PLA/Au Composites: Fabrication And Applications In Biomedical Imaging Used As A Dual Contrast Agents For Ultrasound (US) And Computed Tomography (CT)

The research progress of contrast agents used in biomedical imaging has been reviewed systematically in this dissertation. In special, multi-mode contrast agents were discussed in detail. Misdiagnosis and missed diagnosis might appear when just one kind of biomedical imaging technique was used. Therefore, more than one kind of biomedical imaging techniques was used to diagnose the diseases. Contrast agents are helpful for the enhancement of the contrast from the dieseased tissues. So they are widely used in diagnosing many typies of dieseases. Finding a kind of contrast agent that could be simultaneously applied to a variety of biomedical imaging is the development trend of clinic diagnosis and biomedical imaging.This dissertation is focusing on the design and preparation of a new kind of dual-mode contrast agent both for ultrasound (US) and computed tomography (CT). The structures and properties of the composites were confirmed and characterizated by TEM, SEM, XRD, XPS and UV-vis and other characterization methods. In addition, the contrast enhancement properties of the as-prepared composites have been investigated by both US and CT. The main study results are as follows:1. Different sizes and size distribution of PLA micro-bubbles have been prepared by double-emulsion solvent evaporation method. The effect of process parameters that affected the size and size distribution of PLA micro-bubbles were also investigated. PLA micro-bubbles that could be used as an US contrast agent were selected and modified by CTAB. The PLA@Au composite was prepared by the electrostatic attraction between the modified PLA micro-bubbles and gold nanoparticles which could be a type of contrast agent for CT. The characterization results confirmed the structure of the PLA@Au composite. The results indicated that this kind of composite material could be used as a dual-mode contrast agent both for US and CT.2. Water-soluble gold nanoparticles of different sizes were synthesized using glutathione and sodium borohydride. The size effect of gold nanoparticles on CT attenuation was investigated. The experimental results indicated that the smaller size of gold nanoparticles showed a higher X-ray attenuation than the bigger ones at the same concentration. PLA micro-bubbles encapsulated of gold nanoparticles were prepared by double-emulsion solvent evaporation method using the smallest gold nanoparticles colloid as inner aqueous phase. The effect of process parameters that affected the size of PLA micro-bubbles and encapsulation efficiency of gold nanoparticles were also investigated. The imaging results indicated that this kind of composite material could be used as a dual-mode contrast agent both for US and CT.The imaging results confirmed the imaging contrast enhancement properties of these two kinds of composite material based on PLA micro-bubbles and gold nanoparticles designed in this dissertation, indicating its potential application as the dual-mode contrast agent both for US and CT in future.