【作者】 温亚楠；

【导师】 杨延强；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2010， 博士

【摘要】 近年来,光动力治疗作为一种新型的肿瘤治疗方法逐渐发展起来并在生物医学研究领域受到了广泛的关注。光动力治疗是指利用光敏剂的光照激发来产生毒性物质如单线态氧等从而杀伤肿瘤细胞的方法,是一种无损伤的物理性肿瘤治疗方法。在制约光动力治疗技术发展进步的各个环节中,光敏剂的开发研制无疑是举足轻重的一环。目前已有大量工作投入到了新型光敏剂的研究中并取得了很大进展。其中卟啉类光敏剂是最早应用于光动力治疗中的光敏药物,其肿瘤富集性好,单线态氧量子产率高,分子可塑性大,是光敏药物研究的主流;而半导体量子点则是一种新兴的光敏材料,独特的尺寸效应使得其吸收和发射光谱可连续调谐,光源选择范围广,稳定性好,量子产率高,双光子吸收截面大,因而成为极具应用潜力的光敏药物。随着光动力治疗临床应用领域的扩大,光敏剂的研究工作也在不断地开展和深入。然而,由于光敏剂属于交叉学科研究范畴,各学科研究侧重点不同,很容易顾此失彼,导致目前关于光敏剂生物化学反应机制方面的工作报道较多,而对其本身的发光特性及潜在的物理机制研究不够深入。卟啉和量子点作为典型的光敏剂材料,其自身的光致发光过程是实现光敏化作用的前提,也是肿瘤诊断和定位的依据,对其发光特性的研究还可以获取大量分子信息,为新型光敏药物的开发研制和已有光敏剂的性质改良提供依据。因此,本课题以极具光动力治疗应用潜力的飞秒脉冲激光作为激发光源,搭建了稳态和纳秒时间分辨荧光光谱探测系统,对几种典型的水溶性和非水溶性卟啉及量子点光敏剂进行了光谱表征和分析;针对双光子激发光动力治疗的需求研究了材料的双光子激发荧光特性;观察了光致损伤行为;并成功的利用量子点作为能量给体实现了卟啉光敏剂的间接活化,讨论了二者间的能量转移机制及可能的转移通道。首先,对合成多种卟啉衍生物的母体材料四苯基卟啉(TPP)进行了详细的光谱表征,并在单光子和双光子两种不同激发条件下对其光损伤特性进行了研究分析,发现在光损伤过程中伴随有产物生成。损伤产物表现出良好的光稳定性和双光子荧光特性,具有光动力治疗的潜在应用价值。通过光谱分析推测产物应为苯环断裂基础上氧化形成的二氢卟吩类氧化物。另外,通过计算不同激发功率下的损伤速率,发现TPP分子在单光子和双光子激发下表现出不同的损伤速率—功率关系,暗示双光子激发下有更高阶光损伤机制存在。其次,对水溶性四磺酸苯基卟啉(TSPP)单体及二聚体进行了对比研究。通过调节pH值获得了TSPP单体和二聚体溶液样品,实验结果表明,TSPP二聚体为单体间J-聚合形式形成,聚合效应对TSPP的光谱特性产生了很大的影响,使得二聚体和单体的光谱具有显著区别。且这种聚合现象具有光稳定性,不会因光照而分离。单体表现出比二聚体更好的光稳定性,几乎没有损伤现象发生,而二聚体的荧光损失在一次常规光动力治疗的时间范围内也不超过15%。再次,对非水溶性CdSe量子点和水溶性CdTe量子点进行了稳态和时间分辨光谱特性研究,结果表明量子点荧光由带边激子态和表面诱捕态两种发射成分组成,其中带边激子态能量较高,发射中心波长较短,而诱捕态能量较低,发射中心波长较长。对大小尺寸CdTe量子点混合体系研究发现,小尺寸绿光量子点对大尺寸红光量子点具有荧光增强效应,且这种效应与激发方式和粒子间距离无关,讨论了这种增强效应可能的物理机制。另外研究了共存体系的稳定性,发现静置后的混合体系中发生了Ostwald熟化作用。最后,以量子点为能量给体,卟啉为能量受体,在800nm双光子激发下,分别对非水溶性CdSe-TPP和水溶性CdTe-TSPP两种不同样品体系进行了稳态和时间分辨光谱研究。实验表明两种体系中都存在明显的能量转移现象,量子点荧光强度显著下降而卟啉荧光强度上升,实现了卟啉光敏剂的有效间接激活,弥补了卟啉光敏剂双光子吸收截面较小的缺陷,为体系在双光子激发光动力治疗中的应用提供了依据。另外,通过对量子点时间分辨动力学数据的分析,判断体系中的主要能量转移机制为电子交换机制,并发现能量转移很可能是经由量子点表面诱捕态而发生的,因此可以通过表面修饰来增加能量转移效率,进而提高卟啉的敏化效率。更多还原

