Gene

Biotechnology

Neuroscience

Biology

Photochemistry

Infrared

Heme

Biochemistry

Biliverdin

Fluorescence-lifetime imaging microscopy

Preclinical imaging

In vivo

Physics

Optics

Green fluorescent protein

Near-infrared spectroscopy

Enzyme

Fluorescence

Chromophore

Chemistry

Heme oxygenase

Fluorescent protein

Biophysics

Molecular imaging

Nature Methods

Applying rational design, we developed 17 kDa cyanobacteriochrome-based near-infrared (NIR-I) fluorescent protein, miRFP718nano. miRFP718nano efficiently binds endogenous biliverdin chromophore and brightly fluoresces in mammalian cells and tissues. miRFP718nano has maximal emission at 718 nm and an emission tail in the short-wave infrared (SWIR) region, allowing deep-penetrating off-peak fluorescence imaging in vivo. The miRFP718nano structure reveals the molecular basis of its red shift. We demonstrate superiority of miRFP718nano-enabled SWIR imaging over NIR-I imaging of microbes in the mouse digestive tract, mammalian cells injected into the mouse mammary gland and NF-kB activity in a mouse model of liver inflammation. miRFP718nano is a rationally designed small near-infrared fluorescent protein with an emission tail that extends into the short-wave infrared range for improved multiplexed and deep-tissue imaging applications.

Deep-tissue SWIR imaging using rationally designed small red-shifted near-infrared fluorescent protein