Diagram of the skin equivalent model.

<p>Fibroblasts were mixed with collagen and allowed to contract over a period of 4–7 days. Keratinocytes were then plated, using a cloning ring, at a density of 200,000 cells/cm². The cells were allowed 4 hours to settle and attach to the upper surface of the contracted collagen lattice. After 4 days of submerged culture, the skin equivalents were raised to the air/liquid interface through subsequent culturing in the upper chamber of a Transwell™ plate. Skin equivalents of emerged cultures were harvested at 7, 14, and 21 days.