Mechanistic of Vesicular Ethosomes and Elastic Liposomes on Permeation Profiles of Acyclovir across Artificial Membrane, Human Cultured EpiDerm, and Rat Skin: In Vitro-Ex Vivo Study

Abstract

Acyclovir (ACV) controls cutaneous herpes, genital herpes, herpes keratitis, varicella zoster, and chickenpox. From previously reported ACV formulations, we continued to explore the permeation behavior of the optimized ACV loaded optimized ethosome (ETHO2R) and elastic liposome (ELP3R) and their respective carbopol gels across artificial membrane, cultured human EpiDerm, and rat skin. Transepidermal water loss (TEWL), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), and atomic force microscopy (AFM) were used to investigate the mechanistic perspective of permeation behavior. The size values of reformulated ELP3-R and ETHO2-R were observed as 217 and 128 nm, respectively (close to previous report), whereas their respective gels showed as 231 and 252 nm, respectively. ETHO2R showed high elasticity, %EE, and low vesicle size. These were investigated for the diffusion rate of the drug permeation (3 h) across the artificial membrane, cultured human EpiDerm, and rat skin. ETHO2GR showed the highest permeation flux (78.42 µg/cm2/h), diffusion coefficient (8.24 × 10−5 cm2/h), and permeation coefficient (0.67 × 10−3 cm/h) of ACV across synthetic membrane, whereas diffusion coefficient (2.4 × 10−4 cm2/h) and permeation coefficient (0.8 × 10−3 cm/h) were maximum across EpiDerm for ETHO2GR. ETHO2R suspension showed maximized permeation flux (169.58 µg/cm2/h) and diffusion rate (0.293 mg/cm2/h1/2), suggesting the rapid internalization of vesicles with cultured skin cells at low viscosity. A similar observation was revealed using rat skin, wherein the permeation flux (182.42 µg/cm2/h), permeation coefficient (0.3 × 10−2 cm/h), and diffusion rate (0.315 mg/cm2/h1/2) of ETHO2R were relatively higher than ELP3R and ELP3GR. Relative small size (128 nm), low viscosity, ethanol-mediated ultra-deformability, high drug entrapment (98%), and elasticity (63.2) are associated with ETHO2R to provide remarkable permeation behavior across the three barriers. The value of TEWL for ETHO2R (21.9 g/m2h) was 3.71 times higher than untreated control (5.9 g/m2h), indicating ethanol-mediated maximized surficial skin lipid perturbation at 3 h of application, whereas the respective ETHO2GR-treated rat skin had TEWL value (18.6 g/m2h) slightly lower than ETHO2R due to gel-based hydration into the skin. SEL, CLSM, and AFM provided a mechanistic perspective of ETHO2R and ELP3R-mediated permeation across rat skin and carrier-mediated visualization (skin–vesicle interaction). AFM provided detailed nanoscale surface roughness topographical parameters of treated and untreated rat skin as supportive data to SEM and CLSM. Thus, ethosomes ETHO2R and respective gel assisted maximum permeation of ACV across rat skin and cultured human EpiDerm to control cutaneous herpes infection and herpes keratitis.