Dinâmica molecular e particionamento do marcador de spin di-terc-butil nitróxido em membranas de estrato córneo. Efeito de Terpenos

Abstract

Terpenes are a very promising class of skin penetration enhancers especially due to their low potential of irritation in the skin. In this work, we have used the electron paramagnetic resonance (EPR) spectroscopy of the small spin label di-tert-butyl nitroxide (DTBN), which partitions the aqueous and hydrocarbon phases, to study the interaction of the terpenes ®-terpineol, 1,8-cineole, L(-)-carvone and (+)-limonene with the uppermost skin layer, the stratum corneum, and the membrane models of 1,2-dipalmitoyl-sn-glycero- 3-phosphatidylcholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The EPR spectra indicated that the terpenes increase both the partition coe±cient and the rotational di®usion rate of the spin labels in the stratum corneum membranes whereas for DMPC and DPPC bilayers were observed similar e®ects only at temperatures below the liquid-crystalline phase. The EPR parameter associated to probe polarity inside the membranes showed thermotropic induced changes, suggesting relocations of spin probe, which were dependent of the membrane phases. While DMPC and DPPC bilayers showed abrupt changes in the partitioning and rotational correlation time parameters at the phase transitions, the SC membranes were characterized by slights changes in whole interval of measured temperatures, presenting the greatest changes or membranes reorganizations in the temperature range of v50 to v74±C. The results suggest that the terpenes act as spacers that weaken the hydrogen-bonded network at the polar interface thus °uidizing the stratum corneum lipids and, in consequence, increase the permeation of small polar molecules across the membranes. 2