Microcantilever-based Biosensor Research Articles

Development of a microcantilever-based biosensor for detecting Programmed Death Ligand 1

The ongoing global concern of cancer worldwide necessitates the development of advanced diagnostic and therapeutic strategies. The majority of recent detection strategies involve the employment of biomarkers. A critical biomarker for cancer immunotherapy efficacy and patient prognosis is Programmed Death Ligand 1 (PD-L1), which is a key immune checkpoint protein. PD-L1 can be particularly linked to cancer progression and therapy response. Current detection methods, such as enzyme-linked immunosorbent assay (ELISA), face limitations like high cost, time consumption, and complexity. This study introduces a microcantilever-based biosensor designed for the detection of soluble PD-L1 (sPD-L1), which has a specific association with PD-L1. The biosensor utilizes anti-PD-L1 as the sensing layer, capitalizing on the specific binding affinity between anti-PD-L1 and sPD-L1. The presence of the sensing layer was confirmed through Atomic Force Microscopy (AFM) and contact angle measurements. Binding between sPD-L1 and anti-PD-L1 induces a shift in the microcantilever's resonance frequency, which is proportional to the PD-L1 concentration. Notably, the resonance frequency shift demonstrates a robust linear relationship with the increasing biomarker concentration, ranging from 0.05 ng/ml to 500 ng/ml. The detection limit of the biosensor was determined to be approximately 10 pg/ml. The biosensor demonstrates excellent performance in detecting PD-L1 with high specificity even in complex biological matrices. This innovative approach not only provides a promising tool for early cancer diagnosis but also holds potential for monitoring immunotherapy efficacy, paving the way for personalized and effective cancer treatments.

Microelectromechanical system‐based biosensor for label‐free detection of human cytomegalovirus

The human cytomegalovirus (HCMV) is an asymptomatic common virus that is typically harmless, but in some cases, it can be life threatening. Thus, there is an urgent need to develop novel diagnostic methods and strengthen the efforts to combat this virus. A microcantilever-based biosensor functionalised with the UL83-antibody of HCMV (UL83-HCMV antibody) has been developed to detect the UL83-antigen of HCMV (UL83-HCMV antigen) at different concentrations ranging from 0.3 to 300ng/ml. The response of the biosensor to the presence of UL83-HCMV antigen was measured through the shift in resonance frequency before and after antigen-antibody binding. The system shows a low detection limit of 84pg/ml, which is comparable to traditional sensors, and a detection time of less than 15min was achieved. The selectivity of the sensor was demonstrated using three different proteins with and without the UL83-HCMV antigen. The biosensor shows high selectivity for the UL83-HCMV antigen. Mass loading by the UL83-HCMV antigen was roughly estimated with a sensitivity of ∼30fg/Hz. This technique is crucial for the fabrication of portable and low-cost biosensors that can be used in real-time monitoring and enables early medical diagnosis.

Specific Detection of Short-Chain Alcohols, with the Development of an Enzyme-Coated Microcantilever-Based Biosensor

Specific Detection of Short-Chain Alcohols, with the Development of an Enzyme-Coated Microcantilever-Based Biosensor

Synthesis, characterisation and cytotoxicity of gold microwires for ultra-sensitive biosensor development

With the long-term goal of developing an ultra-sensitive microcantilever-based biosensor for versatile biomarker detection, new controlled bioreceptor-analytes systems are being explored to overcome the disadvantages of conventional ones. Gold (Au) microwires have been used as a probe to overcome the tolerance problem that occurs in response to changes in environmental conditions. However, the cytotoxicity of Au microwires is still unclear. Here, we examined the cytotoxicity of Au microwires systems using both commercial and as-synthesised Au microwires. In vitro experiments show that commercial Au microwires with an average quoted length of 5.6 µm are highly toxic against Gram-negative Escherichia coli (E. coli) at 50 µg/mL. However, this toxicity is due to the presence of CTAB surfactant not by the microwires. Conversely, the as-synthesised Au microwires show non-cytotoxicity even at the maximum viable concentration (330 µg/mL). These findings may lead to the development of potentially life-saving cytotoxicity-free biosensors for an early diagnostic of potential diseases.

