Sensors and Actuators Reports最新文献

Herein, we present the design and fabrication of a portable biochemical sensor based on the Screen Printed Electrode (SPE) concept and applied for detecting interleukin-6 (IL-6), a key player in the complex process of inflammation, in real human saliva. The sensing mechanism relies on the antigen-antibody binding between the IL-6 molecule and its antibody immobilized over a surface of a Thermally Exfoliated Graphene Oxide (TEGO) layer. TEGO, deposited by Aerosol Jet Printing (AJP), provides advantages in terms of a time/cost consumingfast, easy and efficient biofunctionalization. The biosensor shows a dynamic range comprising IL-6 concentrations falling within the normal IL-6 levels in saliva. An extensive analysis of device performance, focused on the assessment of the sensor Limit of Detection (LoD) by two modes (i.e. from the lin-log calibration curve and from blank measurements), provides a best value of about 1 × 10⁻² pg/ml of IL-6 in saliva. Our work aims at providing a contribution toward applications in real environment, going beyond a proof of concept or prototyping at lab scale. Hence, the characterization of the sensor was finalized to find a reliable device-to-device reproducibility and calibration through the introduction of a measurement protocol based on comparative measurements between saliva samples without (blank) and with IL-6 spiked in it, in place of the standard addition method used in daily laboratory practice. Device-to-device reproducibility has been accordingly tested by acquiring multiple experimental points along the calibration curve using different individual devices for each point.

Electrochemical impedance spectroscopy (EIS) is a reliable technique for gathering information about electrochemical process occurring at the electrode surface and investigating properties of materials. Furthermore, EIS technique can be a very versatile and valuable tool in analytical assays for detection and quantification of several chemically and biologically relevant (bio)molecules. The first part of this Review (Introduction) provides brief insights into (i) theoretical aspects of EIS, (ii) the instrumentation required to perform the EIS studies and (iii) the most relevant representations of impedance experimental data (such as Nyquist and Bode plots). In the end of this section, (iv) theoretical aspects regarding the fitting of the Randles circuit to experimental data are addressed, not only to obtain information about electrochemical processes but also to illustrate its utility for analytical purposes. The second part of the Review (Impedimetric Detection of Disease Biomarkers) focuses on the applications of EIS in the biomedical field, particularly as analytical technique in electrochemical sensors and biosensors for screening disease biomarkers. In the last section (Conclusions and Perspectives), we discuss main achievements of EIS technique in analytical assays and provide some perspectives, challenges and future applications in the biomedical field.

Accurately measuring interleukin-6 (IL-6) levels is crucial in both clinical medicine and research due to its role in various physiological and pathological processes. We present proof-of-concept of a novel three-dimensional (3D) spatial amplification method for developing highly sensitive and miniaturized IL-6 biosensors. We designed an IL-6 immunosensor platform utilizing a unique 3D microfluidic structure fabricated with femtosecond-pulsed laser processing. This design features a porous transducer element with over 4500 microcavities, thereby increasing the reaction area by 13-fold compared to traditional 2D designs while maintaining transparency. By combining this 3D structure with a competitive antigen-antibody reaction, the sensor achieved an exceptional limit of detection of 0.27 pg/mL for IL-6 in human blood samples. Additionally, we demonstrated effective control of liquid flow within the porous element using a reduction of pressure and centrifugation speeds. This 3D spatial amplification method offers a promising approach for developing highly sensitive and compact IL-6 biosensors. Such miniaturized sensors hold potential for point-of-care testing devices, enabling convenient and timely IL-6 analysis.

