ABSTRACT
The topical use of sunscreens is recommended for avoiding the damaging effects of UV radiation. However, improvements are still needed in the existing products to enhance their photoprotection effectiveness and safety. This involves minimizing the use of chemical UV filters while providing enhanced and prolonged photoprotection. This work investigated novel sunscreen formulations and their UV protection effects by encapsulating Uvinul® A, Tinosorb® S, and Uvinul® T150 into nanostructured lipid carriers (NLCs) based on bacuri butter and raspberry seed oil. First, the impact of critical formulation and process parameters on NLCs' particle size was evaluated using a 22 Face Centered Central Composite Design. Then, formulations were evaluated in terms of critical quality factors, in vitro skin permeation, and in vitro and in vivo photoprotection activities. The developed NLCs-containing formulations exhibited appropriate size (122-135 nm), PdI (<0.3), encapsulation efficiency (>90%), and drug content (>80%), which were preserved for at least 90 days under different stability conditions. Moreover, these NLCs-based formulations had equivalent skin permeation to emulsion-based controls, and the addition of NLCs into sunscreen cream bases in the optimum proportion of 20% (w/w) resulted in enhanced UVA and UVB photoprotection levels, despite a 10% reduction in the total filters content. Altogether, these results describe the application of nanoencapsulated organic UV filters in innovative sunscreen formulations to achieve superior photoprotection and cosmeceutical properties.
ABSTRACT
Wound healing involves the integration of biological and molecular events and, in case of chronic wounds, the use of drugs can be associated to side effects. Therefore, there is a search for alternatives therapeutics that encompass minimal toxicity. The use of natural compounds is an attractive approach for treating inflammatory disorders, wounds and burns. In this context, thymol has antimicrobial, antioxidant and antiseptic properties and is a promising compound in wound healing and inflammation management. However, essential oils and their constituents such as thymol present high volatility and can also easily decompose, thereby the encapsulation of these compounds into nanoparticles may be an efficient approach to modulate the release of the active ingredient, to increase the physical stability and to eventually reduce the toxicity. The aims of this work were to encapsulate thymol in nanostructured lipid carriers (NLCs) composed of natural lipids and assess its in vivo anti-inflammatory and antipsoriatic activity. The carrier containing thymol was produced by sonication method and showed 107.7 (±3.8) nm of size, zeta potential of -11.6 (±2.9) mV and entrapment efficiency of 89.1 (±4.2)%. Thymol-NLCs were incorporated into a gel and the final formulation presented rheological characteristics and pH suitable for topic application. In addition, the gel containing thymol-NLCs was tested in vivo on two different mouse models of skin inflammation, showing anti-inflammatory activity. Finally, this formulation was tested in an imiquimod-induced psoriasis mouse model and showed improved healing, compared to negative control. Therefore, thymol-NLCs is an interesting formulation for future treatment of inflammatory skin diseases.