Design and simulation of diatom-based microcantilever immunobiosensor for the early detection of Karnal bunt.

Fungal pathogen, Tilletia indica, the cause of Karnal bunt disease in wheat, is severely affecting the yield and grain quality, worldwide. Thus, strict quarantine regulations by most wheat growing countries have to be followed, leading to trade barriers for wheat export. The conventional methods being used for pathogen detection at symptomatic stage requires the germination of Tilletia spores for the processing of samples. Thus, it is time-consuming and expensive. This study proposes a simulated microcantilever-based piezoelectric biosensor for the early detection of T. indica. Four different materials, SiO2, SiC, Si3N4, and Poly Si, were used for the microcantilever design. Microcantilever was coated with siliceous frustules of diatom that provides high surface area and enhanced sensitivity for specific antibody against the antigen, T. indica. Ansys software was used for the simulation analysis. Simulation results showed that microcantilever beam of SiO2 length of 150µm, width of 30µm and thickness 1µm enhanced the sensitivity by two times against the antibody in comparison to normal microcantilever beam. The results concluded that SiO2 with coated diatom is the best material for the microcantilever fabrication, thus, providing an excellent protocol for fabrication of microcantilever-based biosensor which is both cost- and time effective.

Precise mass determination of single cell with cantilever-based microbiosensor system.

Having determined the mass of a single cell of brewer yeast Saccharomyces cerevisiae by means of a microcantilever-based biosensor Cantisens CSR-801 (Concentris, Basel, Switzerland), it was found that its dry mass is 47,65 ± 1,05 pg. Found to be crucial in this mass determination was the cell position along the length of the cantilever. Moreover, calculations including cells positions on the cantilever provide a threefold better degree of accuracy than those which assume uniform mass distribution. We have also examined the influence of storage time on the single cell mass. Our results show that after 6 months there is an increase in the average mass of a single yeast cell.

Sensitive Layer Thickness Dependence on Microcantilever Sensor Sensitivity

A sensitive layer is a main component in detecting an analyte target in a microcantilever-based biosensor. The sensitive layer coated on the microcantilever surface can induce a surface stress change as consequence of adsorbate-surface interaction. Therefore, a presence of stress is necessary to be investigated because it determines a deflection which influences the sensor sensitivity. In this work, we study a dependence of the film stress and microcantilever deflection on the gold or 3-Aminopropyltriethoxysilane (aminosilane) layers thickness in static mode operation. It is found that the optimum thickness of the sensitive layer for both aminosilane and gold can be obtained by analyzing the maximum film stress and the maximum microcantilever deflection. We also investigated the effect of Youngs moduli on the maximum stress and the maximum deflection. It is obtained that the Youngs moduli is a function that determines the peaks on the maximum stress and the maximum deflection. Our results indicate that the material properties and the thickness of sensitive layer should be considered to obtain a high sensitivity of microcantilever biosensor.

Sensitive Layer Thickness Dependence on Microcantilever Sensor Sensitivity

A sensitive layer is a main component in detecting an analyte target in a microcantilever-based biosensor. The sensitive layer coated on the microcantilever surface can induce a surface stress change as consequence of adsorbate-surface interaction. Therefore, a presence of stress is necessary to be investigated because it determines a deflection which influences the sensor sensitivity. In this work, we study a dependence of the film stress and microcantilever deflection on the gold or 3-Aminopropyltriethoxysilane (aminosilane) layers thickness in static mode operation. It is found that the optimum thickness of the sensitive layer for both aminosilane and gold can be obtained by analyzing the maximum film stress and the maximum microcantilever deflection. We also investigated the effect of Youngs moduli on the maximum stress and the maximum deflection. It is obtained that the Youngs moduli is a function that determines the peaks on the maximum stress and the maximum deflection. Our results indicate that the material properties and the thickness of sensitive layer should be considered to obtain a high sensitivity of microcantilever biosensor.

