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Microfluidic Testing for LLNA Replacement
By: Katie Schaefer, Cosmetics & Toiletries magazine
Posted: February 26, 2010, from the March 2010 issue of Cosmetics & Toiletries.
In 2004, as a part of the Cosmetics Directive, the European Commission established a timeline for the phasing out of animal testing in Europe by 2013. While some alternative methods have been validated, devising comparable animal replacement tests is a continual challenge. As a specific example, to test for the sensitization potential of topical products, the local lymph node assay (LLNA) often is used. This method assesses whether a test material topically applied on an animal induces the proliferation of lymphocytes.
However, progress is emerging in this area. The Hurel Corp. has developed a microfluidic, non-animal alternative to the LLNA and it has partnered with L’Oréal to make this approach a reality—in the form of a chip. Martin Yarmush, MD, PhD, is the force behind the application of microfluidics in a chip format. Known as the Allergy Test on a Chip, the technology is being developed by Hurel, with a projected completion date of mid 2011.
The Basic Components
According to Yarmush, “The chip mimicks the essential elements of the LLNA assay.” He explained that in the LLNA, a chemical is rubbed in or near the ear of an animal such as a mouse. Then, the local lymph node is excised and the T cells are measured to determine if they have been activated.
To mimick this assay, the chip that Yarmush and a team of researchers created consists of three main compartments involving two different tissues. The first compartment of the chip is an artificial skin provided by L’Oréal. The second compartment includes microfluidic channels, and the third is a lymph node compartment made up of lymphocytes such as T cells or B cells. To replicate the LLNA’s mechanism of action, cells must migrate from the artificial skin to the lymph node compartment when activated by a sensitizer. “We used dendritic cells to migrate from the skin to the lymph node [compartment],” explained Yarmush.
“These cells sit either within the artificial skin or right underneath the skin. The [potential] sensitizer diffuses through it, and if it is an activator, it will turn on the dendritic cells, which will migrate down to the lymph node compartment.”