Polymer Materials Of Ultrasound Microbubble Preparation And Imaging Of Contrast Agent

PARTⅠEXPERIMENT OF HIGH MOLECULAR POLYMER ULTRASOUND CONTRAST AGENT PREPARATION AND ACUTE TOXICITYTESTObject To prepare a ultrasound contrast agent made of a novel biodegradable polymer---poly lactic-co-glycolic acid (PLGA), and to observe its properties and acute toxicity.Method PLGA ultrasound contrast agent (Gao ju xian) was prepared by double emulsion method (W/O/W) and freeze-drying method with PLGA and filled with gas. LM and SEM were used to examine the shape and surface morphology of the PLGA microbubbles. Moreover, to measure the size distribution of the microbubbles with a Laser size analyzer using static light scattering. The acute toxicity was experimented on sixty-two kunming mice and LD50 value was analyzed with Bliss assay method. Additionally, the changes of gross anatomy and histological anatomy were observed.Result This method (W/O/W) prepares spherical microbubbles with a smooth surface and narrow size distribution, as observed under the LM and SEM. LD50 value was 29.174(22.306～38.158) ml/kg in the acute toxicity experiment. The gross anatomy samples showed that there were many bleeding points on the surface of the lung, the kidney was severity engorged, the heart and liver were normal. The histological anatomy samples showed that a bit of red blood cells were in the myocardial matrix observed by LM; there were most red blood cells in the blood capillary of alveolar wall, pulmonary alveolar partly distructed; blood vessels of renal matrix dilatated and engorged, a bit of red blood cells and lymphocytes were in the matrix; some hepatocyte were water change.Conclusion PLGA ultrasound contrast agent fabricated by W/O/W method had many great advantages. And because of its biodegradable character, it has no toxicity in itself. The result of acute toxic experiment was volume overload, without pulmonary embolism, indicating the agent can go through the pulmonary. And no toxicity under dose of diagnosis showed in acute toxicity test, this be experimental basis for clinical application. PARTⅡEXPERIMENTAL STUDY ON MYOCARDIAL CONTRAST ECHOCARDIOGRAPHY USING HIGH MOLECULAR POLYMER ULTRASOUND CONTRAST AGENTObjective (1)To investigate the effects and characteristics of self-made PLGA ultrasound contrast agent(Gao Ju xian) on myocardial perfusion imaging; (2)To explore the value of myocardial contrast enhancement using Gao ju xian on the myocardial necrosis of myocardial infarction;(3)To investigate the influence of different trigger interval on measuring risk areas of acute myocardial infarction from the short-axis plane at mid papillary muscle level.Method (1)Gao ju xian with three different concentration(2.5%,5%,10%)(g/ml) were applied for myocardial contrast echocardiography (MCE) respectively and the quantative and quality analysises were applied for the imagings.(2)Fourteen acute myocardial infarction rabbits were built by left anterior descending artery ligation. MCE was performed using Gao ju xian to evaluate the blood perfusion on the myocardial infarcion group. The heart was cut from the short-axis plane at mid papillary muscle level and dyed with TTC. The infarct tissue was observed by HE staining and TEM.(3)The model of rabbits with acute myocardial infarction were built, and the MCE using intermittent harmonic imaging with fifteen trigger intervals through the intravenous injection of self-made contrast agent was performed. The imagings were stored and analysed as follows: (a) The areas of filling defect showed in imagings of differet trigger interval were measured using"DFY-2 ultrasound imaging analysis system", to investigate the influence of different trigger interval on measuring risk areas of acute myocardial infarction from the short-axis plane at mid papillary muscle level; (b) The risk areas of the short-axis plane at mid papillary muscle level were analysed using statistical software to quantitative the effect of trigger interval on the measurement of risk areas.Results (1)With the decreasement of the concentration, the effect of myocardium imagings and the acoustic shadow bacame significantly strengthen. The echo intensity of anterior wall, posterior wall, lateral wall myocardium and cardiac chamber also increased. The difference between three groups was significant (P<0.05).(2)Defective and poor perfusion were found at the infarcted areas with MCE. There were 20 defective perfusion myocardium segments and 8 poor or delayed perfusion segments. It was compared with TTC.(3)There was significant effect of trigger interval on measurement of risk area of the short-axis plane at mid papillary muscle level. The results showed that, with the increased of trigger interval, the risk area measured at 1-10RR trigger interval reduced. But the risk area measured at more than 10RR trigger interval was no longer reduced, that indicating the contrast agent in the cardiac microvascular be on balance, in other words, the risk area measured at more than 10RR trigger interval was"real"no flow perfusion.Conclusion (1)Gao ju xian was successfully applied to MCE, its dose had significantly effect on imaging of myocardium and cardiac chamber. It is important to choose an ideal dose for MCE.(2)MCE using Gao ju xian has good sensitivity, specificity and precise on identifying necrotic myocardium of AMI rabbits. It has great value in early diagnosis and treatment of acute myocardial infarction.(3)There was significant effect of trigger interval on measurement of risk area of the short-axis plane at mid papillary muscle level, and the parameter of trigger interval must be considered when continuous intravenous injection of contrast agent for MCE to evaluate risk area. PARTⅢRESEARCH ON FABRICATION OF GD-DTPA-LOADED PLGA MICROBUBBLES AS BOTH ULTRASOUND CONTRAST AGENT AND MRI CONTRAST AGENTObjectives To prepare the Gd-DTPA-loaded poly (lactic-co-glycolic acid) (PLGA) microbubbles for both ultrasound imaging and MRI imaging.Method Biodegradable high-molecular-weight poly (lactic-co-glycolic acid) (PLGA) was used as an encapsulating vehicle to fabricate a contrast agent composed of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) and fluorocarbon-filled microbubbles by using double emulsion method. The morphology, size and Gd loading capacity of PLGA microparticles were assessed. The efficacy of the contrast agent for ultrasound and magnetic resonance (MR) imaging was evaluated by in vitro and in vivo imaging of hepatic vessels and the liver parenchyma of rabbit following injection of the contrast agent. Additionally, the liver and kidney functions were examined before and at 7, 14, 30 days after injection.Results Electron microscopy showed Gd loaded PLGA microbubbles were spherical in shape. The mean diameter were 1.47±0.38μm and the Gd loading was 25±2μg/mg. Right after the injection of the PLGA microbubbles, the ultrasound echo intensity of hepatic vessels and the liver parenchyma was significantly enhanced. Moreover, enhanced signal intensity of the liver parenchyma on MR images was observed for approximately 30 min after injection of the contrast agent. Neither marked changes in the liver and kidney functions nor other severe complications were detected during the follow-up period.Conclusion Gd-DTPA-Loaded PLGA microbubbles could enhance both ultrasound imaging and MRI imaging.