Chakrabarty Alok, Das Paramita, Mallick Arabinda, Chattopadhyay Nitin
Department of Chemistry, Jadavpur University, Calcutta 700 032, India.
J Phys Chem B. 2008 Mar 27;112(12):3684-92. doi: 10.1021/jp709818d. Epub 2008 Feb 29.
Steady-state and time-resolved fluorometric techniques have been exploited to study the photophysical and distribution behavior of an efficient cancer cell photosensitizer, norharmane (NHM), in well-characterized, biomimicking nanocavities formed by cationic micelles with varying surfactant chain length. Amphiphiles like dodecyl trimethyl ammonium bromide (DTAB), tetradecyl trimethyl ammonium bromide (TTAB), and cetyl trimethyl ammonium bromide (CTAB) have been used for the purpose. Emission behavior of NHM is very much dependent on the surfactant concentration as well as their hydrophobic chain length. The binding constant (K) and free-energy change (DeltaG) for the interaction of NHM with the cationic micelles have been determined from the fluorescence data. Polarity of the microenvironment around the probe has been determined in the cationic micellar environments from a comparison of the variation of fluorescence properties of the two-prototropic species of the probe in water/dioxane mixture with varying composition. Experimental results demonstrate that the variation in the cationic surfactant chain length plays an important role in promoting a specific prototropic form of the probe molecule. Fluorescence decays are biexponential in all the micelles indicating that the probe molecules are distributed between the two distinct regions of the micelles. The population of the component with a longer lifetime corresponds to the probe in the head group site, while the short-lived component comes from the probe bound to the core region of the micelles. On the basis of the lifetime measurements, the partitioning behavior of the chromophore in the head group and in the core regions in the micelles has been determined.
稳态和时间分辨荧光技术已被用于研究一种高效癌细胞光敏剂去甲哈尔满（NHM）在由具有不同表面活性剂链长的阳离子胶束形成的特征明确的仿生纳米腔中的光物理和分布行为。为此使用了诸如十二烷基三甲基溴化铵（DTAB）、十四烷基三甲基溴化铵（TTAB）和十六烷基三甲基溴化铵（CTAB）等两亲物。NHM的发射行为在很大程度上取决于表面活性剂浓度及其疏水链长度。已根据荧光数据确定了NHM与阳离子胶束相互作用的结合常数（K）和自由能变化（ΔG）。通过比较探针的两种质子转移物种在不同组成的水/二氧六环混合物中的荧光性质变化，在阳离子胶束环境中确定了探针周围微环境的极性。实验结果表明，阳离子表面活性剂链长的变化在促进探针分子的特定质子转移形式方面起着重要作用。在所有胶束中荧光衰减都是双指数的，这表明探针分子分布在胶束的两个不同区域之间。寿命较长的组分对应于位于头部基团位点的探针，而短寿命组分来自与胶束核心区域结合的探针。基于寿命测量，已确定了发色团在胶束头部基团和核心区域中的分配行为。
