Ion-Mediated Regulation of Helical Gold Nanorods With Chirality-Photothermal Properties for Targeted Cancer Therapy

Chiral plasmonic gold nanomaterials held significant promise for tumor photothermal therapy, with their helical pitch depth playing a critical role in determining both chirality and photothermal performance. However, precise pitch depth control remained a major challenge. Herein, we reported a Br^--chiral ligand cooperative strategy to synthesize near-infrared-responsive helical chiral Au nanorods (Au NRs) with finely tunable pitch depths. Systematic investigations revealed distinct ion-regulation mechanisms: Br^- selectively passivated [100] facets to promote [111] anisotropic growth of; I^-/Cu²⁺ strongly adsorbed onto [111] to suppress helical development, Fe³⁺ only altered ligand adsorption without impeding [111] growth. These findings established directional [111] growth as a fundamental for both pitch-depth engineering and chiral structure formation. Optimized chiral Au NRs exhibited a high g-factor of 0.026, a >3-fold stronger localized electromagnetic field, and 16% higher photothermal conversion efficiency with reversibility. In vitro studies show 94% cellular uptake in HepG2 and near-complete cancer ablation under 808 nm irradiation, and high normal cell viability. This work elucidated ion-specific modulation roles, established a "pitch depth-chirality-performance-outcome" correlation, and provided design principles for precision photothermal therapy and chiral sensing.