Photonic Crystal Arrays for Soybean Gene Expression and Protein Analysis

Transcription factors control important gene regulation networks, altering the expression of a wide variety of genes while often expressing at only a low level themselves. This can make detecting transcription factor mRNA and proteins difficult, as current high-throughput methods may not be sensitive enough. Photonic crystal (PC) devices, attached to glass microscope slides, provide an alternative substrate for printing cDNA or protein microarrays which has greater sensitivity through a reduced signal-to-noise ratio as compared to glass alone. We have achieved 8x enhancement of low-expressed genes on cDNA arrays containing approximately 8000 spots using plastic photonic crystal slides. We are currently working to optimize a high-throughput protein microarray using photonic crystal slides to quantitate low-abundance proteins such as transcription factors on a large scale. We have examined nine proteins of varying abundance found in soybean seeds, including low-expressed transcription factors, using the photonic crystal protein array and have detected the proteins at concentrations as low as 250pg/ml. Our current goals are to determine the limits of detection of this technology using even lower concentrations of proteins and to optimize the procedure for new silicon-based photonic crystal devices, which have reduced background and even greater sensitivity than previous versions.