Rheological and interfacial properties of nucleic acid films studied by thickness – shear mode sensor and network analysis

Abstract

Rheological and interfacial properties of nucleic acid films studied by thickness -shear mode sensor and network analysisAbstract: Complete characterization of the thickness -shear mode (TSM) acoustic wave sensor coated with films of nucleic acid and subjected to conductive solution loading is achieved through network analysis of impedance measurements. The responses of coated sensors with respect to series resonant frequency can be separated into two regions. When 0 < u < 0.5 R-I m-' the frequencies for sensors with films of single strand (ss) DNA or polycytidylic (5') (Poly C) in place rise significantly with increasing conductivity. The motional resistances for sensors coated with both species peak at the same value of conductivity where the frequency has the most rapid shift. In the second region (0.5 < u < 12 R-' m-I), the frequency response for the ss DNA system exhibits a bell-shaped curve, with a minimum at u = 4 0-' m-l. The motional resistances for both nucleic acid layers show reversible behaviour, whereas TSM sensors with bare PdO and Au electrodes yield little change. Models that consider only the bulk properties of solutions fail to explain the observed changes in frequency. On the other hand, an equivalent circuit model incorporating the rheological properties of nucleic acid layers on the sensor surface is successful in explaining the various responses.Key words: DNA sensor, network analysis, thickness -shear mode sensor, DNA interfacial properties, RCsumC : Faisant appel i une analyse de rCseau des mesures d3impCdance, on a rkalisC une caracthrisation complkte de senseurs enduits de films d'acide nuclkique, opCrant en mode de cisaillement de I'Cpaisseur et soumis h un chargement de solution conductrice. Les rkponses des senseurs enduits par rapport h la frkquence de rCsonance en sCrie ont pu &tre sCparCe en deux rkgions. Lorsque 0 < a < 0,5 m-I, les frequences des senseurs avec des films d'ADN i simples brins (sb) ou polycytidyliques (5') (Poly C) en place augmentent beaucoup avec une augmentation de la conductivitC. Les rCsistances au mouvement des senseurs enduits avec les deux espkces atteignent un sommet pour la m&me valeur de la conductivitk alors que la frCquence prCsente le dkplacement le plus rapide. Dans la deuxikme region (0,5 < u < 12 m-I), la frkquence de rCponse du systkme ADN sb prCsente une courbe en forme de cloche avec un minimum i u = 4 R-I m-I. Les rCsistances au mouvement pour les deux couches d'acides nuclCiques prksentent dans les deux cas un comportement reversible alors que le senseur MCE avec des Clectrodes de PdO ou de Au nues ne prCsentent pratiquement pas de changements. Les modkles qui ne considkrent que les propriCtCs globales des solutions n'arrivent pas h expliquer les changements observCs dans les frkquences. Par ailleurs, un modkle par circuit Cquivalent incorporant les propriCtCs rhCologiques des couches d'acide nuclCique sur la surface du senseur permet d'expliquer les diverses rkponses.

Protein adsorption on surfaces: dynamic contact-angle (DCA) and quartz-crystal microbalance (QCM) measurements

“…The assumption of viscoelasticity variations due to conformational changes near a surface is often applied to explain the resonant behavior of a biomacromolecule-loaded QCM [24,25] including molecule swelling or shrinking because of absent or present charge screening in low or high ionic-strength electrolytes, respectively, and water migration into the porous biofilm structure. For the experimental data in this work, an unique attribution to one of the mentioned mechanisms cannot be given at the moment.…”

Acoustic waves and the study of biochemical macromolecules and cells at the sensor–liquid interface

“…In several earlier studies, the hybridization of nucleic acids adsorbed on PdO sputtered on gold TSM electrodes was investigated. [112][113][114][115][116][117] Applying radiochemical labelling with 32 P, the authors showed that the added mass resulting from the formation of a DNA hybridization complex corresponded to a considerably larger change of frequency than that predicted by Sauerbrey's equation. 113 The observation of an enhanced frequency response was interpreted in terms of the perturbation of acoustic energy transmission by changes in interfacial properties upon hybridization.…”

Biosensors Based on Acoustic Wave Devices

“…The change in the resonant frequency of the TSM sensor was 18 times that predicted based on mass increase alone. The additional response is ascribed to changes in interfacial viscosity and conductivity [105]. Hybridization of RNA homopolymers has also been studied with the TSM sensor [106].…”