Ligand-Defined Interfacial Chemistry Enables Instant and Sequence-General DNA Chemisorption on Gold Nanoparticles Toward Label-Free SERS With Single-Base Resolution.

A coherent mechanistic framework for DNA adsorption on gold nanoparticles (AuNPs) remains elusive, hindering the rational construction of spherical nucleic acids (SNAs). Here, we show that ligand-defined interfacial charge regulation, achieved using weakly ionized ascorbic acid (AA) ligands, markedly lowers the kinetic barrier for DNA chemisorption on AuNPs. Under near-neutral conditions, this interface enables rapid, sequence-general functionalization of AuNPs with both thiolated and non-thiolated oligonucleotides through simple vortex mixing, even for DNA containing only a single terminal adenine. The AA-regulated interface also overcomes the long-standing incompatibility between -butanol dehydration and non-thiolated DNA, enabling sequence-general SNA formation under dehydration conditions across multiple nanoparticle systems. Mechanistic studies indicate that AA reduces interfacial electrostatic repulsion while promoting hydrogen-bond-assisted surface interactions, and base-substitution experiments identify the adenine N6-amino group as a critical site for chemisorption. The resulting ordered DNA corona generates uniform plasmonic nanogaps, enabling reproducible, label-free SERS with single-base resolution for nucleotide discrimination and cytosine methylation analysis. This work establishes a general interfacial design strategy for constructing uniform plasmonically active nucleic acid nanostructures under mild conditions.