Tailoring the NIR-II Photoluminescence of Single Thiolated Au25 Nanoclusters by Selective Binding to Proteins

Atomically precise gold nanoclusters are a fascinating class of nanomaterials that exhibit molecule-like properties and have outstanding photoluminescence (PL). Their ultrasmall size, molecular chemistry, and biocompatibility make them extremely appealing for selective biomolecule labeling in investigations of biological mechanisms at the cellular and anatomical levels. In this work, we report a simple route to incorporate a preformed Au-25 nanocluster into a model bovine serum albumin (BSA) protein. A new approach combining small-angle X-ray scattering and molecular modeling provides a clear localization of a single Au-25 within the protein to a cysteine residue on the gold nanocluster surface. Attaching Au-25 to BSA strikingly modifies the PL properties with enhancement and a redshift in the second near-infrared (NIR-II) window. This study paves the way to conrol the design of selective sensitive probes in biomolecules through a ligand-based strategy to enable the optical detection of biomolecules in a cellular environment by live imaging.

Automated summary

Atomically precise gold nanoclusters with molecule-like properties and outstanding photoluminescence (PL) are highly attractive for selective biomolecule labeling in biological mechanism investigations. In this study, a simple method to incorporate a preformed Au-25 nanocluster into bovine serum albumin (BSA) protein was reported. The combination of small-angle X-ray scattering and molecular modeling successfully localized a single Au-25 within the protein to a cysteine residue on the gold nanocluster surface. Attaching Au-25 to BSA significantly modified the PL properties, resulting in enhancement and a redshift in the second near-infrared window. This research paves the way for the design of selective sensitive probes using a ligand-based strategy for optical detection of biomolecules in a cellular environment by live imaging.