Assessment of the Effect of PLGA Co-polymers and PEG on the Formation and Characteristics of PLGA-PEG-PLGA Co-block PolymerUsing Statistical Approach

To assess the effect of the lactic acid (LA)-to-glycolic acid (GA) molar ratio andpolyethylene glycol (PEG) concentration on the formation of poly-lactide co-glycolide acid(PLGA)-PEG-PLGA co-block polymers simultaneously using statistical approach. A 22 full factorial design with the addition of a point in the center of the design, namelycurvature, was applied. Fourier transform infrared (FTIR), differential scanning calorimetry(DSC), and nuclear magnetic resonance (NMR) were performed to confirm the formation of theco-block polymer. Simvastatin (SMV), a drug model was incorporated into the nano-polymericmicellar (NpM) of PLGA-PEG-PLGA followed by solubility phase, particle size, zeta potential,and entrapment efficiency characterizations. FTIR, DSC, and NMR successfully confirmed the formation of co-block polymers.Solubility of SMV increased from 2 to 44-folds depending on co-block concentration withentrapment efficiency of 59%-80%. The NpM had size in the range of 206 to 402 nm withnegative zeta potential. LA to GA ratio had greater effect on particle size reduction and increasingof co-polymer length. In addition, it had higher contributions on increasing of solubility andentrapment efficiency of SMV than PEG. According to these findings, the LA to GA ratio and PEG concentration gained agreat consideration in order to prepare the PLGA-PEG-PLGA co-block which fulfilled the qualitytarget product profile of NpM delivery system.