The Analysis of Differentially Expressed circRNAs Under the Antiproliferative Effect From 5-Fluorouracil on Osteosarcoma Cells.

BACKGROUND: 5-fluorouracil (5-FU) is a widely used drug for cancer treatment, but its effect and underlying mechanisms on osteosarcoma (OS) cells remain unclear. METHODS: U2OS and MG63 cells were treated with 0, 50, 100, and 500 µM 5-FU. MTS and flow cytometry were used to examine the effect of 5-FU on cell viability and apoptosis, respectively. Circular RNA (circRNA) expression was detected using RNA sequencing and quantitative real-time PCR (qPCR). Differentially expressed circRNAs were further subjected to the Kyoto Encyclopedia of Genes and Genomes (KEGG) and gene ontology (GO) analysis to predict their functions. A circRNA-miRNA-mRNA interaction network was generated to analyze the regulatory networks of 5-FU-induced differentially expressed circRNAs. Western blotting (WB) was used to verify the protein in the downstream of circRNAs. RESULTS: 5-FU inhibited the cell viability of the MG63 cells in a concentration-dependent manner. The most significant effect was observed in the cells treated with 500 µM 5-FU. Apoptosis was also increased in the MG63 cells after 500 µM 5-FU treatment for 3 days. RNA sequencing results showed that 183 differentially expressed circRNAs (172 upregulated and 11 downregulated) in 5-FU-treated cells. KEGG and GO analysis showed that the differentially expressed circRNAs were primarily enriched in proliferation-, apoptosis-, and metabolism-related functions. qPCR was used to verify the most upregulated and downregulated circRNAs. The circRNA-miRNA-mRNA interaction network showed that these 8 circRNAs had a sizable regulatory network that links a series of genes involved in tumor suppression. CONCLUSION: 5-FU treatment resulted in the differentially expressed circRNAs that were proliferation- and apoptosis-associated and were involved in the 5-FU-induced inhibition of tumor proliferation in OS cells.

A brand-new generation of fluorescent nano-neural tracers: biotinylated dextran amine conjugated carbonized polymer dots.

The anterograde neuroanatomical tracing technique plays a crucial role in studying and charting the complex interconnections of the nervous system. But there are several major limitations for traditional neural tracers, such as complex immunohistochemical staining procedures, low fluorescence intensity and quick fluorescence quenching. Carbon dots (CDs) as fluorescent bio-probes have been widely used in the biological studies due to their superior optical properties, excellent chemical stability, low toxicity, and easy modifications. In this study, biotinylated dextran amine (BDA) and red fluorescent carbonized polymer dots (CPDs) are successfully conjugated to develop a brand-new generation of fluorescent nano-neural tracers: BDA-CPDs. They are successfully applied as fluorescent probes for in vitro and in vivo bioimaging. In vitro biodistribution of BDA-CPDs shows that they distribute mainly in lysosomes and endoplasmic reticulum. Moreover, two metabolic pathways of BDA-CPDs are found through the investigation of in vivo biodistribution of BDA-CPDs. Furthermore, they can be taken up and anterogradely transported by neurons within the peripheral nervous system of rats. Our results suggest that BDA-CPDs have many advantages over traditional tracers, such as low toxicity, high photoluminescence intensity, excellent photostability and easy procedures. Anterograde pathway tracing with BDA-CPDs is a simple, direct and economical way of studying the connections in the nervous system. Therefore, BDA-CPDs are reliable and valuable fluorescent anterograde neural tracers.

Noninvasive Brain Tumor Imaging Using Red Emissive Carbonized Polymer Dots across the Blood-Brain Barrier.

Surgical resection is recognized as a mainstay in the therapy of malignant brain tumors. In clinical practice, however, surgeons face great challenges in identifying the tumor boundaries due to the infiltrating and heterogeneous nature of neoplastic tissues. Contrast-enhanced magnetic resonance imaging (MRI) is extensively used for defining the brain tumor in clinic. Disappointingly, the commercially available (MR) contrast agents show the transient circulation lifetime and poor blood-brain barrier (BBB) permeability, which seriously hamper their abilities in tumor visualization. In this work, red fluorescent carbonized polymer dots (CPDs) were systematically investigated with respect to their BBB-penetration ability. In summary, CPDs possess long excitation/emission wavelengths, low toxicity, high photostability, and excellent biocompatibility. CPDs exhibit high internalization in glioma cells in time- and dose-dependent procedures, and internalized CPDs locate mainly in endolysosomal structures. In vitro and in vivo studies confirmed the BBB permeability of CPDs, contributing to the early stage diagnosis of brain disorders and the noninvasive visualization of the brain tumor without compromised BBB. Furthermore, owing to the high tumor to normal tissue ratio of CPDs under ex vivo conditions, our nanoprobe holds the promise to guide brain-tumor resection by real-time fluorescence imaging during surgery.