Abstract
The preconcentration of proteins with low concentrations can be used to increase the sensitivity and accuracy of detection. A nonlinear electrokinetic flow is induced in a nanofluidic channel due to the overlap of electrical double layers, resulting in the fast accumulation of proteins, referred to as the exclusion-enrichment effect. The proposed chip for protein preconcentration was fabricated using simple standard soft lithography with a polydimethylsiloxane replica. This study extends our previous paper, in which gold nanoparticles were manually deposited onto the surface of a protein preconcentrator. In the present work, nanofractures were formed by utilizing the self-assembly of gold-nanoparticle-assisted electric breakdown. This reliable method for nanofracture formation, involving self-assembled monolayers of nanoparticles at the junction gap between microchannels, also decreases the required electric breakdown voltage. The experimental results reveal that a high concentration factor of 1.5×104 for a protein sample with an extremely low concentration of 1 nM was achieved in 30 min by using the proposed chip, which is faster than our previously proposed chip at the same conditions. Moreover, an immunoassay of bovine serum albumin (BSA) and anti-BSA was carried out to demonstrate the applicability of the proposed chip.
Highlights
In biochemical analysis, numerous strategies, such as field-amplified sample stacking (FASS) [1,2], isotachophoresis (ITP) [3], isoelectric focusing (IEF) [4], temperature gradient focusing (TGF) [5], nanofilters [6], and nanoporous membrane/nanochannel techniques [7,8,9,10], have been broadly exploited to preconcentrate the low-concentration protein samples [11] and described in detail previously [12]
Gold nanoparticles self-assembled onto the surface of the protein preconcentrator
The results reveal that both the concentration of bovine serum albumin (BSA) and the size of the preconcentration area increased with time, which demonstrates that proteins can be concentrated using the proposed chip with self-assembled monolayers (SAMs) of gold nanoparticles on a glass substrate underneath the junction gaps
Summary
Numerous strategies, such as field-amplified sample stacking (FASS) [1,2], isotachophoresis (ITP) [3], isoelectric focusing (IEF) [4], temperature gradient focusing (TGF) [5], nanofilters [6], and nanoporous membrane/nanochannel techniques [7,8,9,10], have been broadly exploited to preconcentrate the low-concentration protein samples [11] and described in detail previously [12]. FASS, ITP, and IEF procedures are complex, and at least two PLOS ONE | DOI:10.1371/journal.pone.0126641. Preconcentration in Nanofractures Generated by SAM-Assisted Breakdown FASS, ITP, and IEF procedures are complex, and at least two PLOS ONE | DOI:10.1371/journal.pone.0126641 May 13, 2015
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