SAX microscopy with fluorescent nanodiamond probes for high-resolution fluorescence imaging

We report the use of fluorescent nanodiamonds (FNDs) as a photostable fluorescent probe for high resolution saturated excitation (SAX) microscopy. We confirmed that FNDs show a nonlinear fluorescence response under saturated excitation conditions generated by intense excitation light. Using FNDs, we quantified the spatial resolution improvement inherent in SAX microscopy, and experimentally demonstrated the scalability of the spatial resolution of SAX microscopy. The photostability of the FNDs allowed us to perform nanoparticle imaging of a multicolor-stained macrophage cell with a spatial resolution beyond the diffraction limit.