Synthesis, Characterization and Antimicrobial Evaluation of Zinc Oxide Nanoparticle Peptide Conjugates

Abstract

Aim: The study aimed to develop a zinc oxide nanoparticle–peptide conjugate (ZONPC) using peptides derived from whey fermentation and to compare its physicochemical and antimicrobial properties with conventional zinc oxide nanoparticles (ZONP). The goal was to enhance antimicrobial efficacy, particularly against antibiotic-resistant organisms. Place and Duration of Study: Department of Dairy Microbiology, National Dairy Research institute, Karnal, Haryana, between June 2022 and July 2023. Study Design: This was a laboratory-based experimental study involving the synthesis of zinc oxide nanoparticle–peptide conjugates (ZONPC) using whey-derived peptides, followed by characterization and antimicrobial testing. A comparative approach was used to evaluate the physicochemical and antibacterial properties of ZONPC against conventional zinc oxide nanoparticles (ZONP). Methodology: ZONPC was synthesized under optimized conditions using a 1 mol/L solution of Zn(NO₃)₂·6H₂O and peptides at a 1:3 ratio, reacted at 90°C for 4 hours. Characterization involved particle size and zeta potential measurements, along with FTIR analysis to confirm peptide conjugation. Antimicrobial efficacy was assessed using zone of inhibition (ZOI), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) tests. Result: ZONPC showed an increase in particle size from 36.87 to 152.6 nm and a reduction in zeta potential from –19.4 to –4.16 mV. FTIR confirmed peptide binding via the presence of an amide III bond. Antimicrobial tests revealed a ZOI of 34–40 mm. While both ZONP and ZONPC had an MIC of 2 µg/mL, the MBC of ZONPC was significantly lower (16.5 µg/mL vs. 65 µg/mL), indicating enhanced bactericidal activity. Conclusion: The study concluded that peptide conjugation significantly enhanced the antimicrobial efficacy of zinc oxide nanoparticles, especially against antibiotic-resistant bacteria.