This manuscript describes the fabrication and characterization of a highly conductive paper-based nanoplatform for immobliztion of anti-CA 15-3 antibodies. For this purpose, cellulosic filter paper (FP) was first coated with Cu nanosponges (CuNSs) through ion beam sputtering deposition (IBSD) method and then covered with Cu-doped polydopamine nanospheres (Cu-PDA). Polydopamine doped with copper exhibited laccase (multi-copper oxidase)-mimicking properties. Bioinspired by the structure of the active site and the electron transfer mechanism of laccase, Cu-PDA nanozyme catalyzed the oxidation of hydroquinone (HQ) signal probe. In this design, CA-15-3, a prognostic biomarker in the breast cancer, was chosen as a model target. To the best of our knowledge, this is the only paper on the design of an electrochemical biosensor based on dense and uniform CuNSs produced by IBSD. More importantly, Cu-PDA is biocompatible and biodegradable, which makes it a potential competitor in the point-of-care (POC) biosensing applications. Thus, this paper-based sensing strategy can be used in designing cost-effective flexible chips consisting of electrodes printed on paper for in-situ and real-time monitoring biomarkers under clinical conditions. In addition to these outstanding features, the LOD (1.3 mU mL 1) and LOQ (4.3 mU mL 1) of the Ab/HQ/Cu-PDA/CuNSs/FP-based immunosensor was significantly lower than the clinically relevant cut-off level (30 U mL 1). In the practical applications, one of the key superiorities of this immuosensor is the wide DLR (5 mU mL 1–280 U mL 1) which covers the ultimate value of healthy and patient individuals.

Porous silicon nitride structures were fabricated for a humidity sensor. The porous silicon structures were fabricated by the metal-assisted chemical etching process, and the conformal silicon nitride thin film was deposited by the atomic layer deposition process. The optimized porous sensor with the 10 nm-thick silicon nitride thin film had a hydrophilic surface and compared to other sensors, had an excellent humidity sensing response. Especially, it showed a superior humidity sensing response at 1 kHz with fast response and recovery times of 13.3 s and 12.4 s, respectively, were observed. Based on the electrochemical impedance spectroscopy results, the equivalent circuits and humidity sensing mechanism were discussed. The chemical stability of the silicon nitride was characterized using Tafel analysis in alkaline electrolytes. Additionally, the sensor's humidity sensing capabilities were tested under cement-embedded conditions.

An all-optical fiber humidity sensor based on a Mach-Zehnder interferometer (MZI) covered with graphene oxide (GO) film is demonstrated. The MZI is formed by inserting a section of etched surface core fiber (SCF) between two standard single mode fibers (SMFs) with a lateral-offset. Such configuration of the interferometer allows a strong evanescent field between the water molecules and the GO layer and hence enhances the change in refractive index of GO nanostructures after water absorption, which significantly improves the humidity sensitivity. Experimental results showed that the fabricated sensor exhibited a super-high humidity sensitivity of 707.3pm/%RH in the RH range of 40–80% and a rapid response/recovery time (4.8/8.4 s). The high-performance of the proposed all fiber humidity sensor is potentially promising for industrial production, medical diagnoses, environmental and health monitoring.

Prostate cancer-derived exosomes have important potential as biomarkers for diagnosis and treatment of prostate cancer. But such specific exosomes towards clinical application remains problematic due to their comparatively low concentration in relation to other constituents of blood. Additionally, the presence of particles in blood that share a similar size with exosomes adds to the complexity of their selective and sensitive detection. Consequently, the detection of exosomes derived from prostate cancer in intricate biological settings necessitates the implementation of highly sensitive and specific biosensors. Herein, we report an electrochemical biosensor for prostate cancer-derived exosomes detection, with two-level selectivity achieved through a sandwich structure involving specific peptides and two-level amplification utilizing the combination of biotin-streptavidin linkage and G-quadruplex hemin mimetic peroxidase to enhance the sensitivity. Evaluation of PSMA positive exosomes at various concentrations demonstrates a remarkable limit of detection as low as 26 particles/μL, as well as an excellent linear sensor response spanning from 1.0 × 10² to 1.0 × 10⁷ particles/μL. Compared to the enzymatic biosensor, this biosensor proves more versatile without a label or enzyme, and may be more promising for clinical applications.

