Correction to "Reactivity of (Vicinal) Carbonyl Compounds with Urea".

[This corrects the article DOI: 10.1021/acsomega.9b01177.].

Phenylglyoxaldehyde-Functionalized Polymeric Sorbents for Urea Removal from Aqueous Solutions.

For realization of a wearable artificial kidney based on regeneration of a small volume of dialysate, efficient urea removal from dialysate is a major challenge. Here a potentially suitable polymeric sorbent based on phenylglyoxaldehyde (PGA), able to covalently bind urea under physiological conditions, is described. Sorbent beads containing PGA groups were obtained by suspension polymerization of either styrene or vinylphenylethan-1-one (VPE), followed by modification of the aromatic groups of poly(styrene) and poly(VPE) into PGA. It was found that PGA-functionalized sorbent beads had maximum urea binding capacities of 1.4-2.2 mmol/g and removed ∼0.6 mmol urea/g in 8 h at 37 °C under static conditions from urea-enriched phosphate-buffered saline, conditions representative of dialysate regeneration. This means that the daily urea production of a dialysis patient can be removed with a few hundred grams of this sorbent which, is an important step forward in the development of a wearable artificial kidney.

A Ninhydrin-Type Urea Sorbent for the Development of a Wearable Artificial Kidney.

The aim of this study is to develop polymeric chemisorbents with a high density of ninhydrin groups, able to covalently bind urea under physiological conditions and thus potentially suitable for use in a wearable artificial kidney. Macroporous beads are prepared by suspension polymerization of 5-vinyl-1-indanone (vinylindanone) using a 90:10 (v/v) mixture of toluene and nitrobenzene as a porogen. The indanone groups are subsequently oxidized in a one-step procedure into ninhydrin groups. Their urea absorption kinetics are evaluated under both static and dynamic conditions at 37 °C in simulated dialysate (urea in phosphate buffered saline). Under static conditions and at a 1:1 molar ratio of ninhydrin: urea the sorbent beads remove ≈0.6-0.7 mmol g-1 and under dynamic conditions and at a 2:1 molar excess of ninhydrin ≈0.6 mmol urea g-1 sorbent in 8 h at 37 °C, which is a step toward a wearable artificial kidney.

Reactivity of (Vicinal) Carbonyl Compounds with Urea.

Urea removal from dialysate is the major obstacle in realization of a miniature dialysis device, based on continuous dialysate regeneration in a closed loop, used for the treatment of patients suffering from end-stage kidney disease. For the development of a polymeric urea sorbent, capable of removing urea from dialysate with high binding capacities and fast reaction kinetics, a systematic kinetic study was performed on the reactivity of urea with a library of low-molecular-weight carbonyl compounds in phosphate-buffered saline (pH 7.4) at 323 K. It was found that dialdehydes do not react with urea under these conditions but need to be activated under acidic conditions and require aldehyde groups in close proximity to each other to allow a reaction with urea. Among the 31 (hydrated) carbonyl compounds tested, triformylmethane, ninhydrin, and phenylglyoxaldehyde were the most reactive ones with urea. This is attributed to the low dehydration energies of these compounds, as calculated by Gibbs free energy differences between the hydrated and dehydrated carbonyl compounds, which are favorable for the reaction with urea. Therefore, future urea sorbents should contain such functional groups at the highest possible density.