Denaturation-resistant bifunctional colloidal superstructures assembled via the proteinaceous barnase-barstar interface.

To date, a number of biomolecule-mediated nanoparticle self-assembly systems have been developed that are amenable to controllable disassembly under relatively gentle conditions. However, for some applications such as design of self-assembled multifunctional theragnostic agents, high stability of the assembled structures can be of primary importance. Here, we report extraordinarily high durability of protein-assisted nanoparticle self-assembly systems yielding bifunctional colloidal superstructures resistant to extreme denaturing conditions intolerable for most proteins (e.g., high concentrations of chaotropic agents, high temperature). Among the tested systems (barnase-barstar (BBS), streptavidin-biotin, antibody-antigen, and protein A-immunoglobulin), the BBS is notable due to the combination of its high resistance to severe chemical perturbation and unique advantages offered by genetic engineering of this entirely protein-based system. Comparison of the self-assembly systems shows that whereas in all cases the preassembled structures proved essentially resistant to extreme conditions, the ability of the complementary biomolecular pairs to mediate assembly of the initial biomolecule-particle conjugates differs substantially in these conditions.