Indole-capped gold nanoprisms as multifunctional nano-platforms: DNA binding, mercury sensing, and biological activities

Abstract

Binding of fluorescence nanomaterials with the most relevant biological target, DNA, has attracted considerable interest due to its potential application in biosensing and theranostics. In this study, we have reported the design and comprehensive investigation or characterization of L-tryptophan functionalized gold nanoprisms (L-Trp@GNPrs), which exhibit enhanced optical properties, such as strong plasmonic absorption, fluorescence, and Raman activity due to their unique trigonal prismatic morphology. Multi-spectroscopic, thermodynamic, imaging, and molecular docking studies revealed strong and specific interactions between L-Trp@GNPrs and CT-DNA. Additionally, L-Trp@GNPrs function as effective fluorescence and surface enhanced Raman spectroscopy (SERS)-based sensors for the selective detection of mercury ions (Hg²⁺) in aqueous media, while their surface modification can enhance biocompatibility and antioxidant and antimicrobial properties. To gain deeper mechanistic insight, quantum mechanical density functional theory (DFT) and molecular docking simulation studies were carried out, revealing that Trp undergoes notable conformational changes upon binding to gold clusters (Au₁ and Au₈), which are stabilized by non-covalent interactions, including Au–π, Au–NH₂, and Au–COOH contacts. NCI-RDG analysis confirmed hydrogen bonding and van der Waals interactions, with the Au₈–Trp₄ conformer exhibiting the strongest H-bonding strength with the associated interaction energy of −6.63 kcal mol⁻¹. Kinetic analysis further supported these findings, indicating a fast binding rate accompanied with moderate activation energy for the L-Trp@GNPrs–DNA complex formation. Overall, the combined experimental and theoretical results have demonstrated the multi-functionality and biomedical potential of L-Trp@GNPrs in DNA-targeted sensing and therapeutic applications.