Role of PEG 2000 in the surface modification and physicochemical characteristics of pyrazinamide loaded nanostructured lipid carriers

Hydrogenated soy phosphatidylcholine, tristearin and oleic acid were employed in preparing nanostructured lipid carriers (NLC). Surface modified NLCs (${\text{NLC}}_{PEG})$ were formulated by adding polyethylene glycol 2000 (PEG 2000) in the dispersion medium along with Tween 60. Hot homogenization followed by ultrasonication technique was used as the preparative procedure. 0.01% (w/v, g/mL) PEG 2000 was found to be the saturation limit for the studied formulations. Pyrazinamide (PYZ) was incorporated in NLC; the base and drug-loaded formulations were characterized by combined dynamic light scattering (DLS), differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and atomic force microscopy (AFM). ${\text{NLC}}_{PEG}$ was more stable than the conventional NLC formulations. Added PEG 2000 provided extra steric stability to ${\text{NLC}}_{PEG}$ systems by introducing an additional layer over their surface. The presence of the additional layer of PEG 2000 also offered a preventative barrier towards the expulsion of surface accumulated PYZ. Considerable improvement in entrapment efficiency (EE%), drug loading (DL%) and desirable sustained release profile could be achieved in NLC.

Graphical Abstract

Nanostructure lipid carrier (NLC) formulations were modified with PEG 2000. Pyrazinamide (PYZ) was incorporated into the NLC. Stability, entrapment efficiency and drug loading of the ${\text{NLC}}_{PEG}$ formulations were better than NLC. Sustained release of incorporated PYZ was recorded for ${\text{NLC}}_{PEG}$. .