Emission from Trions in Carbon Quantum Dots

The photoluminescence (PL) spectra acquired from 1 to 6 nm large carbon quantum dots (CQDs) prepared by refluxing activated carbon in HNO₃ show blue emission independent of the excitation wavelength as well as long-wavelength emission depending on the excitation wavelength. The dependence of the two emissions on pH is investigated, and the experimental results show that the peak position of the long-wavelength emission does not change with pH; however, the blue emission becomes more asymmetrical, and obvious shoulder peaks emerge as the pH increases. A model based on defect-bound trions in the CQDs is proposed to explain the shoulder peaks in the blue emission at high pH, and the calculated results agree well with experimental data concerning the integral intensity ratio of the trion to exciton emissions versus pH. Our experimental and theoretical results demonstrate for the first time emission from trions in CQDs

Trimetallic Nitride Endohedral Fullerenes Carboxyl-Gd₃N@C₈₀: A New Theranostic Agent for Combating Oxidative Stress and Resolving Inflammation

Antioxidative and anti-inflammatory effects of trimetallic nitride endohedral fullerenes carboxyl-Gd₃N@C₈₀, a newly developed magnetic resonance imaging (MRI) contrast agent, were investigated. All hydrochalarone and carboxyl-functionalized fullerenes showed effective radical (hydroxyl and superoxide anion) scavenging, whereas the carboxyl-Gd₃N@C₈₀ more efficiently attenuated lipopolysaccharide (LPS) induced oxidative stress in macrophages. Carboxyl-Gd₃N@C₈₀ also suppressed LPS-elicited mRNA expression of pro-inflammatory inducible nitric oxide synthase and tumor necrosis factor-alpha, and upregulated antioxidative enzyme axis Nrf2 and heme oxygenase-1, possibly via ERK but not AKT signaling pathways. Therefore, carboxyl-Gd₃N@C₈₀ held a great promise in becoming a novel theranostic nanoplatform for simultaneously deliver MRI contrast and therapeutic functions to inflammation-related diseases

Detecting Chronic Post-Traumatic Osteomyelitis of Mouse Tibia via an IL-13Rα2 Targeted Metallofullerene Magnetic Resonance Imaging Probe

Differential diagnosis of chronic post-traumatic osteomyelitis (CPO) from aseptic inflammation remains challenging, since both pathological processes share similar clinical symptoms. Here we utilized a novel targeted metallofullerene nanoparticle based magnetic resonance imaging (MRI) probe IL-13-TAMRA-Gd₃N­@C₈₀­(OH)₃₀­(CH₂CH₂­COOH)₂₀ to detect CPO in mouse tibia via overexpressed IL-13Rα2 receptors. The functionalized metallofullerene was characterized by X-ray photoelectron spectroscopy. Upon lipopolysaccharide (LPS) stimulation, macrophage Raw 264.7 cells showed elevated IL-13Rα2 expression via immunofluorescence staining and increased MRI probe binding via built-in TAMRA fluorescence imaging. Trauma was induced in both tibia of mice and bacteria soaked suture was inserted into the right tibia to initiate infection. During the acute phase (1.5 weeks), luminol-bioluminescence imaging revealed much higher myeloperoxidase activity in the infected tibia compared to the sham. In the chronic phase (4 weeks), X-ray radiography illustrated bone deformation in the infected tibia compared to the sham. With <i>T</i>₁ weighted sequences, the probe clearly exhibited hyperintensity in the infection foci at both acute and chronic phases, which was not observed in the sham tibia. Histological analysis revealed severe bone structural destruction and massive inflammatory cell infiltration in the infected tibia. Immunohistochemistry confirmed abundant expression of IL-13Rα2 in the infection site. In summary, we developed a noninvasive imaging approach to detect and differentiate CPO from aseptic inflammation using a new IL-13Rα2 targeted metallofullerene MRI probe. In addition, for the first time, IL-13Rα2 was investigated as a unique biomarker in the context of osteomyelitis. Our data established a foundation for the translational application of this MRI probe in the clinical differentiation of CPO

A New Interleukin-13 Amino-Coated Gadolinium Metallofullerene Nanoparticle for Targeted MRI Detection of Glioblastoma Tumor Cells

The development of new nanoparticles as next-generation diagnostic and therapeutic (“theranostic”) drug platforms is an active area of both chemistry and cancer research. Although numerous gadolinium (Gd) containing metallofullerenes as diagnostic magnetic resonance imaging (MRI) contrast agents have been reported, the metallofullerene cage surface, in most cases, consists of negatively charged carboxyl or hydroxyl groups that limit attractive forces with the cellular surface. It has been reported that nanoparticles with a positive charge will bind more efficiently to negatively charged phospholipid bilayer cellular surfaces, and will more readily undergo endocytosis. In this paper, we report the preparation of a new functionalized trimetallic nitride template endohedral metallofullerene (TNT EMF), Gd₃N@C₈₀(OH)_<i>x</i>(NH₂)_<i>y</i>, with a cage surface bearing positively charged amino groups (−NH₃⁺) and directly compare it with a similar carboxyl and hydroxyl functionalized derivative. This new nanoparticle was characterized by X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), and infrared spectroscopy. It exhibits excellent ¹H MR relaxivity. Previous studies have clearly demonstrated that the cytokine interleukin-13 (IL-13) effectively targets glioblastoma multiforme (GBM) cells, which are known to overexpress IL-13Rα2. We also report that this amino-coated Gd-nanoplatform, when subsequently conjugated with interleukin-13 peptide IL-13-Gd₃N@C₈₀(OH)_<i>x</i>(NH₂)_<i>y</i>, exhibits enhanced targeting of U-251 GBM cell lines and can be effectively delivered intravenously in an orthotopic GBM mouse model