Poly(D,L‐lactide) nanoencapsulation to reduce photoinactivation of a sunscreen agent

Abstract

The use of sunscreens is the 'gold standard' for protecting the skin from ultraviolet light. Octyl methoxycinnamate (OMC) is one of the most widely used UVB filter but it can act as a sensitizer or photoallergen. When exposed to sunlight, OMC can change from the primary trans-form to cis-form and the isomerization, not reversible, conducts to a reduction of the UVB filtering efficiency because the trans-form has a higher extinction coefficient. Photostability is the most important characteristic of effective sunscreens and it can be influenced by formulation ingredients and by applying technological strategies. In this work, photostability experiments, performed on emulsion-gels containing different percentages of OMC free or loaded in poly(D,L-lactide) nanoparticles, were carried out. The presence of a polymeric envelop may act to protect the active ingredient. In this study, the influence of poly(D,L-lactide) matrices on the photochemical stability of the sunscreen agent was investigated. As highlighted in this study, free OMC in different formulations has different photoisomerization degree. Moreover, a dissimilar behaviour was observed by studying different sunscreen concentrations in the same cosmetic formulation. Photostability results show a significant reduction in photoisomerization degree for formulations containing sunscreen loaded in nanoparticles, highlighting that the encapsulation is a suitable strategy to improve OMC photostability. Moreover, sun protection factor (SPF) results show that the UVB filter protective power is also maintained after encapsulation.

Skin Photodamage Prevention: State of the Art and New Prospects

“…The results supported the hypothesis that OMC is protected in nanoparticles and that PLA nanoencapsulation could be used to prevent photoisomerization. An in vitro filter efficacy experiment demonstrated that no SPF could be associated to the nanoparticles whereas the obtained protective effect by OMC was not altered by encapsulation of the sunscreen in nanoparticles [22].…”

Review of sunscreen and the emergence of non-conventional absorbers and their applications in ultraviolet protection

“…Similar to SLNs, poly(d,l-lactide) (PLA), is an established polymer in the drug delivery industry. Nanoencapsulation of octinoxate using PLA results in increased photostability [23]. Similarly, a study by the same research group show that encapsulating octinoxate with poly-d,l-lactide-co-glycolide (PLGA) also has greater photostability than octinoxate alone [24].…”

The real value of novel particulate carriers for sunscreen formulation

“…Embedding in polymethylmetacrylate reduced the amount of sunscreen released from the cream and increased minimal erythemal dose and SPF [73]. In another paper, poly(d,l-lactide-co-glycolide) and poly(d,llactide) polymers protected EMC from photodegradation [74,75] whereas ethylcellulose failed [74].…”