Eco-Friendly Composite of Fe3O4-Reduced Graphene Oxide Particles for Efficient Enzyme Immobilization.

A novel type of spherical and porous composites were synthesized to dually benefit from reduced graphene oxide (rGO) and magnetic materials as supports for enzyme immobilization. Three magnetic composite particles of Fe3O4 and rGO containing 71% (rGO-Fe3O4-M1), 36% (rGO-Fe3O4-M2), and 18% (rGO-Fe3O4-M3) Fe were prepared using a one-pot spray pyrolysis method and were used for the immobilization of the model enzymes, laccase and horseradish peroxidase (HRP). The rGO-Fe3O4 composite particles prepared by spray pyrolysis process had a regular shape, finite size, and uniform composition. The immobilization of laccase and HRP on rGO-Fe3O4-M1 resulted in 112 and 89.8% immobilization efficiency higher than that of synthesized pure Fe3O4 and rGO particles, respectively. The stability of laccase was improved by approximately 15-fold at 25 °C. Furthermore, rGO-Fe3O4-M1-immobilized laccase exhibited 92.6% of residual activity after 10 cycles of reuse and was 192% more efficient in oxidizing different phenolic compounds than the free enzyme. Therefore, these unique composite particles containing rGO and Fe3O4 may be promising supports for the efficient immobilization of industrially important enzymes with lower acute toxicity toward Vibrio fischeri than commercial pure Fe3O4 particles.