High sensitive mesoporous TiO2-coated love wave device for heavy metal detection

Abstract

This work deals with the design of a highly sensitive whole cell-based biosensor for heavy metal detection in liquid medium. The biosensor is constituted of a Love wave sensor coated with a polyelectrolyte multilayer (PEM). Escherichia coli bacteria are used as bioreceptors as their viscoelastic properties are influenced by toxic heavy metals. The acoustic sensor is constituted of a quartz substrate with interdigitated transducers and a SiO2 guiding layer. However, SiO2 shows some degradation when used in a saline medium. Mesoporous TiO2 presents good mechanical and chemical stability and offers a high active surface area. Then, the addition of a thin titania layer dip-coated onto the acoustic path of the sensor is proposed to overcome the silica degradation and to improve the mass effect sensitivity of the acoustic device. PEM and bacteria deposition, and heavy metal influence, are real time monitored through the resonance frequency variations of the acoustic device. The first polyelectrolyte layer is inserted through the titania mesoporosity, favouring rigid link of the PEM on the sensor and improving the device sensitivity. Also, the mesoporosity of surface increases the specific surface area which can be occupied and favors the formation of homogeneous PEM. It was found a frequency shift near -20±1 kHz for bacteria immobilization with titania film instead of -7±3 kHz with bare silica surface. The sensitivity is highlighted towards cadmium detection. Moreover, in this paper, particular attention is given to the immobilization of bacteria and to biosensor lifetime. Atomic Force Microscopy characterizations of the biosurface have been done for several weeks. They showed significant morphological differences depending on the bacterial life time. We noticed that the lifetime of the biosensor is longer in the case of using a mesoporous TiO2 layer.

Morphological and nanostructural surface changes in Escherichia coli over time, monitored by atomic force microscopy

“…PEM are used to keep E. coli bacteria immobilized on the substrate [15,22] over time and to get a stable biofilm. Evolution of the shape, surface morphology and size of bacteria are investigated by AFM over a month.…”

Ultrasensitive Leaky Surface Acoustic Wave Immunosensor for Real-Time Detection of Alpha-Fetoprotein in Biological Fluids

“…SAW sensors have numerous advantages, including simple operation, low cost, rapid response, high sensitivity, and real-time detection capabilities [9]. These features grant SAW sensors advantages in detecting a large variety of analytes, such as biological warfare agents, small molecules, heavy metals, uric acid, and cancer cells [10][11][12][13][14].…”

Study on Fabrication of ZnO Waveguide Layer for Love Wave Humidity Sensor Based on Magnetron Sputtering

“…The Love wave humidity sensor requires that the shear velocities and densities of the waveguide layer materials are smaller than those of the piezoelectric substrate materials, and the waveguide layer materials were required to have good elastic properties and weak acoustic wave absorption performance [ 11 , 12 , 13 ]. At present, some materials can be used as a waveguide layer of the Love wave device, such as polyimide (PI), poly methyl methacrylate (PMMA), silicon dioxide (SiO 2 ) and zinc oxide (ZnO) [ 14 , 15 , 16 , 17 ].…”