【Abstract】 In the resent years, photodynamic therapy (PDT) attracts more attention in the biomedical research field as a new way dealing with tumor. It is a non-invasive physical diagnostic and therapic method using photosensitizers associated with laser irradiation to produce tumor toxicity material which can damage the tumor tissue. Development of photosensitizers is a critical factor affecting the clinical application of PDT. So far, a lot of work has been done on the investigation of new type of photosensitizers and great progress has been made. The first photosensitizer used in PDT is the porphyrin type compound. Porphyrins are typical photosensitizers with high singlet oxygen quantum yields, convenient molecular modification and preferential accumulation in tumor, so that they play the major role in study of the PDT drugs. Whereas semiconductor quantum dot (QD) is a new type of photosensitizer with the unique quantum size effect. QDs possess contiueous absorption and emission wavelength, high photo- and chemical stability, high fluorescence quantum yield and larger two-photon absorption cross section, making them potential photosensitiers in PDT application.With the rapid development of PDT, studies on photosensitizers become faster and deeper. However, photosensitizer is an interdiscipline research topic, and different research fields focus on different problem, resulting in an imbalance in the study of the photosensitizers. Till now, a lot of works have been reported on the biochemical reaction mechanism of the photosensitizers, but studies on the photoluminescence of the sensitizer itself and the correspongding underlying physical mechanism is pretty rare. As typical photosensitizers, the photoluminescent process of porphyrins and QDs is the precondition of the photosensitization and tumor diagnosis and localization. The photoluminescent properties can provide mass of molecular information, whicn can accelerate the decelopment of new sensitizers and improvement of exist sensitizers.So in the present thesis, femtosecon pulsed laser, which is believed to be a potential light source for PDT, is used as the excitation source to build a steady-state and nanosecond time-resolved fluorescence spectral detected system. Several typical hydrophilic and hydrophobic porphyrins and QDs are studied and their spectral characteristics are analyzed. Two-photon excitation fluorescence spectroscopy is performed. Photodamge behavior of the photosensitizers is observed. Porphyrins are successfully activated by the QDs by way of the excited-state energy transfer and the possible energy transfer mechanism and transfer channel is discussed.Firstly, the spectral characteristics meso-tetraphenylporphyrin (TPP) is measured and analyzed. Its photodamage behavior under one- and two-photon excitation is detailed discussed. Results suggest that laser irradiation on TPP mainly causes two simultaneously occurring photoprocesses: photodamage and formation of a porphine-type photoproduct. This product, which is observed to possess superior photostability and two-photon absorbing ability compared with the original TPP sensitizer, is likely to be treated as a secondary photosensitizer in the activation process of photodynamic therapy (PDT). This work might be helpful for the drug evaluation in the practical application of PDT. The damage rate exhibits different power dependence in one-and two-photon excitation, suggesting higher-order photodamage mechanism operated in the two-photon excitation process.Secondly, comparision study has been done between meso-tetra(4-sulfonatophenyl)porphine dihydrochloride (TSPP) monomer and dimmer. TSPP monomer and dimer are achieved by adjusting the pH value of the solution. Results show that TSPP dimer displays a J-aggregation pattern. The aggregation effect influenced the spectral properties of TSPP greatly, and this aggregation effect is stable. The TSPP monomer possess better photostability during the laser irradiation, and the fluorescence intensity loss is less than 15% within a typical PDT time.Thirdly, CdSe and CdTe QDs are studied by steady-state and time-resolved spectroscopy. Results suggest a combination of two components in the luminescence behavior of CdTe QDs. The fast component is the excitonic state emission caused by narrow band-edge effect and the slow component is the trapping state emission caused by surface-related effect, in which the trapping state emits at a relative lower energy level than the excitonic state emission. The mixture of different size of CdTe QDs is studied. Results show that QDs of small size have a fluorescence enhancemet effect on the QDs of large size, and this enhancemet effect is irrelative to the particle distance. Possible enhancemet mechanism is discussed. The stability of the mixture is also observed and Ostwald ripening is found in the sample system.Finally, use QDs as energy donors and porphyrins as energy acceptors to build a hydrophilic CdTe-TSPP and hydrophobic CdSe-TPP model system, and study their steady-state and time-resolved spectra under 800nm two-photon excitation. Energy transfer process is observed in both of the two model systems. The fluorescence intensity of the QDs decreases and that of porphyrins increases, successfully indirectly activated the porphyrin sensitizers and compensates their small two-photon absorption cross section, which could be helpful for taking use of these model systems in the two-photon excitation PDT. In addition, electron exchange is deduced to be the dominant transfer mechanism by analyzing the time-resolved data, and non-radiative energy transfer is supposed to occur through the trapping state of QDs, which presents a way of raising energy transfer efficiency in this type of donor-acceptor pairs.更多还原