dc.description.abstract |
The work reported in the present thesis covers various investigations carried out under
microemulsion conditions. More specifically it includes the encapsulation of nonsteroid anti-
inflammatory drug (piroxicam) and the preparation and recovery of cetyltrimethylammonium
chloride (CTACl) capped metal nanoparticles (Au, Pd, SiO2). Microemulsions are colloidal
self-assembly fluids, function as nanoreactors and are suitable replacement for enhancing the
loading capacity of drugs and recovery of nanoparticles. It was found that high loading
capacity of piroxicam (1 wt%) and paramount recovery of nanoparticles (upto 98%) highlight
the proficiency of the microemulsions in pharmaceuticals and in separation science.
Microemulsion in this thesis has been used for encapsulation of anti-inflammatory
drug (piroxicam). The results have demonstrated the absolute stability of microemulsion
formulation after the incorporation of piroxicam. The main objective of this study was the
development of rapid oil-in-water microemulsion to improve the loading capability of
pharmaceutical
compound
in
highly
hydrophobic
formulation.
Tween-80
based
microemulsion was successfully utilized to encapsulate and to enhance the solubility of
piroxicam. In the present work various rheological and the spectroscopic analyses were
employed to explore the gradual changes occurring in the microstructure of microemulsion.
In addition, the consequence of piroxicam incorporation on the stability, optical consistency
and microstructure of microemulsion formulation was also accomplished. Investigations into
the stability of microemulsion under milder conditions showed that it remained clear and
transparent over 10 months.
During the project a special type of microemulsion was also developed that may make
the recovery, recycling and reuse of nanoparticles easier for the manufacturers. The synthesis
of nanoparticles in microemulsion systems has recently become an important focus of
research. The inverse microemulsion (water-in-oil) technique has been successfully utilized
to synthesize colloidal nanoparticles of inorganic materials. In the project a new approach
towards the synthesis of gold nanoparticles (Au-NPs) in a reverse microemulsion was
established and ‘at the flick of a switch’ water-induced separation route was employed for
their recovery. Water-in-oil microemulsions (w/o MEs) stabilized by the cationic surfactant
CTACl have been used as reaction media to generate Au-NPs. In addition the pure MEs have
also been used as dispersion media for those Au and Pd-NPs, which have been pre-
synthesized in aqueous phases and stabilized by sodium 2-mercaptoethanesulfonate (MES)
ligands, and commercially available SiO2-NPs. A general method for recovery and separation
of the nanoparticles from these mixed NP-ME systems has been demonstrated by tuning
phase behavior of the background microemulsions. Addition of appropriate aliquots of water
drives a clean liquid-liquid phase transition, resulting in two macroscopic layers, the NPs
preferentially partition into an upper oil-rich phase and are separated from excess surfactant
which resides in a lower aqueous portion.
In order to assemble the detailed quantitative and qualitative outcomes of
nanoparticles, UV-vis spectroscopy and transmission electron microscopy (TEM) were
developed respectively. For instance, ~90% of the microemulsion prepared Au-NPs can be
recovered; with even greater separation efficiencies attainable for pre-synthesized MES
stabilized Au-MES-NPs (~98%) and Pd-MES-NPs (92%). For the silica NP-ME dispersions
gravimetry indicates ~ 84% recovery of the NPs. TEM images of all systems showed that NP
shapes and size distributions were generally preserved after these phase transfer processes.
This low-energy and cost-effective purification route appears to be a quite general approach
for processing inorganic NPs, having advantages of being isothermal, using only
commercially available inexpensive components and requiring no additional organic solvents. |
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