Of Coated Microbubble Ultrasound Contrast Agents For Preparation

Ultrasound contrast agent (UCA) is an diagnostic agent that can improve the signal to noise ration of the returning echoes markedly. Microbubble contrast agents have dramatically extended the clinical and research application of ultrasound, and the advent of tissue-specific agents promises to improve the sensitivity and specificity of ultrasound in the detection and characterization of focal liver lesions to rival that of computed tomography (CT) and magnetic resonance imaging (MRI). Microbublles were regarded as the best contrast agents since they can significantly enhance echogenicity. As an idea UCA, microbubbles are safe and effective vascular echo enhancers, which have extended the versatility of ultrasound and allow the microcirculation to be imaged as well as providing functional data. They also have potential tissue-specific and targeted therapeutic agents.Based on the recent advances in UCA, this review describes composition, preparation and tissue beds. From the present study, the preparation of UCA includes two directions, gases inside the microbubbles and material outside the microbubbles. As far as gases are concerned, fluorinated gases, which are higher molecular weight gases such as perfluorocarbon are used widely because of its low diffusivity and higher vapor pressure. But their biological degradation and environment compatibility have not been certificated. So the study on the membrane material is very important. As an UCA, the gas should be encapsulated by membrane material, at the same time, the membrane material should be toughen and reinforced so that microbubbles can remain stabilization both inside and outside the bodies, especially can conquer the pressure of artery. According to different membrane materials, encapsulated microbubbles ultrasound contrast agent can be divided into several categories such as albumin, liposome, and polymer. And polymer of them is the most promising nowadays even in the future.In this paper, microbubbles were prepared by emulsion polymerization. Nitrogen which is cheap and obtain easily was adopted as the gas components in the microbubbles, and synthetical polymer was used as the outside material. After considering the components' toxicity, biocompatible, hemolysis and degradability, besides the species and dosage of monomer, emulsifier and initiator, which are necessary in the reaction, reaction time and agitating velocity were also investigated respectively. As a result, the microbubbles had a diameter of 1 to 4 micrometers, concentration of 4.78×10~9 /ml, the monomer conversion rate of 67 per, all this was benefit for the next step. Furthermore, we mad an attempt to induce the polymerization by Ultraviolet radiation. The outcome of reaction indicated this method was worthy of much more research.