Development of an innovative microcantilever-based biosensor for 17β-estradiol detection in bovine muscles: preliminary results

17β-estradiol is the most powerful substance with estrogenic effect, commonly used as illegal growth promoter in livestock production. To avoid health risks for consumers, sensitive, reliable and low-cost methods for quantification of extremely low concentrations of such carcinogenic residues in food are needed. Antibody-immobilised microcantilever resonators were proposed as innovative biosensors able to quantify an adsorbed target mass thanks to a shift in resonance frequency. Furthermore, the quantification of masses on the order of few picograms has recently shown to be successfully achievable with very high precision. In this study, we analysed the performance of our microcantilever sensors using extracted samples of bovine muscle from experimental animals, containing variable concentrations of 17β-estradiol (HPLC-MS/MS tested). Preliminary data showed that treated animals are correctly revealed, exhibiting large negative frequency shifts. More experiments, though, are needed to obtain a correct quantification of 17β-estradiol concentration.

Comprehensive distributed-parameters modeling and experimental validation of microcantilever-based biosensors with an application to ultrasmall biological species detection

Nanotechnological advancements have made a great contribution in developing label-free and highly sensitive biosensors. The detection of ultrasmall adsorbed masses has been enabled by such sensors which transduce molecular interaction into detectable physical quantities. More specifically, microcantilever-based biosensors have caught widespread attention for offering a label-free, highly sensitive and inexpensive platform for biodetection. Although there are a lot of studies investigating microcantilever-based sensors and their biological applications, a comprehensive mathematical modeling and experimental validation of such devices providing a closed form mathematical framework is still lacking. In almost all of the studies, a simple lumped-parameters model has been proposed. However, in order to have a precise biomechanical sensor, a comprehensive model is required being capable of describing all phenomena and dynamics of the biosensor. Therefore, in this study, an extensive distributed-parameters modeling framework is proposed for the piezoelectric microcantilever-based biosensor using different methodologies for the purpose of detecting an ultrasmall adsorbed mass over the microcantilever surface. An optimum modeling methodology is concluded and verified with the experiment. This study includes three main parts. In the first part, the Euler–Bernoulli beam theory is used to model the nonuniform piezoelectric microcantilever. Simulation results are obtained and presented. The same system is then modeled as a nonuniform rectangular plate. The simulation results are presented describing model's capability in the detection of an ultrasmall mass. Finally the last part presents the experimental validation verifying the modeling results. It was shown that plate modeling predicts the real situation with a degree of precision of 99.57% whereas modeling the system as an Euler–Bernoulli beam provides a 94.45% degree of precision. The detection of ultrasmall immobilized enzyme molecules over the cantilever surface was achieved using a self-exciting piezoelectric-based microcantilever in the dynamic mode.

3,4-Methylenedioxymethylamphetamine detection using a microcantilever-based biosensor

We developed a biomolecular layer with highly specific binding that enables determination of low concentrations of 3,4-methylenedioxymethylamphetamine (MDMA) by the immobilization of antibodies. This study examined the interactions of anti-MDMA antibodies with MDMA using a microcantilever-based biosensor. The detection platform is based on the immobilization of affinity monoclonal antibodies onto a sensing surface using a cysteamine-based self-assembled monolayer. Anti-MDMA antibodies conjugated with various concentrations of MDMA were bound to the sensing surface. The intermolecular interaction was observed by monitoring the simultaneous signals (bending deflection and resonant frequency shift) of microcantilevers in phosphate buffered saline (PBS). We demonstrated that anti-MDMA antibodies can respond specifically to their natural ligand, MDMA. Results revealed that the microcantilever-based biosensor can be used to characterize MDMA response profiles of anti-MDMA and provide rich data for immunoassays. In addition to providing a clearer understanding of the biological mechanisms of protein binding, such a biosensor also holds great potential in numerous other fields, such as drug detection, biomedicine, and environmental protection.

