Structural, electronic and bioactive profiling of a 2′-hydroxychalcone–Ag composite: a DFT-supported biomedical study on anticancer, antioxidant and antibacterial activities

Abstract

Biocompatible and biologically active nanomaterials are currently in demand. This work presents the synthesis of the medicinally significant fluorophore 2′-hydroxychalcone and its subsequent composite with silver nanoparticles (chal–AgNPs) and their characterization using experimental and theoretical techniques and applications. The active organic functional groups present in the chalcone functioned as reducing and stabilizing agents in the composite with AgNPs by solution chemistry method. FESEM reveals spherically shaped and uniformly scattered nanoparticles with an average diameter of 70 nm. X-ray diffraction (XRD) patterns of chalcone-mediated AgNPs confirmed the existence of spherical AgNPs with a crystallite size of 46 nm in a face-centered cubic crystal structure. The surface plasmon resonance of AgNPs was observed at 493 nm in the absorption spectrum. The surface adsorption of chal–AgNPs was further validated by mixing pre-synthesized AgNPs prepared by sodium borohydride reduction with chalcone and real-time monitoring of the UV-visible spectrum. The ¹H NMR and ¹³C NMR spectra of the reaction further elucidated the structure and formation of 2′-hydroxychalcone. Fluorescence quenching of the chalcone moiety by AgNPs was monitored by comparing the steady-state fluorescence spectra of chalcone alone and chal–AgNPs. Theoretical studies were performed on chalcone and its complexes using density functional theory/B3LYP calculations to gain insights into the quenching mechanism. Mulliken charge analysis estimated the polarity and showed that the hydroxyl oxygen in the chalcone is more nucleophilic than the carbonyl oxygen, indicating its stronger reducing ability. The computed binding energies for the chal–AgNP composite were positive, indicating its stability. From the computed molecular electrostatic potential (MEP) surfaces, significant charge transfer was observed for the chalcone–silver complexes, which further validated the experimental results of fluorescence quenching. An assessment of the global reactivity descriptors of chal–AgNPs indicated their softness and higher biological activity compared with that of the free chalcone. DFT calculations showed that the electron from the chalcone was transferred to the Ag center, and consequently, Ag⁺ ions were reduced to Ag⁰ in the composite formation. The synthesized chal–AgNP nanocomposite shows potent antibacterial, anticancer and antioxidant activities.