Application of microemulsion for enhancing topical skin absorption of 20(S)-protopanaxadiol and oral absorption of rebamipide

다국어 초록 (Multilingual Abstract)

20(S)-protopanaxadiol (20S-PPD) is an aglycosylated metabolite of ginsenosides such as compound K and ginsenoside Rb1, and possesses a potent skin anti-aging activity. However, due to its low aqueous solubility and large molecular size, a suitable formulation strategy is required in order to enhance skin deposition of 20S-PPD by improving its solubility and skin permeability. Rebamipide (RBP) is a potent anti-ulcer and anti-oxidative agent, which belongs to biopharmaceutics classification system (BCS) class IV with a poor oral bioavailability of less than 10%. Thus, enhancing the systemic exposure of RBP may increase its pharmacological activities after oral administration. The objective of the study was to develop microemulsion (ME)-based systems for the topical skin delivery of 20S-PPD and for the oral delivery of RBP. 20S-PPD-loaded ME and ME-based hydrogel (MEH) formulations were prepared and evaluated in terms of their particle size distribution, morphology, maximum loading capacity, viscosity, and pH value. Then, the in vitro and in vivo deposition or permeation profiles of 20S-PPD in the selected MEH formulation were studied using hairless mouse skin model and artificial skin model, Strat-M® membrane. A Carbopol-based MEH system of 20S-PPD was successfully prepared with a mean droplet size of 110 nm and polydispersity index of 0.436. The formulation was stable at least for 56 days, and its viscosity was high enough for its topical skin application. It significantly enhanced the in vitro and in vivo skin deposition of 20S-PPD with no influence on its systemic absorption in hairless mice. Notably, it was found that the rank of the tested formulaions in the order of decreasing deposition of 20S-PPD in in vitro Strat-M® membrane and in vitro/in vivo hairless mouse skin was same. For RBP-loaded ME, characterization study (i.e. maximum loading capacity, particle size distribution, and morphology), in vitro drug release study, in vivo pharmacokinetic study, and intestinal toxicity study were performed. Capmul MCM EP and Solutol HS15-based ME system of RBP had spherical nano-sized droplets with polydispersity index of 0.265 and neutral zeta potential. Moreover, the prepared ME significantly enhanced the dissolution and oral bioavailability of RBP with no discernible intestinal toxicity. Taken together, the ME-based systems developed in this study could serve as a potentially effective topical skin and oral delivery system for enhancing the absorption of poorly soluble compounds including 20S-PPD and RBP.

목차 (Table of Contents)

• Background 1
• 1.1. Fick’s diffusion law 1
• 1.2. Microemulsion (ME)-based systems 3
• 1.3. Microemulsion (ME) systems for topical skin and oral delivery 5
• Part I. Microemulsion-based hydrogels for enhancing epidermal/dermal deposition of topically administrated 20(S)-protopanaxadiol: in vitro and in vivo evaluation 8
• 1. Introduction 8
• 2. Materials and Methods 11
• 2.1. Materials 11
• 2.2. Animal 12
• 2.3. Solubility study 13
• 2.4. Construction of pseudo-ternary phase diagrams 13
• 2.5. Preparation of 20S-PPD-loaded ME and MEH formulations 14
• 2.6. Characterization of 20S-PPD-loaded ME and MEH formulations 15
• 2.6.1. Particle size and zeta potential 15
• 2.6.2. TEM 16
• 2.6.3. pH 16
• 2.6.4. Viscosity 16
• 2.6.5. Maximum loading capacity 17
• 2.7. In vitro skin deposition study: hairless mouse skin and Strat-M® membrane 17
• 2.8. In vivo skin deposition study 19
• 2.9. Stability study 20
• 2.10. LC-MS/MS analysis of 20S-PPD 20
• 2.11. Statistical analysis 22
• 3. Results 22
• 3.1. Preparation of 20S-PPD-loaded ME and MEH formulations 22
• 3.2. Characterization of 20S-PPD-loaded ME and MEH formulations 23
• 3.3. In vitro deposition of 20S-PPD in hairless mouse skin and Strat-M® membrane 24
• 3.4. In vivo skin deposition of 20S-PPD after topical application 25
• 3.5. Stability of 20S-PPD-loaded ME and MEH formulations 26
• 4. Discussion 27
• 5. Conclusion 33
• Part II. Capmul MCM EP/Solutol HS 15-based microemulsion for enhanced oral bioavailability of rebamipide 50
• 1. Introduction 51
• 2. Materials and Methods 54
• 2.1. Materials 54
• 2.2. Animal 54
• 2.3. Solubility study 55
• 2.4. Construction of pseudo-ternary phase diagrams 55
• 2.5. Preparation of RBP-loaded MEs 56
• 2.6. Characterization of RBP-loaded MEs 56
• 2.6.1. Maximum loading capacity 57
• 2.6.2. Particle size and zeta potential 57
• 2.6.3. TEM 57
• 2.7. In vitro drug release study 58
• 2.8. In vivo pharmacokinetic study 58
• 2.9. In vivo intestinal toxicity study 59
• 2.10. HPLC-fluorescence analysis of RBP 59
• 2.11. Statistical analysis and data analysis 60
• 3. Results 61
• 3.1. Preparation of RBP-loaded MEs 61
• 3.2. Characterization of RBP-loaded MEs 62
• 3.3. In vitro release of RBP 63
• 3.4. In vivo plasma concentration profiles of RBP after oral administration at the dose of 5 mg/kg in rats 63
• 3.5. In vivo intestinal toxicity after oral administration at the dose of 5 mg/kg in rats 64
• 4. Discussion 64
• 5. Conclusion 67
• References 79
• 국문초록 89
• Appendix 93