Copley Scientific has introduced a new Vertical Diffusion Cell (VDC) for in vitro skin permeation studies. The VDC is for R&D in chemical, pharmaceutical, cosmetics and other industries. The new cell is designed for use with the HDT 1000 Vertical Diffusion Cell Test System; a compact heater stirrer unit for precisely controlled benchtop testing, and the Copley Vacuum De-aeration apparatus.
           

Drug delivery to, or through, the skin is an important approach for various drug types. Topical creams, ointments and gels (semisolid products) are intended to remain on the skin surface where they release an active substance to achieve a localized effect, the relief of a dermatological condition, for example. In contrast, transdermal formulations such as nicotine patches must deliver their active substance through the skin and into the bloodstream for systemic effect. In each case, specific testing is required during product development and quality control of finished products – either to show topical release, or to demonstrate permeation and absorption.    

To meet these requirements, Copley Scientific has added the skin specific cell to its range of VDCs. The new cell has a surface diameter of 15 mm, surface area of ~ 1.77 cm2 and volume of 12 mL. The cell comes with a screw cap designed for “open” or “closed” use, accommodating a range of skin and membranes used for semisolid and permeability testing. The company also offers two other cells – Types ‘B’ and ‘C’, both available in “open” and “closed” top format, targeting semisolids testing in accordance with United States  Pharmacopeia (USP) chapter where thin, artificial membranes are used.

Each cell comprises three main parts: a top sample holder to contain the sample of product to be tested, and a bottom reservoir with the receptor medium. These are separated by a support ring that holds the membrane or skin in place. This construction allows diffusion to take place and ensures that the membrane remains in contact with the receptor medium throughout the testing procedure.

To accommodate ‘full thickness’ membranes or skin, and in contrast to the Type ‘B’ and ‘C’ cells, which use a 3-pronged spring clip, a new screw-type cell closure mechanism has been developed for the skin specific cell that ensures proper contact between the sample and the receptor medium. All components of the cell are made from FDA-approved inert materials and a side sampling arm for filling, sample withdrawal and media replacement.