Synthesis and characterization of hexa-tailed cryptand based amphiphiles: Spontaneous formation of giant vesicular microcapsule with efficient and long-term dye encapsulation

A cryptand with six secondary amino groups has been derivatized by reacting with acid chlorides of different chain lengths (C7, C10 and C18) to get three cryptand based hexa-tailed neutral amphiphiles (L1–L3). The cavity of the cryptand head group accommodates two Cu(II) ion giving another set of three amphiphiles. These amphiphiles and its copper complexes can aggregate spontaneously as giant vesicular microcapsules in 10% ethanolic water medium. In all cases vesicles formed are mostly unilamellar in nature. Vesicular microcapsules prepared from L1–L3 can encapsulate hydrophilic dye 5(6)-carboxyfluorescein (CF). Stability of microcapsules, CF encapsulation efficiencies and release rates were dependent on the hydrophobic chain length of the amphiphiles. Results show the permeability of the L2 and L3 bilayer is lower than that of phosphatidylcholine vesicles and the loading capacity is ∼3 times greater. Microcapsules have been characterized by optical microscopy, freeze fracture scanning electron microscopy and confocal fluorescence microscopy.