BACKGROUND:In an additional changing magnetic field, magnetosomes can invade the tumor cells and inhibit their proliferation.OBJECTIVE: To study the effect of targeted delivery of pHSP70-shPLK1/DOX compounds with magnetosome of magnetotactic bacteria on the treatment of osteosarcoma.METHODS: Human osteosarcoma cell U2OS was divided into four groups: group A: magnetosomes of magnetotactic bacteria+pHSP70-shPLK1/DOX complex; group B: magnetosomes of magnetotactic bacteria; group C: magnetosomes of magnetotactic bacteria+pHSP70-shPLK1/DOX complex, combined with magnetic intervention; group D: magnetosomes of magnetotactic bacteria, combined with magnetic intervention. After 12, 24, 48 and 72 hours of culture, the uptake rate of osteosarcoma cells was observed; cell cycle was evaluated by flow cytometry; PLK1 mRNA and protein expression levels were detected by RT-PCR and western blot, respectively; cell proliferation was explored by MTT assay; cell adhesion and invasion were checked by adhesion assay and Transwel chamber assay, respectively; and the apoptosis rate was measured by apoptosis detection Kit.RESULTS AND CONCLUSION: (1) After culture of 12 and 24 hours, the uptake rate was the highest in group D; meanwhile, the uptake rate was the highest in group B after 48 and 72 hours of culture. (2) The ratio of G2/M phase decreased and the ratio of G0/G1 increased gradualy in group A, group C and group D; the G2/M phase ratio of C group was the lowest at each time point, followed by group D, and that of group A was the highest; and the G2/M phase ratio increased gradualy in group B. (3) Folowing 12 and 24 hours of culture, the expression of PLK1 in group B and group D was higher than that in group A and group C (P < 0.05); in addition, the expression of PLK1 in group B was higher than that in the other three groups after 48 and 72 hours of culture (P < 0.05), and the PLK1 level in group D was higher than that in group A and group C (P < 0.05). (4) The proliferation, adhesion and invasion ability in group B were the highest at different time points, but the apoptosis rate was the lowest. Furthermore, the proliferation, adhesion and invasion abilities in group C were the lowest at different time points, and the apoptosis rate was the highest. To conclude, our experimental results show that the targeted delivery of pHSP70-shPLK1/DOX complex by magnetosomes of magnetotactic bacteria can enhance the apoptosis of osteosarcoma cells and inhibit their proliferation and invasion.