QCM Response to Solvated, Tethered Macromolecules

Abstract

When the quartz crystal microbalance (QCM) is operated in contact with solution and used to detect inertia increases caused by macromolecules binding to its surface, resonance frequency shifts are reported in the literature to be greater than, less than, and the same as an identical macromolecular mass would cause as a dry layer. A previous report of wet and dry M13 DNA giving the same, linear frequency versus mass response is examined. The M13 data are shown to follow the reciprocal of the square root of mass, not the reported linear relationship. New experiments on RNA duplexes oscillated in solution are reported. A lossy polymer layer is placed between the QCM and RNA. When changes in density, viscosity, and included water are eliminated, the response remains linear for a constant adlayer thickness. The expectation that response per unit mass should decrease with distance from the QCM surface is demonstrated. Total decoupling of mass lying beyond the acoustic overlayer is also demonstrated. The present results are placed in context with recently published results from a study of progressively thicker protein layers bound to the QCM.

Quartz Crystal Microbalance for Bioanalytical Applications

“…A desirable, user-demanded detection limit is ca. 10 -18 M, depending on the number of base pairs [51]. In order to minimize the detection limit of a functionalized resonator surface, quartz crystals with higher resonance frequencies were used, and multilayers composed of nucleic acids and polymers/proteins were developed [46].…”

“…Steric hindrance of the hybridization reaction explains this low value; however, the equivalence of mass change and frequency in the detection of nucleic acids in solution is questionable. Although the translation of the frequency shift into mass using the Sauerbrey equation is pursued in many publications, one should refer to papers by Thompson and co-workers [50,[57][58][59] and Fawcett et al [51], who showed that oligonucleotides immobilized on the resonator surface in fluids do not behave like an ideal rigid mass. Thompson and co-workers revealed, for example, that the serial resonance upon binding of DNA exhibits a frequency change that is 18 times larger than predicted by the Sauerbrey equation.…”

Label-free, electrochemical detection of methicillin-resistant staphylococcus aureus DNA with reduced graphene oxide-modified electrodes

“…doi:10.1016/j.bios.2011.03.002 advantages such as simplicity, no requirement for labeling of the analytes (Pan and Rothberg, 2005), higher sensitivity as compared with other type of DNA biosensors based on the surface plasmon resonance (SPR) or quartz crystal microbalance (QCM) techniques . SPR is one kind of optical methods based on the measurement of changes in the refractive index due to the mass adsorption on the sensor chip surface (Kobori et al, 2004 QCM measures the change in frequency of a vibrating crystal due to the binding of molecules to the crystal (Fawcett et al, 1998). The detection limits of SPR and QCM are ∼10 −9 ) and 10 −10 M (Feng et al, 2007), respectively.…”

Mikrogravimetrische Sensoren in der Bioanalytik – eine Alternative zu optischen Biosensoren?

“…Die erste In-situ-Messung in Lösung erfolgte mit einem akustischen Plattenschwinger [44] und die zweite mit einem Dickenscherschwinger, an den eine Einzelstrang-DNA über eine selbstorganisierte 11-Sulfanylundecanolschicht an die Goldoberfläche gebunden war. Die angestrebte und von Anwendern geforderte untere Nachweisgrenze liegt je nach Zahl der Basenpaare bei etwa 10 À18 m. [68] Um die Nachweisgrenze der funktionalisierten Resonatoroberflächen zu erniedrigen, wurden Quarze mit höherer Resonanzfrequenz verwendet, Mehrschichtsysteme aus Nucleinsäuren und Polymeren/Proteinen entwickelt, [63] DNA-Dendrimere synthetisiert [69] und die Nucleinsäuren durch Polymerasekettenreaktion (PCR) an der Oberfläche amplifiziert. Die gängigen Verfahren beruhen auf der Modifizierung der Phosphatgruppe des 5'-Endes durch Einführung von Schwefelgruppen.…”