A highly specific gold nanoprobe for live-cell single-molecule imaging

TL;DR

This paper introduces a highly specific, small, and photostable gold nanoprobe functionalized with camelid antibody fragments, enabling long-term, live-cell single-molecule imaging of GFP-tagged proteins in crowded cellular environments.

Contribution

The development of a novel 5-nm gold nanoprobe with high affinity for GFPs, allowing prolonged, stable tracking of proteins in live cells with minimal perturbation.

Findings

Effective labeling of GFP-proteins in crowded environments

Unparalleled photostability and specificity of the nanoprobe

Long-term tracking enabled in live-cell conditions

Abstract

Single molecule tracking in live cells is the ultimate tool to study subcellular protein dynamics, but it is often limited by the probe size and photostability. Due to these issues, long-term tracking of proteins in confined and crowded environments, such as intracellular spaces, remains challenging. We have developed a novel optical probe consisting of 5-nm gold nanoparticles functionalized with a small fragment of camelid antibodies that recognize widely used GFPs with a very high affinity, which we call GFP-nanobodies. These small gold nanoparticles can be detected and tracked using photothermal imaging for arbitrarily long periods of time. Surface and intracellular GFP-proteins were effectively labeled even in very crowded environments such as adhesion sites and cytoskeletal structures both in vitro and in live cell cultures. These nanobody-coated gold nanoparticles are probes with unparalleled capabilities; small size, perfect photostability, high specificity, and versatility afforded by combination with the vast existing library of GFP-tagged proteins.