Self-Assembly of Temperature-Responsive Protein–Polymer Bioconjugates

Abstract

We report a simple temperature-responsive bioconjugate system comprising superfolder green fluorescent protein (sfGFP) decorated with poly[(oligo ethylene glycol) methyl ether methacrylate] (PEGMA) polymers. We used amber suppression to site-specifically incorporate the non-canonical azide-functional amino acid p-azidophenylalanine (pAzF) into sfGFP at different positions. The azide moiety on modified sfGFP was then coupled using copper-catalyzed “click” chemistry with the alkyne terminus of a PEGMA synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. The protein in the resulting bioconjugate was found to remain functionally active (i.e., fluorescent) after conjugation. Turbidity measurements revealed that the point of attachment of the polymer onto the protein scaffold has an impact on the thermoresponsive behavior of the resultant bioconjugate. Furthermore, small-angle X-ray scattering analysis showed the wrapping of the polymer around the protein in a temperature-dependent fashion. Our work demonstrates that standard genetic manipulation combined with an expanded genetic code provides an easy way to construct functional hybrid biomaterials where the location of the conjugation site on the protein plays an important role in determining material properties. We anticipate that our approach could be generalized for the synthesis of complex functional materials with precisely defined domain orientation, connectivity, and composition.

Biomimetic Mineralization of Protein Nanogels for Enzyme Protection

“…We ando ther researchers have demonstrated that the conjugation of proteins to thermally responsivep olymers could change the phase-transition temperatures of the polymers significantly. [21][22][23][24] The shift in the phasetransition temperature of PNIPAM in PPL nanogelsi sa ttributed to the incorporation of PPL molecules to the network structures and an increase in the hydrophilicity of the polymer. After coating with BSA, the endotherm of PNIPAM shifts to the high-temperature regime.…”

Expansion of bioorthogonal chemistries towards site-specific polymer–protein conjugation

“…Then, the GFP was conjugated to an alkyne-terminated PEG molecule grafted to a functionalized PDMS surface through CuAAC. 173 The sfGFP was genetically introduced with pAzF. 172 The pAzF was incorporated into two different sites of GFP.…”

“…171 A protein-PEG conjugate also served as a monomer to polymerize the generation of a fibrous structure. 173 5 Conjugation of other polymers to proteins Then, the pAzF-containing GFPs were copolymerized with dialkyn-terminated PEGs via CuAAC, generating a protein-based giant fibrous architecture.…”

Temperature and pH Controlled Self‐Assembly of a Protein–Polymer Biohybrid

“…Previous research focused on preparing bioconjugates were mainly based on proteins such as bovine serum albumin (BSA), ovalbumin, chymotrypsin, streptavidin, and green fluorescent protein . Hoffman and co‐workers carried out pioneering work on preparation of various protein–PNIPAm conjugates for regulation of enzyme activity, triggered release, and enzyme recovery .…”