RESUMO
The use of graphene quantum dots as biomedical device and drug delivery system has been increasing. This nanoplatform of pure carbon has showed unique properties and showed to be safe for human use. The imatinib is a molecule designed to specifically inhibit the tyrosine kinase, used for leukemia treatment. In this study, we successfully decorated the graphene quantum dots (GQDs@imatinb) by a carbodiimide crosslinking reaction. The GQDs@imatinb were characterized by FTIR and AFM. The nanoparticles' in vitro behaviors were evaluated by cellular trafficking (internalization) assay and cell viability and apoptosis assays in various cancer cell lines, including suspension (leukemia) cells and adherent cancer cells. The results showed that the incorporation of the imatinib on the surface of the graphene quantum dots did not change the nanoparticles' morphology and properties. The GQDs@imatinb could be efficiently internalized and kill cancer cells via the induction of apoptosis. The data indicated that the prepared GQDs@imatinb might be a great drug nano-platform for cancer, particularly leukemia treatments.
RESUMO
Mechanical loading represents a crucial factor in the regulation of skeletal homeostasis. Its reduction causes loss of bone mass, eventually leading to osteoporosis. In a previous global transcriptome analysis performed in mouse calvarial osteoblasts subjected to simulated microgravity, the most upregulated gene compared to unit gravity condition was Lcn2, encoding the adipokine Lipocalin 2 (LCN2), whose function in bone metabolism is poorly known. To investigate the mechanoresponding properties of LCN2, we evaluated LCN2 levels in sera of healthy volunteers subjected to bed rest, and found a significant time-dependent increase of this adipokine compared to time 0. We then evaluated the in vivo LCN2 regulation in mice subjected to experimentally-induced mechanical unloading by (1) tail suspension, (2) muscle paralysis by botulin toxin A (Botox), or (3) genetically-induced muscular dystrophy (MDX mice), and observed that Lcn2 expression was upregulated in the long bones of all of them, whereas physical exercise counteracted this increase. Mechanistically, in primary osteoblasts transfected with LCN2-expression-vector (OBs-Lcn2) we observed that Runx2 and its downstream genes, Osterix and Alp, were transcriptionally downregulated, and alkaline phosphatase (ALP) activity was less prominent versus empty-vector transduced osteoblasts (OBs-empty). OBs-Lcn2 also exhibited an increase of the Rankl/Opg ratio and IL-6 mRNA, suggesting that LCN2 could link poor differentiation of osteoblasts to enhanced osteoclast stimulation. In fact, incubation of purified mouse bone marrow mononuclear cells with conditioned media from OBs-Lcn2 cultures, or their coculture with OBs-Lcn2, improved osteoclastogenesis compared to OBs-empty, whereas treatment with recombinant LCN2 had no effect. In conclusion, our data indicate that LCN2 is a novel osteoblast mechanoresponding gene and that its regulation could be central to the pathological response of the bone tissue to low mechanical forces.