Mazzaglia Antonino, Angelini Nicola, Lombardo Domenico, Micali Norberto, Patané Salvatore, Villari Valentina, Scolaro Luigi Monsù
Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR, Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina, Salita Sperone 31, 98166 Messina, Italy.
J Phys Chem B. 2005 Apr 21;109(15):7258-65. doi: 10.1021/jp0501998.
The interaction between the anionic 5,10,15,20-tetrakis(4-sulfonatophenyl)-21H,23H-porphyrin (TPPS) and cationic vesicles formed by heptakis(2-omega-amino-O-oligo(ethylene oxide)-6-hexylthio)-beta-cyclodextrin (SC6CDNH2) has been investigated in detail through a combination of elastic light scattering (ELS), quasi-elastic light scattering (QELS), zeta potential measurements, and time-resolved fluorescence anisotropy. ELS experiments provided the first structural characterization of these cationic vesicles both in the absence and in the presence of TPPS porphyrin, modeling the system as a spherical particle described by a single thin shell form factor. The structure of mixed hetero-aggregates is modulated by charge and size of the two components as function of different porphyrin/cyclodextrin (CD) molar ratios. At the limiting molar ratio studied, the absolute value of zeta potential (/zeta/ = 12.5 mV) seems to be a reference value for the formation of stable colloidal CD vesicular aggregates at thermodynamic equilibrium. New insights on the structure of these heterotopic colloids have been obtained by analysis of rotational correlation times at different molar ratios exploiting time-resolved fluorescence anisotropy experiments. At high porphyrin loads, the anisotropy decays behave as monoexponentials and the rotational correlation times (1-2 ns) together with the r(0) values close to zero suggest the presence of small amounts of TPPS embedded in a hydrophobic environment either in monomeric or in aggregated form. At the lower porphyrin/CD molar ratios, the anisotropy decays exhibit a double-exponential behavior showing a predominant component with a slow rotational correlation time (20-25 ns) and limiting anisotropy values of approximately 0.15. This component has been assigned to molecules that are more stabilized onto the CD vesicles, that is, porphyrins embedded into the oligo-ethylene "wall" of the CD vesicles. Scanning near-field optical microscopy of the samples evaporated on glass surfaces gave further insights on the morphology and optical properties of these systems, confirming the embedding of TPPS on the vesicles and evidencing the role of the solvent.
通过弹性光散射（ELS）、准弹性光散射（QELS）、zeta电位测量和时间分辨荧光各向异性相结合的方法，详细研究了阴离子型5,10,15,20-四（4-磺基苯基）-21H,23H-卟啉（TPPS）与由七（2-ω-氨基-O-聚环氧乙烷-6-己硫基）-β-环糊精（SC6CDNH2）形成的阳离子囊泡之间的相互作用。ELS实验首次对这些阳离子囊泡在不存在和存在TPPS卟啉的情况下进行了结构表征，将该系统建模为一个由单个薄壳形状因子描述的球形颗粒。混合杂聚体的结构受两种组分的电荷和大小调节，是不同卟啉/环糊精（CD）摩尔比的函数。在所研究的极限摩尔比下，zeta电位的绝对值（/zeta/ = 12.5 mV）似乎是在热力学平衡时形成稳定胶体CD囊泡聚集体的参考值。通过利用时间分辨荧光各向异性实验分析不同摩尔比下的旋转相关时间，获得了关于这些异位胶体结构的新见解。在高卟啉负载量下，各向异性衰减表现为单指数形式，旋转相关时间（1-2 ns）以及接近零的r(0)值表明存在少量以单体或聚集形式嵌入疏水环境中的TPPS。在较低的卟啉/CD摩尔比下，各向异性衰减呈现双指数行为，显示出一个主要成分，其旋转相关时间较慢（20-25 ns），极限各向异性值约为0.15。该成分已被归因于更稳定地附着在CD囊泡上的分子，即嵌入CD囊泡聚环氧“壁”中的卟啉。对在玻璃表面蒸发的样品进行扫描近场光学显微镜观察，进一步深入了解了这些系统的形态和光学性质，证实了TPPS在囊泡上的嵌入，并证明了溶剂的作用。
