Design,Synthesis And Antitumor Activity Of Novel Chlorin Derivatives As Photosensitizer For Photodynamic Therapy

Cancer is one of the deadliest diseases of our time and throughout the world. The traditional cancer treatments, including surgery, radiation therapy and chemotherapy, result in serious side effects caused by the loss of normal organ function. Therefore, it is not good to improve patient’s quality of life. Photodynamic therapy (PDT) has recently emerged as a promising alternative therapy against cancer, with several PDT agents approved and used clinically since the early 1980s. PDT belongs to a noninvasive antitumor treatment on normal tissue. PDT is now also an emerging clinical mode for the treatment of neoplastic and non-malignant lesions, with extensive potential for application against virus, bacterial and fungal diseases. PDT requires three elements such as photosensitizer (PS), light and oxygen and PS is a core factor. Development of photosensitizers goes through first generation of porphyrins represented by Photofrin and second generation of chlorins marked by verteporfin, talaporfin and temoporfin. An ideal PS should be able to produce singlet oxygen efficiently, and have no dark toxicity. Currently, the research and development of PDT is focused on structure modification of PS in order to develop new generation chlorin PS with longer wavelength, stronger photosentitive activity, lower toxicity and better ADMET properties. In this thesis, our research work is independently composed of two parts. Firstly, a series of novel chlorin PS with high efficiency, low toxicity and good ADMET properties are designed and synthesized via the 3-vinyl etherification and 17-carboxyl connecting amino acids of pyropheophorbide-a which is given by degradation from silkworm chlorophyll. Secondly, novel magnetic nano photosensitizer is designed and prepared by conjugating pyropheophorbide-a with ultrafine superparamagnetic iron oxide (USPIO) for tumor target diagnosis and treatment.1. Design, synthesis and anti-tumor activity of novel chlorin photosensitizer derivatesPyropheophorbide-a is part of chlorin and its hexyl ether derivative (HPPH) is currently in advanced clinical trials, indicating that alkyl ether chain of pyropheophorbide-a played an important role in biological efficacy. Accordingly, we first design and synthesize 5 pyropheophorbide-a ether derivatives (6a-6e). Secondly, based on amino acide as a prodrug design strategy, the solubility and other pharmacokinetic properties of PS always will be improved after it is coupled with amino acid. For example, mono-aspartic acid chlorin e6 (Talaporfin), which approved in clinical application in 2004, is a successful case. We further design and synthesize 15 pyropheophorbide-a ether amino acid derivatives (8a-8o) by pyropheophorbide-a ether derivatives (6a-6e) coupling with amino acids such as aspartic acid, glutamic acid and lysine, respectively. Lastly, in vitro anticancer activities of 19 target compounds against HCT-116, MKN45 and MDA-MB-231 cells are determinated by MTT. The result shows that under the light dose of 10 J/cm2, all the target compounds have excellent PDT anticancer activity against 3 cells. Moreover, their activities are significantly better than Adriamycin. The preliminary structure-activity relationship of target compounds shows that:(1) PDT anti-tumor activity of the target compounds enhances with their ether carbon chain growth, the one with 6-8 carbon atoms as the best. When ether carbon chain length continues to increase, the activity will be reduced. The reasonable explanation is that ether chain length determines the lipophilicity of PS, suggesting that the appropriate lipophilicity of PS is necessary for PDT anticancer activity.(2) In vitro PDT anti-tumor activity and dark toxicity of pyropheophorbide-a ether derivative (6a-6d) is higher than that of its corresponding ether amino acid derivative (8a-8o), indicating that ether amino acid derivative maybe act as prodrug, resulting in decreasement of its activity and toxicity in vitro. These need further research to clarify from the aspects of in vivo pharmacodynamics, pharmacokinetics and molecular mechanism of action.(3) The hexyl ether of pyropheophorbide-a (6d) exhibits the best activity among all pyropheophorbide-a ether derivatives (6a-6d).(4) Among the amino acid derivatives of pyropheophorbide-a ethers (8a-8o), all compounds with hexyl or/and octyl ether (8d,8e,8i,8j,8n) show the better activity than others. Especially,8d and 8j relatively display the best activity and it is worthy of further study.2. Design, synthesis, diagnosis and anti-tumor activity of novel magnetic nanoparticles photosensitizer targeting to cancer cellWith the rapid development of materials science, many related subjects are also experiencing a deeper chiastopic fusion. Some nano materials are wildely used in pharmacy discipline for targeting diagnosis and treatment of tumor. Based on that magnetic nanoparticles such as ultrafine superparamagnetic iron oxide (USPIO) has good biological compatibility and tumor targeting aggregation effect, a novel magnetic nano photosensitizer is successfully prepared via pyropheophorbide-a conjugation with USPIO which is modified by amino, followed by determination its the relaxation rate, in vitro intracellular fluorescence imaging and magnetic resonance (MR) imaging and in vitro PDT anti-tumor activity against human colon cancer cells (HCT-116). The preliminary results show that:(1) Magnetic nano photosensitive molecules possesses good magnetic stability and can quickly enter the HCT-116 cells, which achieving the maximum fluorescence at 3 h after administration, indicating that the magnetic nano photosensitizer provides with good application prospect in tumor fluorescence imaging diagnosis.(2) T2 nuclear magnetic resonance signal of HCT-116 cells administrated for nano magnetic photosensitive molecules was significantly lower than that of the negative control group (without magnetic photosensitizer), suggesting that the magnetic nano photosensitizer can be used for tumor magnetic resonance imaging diagnosis.(3) At a light dose of 0.9-9 J/cm2, magnetic nano photosensitive molecules showed good PDT effects on HCT-116 cells, suggesting that the magnetic nano photosensitizer not only can be used for tumor fluorescence imaging and MR imaging diagnoses, but also can be used for the PDT treatment on tumor. Thus, it can realize the integration diagnosis and treatment of tumor.