Interdigitated impedimetric-based Maackia amurensis lectin biosensor for prostate cancer biomarker.

Highly specific detection of tumor-associated biomarkers remains a challenge in the diagnosis of prostate cancer. In this research, Maackia amurensis (MAA) was used as a recognition element in the functionalization of an electrochemical impedance-spectroscopy biosensor without a label to identify cancer-associated aberrant glycosylation prostate-specific antigen (PSA). The lectin was immobilized on gold-interdigitated microelectrodes. Furthermore, the biosensor's impedance response was used to assess the establishment of a complex binding between MAA and PSA-containing glycans. With a small sample volume, the functionalized interdigitated impedimetric-based (IIB) biosensor exhibited high sensitivity, rapid response, and repeatability. PSA glycoprotein detection was performed by measuring electron transfer resistance values within a concentration range 0.01-100 ng/mL, with a detection limit of 3.574 pg/mL. In this study, the ability of MAA to preferentially recognize α2,3-linked sialic acid in serum PSA was proven, suggesting a potential platform for the development of lectin-based, miniaturized, and cost effective IIB biosensors for future disease detection.

Biological Effects and Applications of Bulk and Surface Acoustic Waves on In Vitro Cultured Mammal Cells: New Insights.

Medical imaging has relied on ultrasound (US) as an exploratory method for decades. Nonetheless, in cell biology, the numerous US applications are mainly in the research and development phase. In this review, we report the main effects on human or mammal cells of US induced by bulk or surface acoustic waves (SAW). At low frequencies, bulk US can lead to cell death. Under specific intensities and exposure times, however, cell proliferation and migration can be enhanced through cytoskeleton fluidization (a reorganization of the actin filaments and microtubules). Cavitation phenomena, frequencies of resonance close to those of the biological compounds, and mechanical transfers of energy from the acoustic pressure could explain those biological outcomes. At higher frequencies, no cavitation is observed. However, USs of high frequency stimulate ionic channels and increase cell permeability and transfection potency. Surface acoustic waves are increasingly exploited in microfluidics, especially for precise cell manipulations and cell sorting. With applications in diagnosis, infection, cancer treatment, or wound healing, US has remarkable potential. More mechanotransduction studies would be beneficial to understand the distinct roles of temperature rise, acoustic streaming and mechanical and electrical stimuli in the field.

Love Wave Sensor with High Penetration Depth for Potential Application in Cell Monitoring.

Love wave (L-SAW) sensors have been used to probe cell monolayers, but their application to detect changes beyond the focal adhesion points on cell monolayers, as viscosity changes on the cytoskeleton, has not been explored. In this work we present for the first time a Love wave sensor with tuned penetration depth and sensitivity to potentially detect mechanical changes beyond focal adhesion points of cell monolayers. We designed and fabricated a Love wave sensor operating at 30 MHz with sensitivity to detect viscous changes between 0.89 and 3.3 cP. The Love wave sensor was modeled using an acoustic transmission line model, whereas the response of interdigital transducers (IDTs) was modeled with the Campbell's cross-field circuit model. Our design uses a substrate with a high electromechanical coupling coefficient (LiNbO3 36Y-X), and an 8-µm polymeric guiding layer (SU-8). The design aims to overcome the high insertion losses of viscous liquid environments, and the loss of sensitivity due to the low frequency. The fabricated sensor was tested in a fluidic chamber glued directly to the SU-8 guiding layer. Our experiments with liquids of viscosity similar to those expected in cell monolayers showed a measurable sensor response. In addition, experimentation with SaOs-2 cells within a culture medium showed measurable responses. These results can be of interest for the development of novel cell-based biosensors, and novel characterization tools for cell monolayers.

Glycosylated biomarker sensors: advancements in prostate cancer diagnosis.

Prostate cancer is currently diagnosed using the conventional gold standard methods using prostate-specific antigen (PSA) as the selective biomarker. However, lack of precision in PSA screening has resulted in needless biopsies and delays the treatment of potentially fatal prostate cancer. Thus, identification of glycans as novel biomarkers for the early detection of prostate cancer has attracted considerable attention due to their reliable diagnostic platform compared with the current PSA systems. Therefore, biosensing technologies that provide point-of-care diagnostics have demonstrated the ability to detect various analytes, including glycosylated micro- and macro-molecules, thereby enabling versatile detection methodologies. This highlight article discusses recent advances in the biosensor-based detection of prostate cancer glycan biomarkers and the innovative strategies for the conjugation of nanomaterials adapted to biosensing platforms. Finally, the article is concluded with prospects and challenges of prostate cancer biosensors and recommendations to overcome the issues associated with prostate cancer diagnosis.

Biosensors to Diagnose Chagas Disease: A Brief Review.

Chagas disease (CD), which mostly affects those living in deprived areas, has become one of Latin America's main public health problems. Effective prevention of the disease requires early diagnosis, initiation of therapy, and regular blood monitoring of the infected individual. However, the majority of the Trypanosoma cruzi infections go undiagnosed because of mild symptoms, limited access to medical attention and to a high variability in the sensitivity and specificity of diagnostic tests. Consequently, more affordable and accessible detection technologies capable of providing early diagnosis and T. cruzi load measurements in settings where CD is most prevalent are needed to enable enhanced intervention strategies. This work analyzes the potential contribution of biosensing technologies, reviewing examples that have been tested and contrasted with traditional methods, both serological and parasitological (i.e., molecular detection by PCR), and discusses some emerging biosensing technologies that have been applied for this public health issue. Even if biosensing technologies still require further research efforts to develop portable systems, we arrive at the conclusion that biosensors could improve the accuracy of CD diagnosis and the follow-up of patients' treatments in terms of the rapidity of results, small sample volume, high integration, ease of use, real-time and low cost detection when compared with current conventional technologies.

