Unveiling Surfactant‐Coated Iron Oxide Nanoparticle Specifications for Enhancing Phosphate Removal in Peritoneal Dialysis‐Simulating Conditions

Chronic kidney disease (CKD) results in the gradual loss of the kidney's blood‐purification functions. Peritoneal dialysis (PD) is one of the two dialysis methods for treating patients with end‐stage CKD while waiting for a kidney transplant. PD is currently less widely used, but it should now be upgraded in view of the significant future demand for dialysis treatment, due, for example, to the aging population. PD also offers several advantages for patients (greater autonomy in treatment; method of choice for treating children and infants; lower cost; etc.), but its removal efficiency for phosphates, a compound often referred to as the “silent killer”, needs to be improved. In this context, we have proposed an innovative approach consisting of adding phosphate adsorbents, such as iron oxide nanoparticles (IONPs), to the formulation of the dialysate, which is usually introduced into the patient's peritoneal cavity, in order to promote the transport of additional phosphates to the dialysate. In this work, we demonstrated an enhancement of phosphate transport (up to ∼30%) by performing dialysis experiments in a “tubing mode” dialysis setup, matching as closely as possible the phosphate transport conditions in PD, by adding in the dialysate tannic acid‐coated raspberry‐shaped iron oxide nanoclusters (RSNs@TA), fitting well the specifications for such application. A phosphate transport driven by electrodiffusion was noticed, and an adsorption‐driven phosphate transport enhancement was confirmed in agreement with phosphate adsorption experiments in batch mode and the proven phosphatation of RSNs@TA. Similar experiments in a commercial “cassette mode” dialysis setup, involving a higher dialysate volume, have confirmed an electrodiffusion mechanism but evidenced a Gibbs–Donnan effect of negatively charged RSNs@TA, affecting the phosphate transport enhancement. Indeed, the TA surfactant brought a negative surface charge, limiting the phosphate transport. Thus, this new dialysate formulation is proved effective and promising to enhance phosphate transport, unveiling a new strategy to upgrade the PD treatment and providing further new specifications for optimizing the design of IONPs by choosing surfactant providing a suitable surface charge.