In every field of science, new techniques for target molecule detection are increasingly required. This work presents itself as a method for developing new sensors that can detect target molecules even in samples with low concentrations. The aim of the current research project is to create an optical sensor substrate that is precise and specific for fluorescent or fluorescently marked targets. We produced nanostructured surfaces on bulk silver substrates using a femtosecond pulsed laser (Laser Libra Ti:Saphira from Coherent). These surfaces have a larger superficial area, which increases the fluorescence of molecules nearby by due to the surface plasmon resonance, in the effect of metal-enhanced fluorescence (MEF). The COVID virus spike antibody (SARS-CoV-2(2019-nCoV)) and a secondary fluorescently marked antibody (Alexa Fluor™ 633 goat anti-human IgG (H+L)) was used to functionalize the nanostructures. Initial results indicated that the functionalization process was successful in achieving our initial goals, presenting the proposal's methods as an effective route for the development of biosensors. The primary antibody was initially detected in a very low concentration (0.0525 ng/uL), and the fluorescent signal was enhanced on the nanostructured portion of the surface by 6.3 times more than it was on the surface without modification.
Metal enhanced fluorescence is a phenomenon that occurs when a fluorophore is positioned near a conductive structure. Structures can be formed by the interaction of high-energy laser with a sample, on which the femtosecond laser pulses interact with the surface without heat effects. This work aims to study nanostructure formation in polished bulk silver, in order to amplify signals of fluorescence. A Titanium-sapphire femtosecond laser was used to mark silver surfaces. SEM images shows nanostructures formed in chaotic agglomerate of nanospheres with size of 50-800nm. Using Protoporphyrin-IX, the fluorescence amplification was around 300 times compared to a surface without the nanostructures.
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