High Yield Sample Preconcentration Using a Highly Ion-Conductive Charge-Selective Polymer

Abstract

The development and analysis of a microfluidic sample preconcentration system using a highly ion-conductive charge-selective polymer (poly-AMPS) is reported. The preconcentration is based on the phenomenon of concentration polarization which develops at the boundaries of the poly-AMPS with buffer solutions. A negatively charged polymer, poly-AMPS, positioned between two microchannels efficiently extracts cations through its large cross section, resulting in efficient anion sample preconcentration. The present work includes the development of a robust polymer that is stable over a wide range of buffers with varying chemical compositions. The sample preconcentration effect remains linear to over 3 mM (0.15 pmol) and 500 μM (15 fmol) for fluorescein and TRITC-tagged albumin solutions, respectively. The system can potentially be used for concentrating proteins on microfluidic devices with subsequent analysis for proteomic applications.

Optofluidic in situ maskless lithography of charge selective nanoporous hydrogel for DNA preconcentration

“…17 The devices were fabricated by standard photolithography and wet etching on 0.9 mm thick glass substrate, followed by thermal bonding to seal the microfluidic channels. The dimensions of the microfluidic channel are 50 m ͑width͒ and 12 m ͑height͒.…”

“…Detailed explanation of the preconcentration mechanism can be found in previous work. 17 Briefly, when P reservoirs are grounded to 0 V, cations are selectively extracted through the negatively charged hydrogel, and anions expelled from the area near the negatively charged hydrogel. As a result, an ion-depleted region develops between the two hydrogel plugs.…”

“…To alleviate these limitations, various techniques have been reported in a form of miniaturized system. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] The conventional way to enhance the sensitivity of detection is to increase the copy number of DNA by the chemical amplification through polymerase chain reaction ͑PCR͒. [1][2][3] However, various components are necessary in PCR chemistry, such as enzymes and primers as well as precise temperature control.…”

“…[4][5][6][7][8][9][10][11][12][13][14][15][16][17] Sample preconcentration exploits various sample characteristics, including electric charge, size, mobility, and affinity. [4][5][6][7][8][9][10][11][12][13][14][15][16][17] DNA has the unique property of having a uniform charge to size ratio, making charge selective preconcentration efficient. Among the preconcentration techniques using the electric property of DNA, the electrokinetic trapping technique has received much attention due to its high sensitivity and easy miniaturization.…”

“…Electrokinetic trapping usually utilizes a charged nanochannel ͑or nanoporous membrane͒ between microchannels, allowing for enrichment of counterions along the structure while excluding coions. [11][12][13][14][15][16][17] The local electric field gradient and concentration polarization are induced when an electric field is applied across the charged nanochannel so that sample preconcentration can be achieved. 17 The electrokinetic trap-ping technique does not suffer from overall device size, since the preconcentration occurs in the immediate proximity of the ion depleted boundary, and has shown a high efficiency for concentrating charged biomolecules.…”