Black Phosphorus Quantum Dots Enhance the Radiosensitivity of Human Renal Cell Carcinoma Cells through Inhibition of DNA-PKcs Kinase.

Renal cell carcinoma (RCC) is one of the most aggressive urological malignancies and has a poor prognosis, especially in patients with metastasis. Although RCC is traditionally considered to be radioresistant, radiotherapy (RT) is still a common treatment for palliative management of metastatic RCC. Novel approaches are urgently needed to overcome radioresistance of RCC. Black phosphorus quantum dots (BPQDs) have recently received great attention due to their unique physicochemical properties and good biocompatibility. In the present study, we found that BPQDs enhance ionizing radiation (IR)-induced apoptotic cell death of RCC cells. BPQDs treatment significantly increases IR-induced DNA double-strand breaks (DSBs), as indicated by the neutral comet assay and the DSBs biomarkers γH2AX and 53BP1. Mechanistically, BPQDs can interact with purified DNA-protein kinase catalytic subunit (DNA-PKcs) and promote its kinase activity in vitro. BPQDs impair the autophosphorylation of DNA-PKcs at S2056, and this site phosphorylation is essential for efficient DNA DSBs repair and the release of DNA-PKcs from the damage sites. Consistent with this, BPQDs suppress nonhomologous end-joining (NHEJ) repair and lead to sustained high levels of autophosphorylated DNA-PKcs on the damaged sites. Moreover, animal experiments indicate that the combined approach with both BPQDs and IR displays better efficacy than monotreatment. These findings demonstrate that BPQDs have potential applications in radiosensitizing RCC cells.

Biotransformation of ginsenoside Rc to Rd by endophytic bacterium Bacillus sp. G9y isolated from Panax quinquefolius.

To isolate endophytic bacterium with the ability to specifically convert ginsenoside Rc from Panax quinquefolius. An endophytic bacterium G9y was isolated from Panax quinquefolius and indentified as Bacillus sp. based on 16s rDNA gene sequence. Ginsenoside Rc was effectively converted to Rd by G9y, which was confirmed by thin-layer chromatography and high performance liquid chromatography (HPLC) analysis. The biotransformation conditions were further optimized as follows: inoculum amount 5%, converting temperature 45 °C, medium beef extract peptone broth at pH of 7, and the time of Rc addition was 4 h after bacterium G9y growth, under which ginsenoside Rc was completely converted to Rd by bacterium G9y within 25 h after inoculation. A strain of G9y with the ability to convert ginsenoside Rc into Rd was screened from endophytic bacteria isolated from P. quinquefolius. The results provide a new microbial resource for preparing ginsenoside Rd via biotransformation, and explore a pathway for Rc utilization, which has great potential application value.

Analysis of the Endophytic Bacteria Community Structure and Function of Panax notoginseng Based on High-Throughput Sequencing.

Panax notoginseng has long been used as a Chinese herb with high medicinal value. The endophytic bacteria in this medicinal plant have multiple biological functions. High-throughput sequencing is a rapidly evolving technique that helps profile the endophytic bacterial community structure of medicinal plants. However, few studies on the endophytic bacteria in P. notoginseng, particularly in dry P. notoginseng roots as a raw medicinal material, have been conducted. In this study, fresh P. notoginseng and dry P. notoginseng were analysed using high-throughput sequencing on an Illumina MiSeq platform to explore the diversity and functions of the endophytic bacteria in different parts of P. notoginseng. The results showed that a total of 201 operational taxonomic units were obtained from fresh P. notoginseng and dry P. notoginseng. The dominant phyla in the fresh and dry P. notoginseng were Proteobacteria (85.9%) and Firmicutes (99.9%), respectively, whereas the dominant genera in these samples were Enterobacter (84.4%) and Bacillus (99.6%), respectively. Fresh P. notoginseng exhibited a higher degree of endophytic bacterial diversity than dry P. notoginseng, but functional prediction of metabolism indicated that the relative abundance of the metabolic function of terpenoids and polyketides synthesis in the dry sample was higher than that in the fresh sample. Our study indicates significant differences in the diversity and metabolic function of the endophytic bacteria between fresh and dry P. notoginseng, providing useful information for the exploitation and utilization of endophytic bacteria resources from P. notoginseng.

In Vitro and In Vivo Toxicity of Black Phosphorus Nanosheets.

As a new kind of two-dimensional nanomaterial, black phosphorus (BP) nanosheets have attracted significant interests in diverse bioapplications due to their unique structure and physicochemical properties. Despite BP nanosheets' advantages in cancer diagnosis and therapy applications, their biosafety issues are still unclear. Herein, we report a systematic study on the In Vitro and In Vivo toxicity of BP nanosheets. In Vitro experiments showed that BP nanosheets decrease the viability of human bronchial epithelial cells in a time- and dose-dependent manner. The mechanism study showed that BP nanosheets interfere with mitochondrial membrane potential, leading to an increase in intracellular ROS. These responses further initiated the activation of the caspase-3 and ultimately dictated cells to undergo apoptosis. Then, the In Vivo experiments of BP nanosheets revealed that single injection of BP nanosheets does not cause toxicity to mice in a short period of time, whereas multiple injections of BP nanosheets exert adverse effects on liver and renal function of mice. Interestingly, the liver and renal function of the mice returned to normal after a recovery period. Our findings provide insights into the rational design of BP nanosheets and guide their applications in biomedical fields.