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

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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.