Cell-Specific Delivery Using an Engineered Protein Nanocage

Abstract

Nanoparticle-based delivery systems have shown great promise for theranostics and bioimaging on the laboratory scale due to favorable pharmacokinetics and biodistribution. In this study, we examine the utility of a cage-forming variant of the protein lumazine synthase, which was previously designed and evolved to encapsulate biomacromolecular cargo. Linking antibody-binding domains to the exterior of the cage enabled binding of targeting immunoglobulins and cell-specific uptake of encapsulated cargo. Protein nanocages displaying antibody-binding domains appear to be less immunogenic than their unmodified counterparts, but they also recruit serum antibodies that can mask the efficacy of the targeting antibody. Our study highlights the strengths and limitations of a common targeting strategy for practical nanoparticle-based delivery applications.

Thermodynamic Size Control in Curvature-Frustrated Tubules: Self-Limitation with Open Boundaries

“…The self-assembly of subunits into large, but finite-size, superstructures plays a central role in the functionalities, pathogenesis, and organization of biological systems ( e . g ., viral capsids, − bacterial microcompartments, − and other shelled cell organelles − ) and is becoming a route to design nanostructured assemblies for technological applications. − In contrast, most subunits with cohesive interactions typically undergo thermodynamically unlimited assembly, for example, into a crystal. In these examples self-limitation arises through “curvature control”, meaning that subunits assemble with a preferred curvature that drives the structure to close upon itself, leaving no boundary for additional subunit association.…”

Protein Cages: From Fundamentals to Advanced Applications

“…707−710 However, noncovalent strategies are problematic in an immunoglobulincompetitive environment. 711 For in vivo applications, chemical cross-linking of the antibodies to the capsid surface may therefore be necessary. 712−714 This approach has the advantage that the number of antibodies per cage can be optimized through systematic variation.…”

“…Antibodies are displayed on capsid surfaces through either chemical ligation or non-covalent interactions. Both types of interactions can be achieved with bispecific antibodies − and other bifunctional molecules; additionally, non-covalent binding can be introduced by genetic fusion of an antibody-binding domain to the external terminus of a capsid protein. − However, non-covalent strategies are problematic in an immunoglobulin-competitive environment . For in vivo applications, chemical cross-linking of the antibodies to the capsid surface may therefore be necessary. − This approach has the advantage that the number of antibodies per cage can be optimized through systematic variation.…”

Engineering Self-Assembling Protein Nanoparticles for Therapeutic Delivery

“…166 Protein nanoparticles have also been reported with modifications that improve circulation half-life and target the nanoparticles to specific cells. 55,167 For systemic, in vivo delivery, protein nanoparticles need to incorporate design features that provide stability during circulation with the ability to recognize, enter, and traffic within target cells. Viruses, VLPs, and some designed delivery vehicles achieve this by responding to the endosomal environment and switching states, satisfying the opposing needs of extracellular and endosomal activity.…”