A systematic investigation on the interaction of l-cysteine functionalised Mn3O4 nanoparticles with lysozyme

Abstract

Biological interactions of magnetic nanoparticles have attracted enormous interest because of their wide applications in medical diagnostics, imaging, and biosensors. Mn₃O₄ nanoparticles are potentially significant among magnetic nanoparticles and have not yet been investigated for their interactions with proteins. Here we report a systematic investigation of the interactions between hen egg white lysozyme and L-cysteine functionalised Mn₃O₄ nanoparticles using calorimetric and spectrophotometric techniques. The L-cysteine functionalised nanoparticles were synthesized by a simple chemical precipitation method and characterized by X-ray diffraction, FTIR, HRTEM, UV-Vis absorption and fluorescence spectroscopy. Mn₃O₄ nanoparticles are in the tetragonal phase with an average size of 10 nm. Thermodynamic parameters, the binding constant and the number of binding sites associated with the interactions were studied using Isothermal Titration Calorimetry (ITC). Quenching of lysozyme fluorescence is observed upon complex formation with Mn₃O₄ nanoparticle and the time resolved fluorescence measurements confirm static quenching. The Circular Dichroism (CD) spectra reveal minor alterations in the secondary structure of lysozyme in the complex indicating that Mn₃O₄ nanoparticles are potential candidates for therapeutic applications.