Biological photonic crystals revealed by multimodality nonlinear microscopy

A novel multi-modality nonlinear microscopy reveals highly optically-active biophotonic crystal structures in living cells. Numerous biological structures, including stacked membranes and arranged protein structures are highly organized in optical scale and are found to exhibit strong optical activities through second-harmonic-generation (SHG) interactions, behaving similar to man-made photonic crystals. The microscopic technology developed is based on a combination of imaging modalities including not only SHG, but also third-harmonic-generation and multi-photon-fluorescence. With no energy deposition during harmonic generation processes, the demonstrated highly-penetrative yet non-invasive microscopy is useful for investigating the dynamics of structure-function relationship at the molecular and subcellular levels and is ideal for studying living cells that require minimal or no preparation.