Poly(methyl ethylene phosphate) hydrogels: Degradable and cell-repellent alternatives to PEG-hydrogels

A degradable and water-soluble polyphosphoester (PPE), namely poly(methyl ethylene phosphate)-dimethacrylate (PMEP-DMA), was synthesized and crosslinked by UV irradiation to prepare PPE-hydrogels. Hydrogels with 10 and 15 wt% of PMEP were prepared after UV-irradiation with an additional 0.2 wt% of photoinitiator. The colorless and transparent PPE hydrogels were studied for their swelling and water uptake. The rheological analysis demonstrated their viscoelastic behavior. The PPE hydrogels were compared to poly(ethylene glycol) (PEG) hydrogels prepared from PEG-macromonomers of similar degrees of polymerization. Hydrolysis experiments proved a successful disintegration of the PPE hydrogels compared to PEG analogs; a faster weight loss for the hydrogels with 10 wt% of PMEP compared to the 15 wt% hydrogels was detected. NMR spectroscopy further proved the release of soluble PPEs from the network and the formation of phosphoric acid diesters during the hydrolysis. Finally, the cytotoxicity with the MG-63 osteoblast cell lines and proved low cell toxicity from the hydrogels with no significant cell adherence towards the gels similar to PEG-based hydrogels. In summary, this work proves PMEP-hydrogels as degradable alternatives to PEG-hydrogels with similar hydrophilicity and low cell adhesion, which might be used in further tissue engineering and to prevent polymer accumulation.