Amphiphilic multiblock copolymers of PLLA, PEO and PPO blocks: Synthesis, properties and cell affinity

• Amphiphilic copolymers combining amorphous and crystalline blocks were synthesized.
• The hydrophilic domains are dispersed in the hydrophobic PLLA matrix.
• All copolymers allow cell adhesion and support osteoblast proliferation.

Poly(l-lactide) (PLLA) is a biodegradable and bioabsorbable polyester recognized for its potential uses in many fields, including biomedical applications. However, its hydrophobic and highly crystalline nature can be limitations for tissue engineering applications; these limitations can be overcome by PLLA copolymerization with more hydrophilic and amorphous blocks. Therefore, PLLA blocks were attached to block copolymers based on poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) – PEO-b-PPO-b-PEO and PPO-b-PEO-b-PPO – and to random PEO-ran-PPO through ring-opening polymerization of l-lactide (LLA) to obtain a series of multiblock copolymers containing amorphous/crystalline blocks with variable mass ratios of hydrophilic/hydrophobic blocks. PLLA-b-P(EO-PO)-b-PLLA copolymers were evaluated for chemical composition and molar mass (hydrogen nuclear magnetic resonance – 1H NMR and gel permeation chromatography – GPC). Phase behavior was investigated using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA), which showed the suppression of the polyether phase’s crystallinity and the complexity of the relaxation spectra of the copolymers, respectively. The combination of AFM and DMA results revealed polyether domains that were segregated from the PLLA matrix morphology. A more hydrophilic surface compared with neat PLLA was evidenced by water contact angle measurements. All copolymers are able to allow cell adhesion and to support a suitable osteoblast cell proliferation rate, as revealed by PicoGreen® assays. These amphiphilic block copolymers are potentially biocompatible candidates for tissue engineering devices.

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