Influence of Hydroxyl Groups on the Cell Viability of Polyhydroxyalkanoate (PHA) Scaffolds for Tissue Engineering

Polyhydroxyalkanoates (PHAs) are biopolyesters that have been studied as tissue engineering materials because of their biodegradability, biocompatibility, and low cytotoxicity. In this study, poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-2,3-dihydroxybutyrate) [PHBVDB] containing hydroxyl groups was produced by recombinant Ralstonia eutropha. R. eutropha were constructed to express the propionate-coenzymeA transferase (pct) gene from Megasphaera elsdenii, and glycolate was used as the carbon source. Disruption of phaA encoding β-ketothiolase in the phaCAB operon increased 2,3-dihydroxybutyrate (2,3-DHBA) compositions to 3 mol %. The PHBVDB film showed a lower water contact angle compared with other PHA films, indicating increased hydrophilicity due to the hydroxyl groups. The mechanical properties of the PHBVDB scaffold met the requirements for a soft tissue matrix. The effect of hydroxyl groups on cytotoxicity was evaluated with human mesenchymal stem cells. Results of cell proliferation and live/dead assays showed that the PHBVDB scaffold did not exhibit significant cytotoxicity toward the cells. These results indicate that PBVDB containing hydroxyl groups could be applied as a hydrophilicity-controlled scaffold for soft tissue engineering.