PART 2 Preparation And Evaluation Of Microemulsion‑based Transdermal Delivery Of Cistanche Tubulosa Phenylethanoid Glycosides
Mar 06, 2022
Contact: Audrey Hu Whatsapp/hp: 0086 13880143964 Email: audrey.hu@wecistanche.com
For the drug molecules, and resulted in a faster release with a diffusion-controlled release mechanism (29). The permeation-enhancing effect of IPM may increase the diffusion coefficient of PG(Phenylethanoild glycoside from cistanche) -loaded ME in skin tissues, which may result in an increased permeation coefficient (30). Furthermore, the water content of MEs may enhance permeation as hydration of the stratum corneum contributes to the development and widening of channels in the keratin layer and the distortion of the lipid bilayer (24). In the present study, the water content in ME5 (65%) was higher than in the other MEs (Table I), implying that ME5 might induce a higher permeation rate. In addition, the droplet size might affect the permeation profiles, whereby ME with smaller droplets tended to increase skin permeation. Taken together, ME5 formulated with the appropriate amount of surfactant mixture (28%) and water (65%), with small droplet size (30.56 nm) and low viscosity (30.43 mPa.s), demonstrated improved permeability compared with the other ME formulations.
The cumulative amount of PG(Phenylethanoild glycoside from cistanche) that penetrated the skin increased with drug loading (Fig. 6). In addition, increased drug solubility contributes to the promotion of transdermal drug delivery (24,31). For ME5, a 6.9-fold increase in transdermal flux was noticed in the presence of 2% drug loading (242.49 µg/cm-2 /h-1 ; Fig. 6) compared with 0.5% drug loading (35.504 µg/cm-2 /h-1 ; Fig. 6). However, due to physical instability at 3.0% drug loading, resulting in the crystallization of PG during storage, the final loading of PG(Phenylethanoild glycoside from cistanche) in ME5 was 2.0%. Comparisons between the optimized ME and the PG aqueous solution are displayed in Table IV. A 1.68-fold increase in the skin permeation rate of PG was observed in the optimized ME group compared with the PG saline group (Fig. 7). The cumulative amount of PG in the optimized ME group (4149.650±37.3 µg·cm-2 ) was significantly increased compared with the PG(Phenylethanoild glycoside from cistanche) saline group (2288.63±20.9 µg•cm-2, P=0.0039; Table IV) The permeability coefficient indicated that the optimized ME (8.87±0.49 cm/h; Table IV) was also increased compared with the PG saline solution [5.41±0.12 (cm/h)x10-3; P=0.041; Table IV], suggesting that optimized ME is a more effective carrier of PG(Phenylethanoild glycoside from cistanche) than saline. According to previous reports (16,32), high concentration (2%) of PG in MEs resulted in a high concentration gradient, which contributed to the permeation of PG into the skin. MEs may act as drug reservoirs, with the drug being released from the inner phase to the outer phase and then onto the skin. Furthermore, the MEs may affect the stratum corneum structure and reduce the diffusional barrier by acting as a permeation enhancer (26,33). Skin retention study. The optimized ME in the present study demonstrated a higher drug deposition capacity than the PG aqueous solution (174.07±1.51 µg·cm-2 vs. 93.25±1.49 µg·cm-2; P=0.029, Table IV). This may be associated with the faster release of PG from the optimized ME, resulting in elevated drug penetration into the skin, or to the higher solubility of the optimized ME compared with the PG saline solution. Due to this effect, an increased amount of PG is retained in the skin.
The optimized ME5 formulation demonstrated higher skin retention than the PG(Phenylethanoild glycoside from cistanche) saline solution (30). The optimized ME was also superior to the PG saline solution the terms of skin permeation profiles and skin retention (Table IV). Taken together, the optimized ME delivered PG more effectively than the PG saline solution. Stability study. Stability studies were performed to detect any changes in pH, droplet size, and drug content. Optimized ME was physically stable (16,29) retaining homogeneity and demonstrating no phase separation after 3 months. No major changes were observed in the droplet size and degradation of PG within 3 months. The centrifuge tests demonstrated that optimized ME is physically stable. No significant changes were recorded in the stored ME, but there was a slight decrease in viscosity. This decrease may be due to the loss of water during storage. Three months later, no difference was noticed in the pH, droplet size, drug content and viscosity between ME stored at 2‑8˚C and at room temperature (Table V). Skin sensitivity test. The intensity criterion of skin irritation followed the protocol, and scores of <0.5 meant no irritation, 0.5-3 slight irritation, 3-6 moderate irritation, and >6 severe irritation. Little visible irritation was observed in animals treated with optimized ME.
