Fabrication of functional bioinorganic nanoconstructs by polymer–silica wrapping of individual myoglobin molecules

Abstract

Discrete core–shell hybrid nanoparticles comprising individual met-myoglobin (met-Mb) molecules incarcerated within an ultrathin polymer/silica shell were prepared without loss of biofunctionality by a facile self-assembly procedure. Solubilisation of met-Mb in cyclohexane in the near-absence of water was achieved by wrapping individual protein molecules in the amphiphilic triblock copolymer poly(ethylene-oxide)₁₉–poly(propylene-oxide)₆₉–poly(ethylene-oxide)₁₉ (EO₁₉–PO₆₉–EO₁₉, P123). Addition of tetramethoxysilane to the met-Mb/P123 conjugates in cyclohexane produced discrete nanoparticles that contained protein, polymer and silica, and which were 3–5.5 nm in size, consistent with the entrapment of single molecules of met-Mb. The hybrid nanoconstructs were isolated and re-dispersed in water without loss of secondary structure, and remained functionally active with respect to redox reactions and CO and O₂ ligand binding at the porphyrin metallocentre. The incarcerated met-Mb biomolecules showed enhanced thermal stability up to a temperature of around 85 °C. These properties, along with the high biocompatibility of silica and P123, suggest that the silicified protein–polymer constructs could be utilised as functional nanoscale components in bionanotechnology.