Well-Defined Poly(lactic acid)s Containing Poly(ethylene glycol) Side Chains

Poly(ethylene glycol) (PEG) side-chain functionalized lactide analogues have been synthesized in four steps from commercially available L-lactide. The key step in the synthesis is the 1,3-dipolar cycloacklition between PEG-azides and a highly strained spirolactide heptene monomer, which proceeds in high conversions. The PEG-grafted lactide analogues were polymerized via ring-opening polymerization using triazabicydodecene as organocatalyst to give well-defined tri- and hepta(ethylene glycol)-poly(lactide)s (PLA) with molecular weights above 10 kDa and polydispersity indices between 1.6 and 2.1. PEG poly(lactide) (PLA) with PEG chain M-n 2000 was also prepared, but GPC analysis showed a bimodal profile indicating the presence of starting macromonomer. Cell adhesion assays were performed using MC3T3-E1 osteoblast-like cells demonstrating that PEG-containing PLA reduces cell adhesion significantly when compared to unfunctionalized PLA.