Pocketable Biosensor Based on Quartz-Crystal Microbalance and Its Application to DNA Detection

Abstract

Quartz-crystal microbalance (QCM) is a technique that can measure nanogram-order masses. When a receptor is immobilized on the sensor surface of a QCM device, the device can detect chemical molecules captured by the mass change. Although QCM devices have been applied to biosensors that detect biomolecules without labels for biomolecular interaction analysis, most highly sensitive QCM devices are benchtop devices. We considered the fabrication of an IC card-sized QCM device that is both portable and battery-powered. Its miniaturization was achieved by repurposing electronic components and film batteries from smartphones and wearable devices. To demonstrate the applicability of the card-sized QCM device as a biosensor, DNA-detection experiments were performed. The card-sized QCM device could detect specific 10-mer DNA chains while discerning single-base differences with a sensitivity similar to that of a conventional benchtop device. The card-sized QCM device can be used in laboratories and in various other fields as a mass sensor.

Keywords: DNA hybridization; IC card size; biosensor; quartz-crystal microbalance; single-base mismatch detection.

Figure 1

Schematic illustrations of (a) a previously fabricated 27 MHz QCM device designed to achieve a low noise level [14] and (b) a pocketable 27 MHz QCM device designed to prioritize portability.

Figure 2

Schematic illustrations of (a) the circuit board of the card-sized QCM device and (b) the sensor chip with a quartz-crystal oscillator combined with a semiflow cell.

Figure 3

Photos of the card-sized QCM device; (a) the circuit board, (b) the overall view of the connected semiflow cell, and (c) the enlarged semiflow cell.

Figure 4

Frequency plots of a 27 MHz quartz oscillator on the sensor chip over time as measured by the card-sized frequency counter using (a) a direct method and (b) a reciprocal method.

Figure 5

(a) Illustration of the water injection experiment on the card-sized QCM device and (b) frequency change in response to the injection of ultrapure water at 21 °C.

Figure 6

(a) Schematic illustration of DNA immobilization process on the QCM sensor surface. Time courses of a frequency change (∆F), responding to bindings of (b) NeutrAvidin to the activated carbonic acids and (c) biotinylated DNA (10-mer) to the NeutrAvidin on the QCM sensor surface in each buffer solution: 10 mM HEPES-NaOH (pH 7.9), 0.2 M NaCl for the NeutrAvidin binding and 10 mM Tris-HCl (pH 8.0), 1 mM EDTA, 0.15 M NaCl for biotinylated DNA binding at 21 °C.

Figure 7

(a) DNA sequences used in this experiment; (b) time courses of frequency changes (∆F), responding to the injection of (1) Target-DNA, (2) Mismatch-DNA, and (3) the buffer solutions onto the semiflow cell of the card-sized QCM in the experimental condition: 10mM Tris-HCl (pH 8.0), 1 mM EDTA, 0.15 M NaCl at 21 °C.