ACS Sensors最新文献

Fruits can emit ethanol, which is generated through fermentation during hypoxic storage. We imaged spatiotemporal changes in the gaseous ethanol emitted by "La France" pear via its epicarp. The gas-imaging system utilized enzymes to transduce the ethanol concentration into fluorescence intensity. Initially, the uniformity of the enzyme and coenzyme distribution was evaluated to validate the imaging capability. Subsequently, two surface-fitting methods were compared to accurately image ethanol emitted from three-dimensional (3D) objects with a double-curved surface. The imaging results of ethanol emitted from the pear indicated that the distribution of ethanol was related to lenticels, which have been reported to possess high ethanol diffusivity, on the epicarp. As quantified by the system (uniformity of coenzyme and enzymes was 93.2 and 98.8%, respectively; dynamic range was 0.01-100 ppm), ethanol concentration increased with the storage period under hypoxic conditions (0.4-5.3 ppm, from day 1 to 10). The system enables the observation of the location, quantity, and temporal pattern of ethanol release from fruit, which could be a useful technology for agricultural applications.

Hydrogen (H₂) is a promising alternative energy source for Net-zero, but the risk of explosion requires accurate and rapid detection systems. As the use of H₂ energy expands, sensors require high performance in a variety of properties. Palladium (Pd) is an attractive material for H₂ detection due to its high H₂ affinity and catalytic properties. However, poor stability caused by volume changes and reliability due to environmental sensitivity remain obstacles. This study proposes a micropatterned thin film of PdAu with optimized composition (Pd_0.62Au_0.38) as a chemoresistive sensor to overcome these issues. At room temperature, the sensor has a wide detection range of 0.0002% to 5% and a fast response time of 9.5 s. Significantly, the sensor exhibits excellent durability for repeated operation (>35 h) in 5% H₂ and resistance to humidity and carbon monoxide. We also report a negative resistivity change in PdAu, which is opposite to that of Pd. Density functional theory (DFT) calculations were performed to investigate the resistance change. DFT analysis revealed that H₂ penetrates specific interstitial sites, causing partial lattice compression. The lattice compression causes a decrease in electrical resistance. This work is expected to contribute to the development of high-performance H₂ sensors using Pd-based alloys.

Flexible large strain sensors are an ideal choice for monitoring human motion, but the current use of flexible strain gauges is hindered by the need for external power sources and long-term operation requirements. Fiber-based sensors, due to their high flexibility, excellent breathability, and the ease with which they can be embedded into everyday clothing, have the potential to become a novel type of wearable electronic device. This paper proposes a flexible self-powered strain sensing material based on the electromagnetic induction effect, composed of a uniform mixture of Ecoflex and Nd₂Fe₁₄B, which has good skin-friendliness and high stretchability of over 100%. The voltage output of the magnetoelectric composite fiber remains stable over 5000 stretch-release cycles, reaching up to 969 μV. Based on this novel sensing material, a remote smart car control scheme for a human–machine interaction system was designed, enabling real-time gesture interaction.

Love-mode surface acoustic wave (SAW) sensors show great promise for biodetection applications owing to their low cost, digital output, and wireless passive capability, but their performance is often restricted by the availability of suitable sensitive membrane layers. Herein, a composite layer of electrospun fibers made from cellulose acetate and polyethylenimine, coated with gold nanoparticles, is proposed as a porous and sensitive membrane coated onto a love-mode SAW biosensor for monitoring gene sequences of Staphylococcus aureus. The results showed that the developed sensor exhibited an impressive sensitivity of 122.56 Hz/(nmol/L) for detecting gene sequences of S. aureus, surpassing the sensitivity of conventional SAW sensors employing a bare Au film as the sensitive layer by 5-fold. The analysis revealed a remarkably linear detection (R² of 0.97827) of S. aureus gene sequences within the range of 0 to 100 nmol/L. The limit of detection was impressively low at 0.9116 nmol/L. The good stability and specificity of the biosensor in liquid environments were demonstrated for clinical diagnostics.

Circulating cancer stem cells (CCSCs) are subpopulations of cancer cells with high tumorigenicity, chemoresistance, and metastatic potential, which are also major drivers of disease progression. Herein, to achieve the prediction of tumor diagnosis and progression in colorectal cancer (CRC), a new, automated, and portable lateral displacement patterned pump-free (LP) microfluidic chip (LP-chip) with the CoPt₃ nanozyme was established for CCSC capture and detection in peripheral blood and feces samples ex vivo. In this design, CoPt₃@HA probes with functions of magnetic separation and colorimetric signal transduction by peroxidase-mimicking activity were applied for the capture of CCSCs and signal output in clinical samples. The generated colors of polydopamine (PDA) were quantifiable through the smartphone APP and visualizable by the naked eye in the test line (T line) and control line (C line) of the LP-chip. In the optimal experimental conditions, the CCSC concentration was sensitive to change in the range 0-10⁵ cells mL^-1, with a detection limit of 3 cells mL^-1 (S/N = 3). Preliminary studies of clinical samples suggest that the platform has the potential for prediction of colorectal cancer progression and poor prognosis. Overall, the LP-chip provides potential strategies for timely diagnosis, therapeutic monitoring, and recurrence prediction to improve home-based patient care.

