Piezoelectric biosensors assisted with electroacoustic impedance spectroscopy: a tool for accurate quantitative molecular recognition analysis

Abstract

In this work, electroacoustic impedance analysis based on a modified Butterworth-Van Dyke (BVD) model is used to complement resonance frequency measurements of piezoelectric crystal sensors for the identification and removal of interfering signals. This approach enables the accurate use of the Sauerbrey correlation to establish a direct relationship between mass deposited at the sensor surface and measured frequency variations. Kinetic models can thus be evaluated and binding constants estimated directly from the measured data. We further demonstrate the usefulness of this approach by applying it to the study of the formation of 11-hydroxy-1-undecanothiol self-assembled monolayers (SAM) as well as to the binding of streptavidin to immobilized biotin. Kinetic and equilibrium parameters were estimated from transient analysis, adsorption isotherms, Scatchard and Hill plots obtained from the frequency data for both the alkanethiol and streptavidin films. This strategy based on electroacoustic impedance assisted quartz-crystal microbalance (QCM) biosensors is expected to be a major contribution for the use of these piezoelectric devices as a reliable and cheap detection system that can easily be integrated into analytical techniques.

Kinetic characterization of the retinoic X receptor binding to specific and unspecific DNA oligoduplexes with a quartz crystal microbalance

“…It is known that, due to stereochemical effects and negative cooperativity, streptavidin cannot interact with more than 2 to 3 of its 4 biotin binding sites. 32 Thus, the 1 : 2.5 ratio obtained from the mass estimations with Df Bmin is actually very close to what was expected considering a full monolayer of DR1 over a streptavidin lm. 32…”

“…32 Thus, the 1 : 2.5 ratio obtained from the mass estimations with Df Bmin is actually very close to what was expected considering a full monolayer of DR1 over a streptavidin lm. 32…”

“…The total frequency variation (Df Bmin ) during streptavidin immobilization was 75 Hz, which from the Sauerbrey equation is translated to a streptavidin surface density of 6.5 pmol cm À2 , which is a value very close to previously published data. 32 When immobilizing DNA over the streptavidin layer, different values of Df s and Fig. 1 Frequency variations (Df s and Df Bmin ), resistance variation (DR) and capacitance variation (DC 0 ) were monitored with (A) and without (B) changes in buffer ionic strength and viscosity.…”

“…Custom-made soware for real-time data acquisition from a Network/Impedance/Spectrum Analyzer 4395A (Agilent Technologies) was used to monitor changes in the conductance, G, and susceptance, B, spectra with a 50 kHz frequency span around the QCM resonance as described elsewhere. 31,32 The immobilized DNA oligoduplexes were challenged with different RXRaDBD concentrations (0.05 to 2 mM), using HEPEST (10 mM HEPES, 0.005% Tween-20, pH 8.0) containing 100, 150 or 250 mM NaCl as the carrier buffer. The ow was maintained at 100 ml min À1 and RXRaDBD solutions were applied for 10 min.…”

Transmission line model analysis of transcription factors binding to oligoduplexes – differentiation of the effect of single nucleotide modifications

“…9,10 Among these, biosensors based on the QCM and SPR technologies have become very popular mostly due to the suitability for detection in real time without the need for any labeling procedure. In particular, QCM can be used both to study binding kinetics to quantify association and dissociation constants [11][12][13] also to characterize and detect alterations of the mechanical properties of the immobilized biomolecules. 10,14 We have established a novel QCM bioanalytical method based on the transmission line model (TLM) to analyze the binding of TFs to immobilized DNA oligoduplexes.…”