Sensor Based on Aptamer Folding to Detect Low-Molecular Weight Analytes

Abstract

Aptamers have emerged as promising biorecognition elements in the development of biosensors. The present work focuses on the application of quartz crystal microbalance with dissipation monitoring (QCM-D) for the enantioselective detection of a low molecular weight target molecule (less than 200 Da) by aptamer-based sensors. While QCM-D is a powerful technique for label-free, real-time characterization and quantification of molecular interactions at interfaces, the detection of small molecules interacting with immobilized receptors still remains a challenge. In the present study, we take advantage of the aptamer conformational changes upon the target binding that induces displacement of water acoustically coupled to the sensing layer. As a consequence, this phenomenon leads to a significant enhancement of the detection signal. The methodology is exemplified with the enantioselective recognition of a low molecular weight model compound, L-tyrosinamide (L-Tym). QCM-D monitoring of L-Tym interaction with the aptamer monolayer leads to an appreciable signal that can be further exploited for analytical purposes or thermodynamics studies. Furthermore, in situ combination of QCM-D with spectroscopic ellipsometry unambiguously demonstrates that the conformational change induces a nanometric decrease of the aptamer monolayer thickness. Since QCM-D is sensitive to the whole mass of the sensing layer including water that is acoustically coupled, a decrease in thickness of the highly hydrated aptamer layer induces a sizable release of water that can be easily detected by QCM-D.

Controlling Multivalent Binding through Surface Chemistry: Model Study on Streptavidin

“…Consistent with this trend, we had previously reported an even lower residual valency of Γ b /Γ rSAv = 1.51 on b20%-SAMs (using different biotinylated probe and buffer). 8 …”

Tuning the Interfacial Chemistry of Redox‐Active Polymer for Bifunctional Probing

“…The sensing architecture consists of a polyaniline (PANI) conducting polymer probe (with and without a cation selective upper layer) in combination with a non‐polarizable interface such as Ag/AgCl (3 M KCl) housed in double junction Luggin capillary. The scanning electron micrographs – of as‐deposited PANI (see experimental section) show a near granular morphology, Figure S1a (Supporting Information) and the energy dispersive spectroscopy (EDS), Figure S1b (Supporting Information), shows the presence of chloride dopant along with carbon and nitrogen indicating as‐synthesized PANI is in the conducting form . The cyclic voltammogram of PANI without a cation selective upper layer in protic acids (for example in HClO 4 ), Figure a, shows mainly two pairs of redox peaks corresponding to the redox trans formation of lucoemeraldine (EB) to emeraldine (ES) and ES to pernigraniline (PG) during the positive going scan and their reversal during the negative going scan .…”

“…The scanning electron micrographs -of as-deposited PANI (see experimental section) show a near granular morphology, Figure S1a (Supporting Information) and the energy dispersive spectroscopy (EDS), Figure S1b (Supporting Information), shows the presence of chloride dopant along with carbon and nitrogen indicating as-synthesized PANI is in the conducting form. [5][6][7][8][9][10][11][12][13][14][15][16][17] The cyclic voltammogram of PANI without a cation selective upper layer in protic acids (for example in HClO 4 ), Figure 1a, shows mainly two pairs of redox peaks corresponding to the redox trans formation of lucoemeraldine (EB) to emeraldine (ES) and ES to pernigraniline (PG) during the positive going scan and their reversal during the negative going scan. [18][19][20] A minor peak pair observed in the mid potential region is attributed to defects in the polymeric backbone by many researchers.…”

“…pH meter has got an inevitable position cutting across various scientific disciplines and is an important device in clinical diagnostics, environmental and industrial analysis . State of the art pH meters work mainly based on the membrane potential developing across the thin glass membrane and is referenced vs. a proper non‐polarizable interface . The heart of the state of art pH meter, the delicate glass membrane respond in a Nernstian way to changes in H + ion concentration by exchanging the cations present in its silicate functionalities and are prone to alkaline error at pH>10 …”

“…[1][2][3] State of the art pH meters work mainly based on the membrane potential developing across the thin glass membrane and is referenced vs. a proper non-polarizable interface. [4][5][6] The heart of the state of art pH meter, the delicate glass membrane respond in a Nernstian way to changes in H + ion concentration by exchanging the cations present in its silicate functionalities and are prone to alkaline error at pH > 10. [7,8] The response of the state of the art pH meter is generally independent of the nature of the anion and hence it is an ideal candidate for pH measurement.…”