Intercalation of papain enzyme into hydrotalcite type layered double hydroxide Original Research Article

Intercalation of proteolytic enzyme papain into hydrotalcite type LDH structure was achieved by controlled co-precipitation at pH=9.0 in the presence of papain. Characterization of the MgAl–papain–LDH phase was carried out using X-ray powder diffraction (XRD), elemental analysis, infrared spectroscopy (IR) and thermogravimetry (TG). According to XRD, papain was successfully intercalated. The d-value for the basal spacing of MgAl–papain–LDH was found at ∼5.3 nm. Consequently, original papain (hydrodynamic diameter ∼7.2 nm) attains a compressed conformation during intercalation. Formation of MgAl–papain–LDH was confirmed by elemental analysis and transmission electron microscopy (TEM). Under SEM, MgAl–papain–LDH phases appear as nanothin platelets which are intergrown to flower-like aggregates. Steric size and activity of the enzyme was retained after deintercalation from MgAl–LDH framework, as was evidenced by light scattering and UV/vis measurements. Thus, papain is not denatured during intercalation, and LDH is a suitable host structure which can provide a time-controlled release of the biomolecule.