized using potassium permanganate-based oxidation and exfoliation followed by reduction with hydroiodic acid (rGNP-HI), have intercalated manganese ions within the graphene sheets, and upon functionalization with iodine, show excellent potential as biomodal contrast agents for magnetic resonance imaging (MRI) and computed tomography (CT). Structural characterization of rGNP-HI nanoparticles with low- and high-resolution transmission electron microscope (TEM) showed disc-shaped nanoparticles (average diameter, 200 nm, average thickness, 3 nm). Energy dispersive X-ray spectroscopy (EDX) analysis confirmed the presence of intercalated manganese. Raman spectroscopy and X-ray diffraction (XRD) analysis of rGNP-HI confirmed the reduction of oxidized GNPs (O-GNPs), absence of molecular and physically adsorbed iodine, and the functionalization of graphene with iodine as polyiodide complexes (I3− and I5−). Manganese and iodine content were quantified as 5.1 ± 0.5 and 10.54 ± 0.87 wt% by inductively-coupled plasma optical emission spectroscopy and ion-selective electrode measurements, respectively. In vitro cytotoxicity analysis, using absorbance (LDH assay) and fluorescence (calcein AM) based assays, performed on NIH3T3 mouse fibroblasts and A498 human kidney epithelial cells, showed CD50 values of rGNP-HI between 179-301 µg/ml, depending on the cell line and the cytotoxicity assay. CT and MRI phantom imaging of rGNP-HI showed high CT (approximately 3200% greater than HI at equimolar iodine concentration) and MRI (approximately 59% greater than equimolar Mn2+ solution) contrast. These results open avenues for further in vivo safety and efficacy studies towards the development of carbon nanostructure-based multimodal MRI-CT contrast agents.

Porous three-dimensional carbon nanotube scaffolds for tissue engineering

“…Conversely, LDH assay measures the amount of cytosolic enzyme lactate dehydrogenase released in the media by apoptotic and necrotic cells therefore no interference is observed. We had previously validated the suitability of LDH assay of cytotoxicity studies involving carbon nanoparticles including nanotubes [14, 19, 58]. No significant difference in the total LDH release was observed between PLGA, MWCNT and SWCNT scaffold groups at days 3 and 5, suggesting a good cytocompatibility of MWCNT and SWCNT scaffolds, comparable to the FDA approved PLGA.…”

“…Porous PLGA scaffolds were used as live controls. LDH assay is a widely recommended method to analyze the cytotoxicity of carbon nanomaterials [14, 19, 57, 58]. It is well known that several cytotoxicity assays (such as MTT, XTT) produce erroneous results due to strong binding of formazan crystals on the nanotube surface [57].…”

“…Carbon nanomaterials such as fullerenes, carbon nanotubes and graphene exhibit excellent physiochemical properties such as high mechanical strength, and electrical conductivity as well as unique electromagnetic, opto-acoustic response, and thus, their multifunctional characteristics have been exploited for several biomedical applications such as bioimaging[14–16], stem cell applications[17, 18], drug and gene delivery[19, 20], and photodynamic therapy [21, 22]. They have also been incorporated into polymeric scaffolds as mechanical reinforcing agents [23, 24] or contrast agents [25] to improve non-invasive imaging of the structural properties and biological response of polymeric scaffolds (e.g.…”

Dose ranging, expanded acute toxicity and safety pharmacology studies for intravenously administered functionalized graphene nanoparticle formulations

“…Recently, graphene nanoparticles, (also known as graphene nanoplatelets (GNPs) or simply graphene oxide (GO), (herein referred as GNPs)) show promise in vitro and in vivo for drug/gene delivery and biological sensing/imaging applications due to their nanoscopic size, large specific surface area, and physicochemical properties [4–10]. For instance, GNPs could be loaded with aromatic drugs via Van der Waals (pi-pi stacking) interactions [5], or non-covalently complexed with cationic polymers such as polyethyleneimine via weak electrostatic interactions to facilitate plasmid DNA (pDNA) and small interfering RNA (siRNA) delivery [7].…”

“…GNPs could also be intercalated or covalently functionalized with important elements (e.g. manganese, iodine) in medicine to develop highly efficacious contrast agents for magnetic resonance imaging (MRI) [8, 9], computed tomography (CT) [10], and their intrinsic electromagnetic properties could be harnessed towards the development of probes for fluorescence [4], photoacoustic and thermoacoustic imaging [11]. There is now a wide body of research documenting the toxicology and pharmacology of fullerenes, metallofullerenes and carbon nanotubes (CNTs) [1–3, 12].…”