Enhancement Of Radiation Effect On SMMC-7721 Cells By C225-GNPs And Its Potential Michanisms

Objective:To study the radiosensitizing effect of C225-GNPs on SMMC-7721 cells, and to evaluate the influence of cell uptake, cell porliferation, apoptosis, cell-cycle regulation, ER stress pathway, by C225-GNPs on SMMC-7721 cells. Finally to investigate its possible mechanism.Methods:In this study, we firstly synthesized 20nm GNPs via the mothed of sodium citrate reduction and C225. GNPs through electrostatic interaction by Au-S and Au-N bonding, GNPs and its nanoconjugates were characterized using transmission electron microscopy(TEM), ultra-violet visible spectroscopy, dynamic light scattering(DLS). The growth inhibition of SMMC-7721 cells was determined using the CCK-8 assay. SMMC-7721 cells with different numbers(50,100,200,400,800 and 1500)were incubated with C225-GNPs for 24h. Then replace culture medium and expose cells to different radiation doses(0Gy,0.5 Gy, 1Gy,2Gy,4Gy, and 6Gy) according to different cell numbers. Two weeks later, count the clonies and protract clonogenic survival assay curves. The radiosensitivity effect of C225-GNPs on SMMC-7721 cells by fitting the irradiation dose-survival curve using ’multitarget click mathematical model’. Flow cytometry(FCM) was used to detect the change of cell apoptosis and cell cycle. Test the expression of several critical proteins related to apoptosis and ERS.Results:TEM image showed the uptake of C225-GNPs in high EGFR-expression SMMC-7721 cells was higher than GNPs. After treatment with 6.14μg/ml GNPs and 4.11μg/ml C225-GNPs for 24h, the sensitization enhancement ratio(SERD0) is 1.54、 1.66, SERDq is 1.38、 1.85。The apoptotic index was significantly increased (P<0.05), compared with the control group. The G2/M phase ratio is increased while the G0/G1 phase ratio decreased after treatment. Western Blot showed that C225-GNPs play an important role by upregulating the expression of Bax、 Caspase-3 GRP78、 IREa and downregulating the expression of Bcl-2 and PERK(P<0.05).Conclusion:C225-GNPs has an obvious radio sensitivity effect on SMMC-7721 cells, and the mechanism of action may be related to decreased repair capacity of the SMMC-7721 cells,the cell cycle arresting is G2/M phase,the decreased cell number of G0/G1, enhancing apoptosis and impairing DNA repaircapacity via ER stress induction.