Fabrication of functional protein–organoclay lamellar nanocomposites by biomolecule-induced assembly of exfoliated aminopropyl-functionalized magnesium phyllosilicates

Abstract

An aminopropyl-functionalized magnesium phyllosilicate clay was synthesized and used as an exfoliated precursor for the intercalation of myoglobin (Mb), haemoglobin (Hb) or glucose oxidase (GOx). Intercalation was achieved by exfoliation of the as-synthesized organoclay in water followed by room temperature re-assembly of the lamellar phase in the presence of negatively charged protein molecules. X-Ray diffraction data of the resulting nanocomposites showed an expansion of the interlayer d₀₀₁ spacing from 1.6 nm in the parent organoclay to 4.3 and 6.4 nm for samples prepared with Mb and GOx, respectively, indicating that these biomolecules were successfully incorporated into the gallery regions. In both cases, FTIR and circular dichroism spectroscopies showed that secondary structures of the intercalated biomolecules were preserved. In addition, UV-vis spectroscopy revealed that the redox and CO/O₂ binding properties of the intercalated Mb, as well as the enzymatic activity of GOx, were retained in the protein–organoclay nanocomposites. Significantly, the relative catalytic activities of GOx between pH values of 3 to 10, and up to temperatures of 65 °C, were higher in the hybrid nanocomposites compared with the native enzyme in solution. Similar experiments with Hb produced composites consisting of structurally and functionally intact protein molecules immobilized within a disordered matrix of organoclay lamellae.