Intermittent Time-set Technique Controlling Temperature Of Magnetic-hyperthermia-ablation For Tumor Therapy

PART Ⅰ PREPARATION OF POLYLACTIC-CO-GLYCOLIC ACID-FE₃O₄ AND EVALUATION THE HEATING EFFICIENCY IN VITROObjective we develop an injectable,liquid-solid phase transitional magnetic material,Polylactic-co-glycolic acid（PLGA）-Fe₃O₄,explore its physical characteristics and evaluate the heating outputs in vitro under the continuous and intermittent heating modes.Method Four kinds of liquid gels were prepared by mixing up the PLGA,NMP liquid and the different proportion of Fe₃O₄ nanoparticles（PLGA-0、PLGA-10%Fe₃O₄、PLGA-20%Fe₃O₄、PLGA-30%Fe₃O₄）.The microstructure of PLGA-20%Fe₃O₄ powder was tested by using scanning electron microscope and the element analysis was observed by an energy dispersive X-ray spectrometer.The magnetic properties of pure Fe₃O₄nanoparticles and PLGA-Fe₃O₄ powder were measured by Physical Property Measurement System（PPMS-9）at room temperature.The liquid PLGA-Fe₃O₄ was injected into the PBS to observe the progress of liquid-solid phase transformation.PLGA-Fe₃O₄ with different iron contents and various volumes were exposed to the altering current magnetic field for evaluating the continuously heating efficiency in vitro.Choosing the best iron content and volume for intermittent heating experiment to evaluate the output.Results PLGA-Fe₃O₄ liquid gel was black.Scanning electron microscope showed rough surface in PLGA gel.The element mapping analysis of PLGA-Fe₃O₄ showed that the C、O、Fe element was well dispersed in PLGA.The Fe₃O₄ nanoparticles and the PLGA-Fe₃O₄ were ferromagnetic.The saturation magnetization value（Ms）for the pure Fe₃O₄ nanoparticles、PLGA-20%Fe₃O₄ were 73、43emug^-1,respectively.Liquid PLGA-Fe₃O₄ could be successfully injected from syringe,and then it can transform to be solid and precipitate when contacting with PBS.And it will not be dispersed or defeated.Once exposed to the altering current magnetic field in vitro,the magnetic PLGA-Fe₃O₄ generated heat.The heating efficiency was positively correlated with the Fe₃O₄ content and material volume.The 60μL PLGA-20%Fe₃O₄ was the best candidate for next experiment.After the specific intermittent mode was applied,the temperature of 60μL PLGA-20%Fe₃O₄ reached 45.65±1.63℃ in 110seconds and the fluctuation range was only 2.87±1.08℃.The ablated liver tissue area of intermittent heating group increased from 1.14±0.16cm² for 1 min to 4.84±0.17 cm² for 5 min under AMF.Conclusions The injectable and fast liquid-solid phase transitional PLGA-Fe₃O₄ is successfully prepared.Fe₃O₄ nanoparticles are evenly distribute in PLGA.The Ms of PLGA-Fe₃O₄ was high enough to heat efficiently.In addition,the temperature was well controlled.These merits lay a firm foundation for the following tumor hyperthermia therapy.PART Ⅱ ULTRASOUND VISUAL MAGNETIC HYPERTHERMIA ABLATION OF TUMOR USING PLGA-Fe₃O₄ Objective To compare the intermittent heating efficiency and continuously heating efficiency in MDA-MB-231 human breast cancer xenograft in nude mice.Method The PLGA-Fe₃O₄ was prepared as previously.MDA-MB-231 breast cancer xenograft model was established in nude mice,which were divided into three groups: intermittent heating group;continuous heating group and blank control group.Liquid PLGA-Fe₃O₄ was injected into the tumor center under ultrasound guidance.After that,the 3D ultrasound and CT images were acquired to observe the position and shape of implant when the treatment finished.Next,the nude mice were intermittently and continuously exposed to the altering current magnetic field.The surface temperature of tumor was recorded by infrared thermometer.Evaluation of blood flow perfusion before and after ablation by contrast-enhanced ultrasonography were conducted.At last,all of the nude mice were under a carefully observation to keep a record of its weights,tumor volume and activities every day.The macroscopic images of nude mice and the HE staining were studied as well.The nude mice had no treatment as blank control group.Results When the tumor volume of the mice reached 0.453±0.109 cm³,these mice can be used for the next experiment.60 μL PLGA-20%Fe₃O₄ was injected accurately under ultrasound guidance.Both 3D ultrasound and computer tomography images showed that material was tightly limited in the center of tumor without significant leaking or deformation.The temperature of tumor achieved 55.53±0.50 ℃ at 40 seconds,and fluctuated at the range of 6.45±1.34 ℃ for 4 minutes in the intermittently heating group.In contrast,the temperature of the tumor rapidly increased to over 90 ℃ within 80 seconds in the continuously heating group.Before the treatment,the tumor was abundant in blood flow in the Color Doppler Flow Imaging.When injected 100 μL Sono Vue,it immediately developed in the way that filled from the peripheral boundary into center within 10 seconds.After the treatment,there is no blood flow and contrast agent signal in the same tumor.In intermittent group,the skin of tumor was unbroken and intact.On the 14 th day,the scab began to desquamate.While in the continuously heating group,the skin was broken on the first day causing a terrible huge wound.The pathology images showed that there was an obvious difference between the material and ablated tumor tissue in the intermittent heating group and the significant cell necrosis in the continuous heating group.On the other hand,the tumor volume had an increasing tendency in the blank control group.Integrated nucleus and cytoplasm were found while no evident cell destruction was discovered.Conclusions Both the intermittent heating and continuously heating could successfully ablate the tumor.While,the effect of intermittent heating group is more mild and comfortable.It is more appropriate for clinic magnetic hyperthermia.