Poly(sarcosine)-block-oligo(l-tryptophan) Copolymers as Noncovalent Inhibitors of Protein Aggregation

Irreversible protein aggregation can cause loss of function of proteins during storage and transport, presenting a challenge in biotherapeutics, biocatalysis, and the food industry, as well as in basic research. New tools to inhibit protein aggregation are required to unlock ambient temperature biologic transportation to reduce the reliance on the cold chain, lower the carbon footprint of biopharmaceutic delivery, and for equitable sharing of medicines. Here we use N-carboxyanhydride polymerization to synthesize block copolymers with short oligo-tryptophan tails to target aggregation-prone regions in proteins, with a hydrophilic and biocompatible poly(sarcosine) solubility block. Poly(sarcosine) is an emerging low toxicity and nonimmunogenic alternative to poly(ethylene glycol), for which immunogenicity is known. Using lysozyme as a fast-aggregating model protein, we show inhibition of aggregation during solution phase agitation challenges by simply mixing the polymer with the protein. Other hydrophobic amino acid blocks were too insoluble to stabilize, and random copolymers had no activity, highlighting the essentiality of the block structure and choice of hydrophobic amino acid residues.