Theoretical Application of Irreversible (Nonequilibrium) Thermodynamic Principles to Enhance Solute Fluxes across Nanofabricated Hemodialysis Membranes

Abstract

Objective. Nanotechnology has the potential to improve hemodialysis membrane technology. Thus, a major objective is to understand how to enhance toxic solute fluxes across these membranes. The aim of this concept building study is to review the application of irreversible thermodynamic (IT) to solute fluxes. Methods. We expanded the application of the Nernst-Planck equation to include the Kedem-Katchalsky equation, pH, membrane thickness, pore size, and electric potential as variables. Results. (1) Reducing the membrane's thickness from 25 μm to 25 nm increased the flux of creatinine, β2-microglobulin, and tumor necrosis factor-α (TNF-α) by a thousand times but prevented completely albumin flux, (2) applying an electric potential of 50–400 mV across the membrane enhanced the flux of the respective molecules by 71.167 × 10−3, 38.7905 × 10−8, and 0.595 × 10−13 mol/s, and (3) changing the pH from 7.35 to 7.42 altered the fluxes minimally. Conclusions. The results supported an argument to investigate the application of IT to study forces of fluxes across membranes. Reducing the membrane's thickness—together with the application of an electrical potential—qualities achievable by nanotechnology, can enhance the removal of uremic toxins by many folds. However, changing the pH at a specific membrane thickness does not affect the flux significantly.

Assessment of removal and adsorption enhancement of high-flux hemodialyzers in convective therapies by a novel in vitro uremic matrix

“…Of note, however, the poor results for the PA hemodialyzer, despite the large pore size of the innermost layer. According to Hedayat et al 30 , reduced porosity (i.e. less number of pores), rather than pore size, may affect the removal efficiency of this particular hemodialyzer in mid-range MW solutes.…”

Study of Uremic Toxin Fluxes Across Nanofabricated Hemodialysis Membranes Using Irreversible Thermodynamics

“…Accordingly, irreversible thermodynamic modeling was the tool of preference to estimate the contribution of specific forces responsible for the transport of the middle molecules across nanofabricated membranes. In a previous publication [ 4 ] the Nernst-Plank equation was expanded to include the Kedem-Katchalsky equation [ 8 ], and the pH, as follows: …”

“…Previously, the different segments of the equation were used to theoretically estimate the fluxes of creatinine, β 2 -microglobulin, and tumor necrosis factor - α across nanofabricated membranes as a function of applied electric potential and changing pH at a reduced membrane thickness [ 4 ].…”

“…The advantages of nanofabricated hemodialysis membranes as we envision can be summarized as follows: Improved pore density on the inner surface in contact with the blood Improved, non-tortuous channel structure Improved surface area / volume ratio Improved selective removal of uremic toxins Higher efficiency of removing uremic toxins Synergy between the driving forces of molecular sieving Relatively low ratio of the length of the straight transport path to the maximum dimension of the uremic toxins molecules Improved channel structure can produce more accurate kinetic models that can explain the transport mechanism inside the membrane and the sieving process Fluxes attributed to surface electric potential and other driving forces of filtration can be predicted with high precision and reliability using irreversible thermodynamic (non-equilibrium) modeling [ 4 ] …”

“…Fluxes attributed to surface electric potential and other driving forces of filtration can be predicted with high precision and reliability using irreversible thermodynamic (non-equilibrium) modeling [ 4 ]…”