Ultrasensitive optical DNA biosensor based on surface immobilization of molecular beacon by a bridge structure

A novel biotinylated molecular beacon (MB) probe was developed to prepare a DNA biosensor using a bridge structure. MB was biotinylated at the quenche r side of the stem and linked on a biotinylated glass cover slip through st reptavidin, which acted as a bridge between MB and glass matrix. An efficie nt fluorescence microscope system was constructed to detect the fluorescenc e change caused by the conformation change of MB in the presence of complem entary DNA target. The proposed biosensor was used to directly detect, in r eal-time, the target DNA molecules. The bridge immobilization method caused the proposed DNA biosensor to have a faster and more stable response. Unde r the optimal conditions, the newly developed DNA biosensor showed a linear response toward ssDNA in the range of 5 - 100 nM with a detection limit of 2 nM. It was interesting to note that the described biosensor was reproduc ible after being regenerated by urea.