Encapsulation and Release of Non-Fluorescent Bio-Active Drug Confined in Bile-Salt Aggregates

Abstract

In this thesis, the entrapment of anti-fungal, anti-bacterial non-fluorescent dye Crystal Violet (CV) in presence of bio-mimetic confined bile-salt aggregates has been studied. The photophysical characteristic behaviour of CV has been carried out by changing different kinds of hydrophilic head groups and hydrophobic skeletons of bile-salt aggregates (e.g. NaC, NaDC, NaTC and NaTGC). The main aim of the thesis is to modulate the solubility behaviour, fluorescence property and elucidation of different kinds of non-covalent interaction of CV confined in bile-salt aggregates. To interpret the result, steady state absorption and fluorescence emission techniques have been employed. In aqueous buffer, CV molecule exhibits non-fluorescent in nature. The value of fluorescence quantum yield (Φ) is ~10-4. It has been observed that CV molecule confined in bile-salt aggregates becomes highly fluorescent in nature. The enhancement of ‘Φ’ value of CV in bile-salt aggregates is ~1000 folds compared to that of aqueous buffer medium. It has also been observed that in presence of different bile-salt aggregates, CV molecule exhibits remarkable enhancement of absorption and fluorescence emission spectral behaviour. The ground state and the excited state binding constant values of CV molecule in presence of different bile-salt aggregates have been determined by using non-linear regression analysis method. In presence of different bile-salt aggregates; the partition coefficient values of CV are very high. This clearly depicts the dye molecule resides in bile-salt aggregates. Moreover, another aim of the thesis is to release of the dye molecule from the confined bile-salt aggregates to the aqueous medium. Since, the dye molecule exhibits strong fluorescent in presence of bile-salt aggregates, therefore the target was by addition of foreign substance (non-toxic and green), the dye molecule return backs (from confined bile-salt environments) to its original position (aqueous buffer medium). It will be possible only when CV molecule will exhibit again non-fluorescence property. It has been found that addition of very minute concentration of KCl salt (100 nM) to the bile-salt aggregates leads to extreme modification of the photophysical property of CV molecule. The absorption, fluorescence intensity, fluorescence quantum yield, ground state and excited state binding constant values, partition coefficient and aggregation number of CV molecule entrapped in bile-salt aggregates significantly reduces by addition of KCl. This result clearly confirms that the studied molecule releases from the confined system to the aqueous medium. The work involved in this thesis might be valuable for potential targeted drug-delivery implications, detection analysis, sensors, and also in physiological systems.