Near-Infrared Fluorescence Enhanced (NIR-FE) Molecular Imaging of Live Cells on Gold Substrates

TL;DR

This study introduces a novel near-infrared fluorescence enhancement technique using gold substrates, significantly improving imaging of live cells with SWNTs and organic dyes, enabling detection at ultralow concentrations and tracking transmembrane behavior.

Contribution

First demonstration of NIR-FE cell imaging with nanostructured gold substrates, enhancing fluorescence and enabling detection at ultralow concentrations of NIR fluorophores.

Findings

Enhanced fluorescence intensity and cell targeting specificity.

Detected SWNT-stained cells at ~50 pM concentration.

Observed differences in fluorescence enhancement between intracellular and membrane-bound nanotubes.

Abstract

Low quantum yields of near infrared (NIR) fluorophores have limited their capabilities as imaging probes in a transparent, low background imaging window. Here for the first time we reported near-infrared fluorescence enhance (NIR-FE) cell imaging using nanostructured Au substrate, which was employed as a general platform for both single-walled carbon nanotubes (SWNTs) and organic fluorescent labels in the NIR region. Fluorescence intensity, as well as cell targeting specificity, was greatly improved by this novel imaging technique. With NIR-FE imaging, we were able to image SWNT-stained cells at short exposure time of 300ms, and push the detectable limit of SWNT staining of cells down to an ultralow concentration of ~50 pM. Further, different degrees of fluorescence enhancement for endocytosed, intracellular SWNTs vs. nanotubes on the cell membrane at the cell/gold interface were observed, suggesting the possibility of using this technique to track the transmembrane behavior of NIR fluorophores.