Phenylglyoxaldehyde-functionalised chemisorptive nanofibres for the effective removal of urea as a blood purification membrane.

Urea is the most abundant nitrogenous waste that accumulates in patients with end-stage kidney disease (ESKD), yet its low molecular weight, neutrality, and weak nucleophilicity make it the most difficult target for adsorption-based blood purification. Achieving practical wearable haemoperfusion therefore requires a sorbent that chemisorbs urea selectively at body temperature and can be transformed into a leak-free, blood-contacting filter. Here we report the design, synthesis, and evaluation of phenylglyoxaldehyde-functionalised polystyrene (PS-Ac-Ox; hereafter "PGA sorbent") and its conversion into electrospun nanofibre filters. PS-Ac-Ox was prepared from polystyrene by Friedel-Crafts acetylation followed by Kornblum-type oxidation; FTIR and 13C CP/MAS solid-state NMR confirmed installation of the glyoxaldehyde moiety. Electrospinning from N,N-dimethylformamide afforded bead-free, micron-scale fibres whose diameter could be tuned from 0.91 ± 0.35 µm to 3.36 ± 0.90 µm by varying the polymer concentration from 50 to 70% w/v. The fibrous sorbent retained the urea-chemisorption capacity of the parent powder (0.30 mmol g-1 in pure water, 0.23 mmol g-1 in PBS) while markedly improving blood compatibility (haemolysis < 2%, less than half that of the powder). A side-by-side comparison of powder and nanofibre sorbents under identical conditions confirmed statistically indistinguishable per-mass capacities, indicating that adsorption is governed by intra-chain functional-group density rather than by external surface area. Taken together, these results establish phenylglyoxaldehyde-functionalised nanofibres as a versatile chemisorptive platform for urea capture and provide design guidelines for adsorption-based wearable blood-purification membranes.