PEG Analogs Synthesized by Ring-Opening Metathesis Polymerization for Reversible Bioconjugation

Abstract

Poly(ethylene glycols) (PEGs) with protein-reactive end-groups are widely utilized in bioconjugation reactions. Herein, we describe the use of ring-opening metathesis polymerization (ROMP) to synthesize unsaturated protein-reactive PEG analogs. These ROMP PEGs (rPEGs) contained terminal aldehyde functionality and ranged in molecular weight from 6 to 20 kDa. The polymers were readily conjugated to free amines on the protein hen egg-white lysozyme (Lyz). Biocompatibility of the unsaturated PEGs was assessed in vitro, revealing the polymers to be nontoxic up to concentrations of at least 1 mg/mL in human dermal fibroblasts (HDFs). The resulting unsaturated rPEG-lysozyme conjugates underwent metathesis-based depolymerization, resulting in decreased molecular weight of the conjugate.

Preparation of biomolecule-polymer conjugates by grafting-from using ATRP, RAFT, or ROMP

“…The grafting-to strategy is utilized to a greater extent for the conjugation of polymers prepared through ROMP. [12,154,155] Though grafting-from is under-utilized in the context of ROMP, the initial disclosure from Isarov and Pokorski provides an important foundation with which to develop improved systems through careful tuning of catalyst systems. [151,153]…”

“…[9][10][11] This has led to the development of diverse polymers able to invoke unique characteristics such as pH responsiveness, increased storage and in-vivo stability, thermo-responsiveness, and in PEG alternatives which exhibit lower immunogenicity. [1,[12][13][14][15][16] Commonly used controlled polymerization techniques for biomolecule-polymer modification are atom-transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer polymerization (RAFT), and ring opening metathesis polymerization (ROMP), which are the focus of this review. [11,[16][17][18] It is important to note that nitroxide-mediated radical polymerization (NMP) has also been used to great extent to prepare bioactive polymers and conjugates, and interested readers are directed to the many interesting reviews and manuscripts which detail the use of NMP.…”

New Aldehyde‐Functional Methacrylic Water‐Soluble Polymers

“…4‐vinylbenzaldehyde) and hence produce water‐insoluble polymers [16, 19–23, 26–32] . This is unfortunate, because aldehyde groups enable facile conjugation to peptides/proteins and water‐soluble dyes in aqueous solution under mild conditions [2–5, 10, 25, 33–38] . In principle, this problem can be circumvented by statistical copolymerization of the hydrophobic aldehyde‐functional monomer with a sufficiently hydrophilic comonomer [12, 13, 15, 25, 33, 39] .…”

Bioorthogonal Chemistry and Bioconjugation: Synergistic Tools for Biology and Biomedicine

“…“Traditional” organic processes such as Diels–Alder and other “click” reactions , provide reactions truly orthogonal to biology, while tandem and multicomponent reactions can rapidly introduce new diversity to bioconjugation processes. The same holds for ring-opening metathesis, which affords the synthesis of polymers with orthogonal handles . Bioorthogonal chemistry can also incorporate and employ elements such as boron, providing structures and properties that biology cannot access. , …”

“…The fact that bioorthogonal reactions do not interfere with biological processes makes them ideal for use in vitro and in vivo for cell labeling, , and tagging of exosomes . Novel conjugation chemistries are employed inside cells, providing a new direction for therapeutic and intracellular protein labeling strategies.…”