Polymer Nanoparticles with Uniform Monomer Sequences for Sequence-Specific Peptide Recognition.

Synthetic polymer nanoparticles (NPs) that recognize and neutralize target biomacromolecules are of considerable interest as "plastic antibodies", synthetic mimics of antibodies. However, monomer sequences in the synthetic NPs are heterogeneous. The heterogeneity limits the target specificity and safety of the NPs. Herein, we report the synthesis of NPs with uniform monomer sequences for recognition and neutralization of target peptides. A multifunctional oligomer with a precise monomer sequence that recognizes the target peptide was prepared via cycles of reversible addition-fragmentation chain transfer (RAFT) polymerization and flash chromatography. The oligomer or blend of oligomers was used as a chain transfer agent and introduced into poly(N-isopropyl acrylamide) hydrogel NPs by radical polymerization. Evaluation of the interaction with the peptides revealed that multiple oligomers in NPs cooperatively recognized the sequence of the target peptide and neutralized its toxicity. Effect of sequence, combination, density and molecular weight distribution of precision oligomers on the affinity to the peptides was also investigated.

Homogeneous Oligomeric Ligands Prepared via Radical Polymerization that Recognize and Neutralize a Target Peptide.

Abiotic ligands that bind to specific biomolecules have attracted attention as substitutes for biomolecular ligands, such as antibodies and aptamers. Radical polymerization enables the production of robust polymeric ligands from inexpensive functional monomers. However, little has been reported about the production of monodispersed polymeric ligands. Herein, we present homogeneous ligands prepared via radical polymerization that recognize epitope sequences on a target peptide and neutralize the toxicity of the peptide. Taking advantage of controlled radical polymerization and separation, a library of multifunctional oligomers with discrete numbers of functional groups was prepared. Affinity screening revealed that the sequence specificity of the oligomer ligands strongly depended on the number of functional groups. The process reported here will become a general step for the development of abiotic ligands that recognize specific peptide sequences.

Design of abiotic polymer ligand-decorated lipid nanoparticles for effective neutralization of target toxins in the blood.

Macromolecular toxins often induce inflammatory cytokine production, multiple-organ dysfunction, and cell death. Synthetic polymer ligands (PLs) prepared with several functional monomers have the potential of neutralizing target toxins after binding to them; therefore, they are of significant interest as abiotic antidotes. Although PLs show little toxin neutralization effect in the bloodstream because of immediate elimination from there, the toxin neutralization effect is significantly improved by the direct decoration of PLs onto lipid nanoparticles (PL-LNPs). However, this direct decoration decreases PL mobility, induces LNP aggregation after capturing the target, and decreases LNP blood circulation time. We designed novel PL-LNPs to improve PL mobility, inhibit the aggregation tendency after capturing the target, and increase LNP blood circulation time in order to achieve highly effective toxin neutralization in vivo. Specifically, LNPs were modified with PLs-conjugated polyethylene glycol (PEG), and additional PEG was used to modify the PL-decorated LNPs (PL-PEG-LNPs). Histones were used as target toxins, and N-isopropylacrylamide-based PLs were used for histone capture. PEGylation increased the plasma LNP level 24 h after intravenous injection by ∼90 times and inhibited LNP aggregation after histone capture. The dissociation constant (Kd) of PL-PEG-LNPs against histone was two times smaller compared to that of PL-LNPs. Although PL-LNPs inhibited histone-platelet interaction in the bloodstream, a large amount of histone-PL-LNP complexes accumulated in the lungs because of aggregation. However, PL-PEG-LNPs inhibited both histone-platelet interaction and histone accumulation in the lungs. Importantly, PL-PEG-LNP treatment increased the survival rate of histone-treated mice compared to PL-LNPs. These results provide a platform for the development of abiotic antidote nanoparticles in vivo.