Dynamic, Polymer-Integrated Crystals for Efficient, Reversible Protein Encapsulation

Abstract

Crystalline materials are increasingly being used as platforms for encapsulating proteins to create stable, functional materials. However, the uptake efficiencies and stimuli-responsiveness of crystalline frameworks are limited by their rigidities. We have recently reported a new form of materials, polymer-integrated crystals (PIX), which combine the structural order of protein crystals with the dynamic, stimuli-responsive properties of synthetic polymers. Here we show that the crystallinity, flexibility, and chemical tunability of PIX can be exploited to encapsulate guest proteins with high loading efficiencies (up to 46% w/w). The electrostatic host–guest interactions enable reversible, pH-controlled uptake/release of guest proteins as well as the mutual stabilization of the host and the guest, thus creating a uniquely synergistic platform toward the development of functional biomaterials and the controlled delivery of biological macromolecules.

Solid-state NMR – a complementary technique for protein framework characterization

“…This feature is particularly relevant for the characterization of new protein-based materials where the presence of additional guest molecules can lead to decreased crystallinity, thus preventing X-ray characterization. 4 This advance is relevant to ferritin, which has been characterized by ssNMR 17 and is prevalent in protein framework studies. 1,3…”

“…Considerable effort is being invested in porous protein crystals, which possess large well-defined pores that permit the uptake and release of substrate/product cargo, enabling, for example, controlled drug delivery. Such ''frameworks'', with solvent contents 450%, can be achieved by using naturally porous cage proteins such as ferritin 3,4 and viral capsids, 5,6 or by engineered protein assembly with inducers that direct the formation of porous structures. [7][8][9][10][11][12] Among the assembly inducing strategies, metal ions/complexes 3,9 and organic ligands 7,8,10,11 are being used to noncovalently crosslink proteins.…”

“…[10][11][12] To date, the structural characterization of protein frameworks has relied mainly on X-ray diffraction or scattering techniques. 4,6,10,11 However, alternative strategies are required to cater for frameworks that have reduced crystallinity or that lose crystallinity upon guest uptake. 4,10,12 Spectroscopic methods could be useful for framework characterization, providing additional information on the residues involved in ligand complexation.…”

Assembly of chemically modified protein nanocages into 3D materials for the adsorption of uremic toxins

“…Formation of macroscopic materials from the soluble protein cages allow the easy separation of the adsorbent and the patient blood in later applications. Furthermore, crystalline ferritin assemblies or other protein crystals have already reported to trap proteins in vitro 25 and in vivo 26 as well as inorganic materials 27 or a combination of organic and inorganic components. 28 In this study, a variant of the human heavy chain ferritin with negatively charged outer surface was utilized.…”

Spatiotemporal control over 3D protein nanocage superlattices for the hierarchical encapsulation and release of different cargo molecules

“…Recently, the interglobular lattice cavities have also been used to encapsulate guest molecules. 32 Furthermore, protein nanocage superlattices have served as a platform for encapsulating different molecules, either both in the inner cavity, 33 or one in the inner cavity and the other in interglobular cavity. 34 By contrast, the hierarchical encapsulation of two different cargoes through spatiotemporal control over the self-assembly behavior of the two-compartment systems remains a challenge.…”