Advancements in nanotechnology led to significant improvements in synthesizing plasmon-enhanced nanoarchitectures for biosensor applications, and high-yield productivity at low cost is vital to step further into medical commerce. Metal nanoframes via wet chemistry are gaining attention for their homogeneous structure and outstanding catalytic and optical properties. However, nanoframe morphology should be considered delicately when brought to biosensors to utilize its superior characteristics thoroughly, and the need to prove its clinical applicability still remains. Herein, we controlled the frameworks of double-walled nanoframes (DWFs) precisely via wet chemistry to construct a homogeneous plasmon-enhanced nanotransducer for localized surface plasmon resonance biosensors. By tuning the physical properties considering the finite-difference time-domain simulation results, biomolecular interactions were feasible in the electromagnetic field-enhanced nanospace. As a result, DWF₁₀ exhibited a 10-fold lower detection limit of 2.21 fM compared to DWF₁₄ for tau detection. Further application into blood-based clinical and Alzheimer's disease (AD) diagnostics, notable improvement in classifying mild cognitive impairment patients against healthy controls and AD patients, was demonstrated along with impressive AUC values. Thus, in response to diverse detection methods, optimizing nanoframe dimensions such as nanogap and frame thickness to maximize sensor performance is critical to realize future POCT diagnosis.

This paper presents a platform for amyloid-β (Aβ) biosensors, employing nearly monolayer semiconducting single-walled carbon nanotubes (sc-SWNTs) via click reaction. A high-purity sc-SWNT ink was obtained by employing a conjugated polymer wrapping method with the addition of silica gel. Aβ detection involved monitoring the electrical resistances of the sc-SWNT layers. Electrical resistances increased rapidly corresponding to the concentration of amyloid-β 1-42 (Aβ1-42) peptides. Furthermore, we introduced Aβ peptides onto the 1-pyrenebutanoic acid succinimidyl ester (PBASE) linker, confirming that only the chemical adsorption of the peptide by the antibody-antigen reaction yielded a significant change in electrical resistance. The optimized sensor exhibited a high sensitivity of 29% for Aβ at a concentration of 10 pM. Notably, the biosensor platform featuring chemically immobilized sc-SWNT networks can be customized by incorporating various bioreceptors beyond Aβ antibodies.

Heavy metal contamination is an increasing global threat to human and environmental health, particularly in resource-limited areas. Traditional platforms for heavy metal detection are labor intensive and expensive and require lab facilities. While paper-based colorimetric sensors offer a simpler approach, their sensitivity limitations prevent them from meeting legislative requirements for many metals. Existing preconcentration systems, on the other hand, can achieve lower detection limits but typically focus on analyzing only one metal, making comprehensive monitoring difficult. We address these limitations by introducing a low-cost preconcentration system coupled with colorimetric analysis for the simultaneous detection of seven metal ions at low ppb levels without the need for external equipment outside a smartphone. The system achieved detection limits of 15 ppb (Ni(II)), 7 ppb (Cu(II)), 2 ppb (Fe(III)), 20 ppb (Cr(VI)), 13 ppb (Pb(II)), 26 ppb (Hg(II)), and 15 ppb (Mn(II)) with six out of seven limits of detection values falling well below EPA regulatory guidelines for drinking water. The user-friendly Fill, Fold, Photo approach eliminates complex pretreatment steps. Smartphone-based detection offers portable quantification within seconds. Employing masking strategies ensured higher selectivity for each assay on the card, while our packaging protocols enable system stability for over 4 weeks of study, facilitating mass production and deployment within a realistic time frame. To validate the sensor's performance in real-world scenarios, the sensor was tested with environmental water samples. The sensor demonstrated good recovery, ranging from 77% to 94% compared to the standard ICP-MS method. Furthermore, spike recovery analysis confirmed the sensor's accuracy, with a relative standard deviation (RSD) of less than 15%. This technology holds significant promise for future development as a convenient, portable solution for field-based monitoring of a broad spectrum of water contaminants, including pesticides, PFAS, fertilizers, and beyond.