Polysarcosine-Functionalized Lipid Nanoparticles for Therapeutic mRNA Delivery

Abstract

Polysarcosine (pSar) is a polypeptoid based on the endogenous amino acid sarcosine (N-methylated glycine), which has previously shown potent stealth properties. Here, lipid nanoparticles (LNPs) for therapeutic application of messenger RNA were assembled using pSarcosinylated lipids as a tool for particle engineering. Using pSar lipids with different polymeric chain lengths and molar fractions enabled the control of the physicochemical characteristics of the LNPs, such as particle size, morphology, and internal structure. In combination with a suited ionizable lipid, LNPs were assembled, which displayed high RNA transfection potency with an improved safety profile after intravenous injection. Notably, a higher protein secretion with a reduced immunostimulatory response was observed when compared to systems based on polyethylene glycol (PEG) lipids. pSarcosinylated nanocarriers showed a lower proinflammatory cytokine secretion and reduced complement activation compared to PEGylated LNPs. In summary, the described pSar-based LNPs enable safe and potent delivery of mRNA, thus signifying an excellent basis for the development of PEG-free RNA therapeutics.

mRNA-lipid nanoparticle COVID-19 vaccines: Structure and stability

“…Therefore, alternative lipids to prevent aggregate formation have been investigated. Introduction of polysarcosine-modified lipids stabilized lipid-based systems against aggregation while reducing the immunostimulatory response ( Nogueira et al, 2020 ). Additional testing is needed to establish whether such PEG-lipid alternatives improve the mRNA stability (e.g., owing to lack of peroxides).…”

Non-Immunotherapy Application of LNP-mRNA: Maximizing Efficacy and Safety

“…While structural lipids allow the maintenance of the particle structure, cholesterol enhances particle stability, thereby most likely affecting LNP morphology and mRNA delivery [ 57 , 58 ]. Stealth coating lipids such as polyethylene glycol (PEG)-lipid or polysarcosine (pSar) enable the control of physicochemical characteristics of the LNP-mRNA (e.g., particle size and the structure) and influence the circulation half-life of the particle [ 56 , 59 , 60 ].…”

Secondary Structure-Driven Self-Assembly of Thiol-Reactive Polypept(o)ides

“… 26 − 28 As such, polysarcosine (pSar, poly( N -methyl glycine)) adopts random coil conformation in aqueous solution, is highly water-soluble (A2 parameter of 3.50·10 –6 mol·dm 3 ·g –2 for pSar 185 at 20 °C), and can be considered a stealth-like material. 29 − 33 For medical applications, polysarcosine is considered the most promising alternative to polyethylene glycol since substantial advantages like reduced proinflammatory cytokine secretion and reduced complement activation as well as evasion of the accelerated blood clearance (ABC) phenomenon have been reported. 30 , 33 − 35 The combination of polypeptides and polysarcosine in polypept(o)ides thus represent a promising class of biobased or even endogenous materials.…”

“… 29 − 33 For medical applications, polysarcosine is considered the most promising alternative to polyethylene glycol since substantial advantages like reduced proinflammatory cytokine secretion and reduced complement activation as well as evasion of the accelerated blood clearance (ABC) phenomenon have been reported. 30 , 33 − 35 The combination of polypeptides and polysarcosine in polypept(o)ides thus represent a promising class of biobased or even endogenous materials. 26 , 36 , 37 While the concept of polypept(o)ides extends from linear block copolymers to cylindrical bottle-brush and star-shaped polymers including miktoarm stars, 36 , 38 − 40 polysarcosine itself has further been successfully combined with various other classes of synthetic polymers.…”