Development, Optimization and Evaluation of Solid Lipid Nanoparticle-based Broad-Spectrum Sunscreen Hydrogel using a Quality by Design Approach

Abstract

Background: Ultraviolet (UV) radiation is an important environmental factor associated with erythema, hyperpigmentation, premature skin aging and photocarcinogenesis. Conventional sunscreen formulations may exhibit limitations such as inadequate photostability, poor skin retention, greasy texture and the need for frequent reapplication.
Objective: The present study aimed to develop and optimize a broad-spectrum sunscreen hydrogel incorporating UV-filter-loaded solid lipid nanoparticles (SLNs) using a Quality by Design (QbD) approach.
Materials and Methods: The SLNs incorporated Uvinul® T150 and Uvasorb® HEB as organic UV filters and zinc oxide as an inorganic UV filter. Glyceryl monostearate, Cetiol® CC, C12–C15 alkyl benzoate and lecithin were used as the lipid components. A 2³ full factorial design was employed using glyceryl monostearate, Cetiol® CC and lecithin as formulation variables. Particle size, viscosity and entrapment efficiencies of Uvinul T150 and Uvasorb HEB were selected as critical responses. The optimized formulation was further characterized for physicochemical properties, drug content, SPF, in-vitro release and stability.
Results and Discussion: Eight formulations (F1–F8) were prepared according to the factorial design. Particle size ranged from 132.1 to 210.5 nm, viscosity from 2150 to 3400 cP, while entrapment efficiencies ranged from 86.1–96.2% for Uvinul T150 and 88.5–97.8% for Uvasorb HEB. F6 was selected as the optimized formulation with a particle size of 174.6 nm, PDI of 0.225, zeta potential of −27.9 mV and SPF of 36.37. F6 showed pH 5.9, viscosity of 3400 cP, spreadability of 462.96 ± 17.14 g·cm/sec and drug contents of 97.7 ± 0.2% and 97.9 ± 0.2% for Uvinul T150 and Uvasorb HEB, respectively. The formulation exhibited sustained UV-filter release over 10 h and remained physically stable during three months of storage.
Conclusion: The optimized F6 formulation demonstrated desirable physicochemical properties, high entrapment efficiency, satisfactory SPF, sustained release and stability, indicating its potential as a broad-spectrum sunscreen formulation.