Fengyi Du

Economical and green synthesis of bagasse- derived fluorescent carbon dots for biomedical applications

Carbon quantum dots (CDs) are promising nanomaterials in biomedical, photocatalytical and photoelectronic applications. However, determining how to explore an ideal precursor for a renewable carbon resource is still an interesting challenge. Here, for the first time, we report that renewable wastes of bagasse as a new precursor were prepared for fluorescent CDs by a hydrothermal carbonization (HTC) process. The characterization results show that such bagasse-derived CDs are monodispersed, contain quasi spherical particles with a diameter of about 1.8 nm and exhibit favorable photoluminescence properties, super-high photostability and good dispersibility in water. Most importantly, bagasse-derived CDs have good biocompatibility and can be easily and quickly internalized by living cancer cells; they can also be used for multicolour biolabeling and bioimaging in cancer cells. It is suggested that bagasse-derived CDs might have potential applications in biomedical and photoelectronic fields.

Nitrogen-doped carbon dots with heterogeneous multi-layered structures

Photoluminescent carbon dots (CDs) with graphite-like phase structure have been widely reported. Herein, we first report nitrogen-doped carbon dots (NCDs) with heterogeneous multi-layered structures by bottom-up hydrothermal carbonization process. The formation and surface passivation of NCDs was accomplished simultaneously. The as-prepared NCDs possess stable photoluminescence, solubility in water and various functional groups on their surface. XRD results clearly showed that there were two kinds of interlayer lattice spaces in the phase structure of prepared NCDs, which corresponded to the {002} plane of graphite and the {001} plane of graphite oxide. We further demonstrated that NCDs with good biocompatibility were easily and quickly internalized by cancer cells and are particularly suitable for multicolour real-time cellular imaging.

Engineering iodine-doped carbon dots as dual-modal probes for fluorescence and X-ray CT imaging

X-ray computed tomography (CT) is the most commonly used imaging technique for noninvasive diagnosis of disease. In order to improve tissue specificity and prevent adverse effects, we report the design and synthesis of iodine-doped carbon dots (I-doped CDs) as efficient CT contrast agents and fluorescence probe by a facile bottom-up hydrothermal carbonization process. The as-prepared I-doped CDs are monodispersed spherical nanoparticles (a diameter of ~2.7 nm) with favorable dispersibility and colloidal stability in water. The aqueous solution of I-doped CDs showed wavelength-dependent excitation and stable photoluminescence similar to traditional carbon quantum dots. Importantly, I-doped CDs displayed superior X-ray attenuation properties in vitro and excellent biocompatibility. After intravenous injection, I-doped CDs were distributed throughout the body and excreted by renal clearance. These findings validated that I-doped CDs with high X-ray attenuation potency and favorable photoluminescence show great promise for biomedical research and disease diagnosis.

Fabrication of HA/PEI-functionalized carbon dots for tumor targeting, intracellular imaging and gene delivery

Carbon quantum dots (CDs) as emerging carbon nano-materials have attracted tremendous attention in biomedical fields due to unique properties. In this study, hyaluronate (HA) and polyethylenimine (PEI) functionalized carbon dots (HP-CDs) were synthesized by a facile bottom-up method for tumor targeting and gene delivery. After HA modification, the HP-CDs exhibited superior dispersibility in water and good biocompatibility and were internalized readily into the cytoplasm of cancer via HA-receptor mediated endocytosis. Meanwhile, the HP-CDs with PEI functionalization were shown to have excellent gene condensation capability via electrostatic attraction and protective capacity by preventing nuclease degradation. By virtue of good photoluminescence properties, the HP-CDs as a gene carrier were successfully applied to intracellular imaging and gene delivery. Taken together, the resultant HP-CDs displayed great potential in tumor targeting, intracellular imaging and gene delivery.

Egr-1 promotes hypoxia-induced autophagy to enhance chemo-resistance of hepatocellular carcinoma cells.

Previous studies suggest that early growth response gene-1 (Egr-1) plays an important role in hypoxia-induced drug-resistance. However, the mechanism still remains to be clarified. Herein, we investigated the role of Egr-1 in hypoxia-induced autophagy and its resulted hypoxia-driven chemo-resistance in Hepatocellular Carcinoma (HCC) cells. Our data demonstrated that Egr-1 was overexpressed in HCC tissues and cells and conferred them drug resistance under hypoxia. Mechanistically, Egr-1 transcriptionally regulated hypoxia-induced autophagy by binding to LC3 promoter in HCC cells, which resulted in resistance of HCC cells to chemotherapeutic agents; while dominant negative Egr-1 could inhibit autophagy level, and thus enhanced the sensitivity of HCC cells to chemotherapeutic agents, indicating that hypoxia-induced Egr-1 expression enhanced drug resistance of HCC cells likely through autophagy. Accordingly, it is suggested that a mechanism of hypoxia/Egr-1/autophagy axis might be involved in drug resistance in HCC.

FoxM1-mediated RFC5 expression promotes temozolomide resistance

Although methylguanine-DNA-methyltransferase (MGMT) plays an important role in resistance to temozolomide (TMZ) in glioma, 40% of gliomas with MGMT inactivation are still resistant to TMZ. The underlying mechanism is not clear. Here, we report that forkhead box M1 (FoxM1) transcriptionally activates the expression of DNA repair gene replication factor C5 (RFC5) to promote TMZ resistance in glioma cells independent of MGMT activation. We showed that RFC5 expression is positively correlated with FoxM1 expression in human glioma cells and FoxM1 is able to transcriptionally activate RFC expression by interaction with the RFC5 promoter. Furthermore, knockdown of FoxM1 or RFC5 partially re-sensitizes glioma cells to TMZ. Consistently, thiostrepton, a FoxM1 inhibitor, in combination with TMZ significantly inhibits proliferation and promotes apoptosis in glioma cells. Taken together, these findings suggest that the FoxM1-RFC5 axis may mediate TMZ resistance and thiostrepton may serve as a potential therapeutic agent against TMZ resistance in glioma cells.

