Final Report Summary - INSTANTCOUNT (Printed microfluidic counting chambers for low-cost point-of-care diagnostics)
Within this project, we developed printing processes for the fabrication of cell counting chambers with on-chip sample preparation. In a first step, a reagent layer consisting of a release matrix and fluorescently labelled antibodies is deposited using an inkjet printing. In a second step, UV-curable glue containing polystyrene microspheres acting as spacers is deposited and a cover is attached by curing the glue with UV light. When the device is used, the sample, e.g. whole blood from a finger prick, fills the chamber by capillary action, while the release matrix prevents the wash-off of the antibodies during inflow. After the inflow has stopped, the antibodies are slowly released from the matrix material. We have optimized this process by investigating the release kinetics, compatibility with the printing techniques, and long-term stability (shelf-life) of reagents as well as release matrix under various storage conditions. While the initially used matrix material gelatin provided excellent tunability of the release (DOI: 10.1039/C5AN02090E) inkjet-printing strongly influenced the release kinetics, presumably because physical crosslinks between collagen molecules (triple-helices) are destroyed during jetting and are slowly rebuilt within weeks and months during storage. By exposing printed gelatin layers to high humidity, we actively speeded up this maturation process. The antibody release from the resulting gelatin layers can then be actively controlled by heating the chip above the sol-gel transition temperature of gelatin (~40ºC) (DOI: 10.1021/acsami.6b09206). Using this release mechanism, we fabricated a series of CD4 counting chips and tested their performance using blood samples from HIV patients. In parallel, gellan gum was identified as a good alternative matrix material with excellent long-term stability, with completely passive antibody release. A second series of patient samples was tested using this approach. Both approaches showed excellent correlation between CD4 counts from printed counting chambers and the reference counts from flow cytometry.
We also applied the method, as well as similar approaches, to work towards a complete blood count on the same platform.
At the time of writing of this report, several manuscripts are under review or in preparation.
We also applied the method, as well as similar approaches, to work towards a complete blood count on the same platform.
At the time of writing of this report, several manuscripts are under review or in preparation.