Growth and toxic gas sensing properties of poly(urethaneimide) thin films.

In this work we present a study on the growth and the gas sensing properties of poly(urethane imide) thin films. We first deeply characterized by atomic force microscopy (AFM) the nanostructuration of the poly(urethane imide) holding different amine groups. We further studied the interaction between highly toxic gases such as hexamethyleneimine (HMI) and pyridine and the polymer by using an unconventional method based on Quartz Crystal Microbalance (QCM) measurement. We showed for the first time that weak interactions, i.e. hydrogen bonding between the gas molecules and the polymer film allow the diffusion of the gas molecule deep in the polymeric film and the recovery of the film once the gas molecules leave the sensor. This first work paves a new way for the design of a completely recoverable sensor able to detect highly toxic gases for environmental concern.

Surface Acoustic Wave Device with Reduced Insertion Loss by Electrospinning P(VDF-TrFE)/ZnO Nanocomposites.

Surface acoustic wave (SAW) devices have been utilized for the sensing of chemical and biological phenomena in microscale for the past few decades. In this study, SAW device was fabricated by electrospinning poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) incorporated with zinc oxide (ZnO) nanoparticles over the delay line area of the SAW device. The morphology, composition, and crystallinity of P(VDF-TrFE)/ZnO nanocomposites were investigated. After measurement of SAW frequency response, it was found that the insertion loss of the SAW devices incorporated with ZnO nanoparticles was much less than that of the neat polymer-deposited device. The fabricated device was expected to be used in acoustic biosensors to detect and quantify the cell proliferation in cell culture systems.

Rayleigh surface acoustic wave as an efficient heating system for biological reactions: investigation of microdroplet temperature uniformity.

When a microdroplet is put on the Rayleigh surface acoustic wave path, longitudinal waves are radiated into the liquid and induce several phenomena such as the wellknown surface acoustic wave streaming. At the same time, the temperature of the microdroplet increases as it has been shown. In this paper, we study the temperature uniformity of a microdroplet heated by Rayleigh surface acoustic wave for discrete microfluidic applications such as biological reactions. To precisely ascertain the temperature uniformity and not interfere with the biological reaction, we used an infrared camera. We then tested the temperature uniformity as a function of three parameters: the microdroplet volume, the Rayleigh surface acoustic wave frequency, and the continuous applied radio frequency power. Based on these results, we propose a new device structure to develop a future lab on a chip based on reaction temperatures.

AlN/ZnO/diamond waveguiding layer acoustic wave structure: theoretical and experimental results.

We present a theoretical calculation and experimental results for a waveguiding layer acoustic wave (WLAW). The experimental device is modeled by the finite element method (FEM) for the AlN/ZnO/diamond structure. It was found that the AlN thickness must be at least larger than 3lambda/2 to obtain negligible surface displacement. In the same way, the ZnO thickness for a fixed value of AlN thickness at 2lambda must be larger than lambda/4 to confine the acoustic wave. The electromechanical coupling of the wave presents an optimum around lambda/2 for the ZnO layer thickness. A first experimental AlN/ZnO/diamond device has been developed and shows the WLAW at 412 MHz.

Wide vacuum pressure range monitoring by Pirani SAW sensor.

A new kind of surface acoustic wave (SAW) sensor has been developed to measure sub-atmospheric pressure below 100 mtorr with accuracy better than 0.1 mtorr. It provides an efficient measuring solution in the pressure range inaccessible in past by conventional diaphragm-based SAW sensors. Indeed, because of the small bending force in lower pressure and limited sensitivity, diaphragm-based SAW sensors are only suited to monitor relatively high pressure with a precision hardly better than 0.5 torr. To reach precision level better than 1 mtorr at sub-atmospheric pressure for vacuum technology applications, a radically different SAW-based solution is necessary. Our device aims to measure sub-atmospheric pressure less than 100 mtorr with a threshold resolution better than 0.1 mtorr. The concept is similar to the one used by Pirani pressure gauges. However, it is claimed that a heated and suspended SAW device should have better sensitivity. A theoretical model based on the basic concepts of gas kinetic theory and thermodynamics is presented. The validity of the model is checked by comparison between theoretical and experimental results.

GHz frequency ZnO/Si SAW device.

The demand for high-frequency low-loss filters generates intensive research on innovative wave guide solutions. In this work, a GHz SAW device based on a ZnO/Si structure was fabricated using classical UV photolithography. The thickness of the piezoelectric thin film was optimized and a specific interdigital transducer structure was used to generate third and fifth harmonic guided waves at 2.5 GHz and 3.5 GHz, respectively, with an aluminum strip larger than 1 micrometer. Different modes have been measured and theoretically identified thanks to an advanced finite-element/boundary-elementbased model. Good agreement is found between theory and experiments. The high-frequency modes have been fully characterized, allowing for accurate design of SAW devices exploiting such modes.

Sezawa mode SAW pressure sensors based on ZnO/Si structure.

Surface acoustic wave (SAW) devices have been shown to be suitable for many sensor applications. One of these applications is pressure sensor. In this study we investigate the performance of SAW pressure sensors formed with ZnO/Si(001) structure. The pressure sensitivities of Rayleigh mode as well as the Sezawa mode are studied as a function of normalized thickness (kh = 2pihZnO/lambda). The experimental results show an opposite strain effect in the ZnO layer and Si substrate. A theoretical approach based on the perturbation method has been developed for the evaluation of pressure sensitivity in the Sezawa mode. Experimental and theoretical results obtained for the ZnO/Si SAW sensor prepared with kh = 1.18 are in good agreement. For kh < or = 1.2, the ZnO contribution to the sensor sensitivity can be neglected in the Sezawa mode in which ZnO acts mainly as an electromechanical conversion layer.