The average response scores of skin irritation for a saline solution with 2% (w/w) PG (Phenylethanoild glycoside from cistanche) were 0.1±0.05, 0.1±0.13, and 0.1±0.07 at 24, 48 and 72 h, respectively. For the optimized ME, the scores were 0.28±0.02, 0.16±0.11 and 0.15±0.08 at 24, 48, and 72 h, respectively. Despite a slight increase in the scores, optimized ME did not appear to irritate the skin. For these reasons, PG(Phenylethanoild glycoside from cistanche) treatment with optimized ME appears to be safe. A novel ME was prepared using IPM as the oil phase, CremophorEL as the surfactant, and propylene glycol as the cosurfactant. This formulation was characterized by a transparent appearance, low viscosity, a spherically uniform distribution, stable physical and chemical properties, as well as good stability. Compared with saline solution, an a1.68-fold increase was noted in the skin permeation rate of PG(Phenylethanoild glycoside from cistanche) for optimized microemulsion. The cumulative amount of PG in the microemulsion (4149.650±37.3 µg·cm-2 ) was significantly higher than that of PG in the saline solution (2288.63±20.9 µg·cm-2 ). Furthermore, the permeability coefficient indicated optimized microemulsion was a more efficient carrier for transdermal delivery of PG than the control solution (8.87±0.49 cm/hx10-3 vs. 5.41±0.12 cm/hx10-3 ), the skin permeation ability of PG(Phenylethanoild glycoside from cistanche) was significantly increased by this ME, which may be due to the special characteristics of MEs.
References
Qiu Y, Chen M, Su M, Xie G, Li X, Zhou M, Zhao A, Jiang J and Jia W: Metabolic profiling reveals therapeutic effects of Herba Cistanches in an animal model of hydrocortisone‑induced kidney‑deficiency syndrome’. Chin Med 3: 3, 2008.
Fu G, Pang H and Wong YH: Naturally occurring phenylethanoid glycosides: Potential leads for new therapeutics. Curr Med Chem 15: 2592-2613, 2008.
Saracoglu I, Harput US, Inoue M and Ogihara Y: New phenylethanoid glycosides from Veronica pectinata var. glandulosa and their free radical scavenging activities. Chem Pharm Bull (Tokyo) 50: 665-668, 2002.
Yamaguchi K, Mitsui T, Aso Y and Sugibayashi K: Structure-permeability relationship analysis of the permeation barrier properties of the stratum corneum and viable epidermis/dermis of rat skin. J Pharm Sci 97: 4391-4403, 2008.
Tandel H, Raval K, Nayani A and Upadhyay M: Preparation and evaluation of cilnidipine microemulsion. J Pharm Bioallied Sci 4 (Suppl 1): S114-S115, 2012.
M El Maghraby G: Microemulsions as transdermal drug delivery systems. Curr Nanoscience 8: 504-511, 2012.
Mou D, Chen H, Du D, Mao C, Wan J, Xu H and Yang X: Hydrogel-thickened nanoemulsion system for topical delivery of lipophilic drugs. Int J Pharm 353: 270-276, 2008.
Barot BS, Parejiya PB, Patel HK, Gohel MC and Shelat PK: Microemulsion-based gel of terbinafine for the treatment of onychomycosis: Optimization of formulation using D-optimal design. AAPS PharmSciTech 13: 184-192, 2012.
sai YH, Lee KF, Huang YB, Huang CT and Wu PC: In vitro permeation and in vivo whitening effect of topical hesperetin microemulsion delivery system. Int J Pharm 388: 257-262, 2010.
Li G, Fan Y, Li X, Wang X, Li Y, Liu Y and Li M: In vitro and in vivo evaluation of a simple microemulsion formulation for propofol. Int J Pharm 425: 53-61, 2012.
Yang JH, Wu SS, Xu HH, Yan Y, Ju B, Zhu D, Liang X and Hu J: Inhibitory effects of phenylethanoid glycosides on melanin synthesis in cultured human epidermal melanocytes. Int J Clin Exp Med 9: 18019-18025, 2016.
Shen LN, Zhang YT, Wang Q, Xu L and Feng NP: Preparation and evaluation of micro emulsion-based transdermal delivery of total flavone of rhizoma arisaematis. Int J Nanomedicine 9: 3453-3464, 2014.
Draize JH, Woodard G and Calvery HO: Methods for the study of irritation and toxicity of substances applied topically to the skin and mucous membranes. J Pharmacol Exp Therapeutics 82: 377-390, 1944.
Sahoo S, Pani NR and Sahoo SK: Microemulsion based topical hydrogel of sertaconazole: Formulation, characterization and evaluation. Colloids Surf B Biointerfaces 120: 193-199, 2014.
