Fluorescence enhancement achieved by functionalized microstructures made by two-photon
polymerization (TPP) is reported for the first time. Microstructures of various shapes
made of SU-8 photoresist were prepared and coated with gold nanoparticles (NP) of
80 nm. Localized fluorescence enhancement was demonstrated by microstructures equipped
with tips of sub-micron dimensions. The enhancement was realized by positioning the
NP-coated structures over fluorescent protein layers. Two fluorophores with their
absorption in the red and in the green region of the VIS spectrum were used. Laser
scanning confocal microscopy was used to quantify the enhancement. The enhancement
factor was as high as 6 in areas of several square-micrometers and more than 3 in
the case of local enhancement, comparable with literature values for similar nanoparticles.
The structured pattern of the observed fluorescence intensity indicates a classic
enhancement mechanism realized by standing waves over reflecting surfaces. With further
development mobile microtools made by TPP and functionalized by metal NPs can be actuated
by optical tweezers and position to any fluorescent micro-object, such as single cells
to realize localized, targeted fluorescence enhancement. (C) 2014 Elsevier B.V. All
rights reserved.
