Mishra Padmaja P, Adhikary Ramkrishna, Lahiri Priyanka, Datta Anindya
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, India 400 076.
Photochem Photobiol Sci. 2006 Aug;5(8):741-7. doi: 10.1039/b601172a. Epub 2006 Jun 2.
Cyclodextrins (CD) are often proposed as potential vehicles in targeted drug delivery. However, if the membrane structure is disrupted by CD, then it cannot be considered to be a good drug delivery vehicle. When an extrinsic fluorescence probe is used to monitor such interactions, there are no less than three possible equilibria that can operate simultaneously: surfactant-cyclodextrin, surfactant-fluorophore and cyclodextrin-fluorophore. The fluorescence intensity/lifetime might be affected by all these and so, the results depend strongly on the fluorophore used as well as the nature of the surfactant. This aspect highlights the importance of the suitability of the fluorescence probe to be used to study complicated systems and interaction. In the present work, chlorin p6, prepared from chlorophyll from spinach leaves, has been used as the fluorescence probe to investigate the interaction between alpha-CD and beta-CD with the neutral surfactants Triton X 100 (TX 100) and cetyl trimethyl ammonium bromide (CTAB). The fluorophore is found to be a sensitive one for the study of the interaction of alpha, beta and gamma-CD with the surfactants TX 100 and CTAB. It is found that contrary to earlier reports, a complex between alpha-CD and TX 100 is formed, even though the binding constant is not very high. This observation can be obtained with chlorin p6, which does not bind to the CDs, but not with a fluorophore, which binds to the CD as well and thus complicates the situation as the binding with CD is stronger than that between TX 100 and alpha-CD as compared to that between TNS and CD.
环糊精（CD）常被提议作为靶向药物递送的潜在载体。然而，如果膜结构被CD破坏，那么它就不能被认为是一种良好的药物递送载体。当使用外在荧光探针监测此类相互作用时，至少有三种可能的平衡可以同时起作用：表面活性剂 - 环糊精、表面活性剂 - 荧光团和环糊精 - 荧光团。荧光强度/寿命可能会受到所有这些因素的影响，因此，结果在很大程度上取决于所使用的荧光团以及表面活性剂的性质。这方面凸显了用于研究复杂系统和相互作用的荧光探针适用性的重要性。在本工作中，由菠菜叶中的叶绿素制备的二氢卟吩p6已被用作荧光探针，以研究α - CD和β - CD与中性表面活性剂吐温X 100（TX 100）和十六烷基三甲基溴化铵（CTAB）之间的相互作用。发现该荧光团对于研究α、β和γ - CD与表面活性剂TX 100和CTAB的相互作用是灵敏的。发现与早期报道相反，即使结合常数不是很高，α - CD和TX 100之间也形成了复合物。使用不与CD结合的二氢卟吩p6可以得到这一观察结果，但使用也与CD结合的荧光团则无法得到，因为与CD的结合比TX 100与α - CD之间的结合更强，这使得情况变得复杂，与TNS和CD之间的结合相比。
