Responsive Polymer‐Protein Bioconjugates Prepared by RAFT Polymerization and Copper‐Catalyzed Azide‐Alkyne Click Chemistry

Abstract

Responsive polymer‐protein conjugates were synthesized by combination of reversible addition‐fragmentation chain transfer (RAFT) polymerization and a grafting‐to approach by a highly efficient “click chemistry” strategy. A model protein, bovine serum albumin (BSA), was functionalized with an alkyne moiety by reaction of its free cysteine residue with propargyl maleimide. Azido‐terminated poly(N‐isopropylacrylamide) (PNIPAM‐N3) was prepared via RAFT, and polymer‐protein coupling was accomplished by copper‐catalyzed azide‐alkyne cycloaddition. In aqueous solution, the conjugates were observed by dynamic light scattering to be larger than the free polymer or the unmodified protein. Upon heating above the PNIPAM lower critical solution temperature (LCST), the PNIPAM‐BSA bioconjugates formed stable nanoparticles composed of dehydrated polymer and hydrophilic protein.magnified image

Living Radical Polymerization by the RAFT Process - A Second Update

“…St [325] 134 [326,327] MA [328] MA-b-tBA [328] 136 [ BA [330] St [171] DMAM [171] NIPAM [331] St-b-DMAM [171] DMAM-b-St [171] NIPAM-b-DMAM [332] 138 [333] PEO macro-RAFT agent…”

“…Azide-functional RAFT agents used in this context include 137 [331,332] and 181 (Scheme 18). [364] (e) the attachment of ligands that show specific protein binding, for example, that of biotin with streptavidin (Scheme 19).…”

“…Propargyl folate Azide-alkyne click [332] 137 (NIPAM) BSA Azide-alkyne click [331] 54 (NAM) Protein Biotin conjugation [211] 182 (PEGA) siRNA Pyridyl disulfide [365] 181 (NIPAM) BSA, avidin (heterotelechelic) 1. Pyridyl disulfide, 2. azide-alkyne click [364] 166 (AA-b-NIPAM) Streptavidin Biotin conjugation [412] 189 (NIPAM/321) BSA (telechelic) Thiol-ene [374] 185 (NIPAM) Streptavidin, BSA (heterotelechelic) 1.…”

RAFT polymerization mediated bioconjugation strategies

“…139,140 Particularly, reactions that do not require metal catalysts and extensive modifications on the biomolecule structure are highly promising to improve the homogeneity of biomolecule-polymer conjugates.…”

Thermoprecipitation of Glutathione S‐Transferase by Glutathione–Poly(N‐isopropylacrylamide) Prepared by RAFT Polymerization

“…forming responsive, well-defined BSA-pNIPAAm conjugates via dithiol exchange chemistry, [6] thiol-ene chemistry, [7] and click chemistry [8] while maintaining the bioactivity of BSA. Another example is the use of poly[(Nisopropylacrylamide)-co-(vinylimidazole)] for thermoprecipitation of histidine (His)-tagged proteins.…”