A PDMS Sample Pretreatment Device for the Optimization of Electrokinetic Manipulations of Blood Serum

Abstract

This project encompasses the design of a pretreatment protocol for blood serum and adaption of that protocol to a microfluidic environment in order to optimize key sample characteristics, namely pH, conductivity, and viscosity, to enable on-chip electrokinetic separations. The two major parts of this project include (1) designing a pretreatment protocol to optimize key parameters of the sample solution within a target range and (2) designing /fabricating a microchip that will effectively combine the sample solution with the appropriate buffers to replicate the same bench-scale protocol on the micro-scale.Biomarker detection in complex samples such as blood necessitates appropriate sample "pretreatment" in order for specific markers to be isolated through subsequent separations. This project, though using conventional mixing techniques and buffer solutions, is one of the first to observe the effects of the combination of micro-mixing and sample pretreatment in order to create an all-in-one "pretreatment chip".Using previous literature related to capillary electrophoresis, a bench-scale pretreatment protocol was developed to tune these parameters to an optimal range. A PDMS device was fabricated and used to combine raw sample with specific buffer solutions. Off-chip electrodes were used to induce electrokinetic micro-mixing in the mixing chamber, where homogeneous analyte mixing was achieved in less than one second using an 800V DC pulse wave. Ultimately, we wish to incorporate this device with pre-fabricated electrokinetic devices to optimize certain bioseparations.

A Pmma Conductivity Pretreatment Microfluidics Device for the Optimization of Electrokinetic Manipulations

“…Over 80 percent of analysis time is spent on the sampling and sample pretreatment steps [9]. In a previous work by the Cal Poly Biofluidics Group [10], several key parameters were outlined as being necessary to pretreatment in order to provide a sample that will be useable by sample preparation or target detection chips downstream. These parameters included fluid viscosity, pH, and electrical conductivity.…”

“…Additionally, obstacles such as these are capable of significantly altering the manner in which liquid flows through a channel. In Tim Abram's thesis, obstacles were used as a passive mixer to cause flow streams to cross one another under laminar flow conditions [10]. Furthermore, the additional surface area can cause issues with protein absorption and create pockets where flow becomes static, a biofouling issue.…”

“…The first of these was also the motivation for this project, as this project aims to address issues discovered in Tim Abram's project [10]. His pretreatment chip used buffers and micromixing to successfully treat bovine calf serum for pH and viscosity.…”

Point of care diagnostics for carbonyl/oxidative stress biomarkers

“…Sample pre-treatment or separation is mainly necessary when sample has interfering matrix components that might result in false positives or negatives, the analyte concentration is too low for detection, or the physical state of the sample is not suitable for the analytical technique [102]. For example, blood is one of the most important biological fluids used for disease diagnostics.…”

“…Even though POC diagnostics are most popular in limited resource settings, it can be also be beneficial for the emergency response, at home and in military settings [100]. They can also be considered as personalized medicine as patients can involve in their own disease management [102].…”