Abstract: Protein nanoparticles encapsulate cargo proteins within an enclosure containing a protected chemical milieu. Encapsulation within such protected chemical milieu enhances the employability and performance of cargo proteins, particularly cargo enzymes, particularly within otherwise hostile chemical environments. Protein nanoparticles are assembled using shell proteins, such as viral coat proteins like Q?, in the presence of a bifunctional polynucleotide and the selected cargo protein. The bifunctional polynucleotide includes two aptameric activities that assist the disposition and retention of cargo proteins within the protein nanoparticle.