Lateral field excited film bulk acoustic resonator for detection of protein–ligand interactions

Abstract

Presented is a lateral field excited film bulk acoustic resonator for realtime sensing of protein -ligand interaction using the biotin -streptavidin system as a model. The film bulk acoustic resonator works at 2 GHz in shear mode. For biosensing, the biotin was immobilised on one face of the resonator as the probe. The resonant frequency of the biotin-immobilised device drops rapidly at first and gradually reaches equilibrium when exposed to the streptavidin solutin due to the biotin -streptavidin interaction. Consequently, the lateral field excited film bulk acoustic resonator can be used to study the kinetics of protein -ligand interaction without the use of labelling or molecular tags. The proposed device shows promising applications for disease diagnostics, prognosis, and drug discovery.Introduction: In the field of biotechnology and pharmaceutics, one of the critical parts is understanding the kinetics of protein-ligand interactions. Traditional studies for protein -ligand interactions require chemical, fluorescent or radioactive labelling, which usually compromise the protein activity and do not give real-time interaction information. Therefore, label-free biosensors have received much attention because they can directly measure biomolecular interactions in realtime and in situ.Over the past ten years, the commercial success of film bulk acoustic resonators (FBARs) in radio frequency communication has motivated researchers to explore their applications for label-free and high sensitive biochemical sensing [1,2]. FBARs make use of standard IC fabrication technology, thereby realising the ability to inexpensively combine a number of sensors on a chip and integrate them with the analytical circuits. The applications of FBARs for real-time biochemical detection require their operation in shear mode due to the minimal damping in the liquid-solid interface. Some investigations demonstrated quasishear mode FBARs based on inclined c-axis oriented ZnO or AlN piezoelectric films coupled with the electrodes which are situated on opposite sides of the films [3,4]. An apparent deficiency of the quasi-shear resonator is the existence of an amount of longitudinal component in the wave polarisation, which inevitably leads to acoustic energy leakage into the liquid. To alleviate this problem, the lateral electric field is employed to excite pure shear mode in ZnO or AlN films [5].In this reported work, we fabricated a lateral field excited FBAR and used it for real-time sensing of protein-ligand interaction. For a demonstrational study, the biotin -streptavidin system was chosen as a model since such a system has been well characterised. High binding affinity and stability makes the biotin -streptavidin system very useful in many biotechnological applications such as in affinity separation, in diagnostics, for molecular tagging, for imaging application, biomolecular delivery, and in the characterisation of surface bound biomolecular species.

Active area optimisation of film bulk acoustic resonator for improving performance parameters

“…In actual FBAR devices, owing to the discontinuous edges and boundaries, these excited spurious modes are able to induce new lateral modes. These transverse modes cause aggravating and unwanted ripples in the pass band of the filter and they also can diminish the quality factor because of energy conversion to these spurious modes [1–3 ].…”

Shear Mode Bulk Acoustic Resonator Based on Inclined c-Axis AlN Film for Monitoring of Human Hemostatic Parameters

“…Usually, the piezoelectric thin films are deposited with normal-plane c -axis crystal orientation and sandwiched between two electrodes, which makes FBAR operate in thickness longitudinal mode (TLM) [ 21 , 22 , 23 ]. However, when these devices work in viscous liquids such as blood, tissue fluids and biocolloids, the longitudinal wave is radiated into the liquid through compressional motion, resulting in a serious damping [ 24 , 25 , 26 ]. Conversely, the thickness shear mode (TSM) wave does not compress and hardly propagates in liquids [ 27 , 28 ].…”

A film bulk acoustic resonator pressure sensor based on lateral field excitation

“…4 The use of FBAR in sensing applications is attractive because the high resonance frequency leads to the excellent sensitivity. 5–7 In addition, FBAR sensors are also popular for many advantages, such as small size, small base mass, and IC compatibility, which make it possible to be integrated on a chip. 8–13 In recent years, the FBAR sensor has become a new research direction for FBAR technology.…”