Synthesis and UCST-type thermoresponsive properties of polypeptide based single-chain nanoparticles?

Polymer Chemistry Pub Date: 2019-09-06 DOI: 10.1039/C9PY01040H

Abstract

Polypeptide based single-chain nanoparticles (SCNPs) were synthesized via intramolecular crosslinking between ABA-type triblock copolymers and 1,4-diiodobutane in dilute solution (0.25 mg·mL?1). Alkylation of the thioether containing SCNPs in the presence of propargyl bromide yielded sulfonium containing SCNPs with “clickable” alkyne pendants, which can be readily modified by azido compounds. Copper-mediated 1,3-dipolar cycloaddition between the alkyne containing SCNPs and (3-azidopropyl)triphenylphosphonium bromide (TPP-N3) afforded SCNPs bearing TPP pendants. An ion-exchange reaction endowed the TPP containing SCNPs with tunable hydrophilicity/hydrophobicity by adjusting the types of counteranions. All the resulting polypeptide based SCNPs adopt α-helical conformation in both the solid-state and solutions. SCNPs bearing triphenylphosphonium iodide formed self-assembled structures in aqueous solutions and showed upper critical solution temperature (UCST)-type thermoresponsive properties. The UCST SCNPs showed increased UCST-type phase transition temperature (Tpt) and improved biocompatibility compared to their linear polymer counterparts. The Tpt increased by intrachain crosslinking, increasing the crosslinking density or concentration. Our work provides a new and facile route to prepare side-chain “clickable” and α-helical SCNPs.

Graphical abstract: Synthesis and UCST-type thermoresponsive properties of polypeptide based single-chain nanoparticles
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