RESUMO
Radiotherapy is an important means to treat malignant tumors in clinical practice. However, tumor radioresistance not only seriously limits the efficiency of radiotherapy, but also leads to poor prognosis of patients, which may eventually lead to tumor metastasis and recurrence. Circular RNA (circRNA) is a new member of noncoding RNA, which is highly specific, stable and conservative. This paper reviewed with the effect of circRNA on the signal pathways related to radiotherapy resistance by analyzing the perspective of DNA damage repair pathway, EMT (epithelial mesenchymal transition) process, Wnt pathway, tumor stem cells and other pathways, and sorted out the mechanism of circRNA in tumor cell resistance to radiotherapy, which may provide valuable clues for further study of circRNA.
RESUMO
Objective:To establish an HPLC method to determine the entrapment efficiency (EE) and drug loading (DL) of curcumin (CUR)and quercetin (QUE)loaded self-microemulsifying drug delivery system.Methods:A centrifugation method was used to isolate the free drug.The content of drug was determined by HPLC.The analytical column was a Purospher STAR LP C18 column (250 mm×4.6 mm,5 μm) and the column temperature was 30 ℃.The mobile phase was acetonitrile-4% acetic acid (50∶50) and the flow rate was 1.0 ml·min-1.The UV detection wavelength was set at 370 nm and the injection volume was 10 μl.Results:CUR and QUE were linear within the range of 10.728-96.552 μg·ml-1 (r=0.999 8) and 1.08-9.72 μg·ml-1 (r=0.999 9),respectively.The average recovery was 99.98%(RSD=1.46%,n=9) and 100.34%(RSD=1.06%,n=9),respectively.In CUR-QUE-SMEDDS,the EE of curcumin and quercetin was (95.97±0.50)% and (95.91±2.52)%,and the DL was (25.82±0.15) mg·g-1 and (1.80±0.05)mg·g-1,respectively.Conclusion:The method is accurate,rapid and simple,and suitable for the determination of DL and EE in CUR-QUE-SMEDDS.
RESUMO
The aim of the study was to prepare and evaluate the quality of negatively charged selfmicroemulsifying drug delivery system of curcumin (NC-CUR-SMEDDS).Based on the CUR-SMEDDS,the optimum amount of excipients was confirmed by the single-factor design experiment taking mean particle size,Zeta potential,drug entrapment efficiency and the drug loadings of curcumin as the evaluation indices for the preparation of NC-CUR-SMEDDS.The quality of NC-CUR-SMEDDS was evaluated by observing its appearance status,transmission electron microscope micrographs and determining particle diameter,Zeta electric potential,drug entrapment efficiency and drug loading.As a result,it was found that the Zeta potential reached -43.43 ± 0.29 mV when 4％ docusate sodium was added.The appearance of NC-CUR-SMEDDS remained clarified and transparent,and the microemulsion droplets appeared spherical without aggregation with uniform particle size distribution.The mean particle size was 14.08 ± 0.082 nm,the drug loading of curcumin was 26.48 mg·g-t and the drug entrapment efficiency was 94.12％.It was concluded that NC-CUR-SMEDDS with high entrapment efficiency and uniform particle size distribution met the requirement of inflammatory target binding in the colon.