PDT Center, Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA.
Bioconjug Chem. 2011 Nov 16;22(11):2283-95. doi: 10.1021/bc200345p. Epub 2011 Oct 21.
Purpurinimide methyl esters, bearing variable lengths of N-substitutions, were conjugated individually to a cyanine dye with a carboxylic acid functionality. The results obtained from in vitro and in vivo studies showed a significant impact of the linkers joining the phototherapeutic and fluorescence imaging moieties. The photosensitizer-fluorophore conjugate with a PEG linker showed the highest uptake in the liver, whereas the conjugate linked with two carbon units showed excellent tumor-imaging and PDT efficacy at 24 h postinjection. Whole body imaging and biodistribution studies at variable time points portrayed enhanced fluorescent uptake of the conjugates in the tumor compared to that in the skin. Interestingly, the conjugate with the shortest linker and the one joining with two carbon units showed faster clearance from normal organs, e.g., the liver, kidney, spleen, and lung, compared to that in tumors. Both imaging and PDT efficacy of the conjugates were performed in BALB/c mice bearing Colon26 tumors. Compared to the others, the short linker conjugate showed poor tumor fluorescent properties and as a corollary does not exhibit the dual functionality of the photosensitizer-fluorophore conjugate. For this reason, it was not evaluated for in vivo PDT efficacy. However, in Colon26 tumor cells (in vitro), the short linker was highly effective. Among the conjugates with variable linkers, the rate of energy transfer from the purpurinimide moiety to the cyanine moiety increased with deceasing linker length, as examined by femtosecond laser flash photolysis measurements. No electron transfer from the purpurinimide moiety to the singlet excited state of the cyanine moiety or from the singlet excited state of the cyanine moiety to the purpurinimide moiety occurred as indicated by a comparison of transient absorption spectra with spectra of the one-electron oxidized and one-electron reduced species of the conjugate obtained by spectroelectrochemical measurements.
带有可变 N-取代基的紫质亚胺甲酯分别与具有羧酸官能团的菁染料缀合。来自体外和体内研究的结果表明，连接光疗和荧光成像部分的接头有显著影响。带有 PEG 接头的光敏剂-荧光团缀合物在肝脏中的摄取量最高，而用两个碳原子单元连接的缀合物在注射后 24 小时显示出优异的肿瘤成像和 PDT 效果。在不同时间点进行的全身成像和生物分布研究表明，与皮肤相比，肿瘤中缀合物的荧光摄取增强。有趣的是，与最短接头和两个碳原子单元连接的缀合物与正常器官（如肝、肾、脾和肺）相比，从正常器官更快清除。在携带 Colon26 肿瘤的 BALB/c 小鼠中进行了缀合物的成像和 PDT 功效评估。与其他相比，短接头缀合物显示出较差的肿瘤荧光特性，因此不表现出光敏剂-荧光团缀合物的双重功能。出于这个原因，它没有被评估用于体内 PDT 功效。然而，在 Colon26 肿瘤细胞（体外）中，短接头非常有效。在具有可变接头的缀合物中，通过飞秒激光闪光光解测量检查，从紫质亚胺部分到菁染料部分的能量转移速率随着接头长度的减小而增加。如通过比较瞬态吸收光谱与通过光谱电化学测量获得的缀合物的单电子氧化和单电子还原物种的光谱所示，没有从紫质亚胺部分到菁染料的单重激发态的电子转移，或从菁染料的单重激发态到紫质亚胺部分。
