Biodegradation and tissue integration of various polyethylene glycol matrices: a comparative study in rabbits

Objectives: To test whether or not chemical and/or physical modifications of polyethylene glycol (PEG) hydrogels influence degradation time, matrix/membrane stability, and integration into surrounding hard and soft tissues. Material and methods: In 28 rabbits, six treatment modalities were randomly applied to six sites on the rabbit skull: a dense network PEG hydrogel (PEG HD), a medium-dense network PEG hydrogel (PEG MD), a medium-dense network PEG hydrogel modified with an RGD sequence (PEG MD/RGD), a medium-dense network PEG hydrogel modified with RGD with reduced carboxymethyl cellulose (PEG MD/RGD_LV), a loose network PEG hydrogel modified with RGD (PEG LD/RGD), and a collagen membrane (BG). Descriptive histology and histomorphometry were performed at 1, 2, 4, and 6 weeks. Results: PEG HD revealed the highest percentage of residual matrix at all time points starting with 47.2% (95% CI: 32.8-63.8%) at 1 week and ending with 23.4% (95% CI: 10.3-49.8%) at 6 weeks. The hydrogel with the loosest network (PEG LD/RGD) was stable the first 2 weeks and then degraded continuously with a final area of 8.3% (95% CI: 3.2-21.2%). PEG HD was the most stable and densely stained membrane, whereas PEG MD and PEG LD matrices integrated faster, but started to degrade to a higher degree between 2 and 4 weeks. PEG MD degradation was dependent on the addition of RGD and the amount of CMC. Conclusions: Chemical and/or physical modifications of PEG hydrogels influenced matrix stability. PEG MD/RGD demonstrated an optimal balance between degradation time and integration into the surrounding soft and hard tissues.