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Three-metal-core-shell nanoparticles (Au@Pt@PdNPs) providing excellent peroxidase-like activity were applied in lateral flow immunoassay (LFIA), designated as Au@Pt@Pd-LFIA, for detecting the nucleocapsid protein (NP) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). An Au@Pt@Pd-LFIA was developed for quantitatively testing of SARS-CoV-2 NP with a range 0.12–31.25 ng/mL. The limit of detection (LOD) of Au@Pt@Pd-LFIA strip was 0.06 ng/mL, which was 16-fold or eightfold more sensitive than that of the gold lateral flow immunoassay (Au-LFIA) and the gold flower flow immunoassay (AF-LFIA) strips, respectively. For detection of clinical samples from nasal swabs using test strips, Au@Pt@Pd-LFIA had 84.09% sensitivity, 100% specificity, and 92.55% accuracy. In terms of detection time, the testing of Au@Pt@Pd-LFIA strip was 16 min similar to Au-LFIA (15 min) and AF-LFIA (10 min), but much shorter than ELISA (2 h). In conclusion, Au@Pt@Pd-LFIA is a sensitive, rapid, and simple test for quantitative detection of SARS-CoV-2 NP in nasal swab samples. [ABSTRACT FROM AUTHOR]

The arrival of surgical robots in high-end medical equipment is a landmark, and the realization of tactile sensation a major challenge in this important cutting-edge research field. Aiming to address this issue, we present ultra-sensitive ionic electronic skin in the form of flexible capacitive pressure sensors, which incorporate multistage bionic microstructures in ion gels for the purpose of monitoring the delicate operations of surgical robots. Significantly, the ionic skin exhibits an ultra-high sensitivity of 9484.3 kPa−1 (<15 kPa), and the sensitivity remains higher than 235 kPa−1 in the wide range of 15–155 kPa. The device has also achieved a detection limit as low as 0.12 Pa or, equivalently, 0.31 mg, fast response within 24 ms, and high robustness (loading/unloading for 5000 cycles without fatigue). The sensor facilitates the challenging task of tele-operated robotic threading, which exceeds the human tactile perception limit when threading a needle. We have also confirmed that ionic skin can be used in robot-assisted invasive surgery, such as incision/resection of tissues and suturing of wounds, providing tactile information to surgeons to improve operation success rates. The flexible ionic skin is capable of conforming to the various shapes of robotic manipulators, thus has great promise for applications in robotic dexterous manipulation, prosthetics and human–machine interfaces. [ABSTRACT FROM AUTHOR]

Recent advances in supercapacitive pressure sensors based on iontronic film have a significant capacitive response and a low detection limit due to their large capacitance change resulting from electrical double layer (EDL) and these pressure sensors are used to detect a wide range of pressure with high resolution for various applications such as prosthesis, wearable devices, and robotics. Thus, the enhancements to the EDL capacitive response are significantly important challenges for advanced applications with outstanding performances. Herein, an ultra‐sensitive and quick‐responsive hybrid‐supercapacitive iontronic pressure sensor using a novel sensing mechanism and facile fabrication technique is reported to overcome the limitations of the existing iontronic pressure sensors. As a sensing material, conductive polymer and carbon nanotube are incorporated into the iontronic film, as pseudo‐ and EDL‐capacitive material, respectively. Moreover, vinyl silica nanoparticle (VSNP) is used to decrease the recovery time by making the iontronic film quick‐response. The developed hybrid‐supercapacitive pressure sensor exhibited an ultra‐high sensitivity of 301.5 kPa−1 over a wide pressure range of up to 63.3 kPa along with a fast recovery time of ≈32 ms. It is believed that the proposed hybrid‐supercapacitive mechanism in iontronic film will significantly enhance the performance of conventional iontronic pressure sensors. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) as a common gas plays an important role in both industrial production and clinical pathology. Therefore, the realization of dynamic detection of trace H 2 S gas is of great significance. In this paper, an ultra-sensitive optical H 2 S sensor based on thermal conversion and ultraviolet differential optical absorption spectroscopy (UV-DOAS) is developed for dynamic measurement of H 2 S concentration. The H 2 S concentration can be derived from the measurement of the change in sulfur dioxide (SO 2) concentration before and after conversion. First, the evaluation method of SO 2 concentration based on UV-DOAS is presented, and the performance indicators of SO 2 concentration measurement are given. Second, the conversion characteristics of H 2 S under different temperatures and flow rates are investigated, and H 2 S can be efficiently converted to SO 2 in the flowing gas state by controlling the conversion conditions. Finally, the performance indicators of H 2 S sensor are evaluated. The sensor realizes H 2 S measurements with a detection limit of 14 ppb * m, while its sensitivity and reliability of measuring H 2 S concentration increase tenfold, making it suitable for dynamic measurements of trace H 2 S. In addition, the feasibility of the sensor for applications in atmospheric monitoring and human exhaled breath detection is demonstrated by practical tests. • An ppb-level H 2 S senor based on thermal conversion and UV-DOAS is reported. • Dynamic detection of H 2 S was achieved by introducing thermal conversion. • Over 98 % H 2 S converted to SO 2 by regulating thermal conversion conditions. • The minimum detection limit of H 2 S in air is 14 ppb per meter. • Practical tests proved the feasibility of the sensor to detect H 2 S in various fields. [ABSTRACT FROM AUTHOR]

