Seeing Elastin: A Near-Infrared Zwitterionic Fluorescent Probe for In Vivo Elastin Imaging

Abstract

Elastic fibers are present in a variety of tissues and are responsible for their resilience. Until now, no optical contrast agent in the near-infrared (NIR) wavelength range of 700–900 nm has been reported for the imaging of elastic fibers. Here, we report the discovery of a NIR zwitterionic elastin probe ElaNIR (elastin NIR) through fluorescent-image-based screening. The probe was successfully applied for in vitro, ex vivo, and in vivo imaging by various imaging modalities. Age-related elastin differences shown by in vivo fluorescent and photoacoustic imaging indicated that ElaNIR can be a potentially convenient tool for uncovering changes of elastin in live models. Technological advancement of microscopic imaging has spurred the development of molecular probes for the detection of biologically and environmentally important analytes. Among fluorescent imaging tools, near-infrared (NIR) fluorescent molecules have been popular for in vivo imaging because of their ability to penetrate tissue deeper with reduced scattering and autofluorescence. Here, we report the discovery of the NIR zwitterionic elastin probe ElaNIR. We found that ElaNIR showed selective binding for elastin, such as those in the aorta, lungs, and skin. ElaNIR also allowed visualization and quantification of elastin levels in young and old mice, which reflect age-dependent changes of elastin in vivo. This makes ElaNIR a unique chemical tool for monitoring changes of elastin in tissue or animal models and provides new opportunities to study the effects of chemical compounds on elastin levels in biological processes. The near-infrared zwitterionic elastin probe ElaNIR for in vivo imaging of elastin structures was found through fluorescent-image-based screening. ElaNIR is well suited for in vitro, ex vivo, and in vivo imaging of elastin and also allows visualization and quantification of elastin levels in young and old mice, which reflect age-dependent changes of elastin in vivo. © 2018 Elsevier Inc