Design, synthesis, and biological application of fluorescent sensor molecules for cellular imaging

Cellular imaging has achieved many new biological findings, among them GFP and other fluorescent proteins and small molecule based fluorescent sensors have been widely used, especially in the last decade. The design concept and application of chemical sensors are described, these being FRET based sensors and Zn(2+) sensors.Fluorescence resonance energy transfer (FRET) has been used extensively as the designing principle for fluorescent sensor molecules. One of the most significant advantages of designing sensor molecules with FRET modulation is that it can enable ratiometric measurement in living cells, which reduces the artifact from microscopic imaging systems. The design strategy for the development of small molecular FRET sensors is described in terms of avoiding close contact of donor fluorophore and acceptor fluorophore in aqueous solution. Furthermore, a strategy to design FRET sensors with modulating overlap integrals of donor and acceptor is introduced.Numerous tools for Zn(2+) sensing in living cells have become available in the last 8 years. Among them, fluorescence imaging using fluorescent sensor molecules has been the most popular approach. Some of these sensor molecules can be used to visualize Zn(2+) in living cells. Some of the biological functions of Zn(2+) were clarified using these sensor molecules, especially in neuronal cells, which contain a high concentration of free Zn(2) (+).