Journal of Microencapsulation, 2010; 27(3): 253–262 RESEARCH ARTICLE Skin absorption studies of octyl-methoxycinnamate loaded poly(D,L-lactide) nanoparticles: Estimation of the UV filter distribution and release behaviour in skin layers M. Vettor 1 , S. Bourgeois 2 , H. Fessi 2 , J. Pelletier 2 , P. Perugini 1 , F. Pavanetto 1 and M. A. Bolzinger 2 1 Department of Pharmaceutical Chemistry, School of Pharmacy, University of Pavia, Pavia, Italy, and 2 Universite ´ de Lyon, Universite ´ Lyon 1, UMR CNRS 5007 (LAGEP), Villeurbanne, France Abstract New formulation strategies have to be developed to limit the skin penetration of UV-filter. Nanoparticles (NP) are very suitable for that purpose. In this study, the skin distribution, at different times (1, 2 and 3 h), of octyl-methoxycinnamate (OMC) from loaded PLA-nanoparticles was compared to a classical formula- tion containing non-encapsulated OMC, using the Franz cell method. The results showed that the OMC penetration was clearly impeded by stratum corneum and that the major part of the OMC-NP was accumulated at the skin surface (480%). A significant lower OMC amount was quantified in viable skin with NP compared to the OMC emulgel. To accurately determine the real OMC amount in close contact with viable skin layers two solvents were used to extract OMC from the skin compartments. Acetone (ACET) allowed quantifying both OMC in NP and OMC released from the particles, while isopropylmyr- istate (IPM), a non-solvent of the NP polymer (PLA), allowed quantifying only OMC released from the particles. Using IPM as an extraction solvent, it appeared that the OMC released from NP, in contact with viable skin, was 3-fold lower than free OMC diffused from the emulgel. Lastly, a sustained release was observed when nanoparticles were used. Key words: Nanoparticles; OMC; poly(D,L-lactide); isopropyl myristate; skin permeation; encapsulation Introduction The spectrum of skin disorders related to ultraviolet (UV) radiations ranges from minor acute sunburn, to many forms of photoallergy, premature photoageing and can- cers. The steady increase in the incidence of melanoma, non-melanoma cutaneous neoplasia and pre-neoplastic disorders and the heightened awareness of the premature photoageing have each contributed to the demand for more effective anti-solar protection (Falco et al. 2000, Nole and Johnson 2004, Ermertcan et al. 2005). Therefore, UV filters are incorporated into many every- day-use cosmetics in order to protect the skin from UV radiations and prevent skin diseases. A modern sunscreen with a broad anti-UVB and anti-UVA spectrum and a long-lasting effect should prevent erythema and skin inflammation (mediated by ROS species) better than sunscreens usually used 10–20 years ago (Diffey 2005). Sunscreens preparations are usually applied to large skin areas to prevent photodamage and they should stay on skin surface and penetrate as little as possible (Gupta et al. 1999, Potard et al. 1999). Cinnamates are very pop- ular UV filters and among them octyl-methoxycinnamate (OMC) is widely used. It absorbs radiation in the 290– 320 nm region of the UV spectrum and its O-CH3 group in para-position facilitates electron delocalization process (Olvera-Martinez et al. 2005). It is a liposoluble absorber with a high log P value of 5.68 and a molar mass of 290.40 g mol 1 . Under UV radiation an E (trans) to Z (cis) photoisomerization of OMC occurs inactivating the Address for correspondence: Sandrine Bourgeois, LAGEP – UMR CNRS 5007, Universite ´ Claude Bernard Lyon 1, Bat. 308G ESCPE, 43, bd du 11 November 1918, 69622 Villeurbanne Cedex, France. Tel: þ33 4 78 77 72 35. Fax: þ33 4 78 77 75 84. E-mail: bourgeois@lagep.univ-lyon1.fr (Received 2 Jun 2009; accepted 8 Jun 2009) ISSN 0265-2048 print/ISSN 1464-5246 online ß 2010 Informa UK Ltd DOI: 10.3109/10717540903097770 http://www.informahealthcare.com/mnc (Received 2 Jun 2009; accepted 8 Jun 2009) ISSN 0265-2048 print/ISSN 1464-5246 online ß 2010 Informa UK Ltd DOI: 10.3109/10717540903097770 http://www.informahealthcare.com/mnc