On-chip, cell-based microarray immunofluorescence assay for high-throughput analysis of target proteins.

We have developed an immunofluorescence-based assay for high-throughput analysis of target proteins on a three-dimensional cellular microarray platform. This process integrates the use of three-dimensional cellular microarrays, which should better mimic the cellular microenvironment, with sensitive immunofluorescence detection and provides quantitative information on cell function. To demonstrate this assay platform, we examined the accumulation of the alpha subunit of the hypoxia-inducible factor (HIF-1alpha) after chemical stimulation of human pancreatic tumor cells encapsulated in 3D alginate spots in volumes as low as 60 nL. We also tested the effect of the known dysregulator of HIF-1alpha, 2-methoxyestradiol (2ME2), on the levels of HIF-1alpha using a dual microarray stamping technique. This chip-based in situ Western immunoassay protocol was able to provide quantitative information on cell function, namely, the cellular response to hypoxia mimicking conditions and the reduction of HIF-1alpha levels after cell treatment with 2ME2. This system is the first to enable high-content screening of cellular protein levels on a 3D human cell microarray platform.