The objective of this grant is to develop optical-sensing systems for measuring in vitro metabolism-based assays with cultured eukaryotic cells. The technique can rapidly analyze in situ multiple cell samples in small culture vessels. The approach is valuable for conducting bioassays in such as cytotoxicity studies, drug sensitivity testing, cell activation and proliferation testing. The innovative approach utilizes an indicator put into assay vessels which is interrogated by an optical reader. It is thereby practical to measure changes in the sample microenvironment due to cell's metabolism. Differences serve as bioassay indices of cell death, proliferation, activation or inhibition. The Phase II aims are to develop the technology for performing assays in different forms of cell culture vessels and to evolve various reading instruments for optically analyzing the assay vessels. The research objectives focus on the features of assaying small samples, kinetic studies, continuous monitoring, economy, speed, and versatility. The technology produced will engender a family of products meeting diverse application-driven needs in research, medicine and industry for cell growth and inhibition bioassays.