서강대학교

초록/요약

In this study, human serum albumin conjugated microbubble was initially developed for the sensitive diagnosis and effective therapy of tumor. Microbubble which was based on the phospholipid (DSPC) was fabricated with the narrow size distribution of 1-2μm. The narrowly size-distributed microbubbles were enhanced ultrasound intensity maximally at the frequency of 3 MHz. This frequency was optimal for the home-made microbubbles and activates the maximal number of microbubble for the ultrasound imaging because resonance frequency of ultrasound is generally related to the shell properties, gas index and mainly size distribution of microbubble. Home-made microbubble with the lipid shell was extremely similar to the commercial contrast agent and theoretically showed similar resonance frequency to the frequency of commercial ultrasound contrast agent. With this property for the enhancement of ultrasound signals, human serum albumin nanoparticle was conjugated to the surface of home-made microbubbles for the effective tumor therapy with the visual guidance by ultrasound imaging. As a vehicle for the transport anti-tumor drug, paclitaxel, paxlitaxel loaded HSA-NPs were successfully conjugated to the microbubble by peptide bond (HSA-NPs-MB). This diagnostic and therapeutic contrast agent enhanced not only the ultrasound contrast intensity and stability in an aspect of biomedical imaging tool but also penetration efficiency to the tumor region by ultrasound exposure in the therapeutic effect. HSA-NP on the surface of microbubble delayed the microbubble collapse against ultrasound exposure for convenience to long periodic imaging. Indeed, the unique property of albumin, which plays a role in transport for hydrophobic molecules, authorized the HSA-NPs-MB binding to the tumor site. In the result, efficiency to suppress tumor growth was highly increased then, survival ratio was increased either. Also, the combination of HSA-NPs-MB to ultrasound enhanced the survival ratio by cavitation of microbubble. Therefore, we firstly expected this HSA-NPs-MB could be talented candidate for the effective tumor therapy with the ultrasound guidance. However, recent biomedical imaging modalities have been generally combined to other biomedical imaging technique. Because diagnosis with only one kind of imaging tool often miss the abnormalities of living tissues. Therefore, it is necessary for biomedical imaging modalities to combine others for the structural imaging and functionalized imaging. Hence, we developed multi modal imaging contrast agent for photoacoustic and ultrasound imaging. Porphyrin microbubbles (porphyrin-MBs). Porphyrin-MBs demonstrated high optical absorption at the 700nm of wavelength and strongly demonstrated PA intensity. And also, porphyrin-MBs maintained the capacity for the ultrasound imaging. Most of all, porphyrin-MBs was uniquely amplified PA contrast intensity. That was frequency-dependent PA signal amplification. Microbubble is optimally structured for the resonance to acoustic wave. Therefore, photoacoustic wave which was generated by porphyrin was resonated to the gas cored microbubble and resonated for the amplification of PA intensity. Regarding this theory, we know that optimal resonance frequency is significantly depended on the size diameters of microbubble. Therefore, we massively control the size distribution of porphyrin-MBs then measured PA signal with the three kinds of ultrasound transducers ranging 2 – 5, 5 – 14, 8 – 20 MHz, respectively. PA intensities of porphyrin-MBs were size-dependently resonated to their optimal resonance frequency. To support the result that PA intensity was amplified at optimal resonance frequency by gas-cored structure, porphyrin liposome was compared as an aqueous cored particle. And porphyrin-MBs demonstrate significantly higher intensity at the 5 - 14 MHz. This multi modal contrast agent was applied for the tumor therapy with photoacoustic and ultrasound imaging guidance. Thus, this theragnostic contrast agent included the function of local delivery by ultrasound stimulus release. This porphyrin-MBs-NP demonstrated high contrast photoacoustic and ultrasound intensities. Also, photoacoustic image by porphyrin-MBs-NPs was maintained over 30 min for long time imaging while ultrasound image was limited after US exposure for 15 min. For the therapeutic effect by ultrasound-stimulus drug delivery, in vitro cell viability and in vivo tumor suppression were conducted. The ultrasound exposure was significantly effective to the burst release of nanoparticle containing paclitaxel and enhancement of penetration efficiency of nanoparticle. Also, biodistribution of porphyrin-MBs-NPs with or without ultrasound exposure at the tumor showed that the local ultrasound exposure enhanced local delivery of nanoparticle to tumor. Then this multifunctional theragnsotic contrast agent could be alternative for the sensitive tumor diagnosis by structural imaging by ultrasound image and optically functionalized PA image and for enhancement of tumor therapy by ultrasound stimulus tumor therapy by local delivery. Thus, this theragnstic contrast agent was expected to reduce side effect by normal cell death via randomly delivered anticancer drugs.