MeCP2 suppresses LIN28A expression via binding to its methylated-CpG islands in pancreatic cancer cells

LIN28A aberrant expression contributes to the development of human malignancies. However, the LIN28A expression profile remains to be clarified. Herein, we report that LIN28A expression is directly associated with the methylation status of its two CpG island sites in pancreatic cancer cells. First, Bisulfite sequencing reveals that PANC1 cells possess the higher methylation rate at LIN28A CpG islands compared with SW1990 and PaTu8988 cells. Subsequently, LIN28A expression is increased at both mRNA and protein levels in pancreatic cancer cells treated with 5-Aza-2′-deoxycytidine (5-Aza-CdR), a DNA methyltransferase inhibitor. Further Chromatin immunoprecipitation (ChIP) assays indicate that methyl-CpG-binding protein 2 (MeCP2) binds preferentially to the two hypermethylated CpG islands sites at LIN28A promoter compare to MBD3. Expectedly, MeCP2 knockdown transcriptionally activates LIN28A expression in above cells, rather than MBD3 knockdown. Moreover, LIN28A overexpression remarkably improves OCT4, NANOG and SOX2 expression, and the ability of sphere and colony formation, and enhances the capacities of invasion in PaTu8988 and SW1990 cells, whereas LIN28A knockdown significantly inhibits the above malignant behaviors in PANC1 cells. These findings suggest that LIN28A is epigenetically regulated via MeCP2 binding to methylated-CpG islands, and may play a crucial role in pancreatic cancer progression.

Knockdown of autophagy-related gene LC3 enhances the sensitivity of HepG2 cells to epirubicin

Hepatocellular carcinoma (HCC) is a major public health problem. Despite new chemotherapeutic treatments, drug resistance remains a major clinical obstacle to successful treatment in HCC patients. Therefore, novel therapeutic targets and new modalities of treatment are urgently required. In this study, tetracycline-inducible lentivirus-mediated RNA interference (RNAi) was employed to knock down microtubule-associated protein 1 light chain 3 (LC3) gene, which encodes a key protein in the induction of autophagy, to study the protective function of autophagy in liver cancer tolerant to epirubicin. The effect of combined treatment with lentiviral shLC3 and epirubicin on cell growth and chemosensitivity to epirubicin in the HCC cell line HepG2 were also investigated. The results demonstrated that lentivirus-mediated LC3 silencing significantly inhibited cell proliferation. In addition, combined treatment with lentiviral shLC3 and epirubicin significantly decreased the survival rate of HepG2 cells, compared with that following treatment with either agent alone. Overall, the results from this study suggest for the first time, to the best of our knowledge, that LC3 plays a key role in HCC tumorigenesis, and is a novel therapeutic target for HCC.

Hyaluronic acid-functionalized bismuth oxide nanoparticles for computed tomography imaging-guided radiotherapy of tumor

The inherent radioresistance and inaccuracy of localization of tumors weaken the clinical implementation effectiveness of radiotherapy. To overcome these limitations, hyaluronic acid-functionalized bismuth oxide nanoparticles (HA-Bi2O3 NPs) were synthesized by one-pot hydrothermal method for target-specific computed tomography (CT) imaging and radiosensitization of tumor. After functionalization with hyaluronic acid, the Bi2O3 NPs possessed favorable solubility in water and excellent biocompatibility and were uptaken specifically by cancer cells overexpressing CD44 receptors. The as-prepared HA-Bi2O3 NPs exhibited high X-ray attenuation efficiency and ideal radiosensitivity via synergizing X-rays to induce cell apoptosis and arrest the cell cycle in a dose-dependent manner in vitro. Remarkably, these properties offered excellent performance in active-targeting CT imaging and enhancement of radiosensitivity for inhibition of tumor growth. These findings demonstrated that HA-Bi2O3 NPs as theranostic agents exhibit great promise for CT imaging-guided radiotherapy in diagnosis and treatment of tumors.

Hyaluronic acid functionalized nitrogen-doped carbon quantum dots for targeted specific bioimaging

Carbon quantum dots (CQDs), a new inorganic quasi-zero dimensional carbon nanomaterial, are extensively applied in biomedical fields. However, the lack of specific cell targeting ligands on the surface has consistently been a critical problem to be overcome in application of CQD technology. In this study, hyaluronic acid-functionalized CQDs (HA-CQDs) were synthesized via hydrothermal carbonization for tumor-targeted bioimaging. The synthesized HA-CQDs possessed highly hydrophilic surfaces, uniform size distribution (approximately 2.3 nm) and heterogeneous multi-layered crystal structures. Due to the superior fluorescence property of HA-CQDs, the labeled cells could be observed and detected using a confocal microscope and flow cytometry. By virtue of the functional HA ligands, HA-CQDs exhibited excellent colloidal stability and favorable biocompatibility, and readily entered into the cytoplasm of CD44-overexpression cancer cells. HA competitive binding assay demonstrated that the internalization process was regulated by CD44 (HA receptor)-mediated endocytosis. These results validated that the as-prepared HA-CQDs could particularly serve as novel cell-specific fluorescent probes for CD44 high expression in tumor-targeted imaging and labelling.