Capsaicin o/w nanoemulsions with enhanced skin permeation were successfully prepared by controlling the ratios of the surfactant mixtures, oleoresin capsicum as the oil phase, and aqueous phase. Oleoresin capsicum contains 22.67 mg/g of capsaicin, which is an active and oil-soluble ingredient. Nonionic surfactants, Tween 80 and Span 80, were used to optimize the weight ratio of surfactant mixtures (85.98:14.02) by calculating the hydrophile-lipophile balance (HLB) value. The optimal processing conditions for stable nanoemulsions were investigated by using a ternary phase diagram. The mean droplet size of nanoemulsions ranged from 20 to 62 nm. Skin permeation studies were performed using a Franz diffusion cell. The permeation profiles and confocal laser scanning microscopy (CLSM) images supported that capsaicin nanoemulsion could well permeate all skin layers from the stratum corneum to the dermis. The selected nanoemulsions showed great potential as transdermal delivery carriers for enhancing the permeation of core materials.
Nanosuspensions (NSs) were fabricated to enhance water solubility, dissolution rate, and oral adsorption of water insoluble curcumin using sonoprecipitation method. As a good stabilizer, d-α-Tocopherol polyethylene glycol 1000 succinate (TPGS) was used to improve the stability of curcumin-TPGS NSs (Cur-TPGS NSs). Ultrasonic homogenization (UH) could effectively enhance the solubility of curcumin and to produce homogeneous NSs with small particle sizes. Water solubility of curcumin was significantly improved from 0.6 μg/mL in pure water to 260 μg/mL in the mixture of curcumin and TPGS (1:10) with UH treatment. The mean particle size of Cur-TPGS NSs was decreased significantly after UH and maintained between 208 and 246 nm. Lyophilized powder of Cur-TPGS NSs was dissolved about 91.08% whereas the pristine curcumin powder was dissolved only 6.5% at pH 7.4. This study showed a great potential of Cur-TPGS NSs as a good nano-formulation of curcumin with enhanced solubility and improved oral adsorption.
This article describes enhanced skin permeation and UV/thermal stability of retinol emulsions by the co-stabilisation of Tween20 and biodegradable poly(ethylene oxide)-block-poly(ε-caprolactone)-block-poly(ethylene oxide) (PEO-PCL-PEO) triblock copolymers having different lengths of hydrophobic PCL block. A triblock copolymer with a longer PCL block has a lower hydrophile-lipophile balance (HLB) value. Commercial Retinol 50C® (BASF Co., Ludwigshafen, Germany) was used as the source of retinol. Ultrasonication of the Retinol 50C® emulsion with the triblock copolymers led to an increase in retinol solubilisation and a decrease in average particle size of the resulting retinol emulsion. These characteristics improved skin permeation of retinol through the stratum corneum of artificial skin and subsequent proliferation of viable epidermis cell. Employment of the triblock copolymer with a longer PCL block increased both UV and thermal stabilization of the retinol. These results suggest that HLB and PCL block length are important factors to enhance the topical delivery of retinol into the skin.
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