Bottiroli G, Croce A C, Balzarini P, Locatelli D, Baglioni P, Lo Nostro P, Monici M, Pratesi R
Centro di Studio per l'Istochimica CNR, Dipartimento di Biologia Animale, Università, Pavia, Italy.
Photochem Photobiol. 1997 Sep;66(3):374-83. doi: 10.1111/j.1751-1097.1997.tb03161.x.
Rose bengal, a xanthene derivative among the most efficient producer of singlet oxygen, was submitted to a chemical modification consisting in the introduction of an acetate group into the aromatic ring fluorophore structure. The acetate group acts as a quencher, thus inactivating both fluorescence and photosensitization properties of the molecule. In the modified structure, rose bengal acts as a fluorogenic substrate giving rise to the cellular reaction termed fluorochromasia. The acetate group is recognized by a carboxylic esterase activity that splits it. Removal of the quencher group results in restoring the native structure of photosensitizer inside the cells. The intracellular turnover of rose bengal acetate was studied in rat glioma-derived cultures cells, in terms of the balance of the processes of influx and enzyme hydrolysis of the fluorogenic substrate, and of the efflux of the fluorescent product. A large intracellular accumulation of photosensitizer is obtained when treatments are performed with the fluorogenic substrate, even at the drug concentration at which rose bengal does not enter the cells. The intracellular localization allows rose bengal to exert a more effective photosensitization effect. Provided that the quencher group is selected according to the metabolic properties of the tumor cells, the use of fluorogenic substrates as photosensitizer precursors could improve fluorescence diagnosis and the photodynamic therapy of tumors, exploiting the biological properties that distinguish pathological from normal conditions.
孟加拉玫瑰红是一种最有效的单线态氧产生剂中的呫吨衍生物，它经历了一种化学修饰，即在芳香环荧光团结构中引入一个乙酰基。乙酰基作为猝灭剂，从而使分子的荧光和光敏化特性失活。在修饰后的结构中，孟加拉玫瑰红作为一种荧光底物引发了称为荧光染色的细胞反应。乙酰基可被一种能将其裂解的羧酸酯酶活性识别。猝灭基团的去除导致细胞内光敏剂的天然结构得以恢复。在大鼠胶质瘤衍生的培养细胞中，研究了乙酰基孟加拉玫瑰红的细胞内周转情况，涉及荧光底物的流入和酶水解过程以及荧光产物的流出之间的平衡。当用荧光底物进行处理时，即使在孟加拉玫瑰红无法进入细胞的药物浓度下，也能在细胞内大量积累光敏剂。细胞内定位使孟加拉玫瑰红能够发挥更有效的光敏化作用。如果根据肿瘤细胞的代谢特性选择猝灭基团，那么将荧光底物用作光敏剂前体可以利用区分病理状态与正常状态的生物学特性，改善肿瘤的荧光诊断和光动力疗法。
