Sensors and Actuators Reports最新文献

The cortisol in human body is a crucial biomarker in terms of wellness management, mental state monitoring and stress-related disorder diagnosis. Therefore, the rapid, reliable and facile measurement of cortisol concentration has attracted extensive research interest. However, traditional cortisol detection such as immunosensing requires demanding laboratory layout, lengthy procedures and high costs, which means, consequently, it is incompatible with the current goal of cortisol sensing. Given the contradiction, an electrochemical sensor based on molecularly imprinted polymer (MIP) for simple, efficient, non-invasive cortisol detection was proposed. The two-step approach employed is simple enough and allows for the mass production of devices. And the embedding of Prussian Blue (PB) within the MIP layer eliminates the need for complex external probes, thereby making the resultant sensors more suitable for integration into wearable devices. We firstly demonstrated the feasibility of the proposed strategy and characterized the successful formation of cavities specific to cortisol molecules. Thereafter, we measured the dependence of the current response on cortisol concentration in Phosphate Buffered Saline (PBS) buffer, which revealed a near-linear relationship between the logarithm of the cortisol concentration and the redox current from 10⁻⁹ mol/L to 10⁻⁵ mol/L, covering the optimal range of cortisol concentration in sweat. Subsequently, sensors with the same specifications were prepared and tested in PBS buffer, exhibiting good consistency. In artificial sweat, we further demonstrated that they have benign selectivity, interference immunity and great potential in practical applications.

Multi-channel neural electrodes as a crucial means are of great significance for information exchange between the brain and computers. Herein, we present a 16-channel Si-based active neural probe system that achieves a monolithic integration between the electrodes and circuits in a single probe, making it a standalone integrated electrophysiology recording system. The ASIC prepared on a base ($2\times 2m{m}^2$) is a 16-channel analog frontend (AFE) for neural recording, and each channel has a low-noise amplifier (LNA), a bandpass filter (BPF), a buffer and a current bias circuit. The 258 neural signal recording electrodes ($22\times 24\mu m^2$) are densely packed on a 50 μm thick, 100 μm wide, and 3 mm long shank. The ASIC of neural probe, internal interconnecting wires are all implemented in commercial SMIC 0.18 μm CMOS technology. The neural probe system achieves a 3.6 μV_rms input-referred noise (IRN) in a bandwidth of 1.1Hz-10 kHz, 70.8 μW power consumption, 0.0785 mm² area per channel, as well as an AFE gain of 58.1 dB Furthermore, the impedances of the Au electrodes can be obtained as 0.5–2.1 MΩ at a frequency of 1 kHz. The functionality of a 16-channel silicon-based neural probe is validated in an in-vivo experiment on lab rats.

To practically utilized the organometallic lead halide perovskites to optoelectronic devices and photoelectrochemical cells, numerous efforts have been utilized to obtain the perovskites with low-energy process with coverage of various inorganic mediums to improve stability against humidity. By utilizing ligand-assisted reprecipitation process, under ambient condition at room temperature, the dimensionally confined perovskite quantum dots in silica matrices (PQD@SiO_x) were obtained, and they were stable under several months under the ambient condition. To apply the PQD@SiO_x to the photoelectrochemical cells by introducing direct contact between PQD@SiO_x and electrolyte, the material/photophysical properties under electrochemical conditions are necessary to be studied. However, the role of silica coverage to the electrochemical behaviors of the PQD cores in the silica medium were not yet studied. In this work, under the electrochemical conditions, the oxidative and reductive behaviors of the PQD@SiO_x were studied. Also, through in-situ spectroelectrochemical study, the electrochemically induced irreversible deformation process were tracked. The findings of this study could be used to understand role of silica coverage and develop the strategy to improve the protecting behavior of the silica for the PQD cores to utilize into the photoelectrochemical cells.

For the 29.8 million people in the world living with HIV/AIDS and receiving antiretroviral therapy, it is crucial to monitor their HIV viral loads. To this end, rapid and portable diagnostic tools that can quantify HIV RNA are critically needed. We report herein a rapid and quantitative digital CRISPR-assisted HIV RNA detection assay that has been implemented within a portable smartphone-based device as a potential solution. Specifically, we first developed a fluorescence-based reverse transcription recombinase polymerase amplification (RT-RPA)-CRISPR assay that can efficiently detect HIV RNA at 42 °C. We then implemented this assay within a commercial stamp-sized digital chip, where RNA molecules were quantified as strongly fluorescent digital reaction wells. The isothermal reaction condition and the strong fluorescence in the digital chip simplified the design of thermal and optical modules, allowing us to engineer a palm-size device measuring 70 × 115 × 80 mm and weighing less than 0.6 kg. We also capitalized the smartphone by developing a custom app to control the device, perform the digital assay, and capture fluorescence images throughout the assay using the smartphone's camera. Moreover, we trained and verified a deep learning-based algorithm for analyzing fluorescence images and identifying positive digital reaction wells with high accuracy. Using our smartphone-enabled digital CRISPR device, we successfully detected as low as 75 copies of HIV RNA in just 15 min, showing its potential toward monitoring of HIV viral loads and aiding the global effort to combat the HIV/AIDS epidemic.

Monolayer tungsten disulfide (1L-WS₂) exhibits excellent optical properties due to its direct bandgap. The extraordinary photoluminescence (PL) emission at room temperature from CVD-grown 1L-WS₂ was utilized for the first time here as a recognition tool for detecting S. aureus bacteria with high sensitivity and selectivity. The 1L-WS₂ possesses sulfur vacancy, which has been utilized for single-standard DNA (ssDNA) aptamer immobilization via the thiol functional group. The small-sized, highly selective ssDNA aptamers identify and selectively interact with targeted S. aureus, enabling selective detection. Interestingly, the PL emission of 1L-WS₂ is strongly influenced by external charge doping. The shape of the PL emission peak of 1L-WS₂ undergoes significant changes in the presence of targeted S. aureus as a result of charge transfer originating from selective interactions between ssDNA aptamer and S. aureus, while it remains unaffected for non-targeted Escherichia coli. The ratio of the integrated intensities of trion to neutral exciton peak was used as a calibration parameter for the quantification of S. aureus concentrations. The PL analysis of 1L-WS₂ with increasing concentration of S. aureus exhibits a linear response over 10² CFU/mL to 10⁷ CFU/ml with a lower detection limit of 2.0 CFU/mL. The proposed sensing system can identify an unknown concentration of S. aureus in human urine with 78% accuracy at a concentration of 10⁵ CFU/mL. These results demonstrate the potential future generation applications of monolayer transition metal dichalcogenides in the optical biosensing of pathogenic species using suitable receptors.

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.