【作者】 程浩；

【导师】 胡一桥；

【作者基本信息】 南京大学 ， 制药工程（专业学位）， 2016， 硕士

【摘要】 光动力疗法(Photodynamic therapy,简称PDT),也称光化学疗法,是一种依靠光敏剂(Photosensitizers,简称PS)将吸收到的辐射能转换给肿瘤周边氧气并产生主要细胞毒性的单线态氧(1O2)用以肿瘤治疗的方法[1,2]。但是,光动力疗法的治疗效果因为肿瘤部位氧气供应不足而大打折扣[3,4]。在大多数实体瘤中,肿瘤先天乏氧的现象司空常见,这是因为肿瘤恶性增殖和混乱的微循环导致该部位氧气供应不足[5]。此外,光动力反应也会继续消耗氧气和导致血管封闭效应造成肿瘤部位进一步乏氧[6]。较低的氧气含量会降低光敏剂的光动力效应,因此光动力药物的疗效也受到了严重限制[7]。目前,已经有很多传统方法尝试优化肿瘤部位氧气水平以提高光动力疗法的疗效。例如,有科研团队利用间隔照射[8]或降低照射强度的方法[9,10]提高肿瘤部位血氧水平,但是这些方法只是降低了肿瘤部位的光动力氧气消耗,并没有根本上改善肿瘤先天乏氧,而且由光动力疗法引起的血管封闭效应依然会使乏氧状况进一步恶化[10]。高压氧舱也曾作为一种尝试提高肿瘤部位氧气含量的方法[11-14],但是血管封闭效应会阻止高含氧的血液流向肿瘤部位[15],而且过高的氧气分压所产生的毒副作用也限制了这一方法的临床上的使用。就目前所知,尚无一种方法能有效的克服肿瘤乏氧[16,17]。因此,改变光动力疗法的氧气限制变得极为重要。为了解决这一问题,我们将光敏剂和全氟化物包裹成纳米粒,发明出一种自供氧气的光动力疗法。这是因为在同样的氧分压之下,全氟化物比肿瘤基质拥有更高的溶氧量[18]。因此,尽管在光动力反应期间肿瘤氧气含量有限,但是全氟化物会富集周边的氧气以供给光敏剂发生光动力反应,从而大大的提高的光动力疗效。这种优化方法不受肿瘤先天乏氧、光动力反应氧气消耗和血管损伤效应的限制；而且,全氟化物还使得单线态氧在其中的寿命相比较于水或细胞基质有了极大地提高,这也同时延长了光动力的反应时间。因此,自供氧光动力疗法极大地提升了光动力反应的潜力。在本研究中,我们也评估了自供氧光动力疗法这一新抗肿瘤方法的效果。首先,研究了自供氧光动力疗法在体外产生单线态氧水平和肿瘤细胞毒性的能力；然后,我们在小动物体内实验中,进行瘤内给药研究自供氧光动力疗法的抗肿瘤增效情况；最后,我们也通过尾静脉注射药物进行自供氧光动力疗法的体内抗肿瘤增效的研究。我们认为这种新颖的方法将有助于光动力疗法在临床上的应用。更多还原

【Abstract】 Photodynamic therapy (PDT) depends on the ability of photosensitizers (PS) to transfer energy from lasers to tumour-dissolved oxygen (O2) to generate cytotoxic singlet oxygen (1O2) for cancer treatment. However, the effectiveness of PDT is impaired by an inadequate oxygen supply in tumours. In most solid tumours, hypoxia is common because the oxygen supply is reduced by disturbed microcirculation and deteriorated diffusion. Moreover, PDT worsens hypoxia through oxygen consumption and vascular shutdown effects. Low oxygen content can reduce the photodynamic efficacy of PS, preventing PDT from achieving its full therapeutic potential.Traditional methods have attempted to optimize tumour oxygenation to ensure PDT efficacy. For example, dividing irradiation into light-dark circles and extending irradiation with a low fluence rate have both been investigated as techniques for better tumour reoxygenation by the blood. However, these approaches only affect PDT-induced oxygen depletion, whereas the pre-existing hypoxia cannot be reversed; moreover, vascular shutdown due to PDT would also result in severe hypoxia. Hyperbaric oxygen inhalation has also been used to actively increase the level of tumour oxygen.However, vascular damage during PDT still prevents further oxygenation from hyperbaric blood; moreover, the potential toxic effects of excessive oxygen are an impediment to its clinical use. To our knowledge, no existing techniques can effectively reverse the tumour oxygen content during PDT. Therefore, optimizing the efficacy with limited oxygen is of great importance for photodynamic therapy.To address this challenge, herein we load photosensitizer into perfluorocarbon nanodroplets to develop a novel oxygen selfenriched photodynamic therapy (Oxy-PDT). Because of its highoxygen capacity, perfluorocarbon can maintain a higher oxygen content than the tumour matrix at a given oxygen partial pressure. Thus, although the tumour oxygen content remains limited during PDT, sufficient O2 can always be enriched in the PFC droplet for photodynamic consumption by the loaded PS, thus obtaining improved efficacy. This type of enhancement is possible regardless of pre-existing hypoxia, photodynamic consumption, or vascular damage; moreover, it has been reported that the 1O2 lifetime in perfluorocarbon is much longer than in the cellular environment or in water, which results in long-lasting photodynamic effects. Therefore, Oxy-PDT might help PS to achieve its full therapeutic potential. In this study, we assessed the therapeutic efficacy of Oxy-PDT as a novel form of PDT in cancer models. First, we studied the photodynamic effect of Oxy-PDT on the generation of 1O2 and its cytotoxicity by incubating tumour cells with Oxy-PDT, which were then irradiated with laser beams. Next, we assessed the effect of Oxy-PDT on tumour growth by intratumoural injections in vivo. Last, we examined the passive targeting of Oxy-PDT by intravenous injections in vivo. We envision that this new approach may guide improvements in the clinical use of PDT.更多还原