Nitrogen‐Doped Carbon Quantum Dot Stabilized Magnetic Iron Oxide Nanoprobe for Fluorescence, Magnetic Resonance, and Computed Tomography Triple‐Modal In Vivo Bioimaging

Abstract

Multimodal imaging, which combines complementary information of two or more imaging modalities, offers huge advantages. In this paper, the synthesis, characterization, and application of superparamagnetic nitrogen-doped carbon-iron oxide hybrid quantum dots (C-Fe 3 O 4 QDs) is reported for triple-modal bioimaging through fluorescence/magnetic resonance/computed tomography (FL/MR/CT). Especially, C-Fe 3 O 4 QDs are synthesized by using poly (γ-glutamic acid) as a precursor and stabilizer via a green and facile one-pot hydrothermal approach. The as-prepared C-Fe 3 O 4 QDs exhibit excellent water dispersibility, wavelength-tunable FL property with high quantum yield of about 21.6%, good photostability, strong superparamagnetic property as well as favorable biocompatibility. Meanwhile, these C-Fe 3 O 4 QDs also show a transverse relaxivity value (r 2 ) of 154.10 mm −1 s −1 for T 2 -weighted MR imaging mode and an observable X-ray attenuation effect for CT imaging mode. Moreover, the in vivo bioimaging of tumor-bearing nude mice by combining FL, MR, and CT images further demonstrates that the as-prepared C-Fe 3 O 4 QDs can be readily and efficiently used in FL/MR/CT triple-modal tumor imaging. Hence, the new and facile one-pot synthesis strategy for preparing multifunctional C-Fe 3 O 4 QDs nanoprobes provides a convenient way for achieving an effective and versatile agent for tumorous bioimaging/or diagnostics.

Carbon Dots as a New Class of Diamagnetic Chemical Exchange Saturation Transfer (diaCEST) MRI Contrast Agents

“…Apost-synthetic surface modification would be av iable option, which is currently under investigation. Compared to the previously reported C-dot/ metal-hybrid nanoparticles, [13,14] our first generation AC-dots have ar elatively low CEST detectability,a ttributed to the inherently inferior sensitivity of CEST MRI (mm range) than those of T 1 or T 2 /T 2 *methods (mm range) and low doping rate of arginine per each particle.W ewill improve the sensitivity of C-dots in future studies by modification with more sensitive CEST probes (those with highly shifted chemical shifts and faster exchange rates) and optimizing the incorporation rates. Secondly,t he in vivo pharmacokinetic properties,b iodistribution, and toxicity of these CEST C-dots need to be investigated thoroughly in animal models,a nd the injection dose needs to be optimized accordingly.Thirdly,although this study was feasible at our preclinical MRI scanner operating at high magnetic field (11.7 T), it will be important to evaluate the CEST and relaxation properties of these C-dots on 3.0 T clinical scanners.F inally,itisstill achallenge to reproducibly perform large-scale synthesis of C-dots in terms of particle size,b ecause even tiny atomic variation could cause significantly distinct clearance pathways of nanoparticles.…”

“…C-dots are considered to be more biocompatible than the more widely used heavy metal-based quantum dots, [3] with both displaying favorable distinctive properties pertaining to electrochemiluminescence, [4] optoelectronics, [5] catalysis, [6] and size-dependent fluorescence behavior. [14] Doping with paramagnetic metals,h owever,r aises toxicity concerns, [15] while the C-dots/iron oxide hybrid produces an unfavorable negative contrast. However, noninvasive in vivo fluorescence imaging using C-dots or quantum dots is hampered by the limited light penetration depth (approximately 1-2 cm) even in the near-infrared spectrum.…”

“…However, noninvasive in vivo fluorescence imaging using C-dots or quantum dots is hampered by the limited light penetration depth (approximately 1-2 cm) even in the near-infrared spectrum. [14] Doping with paramagnetic metals,h owever,r aises toxicity concerns, [15] while the C-dots/iron oxide hybrid produces an unfavorable negative contrast. [14] Doping with paramagnetic metals,h owever,r aises toxicity concerns, [15] while the C-dots/iron oxide hybrid produces an unfavorable negative contrast.…”

“…[12] Unlike fluorescence imaging,magnetic resonance imaging (MRI) is able to acquire images of deeply seated organs.T wo strategies have been pursued to adapt carbon dots for MRI contrast enhancement:1 )toi ncorporate Gd III or Mn II in Cdots for T 1 contrast enhancing, [13] and 2) to hybridize with iron oxide nanoparticles for T 2 /T 2 *c ontrast enhancing. [14] Doping with paramagnetic metals,h owever,r aises toxicity concerns, [15] while the C-dots/iron oxide hybrid produces an unfavorable negative contrast. Herein we propose to take advantage of the natural chemical exchange saturation transfer (CEST) MRI contrast properties of metal-free C-dots to generate contrast without the need for (super)paramagnetic labels.…”

Fabrication of fullerene decorated by iron compound and its effect on the thermal stability and flammability for high‐density polyethylene

“…In C1s spectrum of C 60 , four different chemical shifts appeared, which can be signed as graphitic sp2 CC/CC at 284.4 eV, ether groups (CO) at 286.2 eV, carbonyl groups (CO) at 287.6 eV, and carboxyl groups (OCO) at 288.6 eV, respectively. It is noted that, a new peak at 283.3 eV arises in C1s spectrum of C 60 ‐Fe, which is considered to be the characteristic peak of C‐Fe, showing the direct attachment of Fe to carbon framework. Also, the interaction between Fe compounds and C 60 makes the peak of CC/CC and CO greatly shifted to lower binding energy.…”