Quantification of ultra-trace analytes in complex biological samples using micro-solid-phase extraction followed by direct detection with internal extractive electrospray ionization mass spectrometry (μSPE–iEESI–MS) was demonstrated. 1-Hydroxypyrene (1-OHP) and papaverine at attomole levels in human raw urine samples were analyzed under negative and positive ion detection mode, respectively. The μSPE was simply prepared by packing a disposable syringe filter with octadecyl carbon chain (C18)-bonded micro silica particles, which were then treated as the "bulk sample" after the analytes were efficiently enriched by the C18 particles. Under the optimized experimental conditions, the analytes were readily eluted by isopropanol/water (80/20, V/V) at a high voltage of ± 4.0 kV, producing analyte ions under ambient conditions. The limit of detection (LOD) was 0.02 pg/L (9.2 amol) for 1-hydroxypyrene and 0.02 pg/L (5.9 amol) for papaverine. The acceptable linearity (R2 > 0.99), signal stability (RSD ≤ 10.7%), spike recoveries (91–95%), and comparable results for real urine samples were also achieved, opening up possibilities for quantitative analysis of trace compounds (at attomole levels) in complex bio-samples. [ABSTRACT FROM AUTHOR]

Here, we developed an ultra-sensitive and absolute quantitative detection method of Cu 2+ based on DNAzyme and digital PCR. The binding model between DNAzyme and Cu 2+ and the influence caused by the additional primer sequence were revealed to ensure quantitation independent of standard curves. The binding model of DNAzyme and Cu 2+ showed that one molecular DNAzyme could bind one Cu 2+ in the biosensor step. Thus, the final quantitative results, evaluated by three parallels, showed that the limit of quantitation (LOQ) was as low as 0.5 pmol, while the sensitivity was evaluated as 50 fmol. The specificity evaluation of our methodologies shows that extremely low crossing signal is existed within the non-specific ions. Moreover, the results of practical detection have shown that the quantitative results were stable and accurate among different food substrates. In conclusion, a flexible quantitative detection method with ultra-sensitivity was developed to detect trace amounts Cu 2+ within different substrates. [ABSTRACT FROM AUTHOR]

Sensitive and rapid sensing is extremely vital to in-situ monitor trace chemicals, herein, multiple visual devices have been developed to ultra-sensitively screen antibiotic oxytetracyline (OTC) with shutter-speed. The calcium ion fixed on the nanoprobe sensitively and rapidly coordinates to the hydroxyl group of OTC due to its special electronic orbital structure, resulting in evolutive visual distinct color change from red to bright green within a shutter pressing (<0.1 s) upon adding OTC, and consequently demonstrating visible and dosage-sensitive detection with the detection limit down to 6.83 nM. Particularly, multiple fluorescent ratiometric devices based the designed nanoprobe applied in water, urine and pork samples have proved the practicability and accuracy of this method. This fast, sensitive, and visible sensing strategy holds great promise for wide applications, as well as the practical utilization value of multiple in-situ detection devices. • Shutter speed and ultra-sensitive monitoring of antibiotics. • A variety of in-situ testing equipment to detect antibiotics. • Provides a new way of quick inspection. [ABSTRACT FROM AUTHOR]

A major challenge in controlling the COVID-19 pandemic is the high false-negative rate of the commonly used RT-PCR methods for SARS-CoV-2 detection in clinical samples. Accurate detection is particularly challenging in samples with low viral loads that are below the limit of detection (LoD) of standard one- or two-step RT-PCR methods. In this study, we implemented a three-step approach for SARS-CoV-2 detection and quantification that employs reverse transcription, targeted cDNA preamplification, and nano-scale qPCR based on a commercially available microfluidic chip. Using SARS-CoV-2 synthetic RNA and plasmid controls, we demonstrate that the addition of a preamplification step enhances the LoD of this microfluidic RT-qPCR by 1000-fold, enabling detection below 1 copy/µL. We applied this method to analyze 182 clinical NP swab samples previously diagnosed using a standard RT-qPCR protocol (91 positive, 91 negative) and demonstrate reproducible and quantitative detection of SARS-CoV-2 over five orders of magnitude (<1 to 106 viral copies/µL). Crucially, we detect SARS-CoV-2 with relatively low viral load estimates (<1 to 40 viral copies/µL) in 17 samples with negative clinical diagnosis, indicating a potential false-negative rate of 18.7% by clinical diagnostic procedures. In summary, this three-step nano-scale RT-qPCR method can robustly detect SARS-CoV-2 in samples with relatively low viral loads (<1 viral copy/µL) and has the potential to reduce the false-negative rate of standard RT-PCR-based diagnostic tests for SARS-CoV-2 and other viral infections. [ABSTRACT FROM AUTHOR]