Functionalisation of brush polyethylene glycol polymers with specific lipids extends their elimination half-life through association with natural lipid trafficking pathways

Polymeric prodrugs have been applied to control the delivery of various types of therapeutics. Similarly, conjugation of peptide therapeutics to lipids has been used to prolong systemic exposure. Here, we extend on these two approaches by conjugating brush polyethylene glycol (PEG) polymers with different lipid components including short-chain (1C2) or medium-chain (1C12) monoalkyl hydrocarbon tails, cholesterol (Cho), and diacylglycerols composed of two medium-chain (2C12) or long-chain (2C18) fatty acids. We uniquely evaluate the integration of these lipid-polymers into endogenous lipid trafficking pathways (albumin and lipoproteins) and the impact of lipid conjugation on plasma pharmacokinetics after intravenous (IV) and subcutaneous (SC) dosing to cannulated rats. The IV and SC elimination half-lives of Cho-PEG (13 and 22 h, respectively), 2C12-PEG (11 and 17 h, respectively) and 2C18-PEG (12 h for both) were prolonged compared to 1C2-PEG (3 h for both) and 1C12-PEG (4 h for both). Interestingly, 1C2-PEG and 1C12-PEG had higher SC bioavailability (40 % and 52 %, respectively) compared to Cho-PEG, 2C12-PEG and 2C18-PEG (25 %, 24 % and 23 %, respectively). These differences in pharmacokinetics may be explained by the different association patterns of the polymers with rat serum albumin (RSA), bovine serum albumin (BSA) and lipoproteins. For example, in pooled plasma (from IV pharmacokinetic studies), 2C18-PEG had the highest recovery in the high-density lipoprotein (HDL) fraction. In conclusion, the pharmacokinetics of brush PEG polymers can be tuned via conjugation with different lipids, which can be utilised to tune the elimination half-life, biodistribution and effect of therapeutics for a range of medical applications. STATEMENT OF SIGNIFICANCE: Lipidation of therapeutics such as peptides has been employed to extend their plasma half-life by promoting binding to serum albumin, providing protection against rapid clearance. Here we design and evaluate innovative biomaterials consisting of brush polyethylene glycol polymers conjugated with different lipids. Importantly, we show for the first time that lipidated polymeric materials associate with endogenous lipoprotein trafficking pathways and this, in addition to albumin binding, controls their plasma pharmacokinetics. We find that conjugation to dialkyl lipids and cholesterol leads to higher association with lipid trafficking pathways, and more sustained plasma exposure, compared to conjugation to short and monoalkyl lipids. Our lipidated polymers can thus be utilised as delivery platforms to tune the plasma half-life of various pharmaceuticals.

Improved systemic half-life of glucagon-like peptide-1-loaded carbonate apatite nanoparticles in rats

BACKGROUND

Glucagon-like peptide-1 (GLP1) is an endogenous peptide that regulates blood glucose level. But its susceptibility to rapid metabolic degradation limits its therapeutic use.

AIM

To prepare GLP1-encapsulated nanosize particle with controlled release property to improve the systemic half-life of GLP1.

METHODS

GLP1 nanoparticles were prepared by complexation of GLP1 with carbonate apatite nanoparticles (CA NPs). The physicochemical properties of the CA NPs, the effects of GLP1-loaded CA NPs on cell viability, and the systemic bioavailability of GLP1 after CA NPs administration were determined.

RESULTS

The GLP1-loaded CA NPs was within 200 nm in size and stable in fetal bovine serum. The formulation did not affect the viability of human cell lines suggesting that the accumulation of CA NPs in target tissues is safe. In Sprague Dawley rats, the plasma GLP1 Levels as measured from the GLP1-loaded CA NPs-treated rats, were significantly higher than that of the control rats and free GLP1-treated rats at 1 h post-treatment (P < 0.05), and the level remained higher than the other two groups for at least 4 h.

CONCLUSION

The GLP1-loaded CA NPs improved the plasma half-life of GLP1. The systemic bioavailability of GLP1 is longer than other GLP1 nanoparticles reported to date.