Bright blue fluorescent nanoparticles for live cell imaging by fluorescence microscopy

Abstract

Abstract Fluorescence imaging of labeled cells is an important method to monitor long-term cell behaviors. Long-lasting green stains such as CFSE (carboxyfluorescein succinimidyl ester) and its derivatives are routinely utilized for cell migration studies, but currently there are no commercially available long-lasting (days), non-cytotoxic blue cell stains compatible with a standard DAPI filter that is brighter than the autofluorescence of tissue. Here, we fabricated two bright blue emitting boron dye-polymer nanoparticles (BNPs) (e = 32100 M−1cm −1) from difluoroboron dibenzoylmethane conjugated to poly(lactic acid) (BF2dbmPLA) or poly(e-caprolactone) (BF2dbmPCL). Particles were < 100 nm diameter, and their excitation and emission wavelengths (lex = 381 nm; lem = 439 nm) corresponded to the DAPI filter. When incubated with mouse splenocytes, the blue emitting nanoparticles were taken up by the cells and readily detected by fluorescence microscopy (EVOS microscope) or a plate reader. Viability of the stained cells was assessed by calcein/propidium iodide staining. These data showed that BNPs have the capability to stain cells brightly without significantly diminishing viability and therefore show promise as a new tool for live cell tracking in the blue fluorescence channel. We are currently measuring cell fluorescence and viability over time, determining which types of cells take up the particles, and comparing the staining capabilities of the nanoparticles to commercial blue dyes.