Surface Functionalization of Gold Nanoparticles Using Alkyne Derivatives: Applications in Chemical Sensing

Colloidal gold nanoparticles (AuNPs) are important nanomaterials for chemical sensing and therapeutics. For their application, it is vital to develop a reliable and robust surface functionalization method that can be applied to diverse functional molecules and offer better stability under harsh biological conditions. Currently, thiol (SH) is the most commonly used functional group for forming stable covalent bonds with AuNPs. However, thiolated molecules typically require complicated preparation procedures, are susceptible to oxidation, and are not compatible with many electrophiles and reducing groups. In this study, we report that surface functionalization of AuNPs can be achieved using alkyne derivatives, which exhibit several advantages over classical thiolation and peptide-bond methods, including straightforward preparation of alkyne derivatives, rapid and simple conjugation in buffers and complex media, higher conjugation efficiency, long-term stability, and resistance to decomposition under harsh conditions. Several alkynylated biotin and fluorescein derivatives are prepared, and the alkynylated-AuNPs are characterized using a lateral flow assay, gel electrophoresis, and spectroscopy techniques to investigate the conjugation efficiencies, size distributions, protein interaction properties, and binding mode of the Au–alkyne bond. We also demonstrate that alkynylated-AuNPs can be used for the sensitive detection of hydrogen peroxide and streptavidin proteins.