The test consists of polymer film imprinted with an array of miniature spots. Each spot contains antibodies specific to the two kinds of leukocytes surface antigens (CD4 and CD8) and three types of cytokines printed in the same array.

When the blood is applied to the film and flows across the antibody spots, T-cell leukocytes stick on the spots. Each T-cell type is captured next to antibody spots specific for the cytokines they might produce. When antibodies activate the cells, spots adjacent to the cells capture the cytokines they secrete. This connects a specific T-cell subset to its secreted cytokines. The visible color intensity of antibody spots revealed differences in cytokine production by T-cells.

The antibody microarray is integrated with a lens-free holographic imaging device that takes only seconds to count the number of captured cells and amount of secreted cytokine molecules. The test returns results six to twelve times faster than traditional approaches and tests six parameters simultaneously, based on a small blood sample.

The visible color intensity of antibody spots revealed differences in cytokine production by T-cells. The lens-free on-chip imaging allowed the scientists to rapidly image and count T-cell arrays without the use of any lenses or mechanical scanning. Analysis of CD4 and CD8 T-cell numbers, the CD4/CD8 ratio, and three secreted cytokines takes only seconds.

The device was developed at the University of California (UCDavis; Davis, CA, USA) by Professor Alexander Revzin, Ph.D., the principle biochemical engineer. He explains, "While the point of care field focuses on detection of single parameter (e.g., CD4 counts), we believe that the simplicity of the test need not compromise information content. So, we set out to develop a test that could be simple and inexpensive, but would provide several parameters based on a single injection of a small blood volume." The device will be useful for blood transfusion monitoring, where the safety of blood is frequently in question.

The study was published in the May 2010 issue of Analytical Chemistry.

The tandem use of antibody microarrays and lens free holographic imaging, paves the way for future development of miniature cytometry devices for multiparametric blood analysis at the point of care or in a resource-limited setting.

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University of California at Davis