Ngen Ethel J, Rajaputra Pallavi, You Youngjae
Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007, USA.
Bioorg Med Chem. 2009 Sep 15;17(18):6631-40. doi: 10.1016/j.bmc.2009.07.074. Epub 2009 Aug 3.
Mitochondria are attractive targets in photodynamic therapy. Two conjugates: TPP-Rh (a porphyrin-rhodamine B conjugate) and TPP-AO (a porphyrin-acridine orange conjugate), each possessing a single delocalized lipophilic cation, were designed and synthesized as photosensitizers. Their ability to target the mitochondria for photodynamic therapy was evaluated. The conjugates were synthesized by conjugating a monohydroxy porphyrin (TPP-OH) to rhodamine B (Rh B) and acridine orange base (AO), respectively, via a saturated hydrocarbon linker. To evaluate the efficiency of the conjugates as photosensitizers, their photophysical properties and in vitro photodynamic activities were studied in comparison to those of TPP-OH. Although fluorescence energy transfer (FRET) was observed in the conjugates, they were capable of generating singlet oxygen at rates comparable to TPP-OH. Biologically, exciting results were observed with TPP-Rh, which showed a much higher phototoxicity [IC(50), 3.95 microM: irradiation of 400-850 nm light (3 mW cm(-2)) for 1 h] than either TPP-OH or Rh B (both, IC(50), >20 microM) without significant dark toxicity at 20 microM. This improved photodynamic activity might be due to a greater cellular uptake and preferential localization in mitochondria. The cellular uptake of TPP-Rh was 8 and 14 times greater than TPP-OH and Rh B, respectively. In addition, fluorescence imaging studies suggest that TPP-Rh localized more in mitochondria than TPP-OH. On the other hand, TPP-AO showed some dark toxicity at 10 microM and stained both mitochondria and nucleus. Our study suggests that conjugation of photosensitizers to Rh might provide two benefits, higher cellular uptake and mitochondrial localization, which are two important subjects in photodynamic therapy.
线粒体是光动力疗法中具有吸引力的靶点。设计并合成了两种共轭物：TPP-Rh（一种卟啉-罗丹明B共轭物）和TPP-AO（一种卟啉-吖啶橙共轭物），它们各自含有一个单一的离域亲脂性阳离子，作为光敏剂。评估了它们靶向线粒体进行光动力治疗的能力。通过将单羟基卟啉（TPP-OH）分别经由饱和烃连接基与罗丹明B（Rh B）和吖啶橙碱（AO）共轭来合成这些共轭物。为了评估共轭物作为光敏剂的效率，将它们的光物理性质和体外光动力活性与TPP-OH进行了比较研究。尽管在共轭物中观察到了荧光能量转移（FRET），但它们产生单线态氧的速率与TPP-OH相当。在生物学上，TPP-Rh观察到了令人兴奋的结果，其显示出比TPP-OH或Rh B（两者的IC(50)均>20 microM）更高的光毒性[IC(50)，3.95 microM：照射400 - 850 nm光（3 mW cm(-2)）1小时]，在20 microM时无明显暗毒性。这种改善的光动力活性可能归因于更高的细胞摄取和在线粒体中的优先定位。TPP-Rh的细胞摄取分别比TPP-OH和Rh B高8倍和14倍。此外，荧光成像研究表明TPP-Rh在线粒体中的定位比TPP-OH更多。另一方面，TPP-AO在10 microM时表现出一些暗毒性，并且同时对线粒体和细胞核进行染色。我们的研究表明，将光敏剂与Rh共轭可能带来两个好处，即更高的细胞摄取和线粒体定位，这是光动力疗法中的两个重要课题。
