A sunblock based on bioadhesive nanoparticles

Abstract

The majority of commercial sunblock preparations utilize organic or inorganic ultraviolet (UV) filters. Despite protecting against cutaneous phototoxicity, direct cellular exposure to UV filters has raised a variety of health concerns. Here, we show that the encapsulation of padimate O (PO) - a model UV filter - in bioadhesive nanoparticles (BNPs) prevents epidermal cellular exposure to UV filters while enhancing UV protection. BNPs are readily suspended in water, facilitate adherence to the stratum corneum without subsequent intra-epidermal or follicular penetration, and their interaction with skin is water-resistant yet the particles can be removed via active towel drying. Although the sunblock based on BNPs contained less than 5 wt% of the UV-filter concentration found in commercial standards, the anti-UV effect was comparable when tested in two murine models. Moreover, the BNP-based sunblock significantly reduced double-stranded DNA breaks when compared to a commercial sunscreen formulation.

Cutaneous Permeation and Penetration of Sunscreens: Formulation Strategies and In Vitro Methods

“…The choice of stratum corneum-epidermis membrane instead of full thickness skin was justified since the dermis could act as a further barrier to permeation, distorting in vitro evidence [7]. Analysis of recent literature shows an increasing use of porcine skin with respect to the past [5,14,16,23]. Most of the studies employed the outer surface of freshly excised pig ears, after hair and underlying cartilage removal.…”

“…Lipid nanocarriers are almost made of well-tolerated and biodegradable raw materials, which, together with the colloidal size of the particles that facilitates the formulation in dermatological products, enable confortable skin application. In recent years, several studies focused on the formulation of UV filters in micro and nanocarriers to protect them from photo-degradation and to prevent skin permeation [5,7,14,19,30].…”

“…Another interesting formulation tool is represented by bioadhesive nanoparticles (BNPs), described by Deng et al, [14]. Starting from polylactic acid-hyperbranched polyglicerol (PLA-HPG) nanoparticles, the HPG was converted into an aldeide-rich corona with bioadhesive properties, and padimate-O was incorporated in these new highly skin adherent and not penetrant BNPs.…”

“…Since these preparations are often applied on large skin areas, even low penetration rates can cause significant amount of sunscreen to enter the body. As the site of action of sunscreens is restricted to the skin surface or to the uppermost part of the stratum corneum, they should not penetrate into the viable epidermis, the dermis and into the systemic circulation; furthermore, the follicular uptake should be avoided, in order to not penetrate human cells where they can cause deleterious DNA damages [13,14]. This can happen when the solar-filter has a high substantivity, intended as the capacity of adhering to and of being retained by the skin, thus resisting removal by bathing or perspiration [15].…”

Secondary Plant Metabolites for Sun Protective Cosmetics: From Pre-Selection to Product Formulation

“…Lipid micro-and nano-carriers represent the evolution of the pioneer liposome-based carriers. These were first found to enhance the skin penetration and absorption of the lipophilic sunscreens such as ethyl hexyl methoxycinnamate, as compared to the traditional oil/water emulsions supplied with emulsifiers [96], or the stratum corneum bio-adhesiveness of padimate O [97], although limited in the industrial applications by the unresolved problem of liposome instability. Nano-emulsifier particles also show the ability to inhibit trans-cutaneous absorption of the systemically toxic and immune-suppressing chemical filters [98].…”