title: Enhanced activity of lysozyme-AgNP conjugate with synergic antibacterial effect without damaging the catalytic site of lysozyme.
abstract: BACKGROUND
  The conjugation of silver nanoparticles (AgNPs) with biomolecules such as oligosaccharides, DNA, proteins has attracted great attention of scientists recently.
  
  
  OBJECTIVE
  In this study, lysozyme-AgNP conjugates were evaluated for its synergic antimicrobial effect.
  
  
  METHODS
  AgNPs were synthesized and characterized using UV-Visible, X-ray diffraction analysis (XRD) and atomic force microscopy (AFM). AgNP (0-1 mM) was interacted with lysozyme for multi-spectrophotometric studies. Lysozyme was immobilized on AgNP at different ratios and the resulting nano-bio-conjugate was tested against Escherichia coli for potent synergic antibacterial effects.
  
  
  CONCLUSIONS
  A surface plasmon peak at 420 nm confirmed the presence of AgNPs and spherical to oval-shaped AgNPs were observed by AFM. The particle size was calculated to be 25 nm by XRD analysis. The maximum immobilization efficiency (98%) was achieved at 0.01:1 ratio of enzyme:AgNP. UV-Visible and fluorescence spectral studies revealed the binding of AgNPs to lysozyme by the formation of ground-state complex and the binding parameters were calculated. Circular dichroism studies confirmed decrease by 11% in the α-helical and 29.32% in β-sheets of lysozyme upon AgNP interaction. FTIR spectra revealed the binding of AgNP through thiol (-SH) linkages of lysozyme. Our results showed that the antimicrobial activity of lysozyme-AgNP conjugate was enhanced up to 86% decrease in the cell growth.
  
  
  CONCLUSIONS
  In summary, the immobilization of lysozyme on AgNP has yielded a nano-bio-conjugate with synergistic antibacterial properties.
authors.affiliation: Centre for Nanobiotechnology, VIT University , Vellore , India.
authors.forename: Vinita
authors.initials: V
authors.lastname: Ernest
authors.forename: Sekar
authors.initials: S
authors.lastname: Gajalakshmi
authors.forename: Amitava
authors.initials: A
authors.lastname: Mukherjee
authors.forename: Natarajan
authors.initials: N
authors.lastname: Chandrasekaran
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D020134:Catalytic Domain; D004357:Drug Synergism; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects; D053768:Metal Nanoparticles; D009113:Muramidase / Q000737:chemistry* / Q000494:pharmacology*; D012834:Silver / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D004800:Enzymes, Immobilized; D012834:Silver; D009113:Muramidase
keywords: AgNP; antibacterial activity; lysozyme; synergistic