中文摘要：

开发水溶性的、可双光子激发的且可选择性产生单态氧的系统在光生物与动力治疗等方面具有应用价值．在本文中，利用荧光共振能量转移的原理设计了一套光动力治疗系统，其中带正电的水溶性共轭聚合物PFP作为能量给体，在单双光子激发下均具有较高的光捕获能力．带正电的卟啉作为能量受体，具有极高的单态氧量子产率，带负电的DNA是连接桥，使水溶性共轭聚合物PFP与卟啉之间的能量转移得以实现．通过研究这个体系的吸收、荧光光谱，荧光寿命，单态氧量子产率以及双光子吸收截面等性质，我们发现具有不同DNA序列的系统能量转移效率和单态氧量子产率均不相同，其中癌细胞中富含的四链DNA具有最高的选择性，这使得该系统在光动力治疗上具有非常好的应用前景．

英文摘要：

Photodynamic therapy （PDT） is a particular treatment of tumors, which localizes the biological responses by the way that light is applied. In this paper, we have designed a water-soluble system potentially for PDT, which could selectively generate singlet oxygen efficiently under both of one- and two-photon excitation. This complex consists of a cationic wa- ter-soluble conjugated polymer PFP, anionic DNA and a cationic porphyrin. The cationic conjugated polymer PFP and por- phyrin are connected by anionic DNA through electrostatic interactions. Energy transfer from conjugated polymer PFP （do- nor） to porphyrin （acceptor） is available since the considerable overlapping between the emission of donor and the absorption of acceptor （S0---~$2）. Steady-state spectra and fluorescence lifetime measurements have been performed on the complex with different DNA sequences in order to achieve the energy transfer efficiency. The results of steady-state fluorescence spectra show that there is a remarkable change of fluorescence intensity of the complex with G-quadruplex DNA, which indicates significant energy transfer from the donor to the acceptor. Furthermore, the greatest change of fluorescence lifetime measured by means of time-correlated single photon counting （TCSPC） also proves the highest energy transfer eff~ciency of the system with G-quadruplex DNA. Singlet oxygen quantum yield can be obtained by the detection of singlet oxygen emission spectra. Porphyrin bound to G-quadruplex DNA has the highest singlet oxygen quantum yield, which suggests this system a possible application in PDT since singlet oxygen could kill tumor cells. Two-photon absorption cross section has also been measured, which reflects the light-harvesting efficiency of the conjugated polymer PFP. The result shows that the conjugated polymer PFP owns large two-photon absorption cross section in the region of 720-850 nm where the transmission in tissue is higher compared to the visible light. The energy transfer efficiency and single