Zinc oxide nanoparticles coated with food colorant Brilliant black: Synthesis, characterization, and comparative DNA interaction and antibacterial activity studies

In the present work, preparation and full characterization of the silica‐coated zinc oxide nanoparticles containing Brilliant black food colorant (denoted as ZnO@SiO2@APTES/BB) is reported. The interactions of Brilliant black food colorant and the nanoparticles containing food colorant (ZnO@SiO2@APTES/BB) with calf thymus‐DNA (ct‐DNA) were then investigated by UV‐vis and fluorescence spectroscopies. In the absorption spectra of ct‐DNA, the band centered at 260 nm exposes hyperchromism in the presence of Brilliant black and also ZnO@SiO2@APTES/BB. Moreover, the binding constant (Kb) of Brilliant black and ZnO@SiO2@APTES/BB with DNA were 2.8 × 103 M−1 and 1.87 × 104 M−1 at 25°C, respectively. From the fluorescence spectroscopy, the enthalpy and entropy changes (ΔH0 and ΔS0) for Brilliant black–DNA and ZnO@SiO2@APTMS/BB–DNA formation were determined. In addition, the competitive binding experiments revealed that the Brilliant black and ZnO@SiO2@APTMS/BB could release Hoechst 33,258 from grooves of DNA. Finally, the potential of antibacterial activities of ZnO nanoparticles, Brilliant black, and ZnO@SiO2@APTMS/BB samples was evaluated and compared with tetracycline antibiotic. It is interesting to note that Brilliant black showed excellent antibacterial activity against gram‐negative and gram‐positive bacteria as compared to known tetracycline antibiotic while the ZnO@SiO2@APTMS/BB acts as a weak antibacterial agent against gram‐negative and gram‐positive bacteria. Novelty impact statement The silica‐coated zinc oxide nanoparticles containing Brilliant black food colorant was synthesized and characterized. Brilliant black and the nanoparticles containing Brilliant black interact with calf thymus‐DNA as groove binders. Brilliant black showed excellent antibacterial activity in comparison to tetracycline drug and it is important for food preservation containing this colorant.