In vitro erythemal UV-A protection factors of inorganic sunscreens distributed in aqueous media using carnauba wax-decyl oleate nanoparticles.

This paper describes the in vitro photoprotection in the UV-A range, i.e. 320-400 nm obtained by the use of carnauba wax-decyl oleate nanoparticles either as encapsulation systems or as accompanying vehicles for inorganic sunscreens such as barium sulfate, strontium carbonate and titanium dioxide. Lipid-free inorganic sunscreen nanosuspensions, inorganic sunscreen-free wax-oil nanoparticle suspensions and wax-oil nanoparticle suspensions containing inorganic sunscreens dispersed either in their oil phase or their aqueous phase were prepared by high pressure homogenization. The in vitro erythemal UV-A protection factors (EUV-A PFs) of the nanosuspensions were calculated by means of a sun protection analyzer. EUV-A PFs being no higher than 4 were obtained by the encapsulation of barium sulfate and strontium carbonate, meanwhile by the distribution of titanium dioxide in presence of wax-oil nanoparticles, the EUV-A PFs varied between 2 and 19. The increase in the EUV-A PFs of the titanium dioxide obtained by the use of wax-oil nanoparticles demonstrated a better performance of the sun protection properties of this pigment in the UV-A region.

Artificial sun protection: sunscreens and their carrier systems.

The formulation of sunscreens products requires information about the properties of the substances responsible for the sun protection, their action mechanisms and the vehicles used for their administration. The improvement of the performance of sunscreen substances by a modification of their chemical, physical and technological properties or by the use of conventional and novel carriers is described in this review. The sun protection achieved by the use of sunscreens incorporated into carriers in terms of the sun protection factor (SPF) and other performance indices is also shown. Current manufacturing methods to incorporate sunscreen substances into vehicles are briefly described. Furthermore, basic information related to the dermatological effects of the UV radiation classified according to the different spectral regions of the UV radiation is presented in this manuscript.

Sun protection enhancement of titanium dioxide crystals by the use of carnauba wax nanoparticles: the synergistic interaction between organic and inorganic sunscreens at nanoscale.

Carnauba wax is partially composed of cinnamates. The rational combination of cinnamates and titanium dioxide has shown a synergistic effect to improve the sun protection factor (SPF) of cosmetic preparations. However, the mechanism of this interaction has not been fully understood. In this study, an ethanolic extract of the carnauba wax and an ethanolic solution of a typical cinnamate derivative, ethylcinnamate, were prepared and their UV absorption and SPF either alone or in the presence of titanium dioxide were compared. The titanium dioxide crystals and the cinnamates solutions were also distributed into a matrix composed of saturated fatty acids to emulate the structure of the crystallized carnauba wax. SPF, differential scanning calorimetry (DSC) and X-ray studies of these matrices were performed. Additionally, carnauba wax nanosuspensions containing titanium dioxide either in the lipid phase or in the aqueous phase were prepared to evaluate their SPFs and their physical structure. Strong UV absorption was observed in diluted suspensions of titanium dioxide after the addition of cinnamates. The saturated fatty acid matrices probably favored the adsorption of the cinnamates at the surface of titanium dioxide crystals, which was reflected by an increase in the SPF. No modification of the crystal structure of the fatty acid matrices was observed after the addition of cinnamates or titanium dioxide. The distribution of the titanium dioxide inside the lipid phase of the nanosuspensions was more effective to reach higher SPFs than that at the aqueous phase. The close contact between the carnauba wax and the titanium dioxide crystals after the high-pressure homogenization process was confirmed by transmission electron microscopy (TEM).

Physical stability, centrifugation tests, and entrapment efficiency studies of carnauba wax-decyl oleate nanoparticles used for the dispersion of inorganic sunscreens in aqueous media.

Aqueous nanoscale lipid dispersions consisting of carnauba wax-decyl oleate mixtures acting as carriers or accompanying vehicles for inorganic sunscreens such as barium sulfate, strontium carbonate, and titanium dioxide were prepared by high pressure homogenization. For the manufacture of these nanosuspensions, three pigment concentrations (%wt), namely 2, 4, and 6, and two carnauba wax-decyl oleate ratios, 1:1 and 2:1, were used, being some of these combinations chosen for stability studies. Six-month physical stability tests at 4, 20, and 40 degrees C selecting the mean particle size and the polydispersity index of the nanosuspensions as reference parameters were performed. Centrifugation tests of the nanosuspensions assessed by transmission electron microscopy and by the determination of the content of pigments and carnauba wax in the separated fractions were done. The mean particle sizes and the polydispersity indices of the nanosuspensions were not altered after six-month storages at 20 and at 40 degrees C. However, the storage of those at 4 degrees C considerably increased the particle size and polydispersity of the systems, particularly when wax-oil ratios (2:1) were used for the entrapment of the pigments. Transmission electron micrographs of centrifuged samples denoted the presence of three major fractions showing the different types of particles integrated into the nanosuspensions. Furthermore, it was observed that not all the carnauba wax participated in the entrapment of the pigment. Regarding the amount of pigment being encapsulated or bonded by the wax-oil matrices, entrapment efficiencies higher than 85.52% were reported.

