Ultrasound Visual Magnetic Hyperthermia Ablation Of Tumor Using Injectable Fe₃O₄/Calcium Phosphate Cement

PART Ⅰ PREPARATION OF INJECTABLE FE3O4/CALCIUM PHOSPHATE CEMENT AND EVALUATION OF INDUCTION HEATING EFFICIENCY IN VITROObjective To develop a safety, injectable and biodegradable material using calcium phosphate cement containing Fe₃O₄ nanoparticles（Magnetic calcium phosphate cement: MCPC）, and to test its heating efficiency in vitro.Method Magnetic calcium phosphate cement was prepared and characterized including morphology, washout resistance ability, the confine efficiency of calcium phosphate cement, injectability, degradability, and exotherm during the setting reaction. After that, The MCPCs with three levels of weights and with three levels of iron contents（0.19 g of 10%, 0.36 g of 10%, 0.54 g of 10%, 0.54 g of 5%, 0.54 g of 0%, and 0.54 g of 10% MCPCs after degradation） were placed in PBS in a cylindrical hole of agarose gel model, and exposed to an alternating magnetic field for 300 s, the heating efficiency of the MCPC was evaluated by using an infrared imager to continuously monitor the peak surface temperature of the PBS. Finally, the 10% MCPC with three levels weights were selected and implanted into the excised bovine liver parts and exposed to the same alternating magnetic field for 300 s, the heating efficiency of the MCPC was further evaluated by using the infrared imager to monitor the peak surface temperature of the excised bovine liver, and the temperature at different distances（0, 1, 2, and 3 cm） to the peak surface temperature was recorded at the time point of 300 s.Results CPC was porous and the Fe₃O₄ nanoparticles were uniformly distributed within CPC. The 5% and 10% MCPC were resistant to washout, while the 15% MCPC disintegrated. Under the alternating magnetic field, the PBS containing Fe₃O₄ nanoparticles was heated, and the Fe₃O₄ nanoparticles could not spill out from the agarose gel model with the boiling PBS in CPC + Fe group, while, the Fe₃O₄ nanoparticles spill out from the agarose gel model and flowed everywhere in PEG + Fe group. The injectability increased with the iron content with an injectable percentage 90.67 ± 1.53% for 10% MCPC. The degradability increased with time and the increase in iron content. After 68 days, the weight loss was 24.23 ± 0.02%, 32.62 ± 0.03%, 37.38 ± 0.03% respectively for 0.5 g CPC, 5% MCPC and 10% MCPC. Exotherm during the setting reaction was low, the exotherm during the setting reaction was 1.36 ± 0.14 °C for 10% MCPC. When exposed to the alternating magnetic field, the MCPC could quickly generate a lot of heat to elevate temperature of the PBS and excised bovine liver, and the heat was increased with the MCPC weight, iron content and time. And the temperature at different distances to the peak temperature of the MCPC decreased significantly with distance.Conclusions We have developed a safety, injectable, and biodegradation material using CPC containing Fe₃O₄ nanoparticles. The Fe₃O₄ nanoparticles were good confined within CPC, and the heating efficiency of MCPC was good, which was expected to a safety, efficient and minimally invasive magnetic hyperthermia ablation material.PART Ⅱ ULTRASOUND VISUAL MAGNETIC HYPERTHERMIA ABLATION OF TUMOR USING INJECTABLE FE3O4/CALCIUM PHOSPHATE CEMENTObjective With the assistance of ultrasound imaging, study the ablation efficiency of MCPC in excised bovine liver and MB-231 human breast xenograft on nude mice.Method 0.19, 0.36, and 0.54 g of 10% MCPCs were implanted into the freshly excised bovine liver and exposed to the same alternating magnetic field as above for 60, 180, and 300 s. The ultrasound echo intensity was monitored by ultrasound imaging. The ablated tissue volume was evaluated by a ruler. 32 nude mice were used for experiments when the xenograft volume reached 1.66 ± 0.52 cm3. The 32 nude mice were divided into four groups. Except the control group, CPC group, PEG + Fe group and CPC + Fe group were injected material into subcutaneous xenograft under the real time guidance of ultrasound imaging. After injection and when MCPC was setting in xenograft, ultrasound imaging was used to observe the echo intensity and distribution of materials（including CPC, MCPC, PEG + Fe,） in xenograft. The 32 mice were exposed to the same alternating magnetic field for 180 s, and the peak surface temperature of xenograft was monitored by an infrared imager. After ablation, the shape and echo intensity of xenograft were monitored by ultrasound imaging. At last, 3 mice of each group were selected and euthanized for tumor pathology examination by hexatoxylin and eosin（H & E） staining. The other five mice were fed for further observation of the tumor change trend.Results The ultrasound echo intensity of live had a tendency to increase with the weight of the MCPCs and the extended time under the alternating magnetic field. The ablated liver tissue volumes of 0.36 g 10% MCPC were 0.2 ± 0.03 cm3, 1.01 ± 0.07 cm3, and 1.96 ± 0.19 cm3 respectively at the time point of 60 s, 180 s and 300 s. In the produce of ultrasound visual magnetic hyperthermia ablation, the MCPC could be directly injected into the core position of tumors under the guidance of US imaging which was hyperechoic, with an acoustic shadow after the injection. After setting, the MCPC could confine within the tumors without the occurrence of leakage. Under the alternating magnetic field, compared with other group, 0.36 g of 10% MCPC could completely ablate the breast xenograft with 180 s, the boundary between ablation area and surrounding tissue were regular, and the ablation area was in accordance with the tumor area. HE staining showed that the ablated tumor xenograft were coagulation necrosis and the necrotic tissue separated from the nude mice and fell off after two weeks. However, the PEG + Fe group containing 0.036 g Fe₃O₄ could ablate the breast xenograft, but obvious skin injury was observed on the boundary between ablation area and surrounding tissue, and the ablation area was significantly exceeded the tumor area, furthermore, the surrounding of necrotic area which residual tumor tissue was shown a recurrence trend on some tumors of PEG + Fe group. The tumors of control and CPC group were showed a sustained growth trend.Conclusions With the assistance of ultrasound imaging, MCPC could be used for safety, efficient and minimally invasive magnetic hyperthermia ablation tumor.