Discovery of Transdermal Penetration Enhancers by High-throughput Screening



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             Chemical Penetration Enhancers Properties

                        * Alter stratum corneum structure

                    * Different formulations including surfactant, fatty acids/esters, terpenes and solvent

                    * More design flexibility                                                            

                    * Only a small number of CPEs can induce significant enhancement to skin penetration

                    * Cause irritation to skin



                Fig4. Anatomy of the skin. Stratum corneum layer is composed of several fatty acid, cholesterol, sphingolipid and cholesterol esters



                CPEs Requirements

                * Enhance the permeability to maximize the ability to delivery active ingredient through the skin

                * Avoid skin irritation due to high concentration of use of CPEs


              Introduction to the Combinatorial Effect of CPEs

                * Synergistic combinations of penetration enhancers (SCOPEs) are the enhancer mixtures of two or more CPEs, which exhibit 

                   more efficient and lower irritation.              

                * Identification of appropriate SCOPE is quite challenging due to the interaction between enhancers and with skin and the

                   number of CPEs in the library.

                * The traditional method used to screen SCOPEs is Franz Diffusion Cells (FDC) (Fig.5), which relies on steady-state measurements

                   of drug transport across the skin membrane. This is not ideal for high-throughput screening.               

                * The need to develop a method to screen SCOPEs effectively must emerge to save time and money.

                * New discovered SCOPEs must be validated both in-vitro and in-vivo.



                                                     Fig5. The Franz Diffusion Cells (FDC) aparatus used to screen SCOPEs


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