Microspot surface enhanced fluorescence from sculptured thin films for control of antibody immobilization

Nano-sculptured thin films (STF) are prepared by the glancing angle deposition technique and take different forms of nano columnar structures. Varieties of STFs are investigated to find the optimum structure for biosensing based on the surface enhanced fluourescence (SEF). The highest amplification of fluorescent signal is found for Ag based STFs on fused silica giving an enhancement factor of x23°, where h=400nm, d=75nm, á=23o relative to Ag dense film using fluorescent dye Rhodamine 123. Based on this, a demonstration of monitoring of antibodies and even confirmation of successful immobilization of the receptors presented. Bound antibody to the thiol self assembly monolayer on sample surface is then quantified by means of the fluorescent signal. Upon excitation of the fluorophore by Hg source light, a CCD camera with a controlled exposure time detects the pattern of fluorescent antibody/E-coli bacteria colonies on the STF surface. A fiber optic holder attached to the microscope allowed quantitative measurement of the fluorescence spectrum on a microspot.