Programmable binding of single microspheres to single target tumor cells using a dielectrophoresis (DEP) based “lab-on-a-chip” array.

The Lab-on-a-chip technology will enable laboratory testing to move from laboratories employing complex equipments to non-laboratory settings. One of the ultimate goals of this approach is the programmed manipulation of single biological objects, including cells and microspheres. In this respect, dielectrophoresis (DEP) is very efficient for manipulating single cells within Lab-on-a-chips. In the present study, we employed a DEP-array consisting of a 8.8 mm2 chip featuring 102,400 actuation electrodes (arranged in an array of 320 x 320 microsites), each comprising addressing logic, an embedded memory for electrode programming and an optical sensor. The chip generates spherical DEP-cages, enabling software-controlled displacement of more than 10,000 individual living cells or microspheres. The first objective of our research was to determine whether this DEP-arrayed system allows the programmed software-driven interactions of single microspheres carrying monoclonal antibodies to single target cells. Second, we wanted to determine whether MoAb-antigen interactions occurring between functionalized microspheres and target cells can be monitored, enabling the use of this system for immunophenotyping at the single cell level. As a model system we employed two cultured cell lines, the LCL 721.21 HLA-null cell line and LCL 721.221 HLA-G transfectant cell line, one negative, the other positive for HLA-G antigen. These cells are differently recognized by the monoclonal antibody MEM-G9. The data obtained show that DEP-based arrayed Lab-on-a-chip allows software-controlled binding of individually and independently moved single functionalized microspheres (Dynabeads-MEM-G9) to single target cells. Depending on the phenotype (presence or absence of the HLA-G membrane antigen) the microspheres/cell interactions are stable or not, and the DEP-array system allows the rapid identification of them. In conclusion Lab-on-a-chip platforms appear to be suitable for software-controlled targeting of single cells with programmed numbers of microspheres; this strategy might be considered of relevance in pharmaceutical science and molecular diagnosis.