A ratiometric upconversion nanoprobe enables super-resolution imaging sensing of biothiols in living cells.

We have developed an upconversion luminescent ratiometric nanoprobe, specifically designed for detection of biothiols with high sensitivity (∼25 nM) at the single-particle level. Using a single-particle localization and rendering method, this nanoprobe enables super-resolution imaging sensing of biothiols within a confined 22 nm space in living cells.