Single photon fluorescent microlithography for live-cell imaging

Using fluorescent dyes to trigger the polymerization of a commercial polyurethane resin allows a rapid fabrication of micrometer and submicrometer sized fluorescent structures by one-photon absorption. Here, we show that standard He-Ne lasers emitting at 632.8 nm can be used to start the photopolymerization and that very low laser power is required. This procedure allows the fabrication of fiduciary fluorescent references on standard glass coverslips, mica sheets, or gold-coated coverslips for laser scanning or standard fluorescent microscopy. The biocompatibility of the polymerized resin with cells in culture was tested by growing Xenopus melanophores and a standard laser scanning microscope was used to demonstrate that it is possible to use equipment readily available in several laboratories. We show that fluorescent structure with less than 10 nm in height may be used as references in fluorescence microscopy allowing a smooth environment for cell growth. Different dyes were tested and the conditions for one-photon polymerization were outlined.