Spectral Imaging for Separation of Fluorescent Signals from Autofluorescence

Extract

Autofluorescence , also known as adventitious fluorescence or background fluorescence, ofter poses a significant problem in many applications of fluorescence microscopy. It contributes to unwanted noise and can swamp the desired signal. Particularly difficult samples to image include many pathology specimen that have been processed using crosslinking fixatives (typically formaldehyde). This procedure dramatically increase the autofluorescence level, leading to bright, broad spectrum emissions, particularly from connective tissue components. Unprocessed plant tissue and neuronal tissue also have extremely high levels of endogenous autofluorescence that can make many convenient labeling strategies, including most (green fluorescent protein (GFP) labels, extremely problematic. Various solutions have been proposed for the reduction or elimination of autofluorescence. These include using narrow bandpass emission filters to try to isolate the desired fluorescence signal, the use of labels which can be excited at wavelengths that are much less likely to induce autofluorescence (moving the excitation towards the NIR is effective), and post-processing aldehyde-fixed samples with such reagents as sodium borohydride or toluidine blue to chemically suppress the autofluorescence signal.However, in many cases, these approaches are either infeasible or ineffective.