Synthesis and intracellular tracing surface-functionalized calcium phosphate nanoparticles by super-resolution microscopy (STORM)

Abstract

Calcium phosphate nanoparticles with covalently attached fluorescent dye molecules were prepared by copper-catalysed azide-alkyne cycloaddition (CuAAC) and by strain-promoted azide-alkyne cycloaddition (SPAAC), i.e. click chemistry. The reaction kinetics and labeling degrees of the two click reactions were compared and quantified. For oxidation-sensitive molecules, the SPAAC method is preferable due to the milder reaction conditions and the absence of copper(II). The highly fluorescent AF-488-labeled nanoparticles were applied for super-resolution fluorescence microscopy, i.e. stochastic optical reconstruction microscopy (STORM). By this method, individual nanoparticles (diameter about 60 nm) were observed in endolysosomes inside HeLa cells after cellular uptake at a resolution of 20–30 nm.