Engineering pectin- and sodium alginate-based nanoemulgels for topical delivery of Hibiscus sabdariffa flower extract

Abstract

Recent advances in nanotechnology have enabled nanoscale topical delivery systems with controlled release and enhanced therapeutic performance. This study developed and evaluated a nanoemulgel incorporating Hibiscus sabdariffa L. flower extract obtained via high-speed extraction. An oil-in-water nanoemulsion with a mean droplet size of 419.70 ± 46.95 nm, polydispersity index of 0.48 ± 0.05, and zeta potential of −8.10 ± 0.74 mV was successfully prepared, indicating a stable sterically stabilized dispersion. The nanoemulsion was incorporated into pectin- and sodium alginate-based gel matrices to comparatively investigate polymer influence. Rheological analyses revealed pseudoplastic behavior, while morphological characterization by SEM and TEM revealed polymer-dependent matrix structures and approximately spherical nanoscale features in the optimized formulations. FT-IR analysis revealed only minor spectral differences following extract loading, while EDX provided comparative elemental profiles of the optimized formulations. In vitro diffusion studies demonstrated controlled and sustained release from both formulations, reaching ≈99% within 24 h. Release kinetic analysis indicated that diffusion may contribute to the release process; however, the kinetic parameters were interpreted primarily as empirical descriptors and were not used to assign a definitive transport mechanism. The sodium alginate-based nanoemulgel (N5) exhibited a comparatively more gradual release profile and a pH of 6.71, supporting its selection for further formulation evaluation. Long-term stability studies per ICH Q1A(R2) and Q1E guidelines showed that N5 maintained physicochemical integrity, colloidal stability, and active content for up to 12 months at 4–8 °C in glass containers, whereas elevated temperatures and plastic packaging caused significant destabilization. Overall, the sodium alginate-based nanoemulgel demonstrated favorable formulation and storage characteristics and represents a promising candidate for further investigation as a topical delivery system for Hibiscus sabdariffa extract. Additional studies using validated skin models and appropriate biological evaluations are required to establish its dermal performance and therapeutic applicability.