Macromolecular Photocatalyst for Synthesis and Purification of Protein–Polymer Conjugates

Abstract

We describe the application of a novel eosin Y (EY)-derived polymer photocatalyst for the synthesis of polymeric bioconjugates. The photocatalyst, a copolymer of eosin Y acrylate and N-isopropylacrylamide, can induce light-mediated reversible-deactivation radical polymerization in biologically benign conditions. Heating the reaction mixture to 37 °C causes precipitation of the photocatalyst in a hydrophilic-to-hydrophobic transition, allowing for simple purification of the polymer–protein conjugates via filtration without compromising enzyme activity. We discuss the optimization of the polymerization conditions for imparting control over molecular weight and reaction kinetics and demonstrate the recyclability of the recovered photocatalyst. Overall, this strategy will advance bioconjugate manufacturing through facilitated purification and improved sustainability.

Reusable polymer brush-based photocatalysts for PET-RAFT polymerization

“…It is worth commenting on the choice of fluorescein as the photocatalyst as other organic photocatalysts (e.g., Eosin Y) have shown better PET-RAFT performance in studies by other groups. 22 Following a literature procedure, 84 we synthesized EY monomers and EY@SiO 2 catalysts (see ESI †). PET-RAFT of MMA with EY@SiO 2 indeed achieved higher monomer conver-Fig.…”

A Water‐Soluble Organic Photocatalyst Discovered for Highly Efficient Additive‐Free Visible‐Light‐Driven Grafting of Polymers from Proteins at Ambient and Aqueous Environments

“…The development of new photocatalysts (PCs) that afford an intrinsically "oxygen-tolerant" photocatalytic system would resolve this problem; however, aqueous PET-RAFT polymerization is substantially limited to several specific PCs such as Ru(bpy) 3 Cl 2 , Eosin Y (and its derivatives), and inorganic PCs that require external additives (previously reported systems on aqueous PET-RAFT are summarized in Figure S1 in the Supporting Information). [37,[40][41][42] Here, we report a new water-soluble and biocompatible organic PC (i.e., "3DP-MSDP-IPN"; Figure 1a), which successfully proceeds visible-light-driven "grafting-from" PET-RAFT polymerizations of a protein at ambient and aqueous environments without additives. To achieve this, water-soluble and weakly electron-donating sulfonate moiety was introduced in one of four donor groups of "4DP-IPN" with a strongly twisted donor-acceptor structure that has been known for highly efficient organic PC for various organic reactions and poly merizations.…”

“…While the reductive quenching pathway shows great oxygen tolerance, it should require substantial amount of sacrificial reducing agents such as tertiary amines and ascorbic acid; [58,59] according to very recent reports from Boyer's group, "oxygen acceleration," in which oxygen acts as an electron shuttle, could also be attained in organic solvents through the carefully chosen phthalocyanine PCs in the presence of tertiary amines (vide infra). [60] Moreover, the reductive quenching cycle often affords undesired side reactions and less controllability of the poly merization, [40] which originates from the longer lifetime of one-electron-reduced PC (PC •-) being an active PC species in a reductive quenching cycle as compared to that of the excited PC species ( 1/3 PC * ) being an active PC intermediate in an oxidative quenching cycle.…”

“…However, while "oxygen-tolerance" behavior of PET-RAFT polymerization has been well-investigated in organic solvents (i.e., dimethyl sulfoxide (DMSO)), the studies in aqueous environments are still scarce. [32][33][34][35][36] Therefore, the preparation of PPCs by PET-RAFT polymerization requires a substantial amount of sacrificial reducing agents such as tertiary amines and ascorbic acids or an inert gas purging process, which limits the practicability of this method; [37][38][39][40] it is noted in this context that PPCs should be prepared in an aqueous environment to prevent the denaturation of a protein. The development of new photocatalysts (PCs) that afford an intrinsically "oxygen-tolerant" photocatalytic system would resolve this problem; however, aqueous PET-RAFT polymerization is substantially limited to several specific PCs such as Ru(bpy) 3 Cl 2 , Eosin Y (and its derivatives), and inorganic PCs that require external additives (previously reported systems on aqueous PET-RAFT are summarized in Figure S1 in the Supporting Information).…”

“…The development of new photocatalysts (PCs) that afford an intrinsically “oxygen‐tolerant” photocatalytic system would resolve this problem; however, aqueous PET‐RAFT polymerization is substantially limited to several specific PCs such as Ru(bpy) 3 Cl 2 , Eosin Y (and its derivatives), and inorganic PCs that require external additives (previously reported systems on aqueous PET‐RAFT are summarized in Figure S1 in the Supporting Information). [ 37,40–42 ]…”