Starch microsponges for enhanced retention and efficacy of topical sunscreen

Highlights: • Starch microsponges (SM) were fabricated, characterized and used as a key carrier to adsorb BNZ into its nanopores. • A starch microsponge based novel sunscreen cream was formulated and clinically proven safe for consumer usage. • UV protective efficacy, SPF and sensory profile of sunscreen cream was improved owing to encapsulation of BNZ into SM. • SM based sunscreen cream gave enhanced stratum corneum deposition and minimal skin permeation compared to raw BNZ cream. -- Abstract: Topical sunscreen products are universally applied by numerous individuals to protect their skin from the detrimental effects of UV radiation. However, lately, studies have revealed the risks associated with percutaneous absorption of UV filters leading to undesirable systemic side effects such as hormonal disturbances and allergies. In this study, an innovative sunscreen formulation was developed based on starch microsponges as a key carrier encapsulating an organic sunscreen benzophenone‑3. The developed starch microsponges were characterized by scanning electron microscopy and nitrogen adsorption/desorption analysis. The results showed that starch microsponges possessed a high BET surface area (85.45 m²/g) with spherical porous morphology with pore size <200 nm. Benzophenone‑3 was loaded into the starch microsponges by immersion/solvent evaporation and benzophenone‑3 loaded starch microsponges were characterized by scanning electron microscopy, differential scanning calorimetry, powder X-ray diffraction, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption measurements. Results corroborated that benzophenone‑3 was successfully entrapped within the nanopores of starch microsponges. A starch microsponge based sunscreen cream was formulated, characterized and clinically tested. Rheological, texture and sensorial assessment showed that starch microsponges based sunscreen product showed good spreadability, non-sticky, rich texture favorable for consumer usage. In vitro and ex-vivo studies demonstrated benzophenone‑3 loaded starch microsponges gave improved photoprotection, higher SPF and reduced cutaneous penetration compared to raw benzophenone‑3 cream. Clinically, patch study confirmed that the developed starch microsponges based sunscreen cream was skin safe and biocompatible. Thus, the amalgamation of sunscreen molecule benzophenone‑3 into starch microsponges produced a safe, effective innovative sunscreen product.