Influence of Molecular Structure on the In Vivo Performance of Flexible Rod Polyrotaxanes

Polyrotaxanes,
a family of rod-shaped nanomaterials comprised of
noncovalent polymer/macrocycle assemblies, are being used in a growing
number of materials and biomedical applications. Their physiochemical
properties can vary widely as a function of composition, potentially
leading to different in vivo performance outcomes. We sought to characterize
the pharmacokinetic profiles, toxicities, and protein corona compositions
of 2-hydroxypropyl-β-cyclodextrin polyrotaxanes as a function
of variations in macrocycle threading efficiency, molecular weight,
and triblock copolymer core structure. We show that polyrotaxane fate
in vivo is governed by the structure and dynamics of their rodlike
morphologies, such that highly threaded polyrotaxanes are long circulating
and deposit in the liver, whereas lung deposition and rapid clearance
is observed for species bearing lower 2-hydroxypropyl-β-cyclodextrin
threading percentages. Architecture differences also promote recruitment
of different serum protein classes and proportions; however, physiochemical
differences have little or no influence on their toxicity. These findings
provide important structural insights for guiding the development
of polyrotaxanes as scaffolds for biomedical applications.