Indole-Capped Gold Nanoprisms as Multifunctional Nano-platforms: DNA Binding, Mercury Sensing, and Biological Activities

Abstract

Efficient binding of fluorescent nanomaterial with the most relevant biological target, DNA has attracted considerable interest for it application in biosensing and potential role in theranostics. In this study, we have reported the designing and comprehensive investigation or characterization of L-Trptophan functionalized gold nanoprisms (L-Trp@GNPrs), which exhibits 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, antioxidant, and antimicrobial properties. To gain deeper mechanistic insight, quantum mechanical density functional theory (DFT) and molecular docking simulations 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, amongst which, Au₈–Trp4 conformer exhibited 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.