Aptamer entrapment in microfluidic channel using one‐step sol‐gel process, in view of the integration of a new selective extraction phase for lab‐on‐a‐chip

Abstract

There is a great demand for integrating sample treatment into μTASs. In this context, we developed a new sol-gel phase for extraction of trace compounds in complex matrices. For this purpose, the incorporation of aptamers in silica-based gel within PDMS/glass microfluidic channels was performed for the first time by a one-step sol-gel process. The effective gel attachment onto microchannel walls and aptamer incorporation in the polymerized gel were evaluated using fluorescence microscopy. A good gel stability and aptamer incorporation inside the microchannel was demonstrated upon rinsing and over storage time. The ability of gel-encapsulated aptamers to interact with its specific target (either sulforhodamine B as model fluorescent target, or diclofenac, a pain killer drug) was assessed too. The binding capacity of entrapped aptamers was quantified (in the micromolar range) and the selectivity of the interaction was evidenced. Preservation of aptamers binding affinity to target molecules was therefore demonstrated. Dissociation constant of the aptamer-target complex and interaction selectivity were evaluated similar to those in bulk solution. This opens the way to new selective on-chip SPE techniques for sample pretreatment.

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

“…However, when AuNPs are grafted with aptamers, fluorescence imaging (Figure 9b,d) allows to evidence the interaction with the fluorescent target, even after the rinsing step. This aptamer/target interaction leads to higher and more homogeneous coverage of the functionalized zone by the target at ISx = 50 mM than at ISx = 300 mM, in accordance with previously reported studies [29]. Thanks to a calibration curve plotted for C SB ranging from 0 to 3.3 × 10 −9 M (I = 1 × 10 10 [SB]+37.357, r 2 = 0.9955), the concentration of sulforhodamine B at ISx = 50 mM present at the surface after rinsing is estimated to 1.9 ± 0.1 × 10 −9 M and corresponds to the concentration of the aptamer-sulforhodamine B complex formed.…”

“…The affinity test was performed in open-microchannel functionalized with an aptamer as described in Section 2.5. All experiments were done with non-fluorescent thiolated aptamers (bearing no fluorescent tag at the 5 -end) so as to only measure the signal contribution of the fluorescent target sulforhodamine B [29]. The open-microchannel was immersed for one night in a 14.5 µM sulforhodamine B (fluorescent target) solution prepared in a sodium phosphate buffer (pH 8 at various ISx (x = 50 or 300 mM) + 5 mM MgCl 2 ).…”

“…3 mm. For this study, non-fluorescent thiolated aptamers were used for the functionalization to allow measuring only the signal contribution of the fluorescent target sulforhodamine B [29]. The open-microchannel was then immersed one night in a solution containing sulforhodamine B at 14.5 µM.…”

“…For example, the high affinity between thiol and gold was used to cover a thiol-substituted monolithic oligosorbent with gold nanoparticles and then immobilize thiol-terminated aptamers on the top of it [28]. Sol-gel monoliths also proved to retain aptamers without any modification or covalent grafting of the polymeric structure, while preserving their activity towards their target [29].…”

On-line Aptamer Affinity Solid-Phase Extraction Capillary Electrophoresis-Mass Spectrometry for the Analysis of Blood α-Synuclein

“…The use of aptamer affinity (AA) sorbents has been previously described for offline solid phase microextraction (SPME) 23 , on-chip SPE 24 , and on-line SPE-nanoLC 22 .…”