Experimental Study on Synergistic Effect of HIFU Treatment of Tumors Using Bifidobacterium Bound with Cationic Phase-change Nanoparticles

Objective: Anaerobic bacteria can enter the solid tumor in the hypoxic region to colonize and proliferate. Aggregation of nanoparticles in the tumor area can enhance molecular imaging and therapy. It is hypothesized that the combination of the two could possibly achieve better imaging and tumor treatment. This study presents a biocompatible bacteria-based system that can deliver cationic phase-change nanoparticles (CPNs) into solid tumor to achieve enhanced imaging and treatment integration.

Materials And Methods: Cationic phase-change nanoparticles (CPNs) and Bifidobacterium longum (BF) were mixed to determine the best binding rate and were placed in an agar phantom for ultrasonography. BF-CPNs complex adhesion to breast cancer cells was observed by laser confocal microscopy. In vivo, BF-CPNs and control groups were injected into tumors in breast cancer nude mouse models. Nanoparticles distribution was observed by ultrasound and in vivo fluorescence imaging. HIFU ablation was performed after injection. Gross and histological changes were compared and synergy was evaluated.

Results: Bifidobacterium longum (BF) and CPNs were combined by electrostatic adsorption. The BF-CPNs particles could increase the deposition of energy after liquid-gas phase-change during High Intensity Focused Ultrasound (HIFU) irradiation of tumor.

Conclusions: This study shows a valid method in diagnosis and therapy integration for providing stronger imaging, longer retention time, and more effective tumor treatment.