In this study, we developed a novel electrochemical biosensor for detecting IL-6 that uses a nano-electrode array (NEA) fabricated via standard CMOS processing. Miniaturizing the electrodes to the nanoscale and arranging them in an array to form an NEA facilitated the creation of a higher electric field magnitude, compared to that available via the use of microelectrodes, that could be used to improve biosensor sensitivity. Additionally, the array configuration of the NEA aided in providing sufficient reaction sites. Each nano-electrode in the NEA was cylindrically shaped, with a radius of 0.1 µm, and a top layer formed by TiN physical vapor deposition. Each NEA biosensor was divided into four independent banks, with each bank including a set of WE, CE and RE. These banks were capable of independently inputting and outputting electrical signals. This design allowed the NEA biosensor to undergo selective modification by CV input. In this study, we discuss and address material and contamination issues associated with CMOS-produced NEAs and their uses as biosensors. To ameliorate these issues, we stored materials and products in a nitrogen-controlled cabinet and conducted pretreatment cleaning on the electrodes. Both steps had a noticeable impact on the cleanliness of the electrode surfaces. These optimized conditions resulted in a remarkable 96.6 % reduction in R_ct. The NEA surface was functionalized by electrochemically grafting diazonium salts subsequently immobilized with anti-IL-6 antibodies via EDC/NHS chemistry. The resulting NEA biosensor demonstrated sufficient sensitivity to rapidly distinguish inflammatory conditions and disease severity. This showcases the potential for using NEA devices mass-produced via standard CMOS processing as electrodes for biosensors.

Purpose

As an important reference index for the early diagnosis of non-small cell lung cancer (NSCLC), CYFRA21-1 still lacks the detection of low equipment cost, wide linear range and high sensitivity. Surface-enhanced Raman scattering (SERS) is a vibration spectrum technology based on the surface plasma of precious metal nanoparticles, which has been effectively applied to the detection of tumor markers. The combination of SERS technology and sensors has great potential in the ultrasensitive detection of tumor markers. The purpose of this study was to develop a sensitive method using SERS to quantitatively detect CYFRA21-1 for early diagnosis of NSCLC.

Methods

A double-antibody sandwich immunoassay based on SERS was designed and tested to implement the ultrasensitive detection of CYFRA21-1 in the serum of NSCLC patients.

Results

Gold @Ag nanorods (Au @Ag NRs) with higher Raman signals were prepared and used as probes, while magnetic graphene oxide was used as a magnetic substrate. The immunized probe, immune substrate and CYFRA21-1 standard substance in the buffer system formed a double-antibody sandwich structure. The standard curve displayed a liner range from 1pg mL⁻¹ to 10 ng mL⁻¹, and the detection limit (LOD) is 0.8943pg mL⁻¹. The Raman intensity exhibited a wide linear relationship with the logarithm of CYFRA21-1 concentration.

Conclusion

Our study successfully established a double-antibody sandwich immunoassay based on SERS. This method demonstrated high specificity and sensitivity for detecting CYFRA21-1 protein content in serum. It has the potential to be applied for early detection of lung cancer biomarkers.

Dopamine is an important hormone and neurotransmitter, and its levels in human fluids can indicate stress, depression, and various mental disorders. Food products, as well as medications, affect its level in the human body greatly. Therefore, dopamine monitoring is crucial, and necessary for improving the quality of life. The priority is to search for simple and environmentally friendly sensor systems for the in vitro detection of dopamine, enabling mass utilization.

In this study, we explored the use of o-phthalaldehyde (OPA) as an indicator for the detection of dopamine, with fluorescence in the visible range (λ_ex/λ_em = 390/455 nm), while direct dopamine fluorescence measurement was in the UV range (λ_ex/λ_em = 280/320 nm). The longer excitation/emission wavelengths of dopamine-OPA complex, as well as lower detection limits, are useful for developing a simple detection method using LEDs. Three types of poloxamers were tested as additives to improve the fluorescence signal from the reaction between dopamine and OPA. Pluronic F127 led to a 16-fold increase in the fluorescence. Utilizing 4% Pluronic F127 with OPA at pH 7 resulted in a linear response within concentration ranges of dopamine (0.5–3 µM), achieving a limit of detection of 0.015 µM. In contrast, a direct detection of dopamine within the same range exhibited a detection limit of 0.13 µM.