Development and Characterization of Nanostructured Lipid Carriers of Oral Hypoglycemic Agent : Selection of Surfactants

A new generation of nanostructured lipid carriers (NLCs) consisting of a lipid matrix with a special nanostructure has been developed. This nanostructure improves drug loading and firmly incorporates the drug during storage. Surfactants play important roles in the formation and characterization of nanostructured lipid carriers. In order to investigate the influence of surfactants on properties of NLCs, three types of surfactants (Poloxamer 188, Soya lecithin, Sodium taurocholate) and their mixtures were used. Glipizide loaded NLCs were fabricated using compritol 888 ATO and Oleic acid as a solid lipid and liquid lipid respectively. Solvent diffusion method was employed to produce NLCs and the physicochemical properties of NLCs, such as particle size, zeta potential, entrapment efficiency, DSC analysis and in vitro release studies were investigated. The formulations that contain only single emulsifier exhibited larger particle size. The mean particle size decreased, when combination of surfactant used. The formulation (NL6) prepared with combination of above three surfactants exhibited smallest mean particle size and narrow size distribution. The formulation (NL3) that contains sodium taurocholate (ionic emulsifier) exhibited highest zeta potential leading to improved physical stability. The formulations, in which combinations of surfactant were used, exhibited good entrapment efficiency. TEM images revealed that NLCs are nearly spherical in shape with the particles size ranging from 200 nm to 300 nm that is almost closer to the particle size obtained by PCS. DSC studies indicate that Glipizide incorporated in NLCs was not in a crystalline state but in an amorphous or molecular state. In vitro release study revealed the biphasic release pattern of NLCs systems, initially burst release and then sustained release for prolong period of time. These results suggested that the combination of surfactants produces a stable system with good entrapment efficiency and desired particle size.