Liquid amine–solid carbamic acid phase-separation system for direct capture of CO2 from air

The phase separation between a liquid amine and the solid carbamic acid exhibited >99% CO2 removal efficiency under a large-scale gas stream of 400 ppm CO2. Isophorone diamine [IPDA; 3-(aminomethyl)-3,5,5-trimethylcyclohexylamine] reacted with CO2 in the CO2/IPDA molar ratio of ≥ 1 even in H2O as a solvent. The captured CO2 was completely desorbed at 333 K because the disolved carbamate ion releases CO2 at low temperature. The reusability of IPDA under CO2 adsorption-and-desorption cycles without degradation, the >95% efficinecy kept for 100 hours under direct air capture condition, and high CO2 capture rate (214 mmol/h for 1 mol amine) suggest that the phase separation system using IPDA is robust and durable for practical use

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-<i>co</i>-3-hydroxyvalerate-<i>co</i>-2,3-dihydroxybutyrate) [PHBVDB] containing hydroxyl groups was produced by recombinant <i>Ralstonia eutropha</i>. <i>R. eutropha</i> were constructed to express the propionate-coenzymeA transferase (<i>pct</i>) gene from <i>Megasphaera elsdenii</i>, and glycolate was used as the carbon source. Disruption of <i>phaA</i> encoding β-ketothiolase in the <i>phaCAB</i> 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