Design and Characterization of a New Quercus Suber-Based Pickering Emulsion for Topical Application.

Catarina Carriço,Pedro Pinto,Helena Ribeiro,Angélica Graça,Lídia Gonçalves,Joana Marto

doi:10.3390/pharmaceutics11030131

Abstract

Quercus Suber Bark from Quercus suber L. is a natural, renewable and biodegradable biomaterial with multifunctional proprieties. In this study, we used it as solid particles to stabilize a Pickering emulsion. The main goal was to produce an optimized topical formulation using biocompatible organic particles as stabilizers of the emulsion instead of the common surfactants, whilst benefiting from Quercus suber L. proprieties. In this work, a Quality by Design (QbD) approach was successfully applied to the production of this emulsion. A screening design was conducted, identifying the critical variables of the formula and process, affecting the critical quality attributes of the emulsion (droplet size distribution). The optimization of the production was made through the establishment of the design space. The stability was also investigated during 30 days, demonstrating that Quercus Suber Bark-stabilized emulsions are stable since the droplet size distribution lowers. In vitro studies were performed to assess antioxidant and antiaging efficacy, which revealed that the formulation had indeed antioxidant proprieties. A physicochemical characterization demonstrated that the formulation presents a shear-thinning fluid, ideal for topical administration. The in vivo compatibility study confirmed that the final formulation is not skin irritant, being safe for human use. A sensorial analysis was also performed, using a simple sensory questionnaire, revealing very positive results. Thus, the use of Quercus Suber Bark particles as a multifunctional solid ingredient contributed to achieve a stable, effective and innovative Pickering emulsion with a meaningful synergistic protection against oxidative stress.

Highlights

Emulsions are thermodynamically unstable, their study and development being some of the most difficult and complex subjects in the pharmaceutical and cosmetic fields
Purified water was obtained by reverse osmosis and electrodeionization (Millipore, Elix 3) being afterwards filtered. 2,7 -dichlorodihydrofluorescein diacetate (H2-DCFDA) was from Life Technologies (Carlsbad, CA, EUA), and spontaneously immortalized human keratinocyte cell lines HaCaT (CLS, Eppelheim, Germany) were used for antioxidant activity and cytotoxicity assays with cells
The Quercus Suber Bark (QSB)-stabilized emulsion developed met the predefined goal of using biocompatible organic particles to create a high skin compatible emulsion

Summary

Introduction

Their study and development being some of the most difficult and complex subjects in the pharmaceutical and cosmetic fields. On the other hand, are surfactant-free liquid or semi-solid systems stabilized by solid particles. These solid-stabilized emulsions constitute an interesting alternative strategy for encapsulating drugs in topical pharmaceutical formulations [5]. This type of emulsion was named after Spencer U. Pickering, whose paper first described the phenomenon in 1907 This stabilization of emulsion droplets is due to particle’s dual wettability: partial wetting of the surface of the solid particles by water and oil is the origin of the strong anchoring of these particles at the oil–water interface [6,7]. Wettability allows the spontaneous accumulation of particles at the mentioned interface, which is stabilized against coalescence by volume exclusion and steric hindrance [8]

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Conclusion