Enzyme Immobilization over Polystyrene Surface Using Cysteine Functionalized Copper Nanoparticle as a Linker Molecule

The work focus on the development of a simple and efficient method of enzyme immobilization over a polystyrene surface using cysteine functionalized copper nanoparticle as linker molecule. The polystyrene surface is activated by generating -NO₂ groups by the process of nitration reaction. The nitrated polystyrene plate then is silanized with (3-mercaptopropyl) trimethoxysilane (MPTS) followed with the coupling of cysteine-capped copper nanoparticles on the silanized surface through thiol moiety. A nanoparticle layer is thus created over the polystyrene surface which is efficiently used for covalent immobilization of urease via an amino group of cysteine through glutaraldehyde treatment. The technique resulted in an enhancement in the enzymatic activity by 72.37% over the soluble counterpart. The immobilized enzyme also exhibited appreciable reusability of about 10 times with activity retention of 82% of its initial activity. Immobilization also offered an increased thermal and pH stability to the immobilized enzyme over the soluble enzyme.