The Ohio State University

Abstract

The vast majority of 400,000+ patients in the United States with kidney failure depends on dialysis treatments in dedicated dialysis centers for three to five hours, usually three times weekly, but still suffers from accelerated cardiovascular disease and infections. Extended daily dialysis (EDD), for 6-8 hours every day, appears to be associated with better outcomes, but would overwhelm the dialysis networks and severely limit patient activity.  Technology to miniaturize and automate home dialysis will be necessary to offer EDD to most dialysis patients.

Miniaturization of existing hollow-fiber polymer membranes is constrained by requirements for high driving pressures for circulation and convective clearance. Recent advances in membrane technology based on microelectromechanical system (MEMS) promise to enable the development of continuous implantable renal replacement therapy. Silicon nanoporous membranes with a highly monodisperse pore size distribution have been produced using protocols amenable to low-cost batch fabrication similar those used to produce microelectronics. Hydraulic permeability of the flat-sheet membranes with critical pore sizes in the range of 8-100 nm has been measured to confirm that conventional fluid transport models are sufficiently accurate for predictive design for bulk liquid flow in an implantable hemofilter. Membrane biocompatibility was tested in vitro with human proximal tubule cells and revealed that silicon does not exhibit cytotoxicity as evidenced by the formation of confluent cell layers with tight junctions and central cilia. Filtration characterization demonstrated that the nanoporous membranes exhibit size dependent solute rejection in agreement with steric hindrance models.

These advances in membrane technology are fundamentally enabling for a paradigm shift from an in-center to implantable dialysis systems.