Novel nanoparticulate carrier system based on carnauba wax and decyl oleate for the dispersion of inorganic sunscreens in aqueous media.

The purpose of this study was to characterize carrier systems for inorganic sunscreens based on a matrix composed of carnauba wax and decyl oleate. Ultraviolet radiation attenuators like barium sulfate, strontium carbonate and titanium dioxide were tested. The lipid matrices were used either as capsules or as accompanying vehicles for the pigments in aqueous dispersions. Manufacturing was performed using high pressure homogenization at 300bar and a temperature of 75 degrees C. To evaluate the effect of the pigments on the crystalline structure of the wax-oil mixture, X-ray diffraction and differential scanning calorimetry were used. Further parameters determined were particle size, polydispersity index, z-potential, viscosity and sun protection factor (SPF). Transmission electron microscopy was also applied for visualization of nanoparticles. The X-ray diffraction patterns and the melting points of the lipid mixtures remained unchanged after the pigments were added. The particle sizes of the encapsulated species ranged from 239 to 749.9nm showing polydispersity values between 0.100 and 0.425. Surface charge measurements comprising values up to -40.8mV denoted the presence of stable dispersions. The formulations could be described as ideal viscous presenting viscosities in a range of 1.40-20.5mPas. Significant increases in SPF up to about 50 were reported after the encapsulation of titanium dioxide. Freeze fracture micrographs confirmed the presence of encapsulated inorganic crystals.

High-performance liquid chromatography assay for indorenate in pharmaceutical powders.

A high-performance liquid chromatographic (HPLC) method for quantification of indorenate admixed of pharmaceutical excipients (Pharmatose DCL 21, Povidone USP and Helmcel 200) is described. Indorenate was extracted from the mixtures using a mobile phase composed of acetonitrile and a sodium acetate buffer solution 0.1 M (63:37) and separated from other dissolved components by ion supression-HPLC. The method was standardized using a C-18 column (250 mm x 4.8 mm, i.d., 5 microns). The photometric detector was fixed at 228 or 272 nm depending on the admixed excipients. Validation parameters included linearity, precision, accuracy, reproducibility, and specificity. The method was specific, selective, and capable to distinguish indorenate from their degradation products and the antihypertensive pelanserine.

Effect of carrier excipient and processing on stability of indorenate hydrochloride/excipient mixtures.

The purpose of this investigation was to determine the solid-state chemical stability of a model drug, indorenate hydrochloride, as a function of carrier excipient and mixing process. Physical mixtures and granules were prepared by tumble mixing and alcoholic granulation with and without binder. Stability of the mixtures was estimated using differential scanning calorimetry and isothermal degradation studies at 40, 50, and 60 degrees C. Average first-order degradation constants at 25 degrees C, extrapolated from isothermal studies, were much lower for indorenate hydrochloride after tumbling mixing with microcrystalline cellulose (3.45 x 10(-5) day-1) than those obtained after tumbling mixing with lactose (112.0 x 10(-5) day-1). Distribution of the drug on the excipient's surface, through granulation with and without Povidone, increased the average drug degradation rates in granules with microcrystalline cellulose (36.2 x 10(-5) day-1) as well as in granules with lactose (326 x 10(-5) day-1). Partially amorphous lactose (spray-dried lactose) showed higher average degradation rates (310.5 x 10(-5) day-1) than crystalline lactose (199.3 x 10(-5) day-1). It appears that the amorphous portion of the drug as well as that of reacting excipients play a major role in affecting the reaction rate. The calorimetric studies showed a strong solid-solid interaction between indorenate hydrochloride and lactose, suggesting chemical incompatibility. This strong solid-solid interaction was characterized by disappearance of typical transition peaks of lactose at temperatures above 200 degrees C and the development of new peaks at about 130-170 degrees C. No major changes in transition peaks were observed in mixtures of microcrystalline cellulose and indorenate hydrochloride, suggesting chemical compatibility. Calorimetric results allow the prediction of the chemical incompatibility between indorenate hydrochloride and lactose observed in isothermal degradation studies.