The Effect of Flow Velocity on Microcantilever-Based Biosensors

ABSTRACTThis work focuses on studying the effect of flow velocity on microcantilever-based biosensor by numerical simulation. The microcantilever sensors used in detecting biomolecules have attractive advantages like cost efficiency, real-time and ability of fabricating in array. Both rectangular and triangular shapes of a general model of microcantilever beam are considered. Several important physical phenomena are obtained. Comparing with the first order Langmuir theory, we have calculated the effect on the reactive rate, produced concentration, the distribution of concentration and deflection in the z axis by solving these physical coupled problem involving flow field, concentration field and chemical reaction on the reaction surface. It is found numerically that the transportation of analyte, reactive rate, the distribution of concentration and deflection in the z axis are all effected by changing the flow velocity. The result has shown that flow velocity is an important factor for this biosensor.

Fabrication and characteristics of microcantilever-based biosensor for detection of the protein-ligand binding

This paper describes a proposal for a microcantilever-based biosensor that can be used in investigating the adsorption characteristics of protein-ligand binding on a silicon nitride/gold coated surface. We have detected streptavidin-ligand binding using this microcantilever detection system. The microcantilevers can be mass-produced by a conventional surface micromachining technique. This technique has advantages of cost efficiency, simplicity, and the ability to be fabricated in an array. A transparent fluid cell system, where a gold coated microcantilever was mounted for the injection of bio-molecular solution, was fabricated using polydimethylsiloxane (PDMS) and fused silica glass. The microcantilever was deflected as a result of the difference of surface stress caused by the formation of the self-assembly monolayers (SAMs) of biomolecules on the gold coated side of the microcantilever. The sequential specific interactions of cystamine dihydrochloride/ glutaraldehyde/streptavidin were detected by both optical and electrical methods. We confirmed that the deflections were induced by biomolecular adsorption on the gold coated microcantilever. This study proved to be applicable to real-time monitoring of biological interactions such as specific DNA sequences, proteins, and so on.

Fabrication of piezoresistive microcantilever using surface micromachining technique for biosensors

A microcantilever-based biosensor with piezoresistor has been fabricated using surface micromachining technique, which is cost effective and simplifies a fabrication procedure. In order to evaluate the characteristics of the cantilever, the cystamine terminated with thiol was covalently immobilized on the gold-coated side of the cantilever and glutaraldehyde that would be bonded with amine group in the cystamine was injected subsequently. This process was characterized by measuring the deflection of the cantilever in real time monitoring. Using a piezoresistive read-out and a well-known optical beam deflection method as well, the measurement of deflection was carried out. The sensitivity of piezoresistive method is good enough compared with that of optical beam deflection method.

Optimization modeling of analyte adhesion over an inclined microcantilever-based biosensor

The effect of the microcantilever inclination on analyte adhesion is numerically analyzed in this work. A generalized model for the analyte adhesion is considered based on wall shear stress (WSS) at the microcantilever surface. Several analytical solutions for special cases are obtained. It is found numerically that the total mass transfer is enhanced by increasing the adhesion rate, the Peclet number and the use of converging flows over the microcantilever. Further, it is found that there exists a critical Peclet number that can maximize the total mass transfer when WSS slows down the adhesion process. The critical Peclet number increases as adhesion rate increases while it decreases as the flow becomes more convergent. Correlations are established on the basis of the numerical simulations for predicting flow operating conditions inside fluidic cells under maximized mass transfer rate conditions. Finally, this work paves the way for future experimental work in this area.

Glucose biosensing using an enzyme-coated microcantilever

A microcantilever-based biosensor is described. The enzyme glucose oxidase was immobilized on a micromachined silicon cantilever containing a gold coating, such as those used for atomic force microscopy. Specific, quantifiable deflection of the derivatized cantilevers was observed in the presence of the appropriate analyte. An analysis of the reaction energetics and the expected thermal response of the cantilever indicates that cantilever deflection is not simply a result of reaction-generated heat. This deflection appears to result from surface induced stresses. The combination of a highly specific enzyme and the microcantilever platform provides a unique approach for quantifying enzyme substrates without the complication of sample labeling.