Improvisation of diffusion coefficient in surface modified magnetite nanoparticles: A novel perspective

Surface properties are inevitable in determining the properties of any support involved in tethering biomolecular moieties. Porous carriers impose numerous diffusional limitations and make the need for surface modification significant. To best of our knowledge, this study would be a new perspective on diffusional limitations in nanoparticles for the first time. Chitosan was aimed to alter the porosity of solvo-thermally synthesized magnetite nanoparticles (MNs) through surface coating. Various instrumental techniques were performed on chitosan, MNs, chitosan coated MNs (MN_β) and urease tethered MN_β (U-MN_β) to reveal their behaviour. Maximum absorption with higher bandgap energy (2.76 eV) in visible spectrum, characteristic peaks in diffraction patterns and the presence of required peaks in Fourier transform infra-red (FT-IR) spectra suggested MNs synthesis and surface modification. Electron micrographs and Energy dispersive spectrum (EDS) showed surface variation and pure elemental composition of MNs respectively. Superparamagnetism and narrow size distribution were seen from magnetization curve with lower retentivity and Dynamic Light Scattering (DLS) respectively. Sorption profiles exhibited filling of pores on MNs and lower/higher diffusion co-efficient (D_e) were evaluated through respective conductivity measurements of free/tethered urease. The values of influencing parameters were optimized based on Box-Behnken design (BBD) matrix and the statistical analysis revealed that the optimum operating conditions for producing MN_β. Hence change in surface porosity that enhanced activity of tethered enzyme through improved diffusion was achieved via surface coating.