摘要Objective:This study aims to explore the potential of an in situ tumor vaccine based on guanidine-modified oligo-chitosan in anti-tumor immunity by con-structing such a vaccine,and to provide a theoretical basis for the development of novel tumor immunotherapy strategies.Methods:Chitosan was degraded into oligo-chitosan by cellulase method.Guanidine-modified oligo-chitosan was synthesized using dicyan-diamide,and then loaded with polyinosinic acid-polycytidylic acid(PIC)and mam-malian target of rapamycin(mTOR)small interfering RNA to prepare in situ tumor vac-cine nanoparticles.The expression level of mTOR protein,cell invasion,and prolifera-tion in B16F10-OVA cells treated with different components were observed.B16F10-OVA tumor-bearing mice were prepared and divided into 5 groups.Normal saline(NC),chitosan(CHI),oligo-chitosan(COS),guanidine-based modified oligo-chi-tosan(GBM-COS),and nanoparticles(guanidine-modified oligo-chitosan in situ tumor vaccine,GBM-COS+PIC+mTOR)were respectively injected into the tumor sites.The tumor inhibition rate,infiltration and functional changes of immune cells in tumor tissues and draining lymph nodes,and survival period of the mice were observed.Results:In the GBM-COS+PIC+mTOR group,the expression level of mTOR protein in tumor cells was downregulated,and the cell proliferation rate and invasion rate were significantly lower than those in the other four groups(P<0.05).The tumor volume inhibition rate,DC infiltration proportion,macrophage activation level,CD8+T cell proportion,and survival time in the B16F10-OVA tumor-bearing mouse model of the GBM-COS+PIC+mTOR group were all higher than those in the other four groups(P<0.05).Conclusion:The guanidine-modified oligo-chitosan-based nanoparticles exhibited good anti-tumor ac-tivity both in vitro and in vivo,which can provide a new candidate method for novel tu-mor immunotherapy by inducing immunogenic cell death(ICD)and activating immune cells.