Evaluation of spray congealing as technique for the preparation of highly loaded solid lipid microparticles containing the sunscreen agent, avobenzone

doi:10.1002/jps.21636

Journal of Pharmaceutical Sciences

Volume 98, Issue 8, August 2009, Pages 2759-2769

https://doi.org/10.1002/jps.21636 Get rights and content

Abstract

Solid lipid microparticles (SLMs) loaded with high amounts of the sunscreen agent, butyl methoxydibenzoylmethane (avobenzone) were prepared in order to reduce its photoinstability. The microparticles were produced, using carnauba wax as lipidic material and phosphatidylcholine as the surfactant, by the classical melt dispersion method or the spray congealing technique with pneumatic atomizer. The sunscreen agent loading was 40.1–48.5% (w/w), with no significant differences between the production methods. However, release studies indicated that spray congealing enabled a more efficient modulation of avobenzone release from the SLMs (26% of encapsulated avobenzone released after 2 h as compared to 60% for melt dispersion). The photoprotective efficacy of the SLMs was evaluated after their introduction in a model cream. A statistically significant decrease of the light-induced degradation of avobenzone was obtained by the SLMs prepared by the melt dispersion procedure (the extent of degradation was 38.6 ± 3.6% for nonencapsulated avobenzone and 32.1 ± 4.3% for the microparticle-entrapped sunscreen). On the other hand, the SLMs produced by spray congealing achieved a more marked reduction in avobenzone photodecomposition to 15.4 ± 4.1%. Therefore, the spray congealing technique was superior to the classical melt dispersion method for rapid and solvent free production of SLMs with a high avobenzone loading capacity. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:2759–2769, 2009

Section snippets

INTRODUCTION

The topical use of sun protective products represents one of the most widespread strategy for protecting human skin against the well-documented damaging effects (erythema, cutaneous photoaging, immune suppression, and various forms of skin cancers) of solar UV radiation (290–400 nm).1, 2, 3 The active ingredients in these products, referred to as UV filters or sunscreen agents, decrease the dose of UV light reaching the skin by absorbing, reflecting, or scattering the radiation.¹

While the

Materials

Butyl methoxydibenzoylmethane (avobenzone) was supplied by Merck (Darmstadt, Germany). Hydrogenated soybean phosphatidylcholine (PC) was a gift by Cargill (Hamburg, Germany). Carnauba wax was from Polichimica (Bologna, Italy). The excipients for the cream preparations were from Sigma–Aldrich (Steinheim, Germany) and Henkel (Fino Mornasco, Italy). Methanol, acetonitrile, and water were high-performance liquid chromatography (HPLC)-grade from Merck. All other reagents and solvents were of

Lipid Microparticle Preparation and Characterization

Lipid microparticles with high avobenzone loadings were developed using a conventional melt dispersion method (based on emulsion formation)²⁴ and a spray congealing technique with a novel pneumatic atomizer which enables the nebulization of highly concentrated fluids.²⁷ Both procedures exhibited the advantage of circumventing the use of organic solvents; additionally, spray congealing based on the atomization of a drug dispersion/solution in the molten carrier, is completely solvent free.

CONCLUSIONS

The results reported in this study indicated that the entrapment of avobenzone in lipid microparticles at high loading levels (>40%), represents an effective strategy to reduce the photolability of this UVA filter, while limiting the quantity of SLMs to be introduced in the sunscreen formulation. This is important, since topical products do not support high amount of powder components. Moreover, the spray congealing technique was found to be superior to the traditional method for the

Acknowledgements

The authors are grateful to MIUR (Ministero dell'Istruzione, dell'Università e della Ricerca, Rome, Italy) for financial support.

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Research ArticlesEvaluation of spray congealing as technique for the preparation of highly loaded solid lipid microparticles containing the sunscreen agent, avobenzone

Abstract

Section snippets

INTRODUCTION

Materials

Lipid Microparticle Preparation and Characterization

CONCLUSIONS

Acknowledgements

Regul Toxicol Pharmacol

Toxicol Appl Pharmacol

J Pharm Sci

J Invest Dermatol

J Photochem Photobiol B

Eur J Pharm Biopharm

Int J Pharm

Int J Pharm

Eur J Pharm Biopharm

Adv Drug Deliv Rev

Eur J Pharm Biopharm

J Invest Dermatol

Int J Pharm

Int J Pharm

On the efficacy of sunscreen products and the claims made relating thereto

Off J Eur Union L

Research Articles
Evaluation of spray congealing as technique for the preparation of highly loaded solid lipid microparticles containing the sunscreen agent, avobenzone