Amphiphilic star-shaped poly(sarcosine)-block-poly(ε-caprolactone) diblock copolymers: one-pot synthesis, characterization, and solution properties

Amphiphilic star-shaped block copolymers with biodegradable and biocompatible sequences are attracting increasing attention in biomaterials. Herein, we report the synthesis, characterization, solution properties, and biocompatibility of amphiphilic three-armed star-shaped poly(sarcosine)-block-poly(ε-caprolactone) (s-PSar-b-PCL) diblock copolymers. Tris-(2-aminoethyl)amine initiated ring-opening polymerization (ROP) of sarcosine N-carboxyanhydrides in a controlled manner, yielding star-shaped poly(sarcosine)s (s-PSars) with predictable molecular weights (from 3.3 to 9.8 kg mol⁻¹) and narrow dispersities (Đ_M < 1.1). Well-defined amphiphilic s-PSar-b-PCL diblock copolymers were synthesized by ROP of ε-caprolactone using s-PSars as the macroinitiators in one pot. The obtained s-PSars and s-PSar-b-PCL diblock copolymers were characterized using ¹H NMR, ¹³C NMR, MALDI-ToF MS, and size-exclusion chromatography (SEC). Intrinsic viscosities ([η]) of the s-PSar and s-PSar-b-PCL were estimated using SEC-MALS-VISC-DRI. Dynamic light scattering and transmission electron microscopy analysis showed that the s-PSar-b-PCL diblock copolymers self-assembled into spherical aggregates with average hydrodynamic diameters of 56-169 nm in aqueous solution. MTT assays (cell viability test) certified the biosafety (relative cell viability >80%) of the copolymers and their self-assembled nanostructures. Taken together, we (i) synthesized the novel s-PSar-b-PCL diblock copolymers, (ii) investigated the solution properties of the s-PSar-b-PCLs and s-PSars, and (iii) demonstrated the biocompatibility of s-PSar-b-PCLs.