Bionanocomposite of Dual Antioxidant and Protease Function by Co‐Immobilization of Tannic Acid and Papain on Anionic Clays

The synchronized operation of antioxidants and enzymes is necessary for the proper functioning of living organisms and various industrial processes. The drawback that these biomolecules are susceptible to several environmental factors can be overcome by their immobilization on appropriate host materials. Here, molecular antioxidant tannic acid (TA) and papain enzyme (PPN) were co-immobilized on layered double hydroxide (LDH) nanoparticles to enhance their stability and facilitate their combined function. In the sequential adsorption method governed by electrostatic interactions, TA was first adsorbed on oppositely charged LDH (LDH/TA) and then, PPN was immobilized on the surface of the nanoparticles (LDH/TA/PPN). The optimal TA and PPN doses were determined by systematic size and charge measurements of the particles in dispersions to obtain stable colloids in each preparation step. The co-immobilization of the biomolecules was confirmed by spectroscopy methods. The resulting LDH/TA/PPN nanocomposite exhibited remarkable antioxidant and protease activities. The dual biological function together with the considerable colloidal stability make the LDH/TA/PPN material a promising candidate in various processes in academia and more applied disciplines, where simultaneous antioxidant and proteolytic functions are desired.