Preparation And In Vitro Imaging Of Doxorubicin Ultrasound Contrast Agent And LyP-1-labeled Superparamagnetic Iron Oxide MRI Probe

In this thesis, polylactic acid (PLA) as a kind of biodegradable material, was employed to fabricate the doxorubicin ultrasound contrast agent (DOX-PLA). ultrasound cavitation effect was used to release drugs and to valuate their anfitumor effect in vitro by MTT assay in MDA-MB-231 cells. Their ultrasound imaging in vitro was evaluated, either.The appearance of DOX-PLA contrast agent was red-orange with a powdered form. It has a uniformity distribution and smooth surface, the average diameter is about 1μm and contains about 108 particles per gram, when it completely insoluble in water and there was no aggregate phenomenon. The drug loading content is 3.14% and the encapsulation efficiency is 35.84%.In vitro, the results indicated that DOX-PLA contrast agent can enhance the ultrasound imaging significantly and it was an effective ultrasound contrast agent. When using ultrasound cavitation to release drugs, It exhibites similar cytotoxicity compared to free doxorubicin, the inhibition rate has no obvious difference when treated with the same concentration for 24 hours, however, there was a significant difference when treated with high concentration for 48 hours and 72 hours, especially DOX-PLA contrast agent of 10μg/ml concentration compared with free doxorubicin of 5μg/ml concentration, the intensity of inhibiting effect was similar, this may be due to the drug not all released, some drug was released into cells while others were not.In the evaluation of ultrasound cavitation on drug release effect, it is found that the antitumor effect has no evident different after ultrasonic irradiation treated for 24 hours, ultrasonic irradiation group showed better antitumor effect after 48 hours. The tumor inhibition rate of ultrasonic irradiation group is twice as much as non ultrasonic irradiation group in low concentration (0.1μg/ml) and high concentration (10μg/ml) respectively after 72 hours. Ultrasonic irradiation has significant promoting effect on drug release of DOX-PLA contrast agent. The coprecipitation method was employed to preparation of superparamagnetic iron oxide (SPIO). SPIO was coated with 3-aminopropyltrimethoxysilane (APTMS) and conjugated with LyP-1 to prepare of LyP-1-SPIO molecular probe. The experiment was divided into LyP-1-SPIO group, competition group, SPIO group and control group. The distribution of iron in MDA-MB-231 cells was evaluated by prussian blue stain and its effect on the enhancement of magnetic resonance imaging(MRI) in vitro was also observed.The appearance of SPIO was black and it has superparamagnetic characteristic. The average diameter was 115.6nm. The prussian blue staining showed that there was large amounts of iron in the LyP-1-SPIO group, while there was only a few blue iron particles were observed in the competion group and also very few in the SPIO group, none observed in the control group. The experiments in vitro indicated that it can significantly enhance the negative contrast effects. The SPIO coated with LyP-1 has an effective targeting ability to the MDA-MB-231 cells.