| Optical imaging(OI), positron emission tomography(PET), electronic computer X-ray tomography(CT), magnetic resonance imaging(MRI) as effective diagnostic techniques have an attractive increasing attention and grown to an unprecedented level. However, most of them have their own drawbacks, which restricts the further development of accurate diagnosis. Photoacoustic imaging is an emerging technique that combines the advantages of the high contrast of pure optical imaging features and high penetration depth of pure ultrasonic imaging characteristics, which is based on the absorption of light, thermoelastic expansion and detection of the generated ultrasound waves. It is in principle to avoid the influence of optical scattering, can provide high contrast and high resolution images, so it can be used as a research important means of biological tissue structure and function of information. Non radiation, safety made photoacoustic imaging technique developing rapidly in recent years and being used for cancer imaging in clinic.In order to achieve targeted research on biological tissue and further improve the signal of photoacoustic imaging, researchers have developed a number of near-infrared absorbing of inorganic nanomaterials, such as gold, silver, copper nanoparticles and carbon nanotubes. The toxicity of inorganic nano-materials always has been subject to significant debate. Thus, in recent years, studies on near-infrared absorption of organic material have become a research hotspot of photoacoustic imaging. Based on the research background, my research is to design and synthesize perylene diimide polymer with near infrared absorption and water soluble property, and the light of the basic physical properties and the self-assembly behavior were studied. Also, we made the polymers and magnetic nanoparticles into a composite which have photoacoustic imaging and magnetic resonance imaging properties.(1) We designed and synthesized a kind of perylene bisimide-based polymer, via atom radical polymerization(ATRP) at the ends of perylene diimide, we achieved a water soluble and biocompatible polymer(PAA-PDI-PAA) with near infrared absorption. Photophysics properties of this polymer was studied in different polar solvent as well as in aqueous solution at different pH,and also we studied the influence of different concentrations of polymer to the photoacoustic signal intensity. The experimental data show that polymer concentration is not linear relationship with photoacoustic signal strength, which showed very strong photoacoustic signal strength even in a low concentration.(2) We regulated the different polymerization degree and different concentration of polymer to study the self-assembly behavior(particle size, morphology) and the self-assembly mechanism.When polymerization degree of the polymer was fixed, through regulating the percentage of water in the mixed solvent, respectively, we obtained single, double, three layer structure of polymersome,and the morphology of this vesicles were confirmed by TEM.(3) We made the polymers and magnetic nanoparticles into a composite which have photoacoustic imaging and magnetic resonance imaging properties. Experiments data show that the dual modal imaging nanomaterial has a dramatic solubility in water, and the hydrate particle has a size around 24 nm to ensure material can be degraded and circulate inside the organism. The low cytotoxicity of the polymer demonstrated by MTT assay exhibits its potential in long-term clinical application. The magnetic resonance imaging and photoacoustic imaging research of the polymer show that the polymer in hela cells showed an excellent T2 imaging effect, photoacoustic imaging data also show that even under low concentration, the polymer can also have unexpected imaging results. |
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