APPLICATIONS OF LOW-LIGHT IMAGING TO LIFE SCIENCES

Photon imaging is a new technique for the quantitative analysis of bioluminescence and chemiluminescence and can be performed both at the macro and micro levels. The high sensitivity and spatial resolution of photon-counting cameras have resulted in the development of new applications in the life sciences. At the macro level, imaging is a valuable tool for the rapid identification of biological samples emitting long-lasting glows in assays using microtitre plates or filter formats (immunoassays, DNA probes, phagocytosis, gene expression, metabolite and drug analysis) and also for in vivo studies of promoter activity. At the micro level, low-light imaging can be used for analysing multiple analytes on micro sensors) and for advanced cell analysis (immunocytology, in situ hybridization, identification of cells or tissues expressing the luciferase gene, intracellular or intercellular protein traffic, metabolite analysis and imaging of Ca2+ flux and phosphorylation reactions). Two-dimensional photon-counting instrumentation is a versatile and powerful research tool for imaging and is complementary to conventional luminometers. The main applications to the life sciences involve many types of luminescence assays and can be performed on multiple samples in standard and non-standard formats. Photon-counting coupled to imaging is very helpful in selecting microorganisms or cells expressing bioluminescent genes. Measurements can be made in vitro and in vivo with a sensitivity comparable to that of phototube luminometers.