Study on ultrasonic cqntrast agent for Drug Delivery System (DDS)

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Two method of (a) and (b) were basically investigated to design site-targeted ultrasonic contrast agent. In method (a), a microbubble tagged with biotin is used to localize and characterize an avidin-coated surface of tumor. In method (b), a magnetite incorporated microbubble can be localized to tumor with the aid of an extracorporeal magnet. We confirmed that site-targeted microbubble in all of both methods had the potential to localize the particular target under the condition where the flow is stopping. We also confirmed that these site-targeted microbubbles had the potential to localize the target under slow flowrate by using the blood vessel model that was made to imitate the flow of actual blood. But, it became clear that the targeting ability decreased remarkably with increasing the flowrate in the blood vessel model. Therefore, while we were continuing to study to overcome the problems mentioned above, the study of the new method applying the acoustic cavitation was started. In … More side the space of acoustic cavitation where high temperature and high pressure are generated, a water molecule splits into radicals H2O → H^+ + OH^- producing hydroxyl radical OH^-. Microbubbles produced by the acoustic cavitation had also excellent characteristic of scattering, because acoustic impedance of microbubbles were quite difference from Surrounding organization. As the result, improvement of quality of ultrasonic image is expected. Namely, if the acoustic cavitation is generated near tumor selectively, We will be able to observe the process of the ruin of cancer cell by active oxygen with ultrasonic diagnostic equipment. Prior to our substantial evaluation, we used an ESR (electron spin resonance device) to make a qualitative evaluation of OH radicals produced by the acoustic cavitation generator. Next, suppression of proliferation of cancer cells with ultrasound exposure was studied in our laboratory. An ultrasound exposure experiment was performed on a culture of cancer cells of mouse T lymphoma (EL-4) in a flask. We confirmed that the number of cancer cells did not change remarkably immediately after exposure and increase the number of cells was suppressed remakably with the lapse of time during 24 hours after exposure. Less