Characterization of Off-Stoichiometry Microfluidic Devices for Bioanalytical Applications

Abstract

In this paper, we further investigate the properties of off-stoichiometry thiol-ene polymers (OSTE) aiming its application in microchip electrophoresis for bioanalytical applications. The proportion of 1.3:1 (allyl:thiol) and 1:2.5 (allyl:thiol) presented the best results in terms of sealing. Raman imaging mapping of the polymers surfaces revealed an outstanding homogeneity. Water contact angle were measured as 68° ± 6° and 71° ± 5° for 1.3:1 allyl and 1:2.5 thiol, respectively. Substrates prepared with OSTE demonstrated to be less prone to sorption of nonpolar compounds. The electroosmotic flow measured for this OSTE composition was 3.8 ± 0.3·10 cm s V, 1.5 times higher than the one found for polydimethylsiloxane microchips under the same conditions. As a proof-of-concept for the applicability of OSTE microchips in bioanalysis the immobilization of α-amylase on the polymer surface and the implementation of a Saccharomyces cerevisiae cell counter using contactless conductivity detection are demonstrated.

Multiple Zones Modification of Open Off-Stoichiometry Thiol-Ene Microchannel by Aptamers: A Methodological Study & A Proof of Concept

“…Then OSTE substrate was processed as described below with pentaerythritol tetrakis(2-mercaptoacetate) (thiol) and triallyl-1,3,5-triazine-2,4,6 (1H,3H,5H)-trione (allyl) as monomeric precursors. Thiol and allyl precursors, were mixed to form OSTE plates (1 cm × 3 cm × 0.5 mm) or OSTE open single channels (2 mm × 2.5 cm × 40 µm) in the presence of 0.01% w/w photoinitiator (ethyl phenyl (2,4,6-trimethylbenzoyl)phosphinate)) and UV irradiation (5 × 8 W tubes, 365 nm, 0.025 J, Vilber Lourmat), as described elsewhere [10]. Briefly, the allyl and thiol precursors were mixed with the photoinitiator in the dark.…”

“…Among them, off-stoichiometry thiol-ene polymers (OSTE) possess interesting properties such as rapid prototyping, uncomplicated processing, and optical transparency [8,9]. The OSTE polymer processing is based on thiol-ene click chemistry reaction [8,[10][11][12][13][14], i.e., UV-initiated step-growth radical polymerization between thiol ("thiol") and allyl ("ene") monomers. The first step consists in the formation of a thiyl radical by hydrogen abstraction from a thiol precursor under UV irradiation.…”

“…The second step is a classical propagation chain transfer until thiol-ene polymerization is completed [15][16][17]. This reaction may occur in the presence or not of a photoinitiator [10,13,18]. Due to the presence of allyl and thiol groups on the surface of this substrate, further chemical modifications of the materials can easily be managed.…”

“…Previously reported studies [10,14] proposed simple and fast (less than 2 h) surface modifications of OSTE polymeric substrates. For example, Bou and Ellis have immobilized gold nanoparticles (AuNPs) onto the OSTE surface to prepare gold electrodes [14].…”

“…Thiyl radicals obtained in the first step react with the carbon double bonds of maleic anhydride to form covalent bonds between the polymer and the organic molecule. Similarly, in 2017, Campos et al immobilized cysteine molecules on OSTE surfaces with allyl excess by the click chemistry reaction [10] for further enzyme immobilization.…”