A Reactive Oxygen Species-Scavenging ‘Stealth’ Polymer, Poly(thioglycidyl glycerol), Outperforms Poly(ethylene glycol) in Protein Conjugates and Nanocarriers and Enhances Protein Stability to Environmental and Biological Stressors

Abstract

This study addresses well-known shortcomings of poly(ethylene glycol) (PEG)-based conjugates. PEGylation is by far the most common method employed to overcome immunogenicity and suboptimal pharmacokinetics of, for example, therapeutic proteins but has significant drawbacks. First, PEG offers no protection from denaturation during lyophilization, storage, or oxidation (e.g., by biological oxidants, reactive oxygen species); second, PEG's inherent immunogenicity, leading to hypersensitivity and accelerated blood clearance (ABC), is a growing concern. We have here developed an 'active-stealth' polymer, poly(thioglycidyl glycerol)(PTGG), which in human plasma is less immunogenic than PEG (35% less complement activation) and features a reactive oxygen species-scavenging and anti-inflammatory action (∼50% less TNF-α in LPS-stimulated macrophages at only 0.1 mg/mL). PTGG was conjugated to proteins via a one-pot process; molar mass-and grafting density-matched PTGG-lysozyme conjugates were superior to their PEG analogues in terms of enzyme activity and stability against freeze-drying or oxidation; the latter is due to sacrificial oxidation of methioninemimetic PTGG chains. Both in mice and rats, PTGG-ovalbumin displayed circulation half-lives up to twice as long as PEGovalbumin, but most importantly�and differently from PEG�without any associated ABC effect seen either in the time dependency of blood concentration, in the liver/splenic accumulation, or in antipolymer IgM/IgG titers. Furthermore, similar pharmacokinetic results were obtained with PTGGylated/PEGylated liposomal nanocarriers. PTGG's 'active-stealth' character therefore makes it a highly promising alternative to PEG for conjugation to biologics or nanocarriers.

Polymeric Nanoparticles for Drug Delivery

“…Oxidation results in the hydrophobic sulfide bonds transitioning into hydrophilic sulfoxides, resulting in the whole polymer’s solubility shifting. , The sulfide bonds can be incorporated into the backbone, for example in poly­(propylene sulfide), or as pendant groups on various platforms such as polyacrylamides, polyphosphoesters, and certain peptides (cysteine and methionine) . These polythioethers can act as reactive oxygen species (ROS) scavengers, ,− and as moieties to enhance therapeutic delivery by responsively altering nanoparticle solubility and morphology. ,, Similarly, selenoethers have similar oxidative potential, as they form water soluble selenoxides when exposed to H 2 O 2 . This process, unlike sulfide-based polymers, is reversible under physiological conditions.…”

Antifouling polymers for nanomedicine and surfaces: recent advances

“…More recently, d'Arcy et al have developed an intriguing "active-stealth" polymer called poly(thioglycidyl glycerol) (PTGG) as an alternative to PEG. 101 Chemically, PTGG is a polysulfide that shares some similarities with both PEG and poly (glycerol). The main backbone resembles that of PEG in which the oxygen atom has been replaced by a sulfur.…”

Core Cross‐Linking Enhances the Anti‐Inflammatory Performance of Oxidation‐Sensitive Polymeric Micelles

“…Our group has extensively employed poly(1,2‐alkylene sulfides), hereafter referred to as polysulfides (most commonly poly(propylene sulfide), PPS), as precisely designed oxidation‐sensitive building blocks: for example, they have been employed by us and others to produce water‐soluble “stealth” polymers (as sacrificial conjugates for the protection of proteins, [ 1 ] ) polymeric micelles (countering osteoclastogenesis, [ 2 ] ) temperature‐dependent aggregates (countering neuroinflammation, [ 3 ] ) cross‐linked nanoparticles (ameliorating stroke symptoms [ 4 ] or regressing fibrotic markers and wound contractures, [ 5 ] ) polymersomes (intracellular delivery, [ 6 ] targeting of immune cells, [ 7 ] ) hydrogels (cell‐protective effects, [ 8 ] traumatic brain injury [ 9 ] ) and polysaccharide hybrids (e.g., in various types of gut inflammatory pathologies, [ 10,11 ] and microparticles (peripheral ischemia [ 12 ] and post‐traumatic osteoarthritis. [ 13 ] ) In addition to their oxidative responsiveness, a second, distinctive feature of polysulfides is the mild, versatile, and controlled character of their polymerization chemistry, which is based on the ring‐opening polymerization of episulfides.…”