Acoustic detection of cell adhesion to a coated quartz crystal microbalance - implications for studying the biocompatibility of polymers.

Biocompatibility of polymers is an important parameter for the successful application of polymers in tissue engineering. In this work, quartz crystal microbalance (QCM) devices were used to follow the adhesion of NIH 3T3 fibroblasts to QCM surfaces modified with fibronectin (FN) and poly-D-lysine (PDL). The variations in sensor resonant frequency (Δf) and motional resistance (ΔR), monitored as the sensor signal, revealed that cell adhesion was favored in the PDL-coated QCMs. Fluorescence microscopy images of seeded cells showed more highly spread cells on the PDL substrate, which is consistent with the results of the QCM signals. The sensor signal was shown to be sensitive to extracellular matrix (ECM)-binding motifs. Ethylenediaminetetraacetic acid (EDTA) and soluble Gly-Arg-Gly-Asp-Ser (GRGDS) peptides were used to interfere with cell-ECM binding motifs onto FN-coated QCMs. The acquired acoustic signals successfully showed that in the presence of 30 mM EDTA or 1 mM GRGDS, cell adhesion is almost completely abolished due to the inhibition/blocking of integrin function by these compounds. The results presented here demonstrate the potential of the QCM sensor to study cell adhesion, to monitor the biocompatibility of polymers and materials, and to assess the effect of adhesion modulators. QCM sensors have great potential in tissue engineering applications, as QCM sensors are able to analyze the biocompatibility of surfaces and it has the added advantage of being able to evaluate, in situ and in real time, the effect of specific drugs/treatments on cells.

Acoustic detection of cell adhesion on a quartz crystal microbalance.

An acoustic quartz crystal microbalance (QCM) was used to signal and follow the cell­adhesion process of epithelial cells [human embryonic kidney(HEK) 293T and cervical cancer (HeLa) and fibroblasts [African Green Monkey kidney cells (COS-7)] onto gold surfaces. Cells were applied on the sensor and grown under serum-free and serum-supplemented culture media. The sensor resonance frequency (Δf) and motional resistance (ΔR) variations were measured during cell growth to monitor cell adhesion processes. Fingerprints of the adhesion processes, generated using the QCM signal, were found to be specific for each cell type while enabling the identification of the phases of the adhesion process. Under serum-free conditions, the deposition of HEK 293T and HeLa cells was characterized by a decrease of Δf with constant ΔR, whereas for COS­7 cells, this initial deposition was signaled by variations of ΔR at constant Δf. Toward the end of the adhesion process, fingerprints were characterized by a continuous increase of ΔR consistent with the increase in viscoelasticity. The morphology of adherent cells was visualized by fluorescent microscopy, enabling the association of the cell morphology with QCM signals.

Acoustic wave biosensors: physical models and biological applications of quartz crystal microbalance.

Piezoelectric sensors are acoustic sensors that enable the selective and label-free detection of biological events in real time. These sensors generate acoustic waves and utilize measurements of the variation of the wave propagation properties as a signal for probing events at the sensor surface. Quartz crystal microbalance (QCM) devices, the most widespread acoustic resonators, allow the study of viscoelastic properties of matter, the adsorption of molecules, or the motility of living cells. In a tutorial-like approach, this review addresses the physical principles associated with the QCM, as well as the origin and effects of major interfering phenomena. Special attention is paid to the possibilities offered by QCM that go beyond microweighing, and important recent examples are presented.