Development and Optimization of Polyglutamic acid Enriched Lip BalmUsing Experimental Design Approach

Abstract

Introduction: This study aimed to develop a novel topical lip formulation with enhanced hydration, moisturization,
and barrier protection, addressing the high susceptibility of lips to dehydration and environmental damage.
Materials and Methods: The formulation incorporated shea butter as the primary structural excipient, almond oil
as an emollient to improve spreadability, peppermint oil for sensory appeal, and polyglutamic acid (PGA) as the
principal hydrating agent due to its strong water-binding and film-forming properties. A 2³ full factorial design was
employed, with concentrations of shea butter, almond oil, and PGA as independent variables. pH and spreadability
were selected as critical quality attributes. Statistical analysis was performed to assess individual and interaction
effects, followed by optimization using a desirability function targeting a pH of 5.5–6.5 and spreadability of 6–9 cm.
Results and Discussion: PGA significantly influenced formulation pH, while shea butter and almond oil predominantly
governed spreadability. The factorial design effectively elucidated the relationships between formulation variables
and product performance. Numerical optimization produced an optimized formulation with an overall desirability
value of 1.000, indicating optimal physicochemical and application characteristics. Conclusion: The optimized PGA–
enriched lip formulation demonstrated suitable pH, desirable spreadability, and balanced performance, highlighting
the effectiveness of factorial design and desirability-based optimization in advanced lip care product development.