Immobilisation and encapsulation of functional protein-inorganic constructs

Self-assembly methods for the immobilisation or encapsulation of the positively charged redox protein, cytochrome c (cyt c), in layered organoclays or silica nanoparticles, respectively, are described and contrasted. Protein-polymer-organoclay nanocomposites are produced by spontaneous restacking of delaminated aminopropyl-functionalised magnesium phyllosilicate sheets in the presence of an aqueous solution of poly(sodium 4-styrene sulfonate) (PSS) and cyt c. In contrast, single molecules of cyt c are encapsulated in silica nanoparticles by sol-gel reactions at the oil-water interface of microemulsion water droplets. In both cases, the protein molecules remain structurally intact after entrapment, are accessible to small molecule redox agents, exhibit excellent peroxidase activity in the presence of hydrogen peroxide, and show enhanced stability and catalytic properties under adverse conditions of pH. The ability to prepare functional protein-inorganic conjugates in general could significantly extend the technological scope of biological products and processes, and should therefore be an important adjunct in the translation of synthetic biology to real-life applications.