Highly sensitive metal-enhanced fluorescence biosensor prepared on electrospun fibers decorated with silica-coated silver nanoparticles

A new metal-enhanced fluorescence (MEF)-based biosensor platform was prepared on fibrous substrates. First, polycaprolactone (PCL) fibers were obtained via electrospinning process. PCL fibers were decorated with photoreduced silver nanoparticles followed by silica coating, generating silver-decorated PCL fibers with a silica layer (Ag@SiO₂-PCL). The silica layer acted as a spacer between the silver nanoparticles and the fluorescent molecules to optimize the MEF effect. The MEF was obtained from the silver-decorated PCL fibers, the extent of which could be controlled by the thickness of the silica layer. The fibrous structure of Ag@SiO₂-PCL had higher protein loading capacity than conventional two-dimensional glass slides due to its large surface area, while the presence of silica-coated silver nanoparticles resulted in higher fluorescence intensity than silica-coated PCL fibers (SiO₂-PCL) without silver nanoparticles via the MEF effect. Both features of Ag@SiO₂-PCL were combined to produce combined effects in improving the performance of fluorescence-based biosensing. According to immunobinding assays between fluorescently labeled anti-IgG and IgG immobilized onto different substrates, Ag@SiO₂-PCL had much better sensing performance in terms of sensitivity and detection limit than glass slides and SiO₂-PCL due to the combined effects of a large surface area and the MEF effect.