Ex-vivo Drug Permeation Studies

Further ex-vivo drug permeation studies were conducted to explore the effect of sonophoresis on enhancing the drug permeation from the developed invasomal gel systems, relative to the passive permeation of the aqueous drug dispersion or the best achieved AGM-loaded invasomes (I2).

The pre-treatment protocol for the application of ultrasound waves was adopted, as proposed by Ammar et al.¹⁰ Briefly, the hydrated epidermal layers of the rat skin were carefully placed on Petri dish, taking into consideration that the epidermis is facing upwards. The drug-free coupling gel was placed on the epidermis and the ultrasound horn for LFU (Cole-Parmer, Trenton, USA) or HFU (Radium skin massager, Tokyo, Japan) was fixed and placed directly over the coupling gel.^10,17 The investigated variables were the ultrasound frequency (LFU or HFU), ultrasound mode (pulsed or continuous), the application period (10 or 15 min) and the duty cycle (50% or 100%). A 2⁴ full factorial design was adopted to explore the influences of these variables, Table 2.

Pre-Treatment Sonophoresis Conditions and ex-vivo Characterization Data (Mean ± S.D., n = 3) of the Developed Agomelatine-Loaded I2-Invasomal Gel Systems, in Comparison to the Untreated AGM Dispersion and I2 Invasomes

Abbreviations: LFU, low frequency ultrasound; HFU, high frequency ultrasound; P1–P4, pulsed ultrasound mode; C1–C4, continuous ultrasound mode; Q_24h, cumulative drug permeated per unit area after 24 h; J_ss, flux; ER, enhancement ratio.

After ultrasound pre-treatment, the skin samples were carefully wiped and mounted on the modified Franz diffusion cells. The ex-vivo drug permeation studies for AGM-loaded invasomal gel system were conducted, as previously mentioned.