Modelling of electrokinetic phenomena for capture of PEGylated ribonuclease A in a microdevice with insulating structures

Abstract

Synthesis of PEGylated proteins results in a mixture of protein-polyethylene glycol (PEG) conjugates and the unreacted native protein. From a ribonuclease A (RNase A) PEGylation reaction, mono-PEGylated RNase A (mono-PEG RNase A) has proven therapeutic effects against cancer, reason for which there is an interest in isolating it from the rest of the reaction products. Experimental trapping of PEGylated RNase A inside an electrokinetically driven microfluidic device has been previously demonstrated. Now, from a theoretical point of view, we have studied the electrokinetic phenomena involved in the dielectrophoretic streaming of the native RNase A protein and the trapping of the mono-PEG RNase A inside a microfluidic channel. To accomplish this, we used two 3D computational models, a sphere and an ellipse, adapted to each protein. The effect of temperature on parameters related to trapping was also studied. A temperature increase showed to rise the electric and thermal conductivities of the suspending solution, hindering dielectrophoretic trapping. In contrast, the dynamic viscosity of the suspending solution decreased as the temperature rose, favoring the dielectrophoretic manipulation of the proteins. Also, our models were able to predict the magnitude and direction of the velocity of both proteins indicating trapping for the PEGylated conjugate or no trapping for the native protein. In addition, a parametric sweep study revealed the effect of the protein zeta potential on the electrokinetic response of the protein. We believe this work will serve as a tool to improve the design of electrokinetically driven microfluidic channels for the separation and recovery of PEGylated proteins in one single step. Published by AIP Publishing. [http://dx

Joule heating effects in optimized insulator‐based dielectrophoretic devices: An interplay between post geometry and temperature rise

“…This field is distorted by the presence of a set of insulating structures fabricated within the microchannel, rendering significant spatial non‐uniformities in its distribution . Insulator‐based DEP devices offer many attractive traits (e.g., low cost, low fabrication complexity, and material transparency) and therefore have been used to manipulate many types of bioparticles . Nonetheless, due to the electric charges present in the channel and particles surfaces, and to ions in solution, electrophoresis (EP) and electroosmosis (EO) compete with DEP in controlling particle motion .…”

“…They concluded that observed fluid circulations were due to Joule heating induced flow inhomogeneities in the constriction region of the channel interacting with the electric field. Since then, many reports have become available in the literature where computational models predict electrothermal effects and are validated through flow field experimental observations . These studies made the dependence of Joule heating on the electric field spatial distribution (and therefore on channel geometry) evident.…”

Electrokinetic characterization of synthetic protein nanoparticles

“…The Swami and Chou groups have studied protein particle enrichment in high-conductivity media employing devices with nanoscale gaps and reported both positive and negative DEPs [ 28 , 45 – 47 ]. Other studies have employed triangular insulating posts with nanoscale gaps [ 48 ], cylindrical insulating structures to enrich BSA particles [ 49 ], or diamond-shaped posts to separate PEGylated ribonuclease A from non-PEGylated molecules [ 50 ].…”

Joule heating‐enabled electrothermal enrichment of nanoparticles in insulator‐based dielectrophoretic microdevices

“…However, the presence of insulating structures may cause appreciable thermal effects because of the enhanced resistive heating of the suspending fluid as a result of the locally amplified electric field [27–29]. This phenomenon becomes significant if highly conductive solutions are used [30]. The induced temperature gradients draw nonuniformities to the fluid properties (in particular electric conductivity, permittivity, and viscosity), which interact with the electric field yielding a volumetric body force upon the fluid [31].…”