An oral sorbent to remove NH4+within
the
small intestine of end-stage kidney disease (ESKD) patients could
reduce blood urea levels and diminish their dialysis treatment burden.
But current sorbent materials like amorphous zirconium phosphate particles
Zr(HPO4)2·H2O (ZrP) lack the
selectivity to remove NH4+in water solution
with other competing ions. Our previous work found that a gas-permeable,
hydrophobic polydimethylsiloxane (PDMS) coating on ZrP improved
the material’s selectivity for NH4+.
However, a competing ion Ca2+was still removed by PDMS-coated
ZrP sorbent, and the permeability of the PDMS coating to Ca2+was increased after low-pH stomach-like condition exposure. An alternative
hydrophobic and gas permeable coating has been investigated—perfluorooctyltriethoxysilane
(FOTS). The coating was attached in place of PDMS to a tetraethyl
orthosilicate-coated ZrP surface. Surface atomic composition analysis
and scanning electron microscopy observation verified the successful
application of the FOTS coating. Water contact angle analysis validated
the FOTS coating was hydrophobic (145.0 ± 3.2°).In vitrocompeting ion studies indicated the FOTS coating
attached to ZrP increased NH4+removal by 53%
versus uncoated ZrP. FOTS offers complete selectivity for NH4+over Ca2+with similar NH4+capacity as the previous PDMS coating. Moreover, FOTS-coated
ZrP maintained NH4+removal capacity and selectivity
after the acid exposure study, indicating excellent acid resistance
while NH4+selectivity of ZrP-PDMS decreased
by 72%. The results suggested that FOTS-coated ZrP is promising as
an oral sorbent for ESKD patients.