Point-of-care (POC) detection of herbicides is of great importance due to their impact on the environment and potential risks to human health. Here, we design a single-atomic site catalyst (SASC) with excellent peroxidase-like (POD-like) catalytic activity, which enhances the detection performance of corresponding lateral flow immunoassay (LFIA). The iron single-atomic site catalyst (Fe-SASC) is synthesized from hemin-doped ZIF-8, creating active sites that mimic the Fe active center coordination environment of natural enzyme and their functions. Due to its atomically dispersed iron active sites that result in maximum utilization of active metal atoms, the Fe-SASC exhibits superior POD-like activity, which has great potential to replace its natural counterparts. Also, the catalytic mechanism of Fe-SASC is systematically investigated. Utilizing its outstanding catalytic activity, the Fe-SASC is used as label to construct LFIA (Fe-SASC-LFIA) for herbicide detection. The 2,4-dichlorophenoxyacetic acid (2,4-D) is selected as a target here, since it is a commonly used herbicide as well as a biomarker for herbicide exposure evaluation. A linear detection range of 1-250 ng/mL with a low limit of detection (LOD) of 0.82 ng/mL has been achieved. Meanwhile, excellent specificity and selectivity towards 2,4-D have been obtained. The outstanding detection performance of the Fe-SASC-LFIA has also been demonstrated in the detection of human urine samples, indicating the practicability of this POC detection platform for analyzing the 2,4-D exposure level of a person. We believe this proposed Fe-SASC-LFIA has potential as a portable, rapid, and high-sensitive POC detection strategy for pesticide exposure evaluation.

Heme enzymes, with the pentacoordinate heme iron active sites, possess high catalytic activity and selectivity in biosensing applications. However, they are still subject to limited catalytic stability in the complex environment and high cost for broad applications in electrochemical sensing. It is meaningful to develop a novel substitute that has a similar structure to some heme enzymes and mimics their enzyme activities. One emerging strategy is to design the Fe-N-C based single-atomic site catalysts (SASCs). The obtained atomically dispersed Fe-Nx active sites can mimic the active sites of heme enzymes effectively. In this work, a SASC (Fe-SASC/NW) is synthesized by doping single iron atoms in polypyrrole (PPy) derived carbon nanowire via a zinc-atom-assisted method. The proposed Fe-SASC/NW shows high heme enzyme-like catalytic performance for hydrogen peroxide (H2 O2 ) with a specific activity of 42.8 U mg-1 . An electrochemical sensor based on Fe-SASC/NW is developed for the detection of H2 O2 . This sensor exhibits a wide detection concentration range from 5.0 × 10-10 m to 0.5 m and an excellent limit of detection (LOD) of 46.35 × 10-9 m. Such excellent catalytic activity and electrochemical sensing sensitivity are attributed to the isolated Fe-Nx active sites and their structural similarity with natural metalloproteases.

An electrochemical sensor based on molecularly imprinted polypyrrole nanotubes (MIPNs) has been developed for the detection of glyphosate (Gly) with high sensitivity and specificity. Herein, the MIPNs are prepared by imprinting Gly sites on the surface of polypyrrole (PPy) nanotubes. The synthesized MIPNs have high electrical conductivity and exhibit rapid adsorption rate, enhanced affinity and specificity to Gly. An electrochemical sensor for Gly detection is fabricated by assembling MIPNs-modified screen-printed electrodes with a 3D-printed electrode holder, which is highly portable and suitable for real-time detection. The results demonstrate that the MIPNs-based electrochemical sensor for Gly exhibits a wide detection range of 2.5-350 ng/mL with a limit of detection (LOD) of 1.94 ng/mL. Besides, the Gly sensor possessed good stability, reproducibility, and excellent selectivity against other interferents. The practicability of the sensor is verified by detecting Gly in orange juice and rice beverages, indicating that the sensor is suitable for monitoring pesticides in actual food and environmental samples.

Due to robustness, easy large-scale preparation and low cost, nanomaterials with enzyme-like characteristics (defined as ‘nanozymes’) are attracting increasing interest for various applications. However, most of currently developed nanozymes show much lower activity in comparison with natural enzymes, and the deficiency greatly hinders their use in sensing and biomedicine. Single-atom catalysts (SACs) offer the unique feature of maximum atomic utilization, providing a potential pathway to improve the catalytic activity of nanozymes. Herein, we propose a Fe-N-C single-atom nanozyme (SAN) that exhibits unprecedented peroxidase-mimicking activity. The SAN consists of atomically dispersed Fe─Nx moieties hosted by metal–organic frameworks (MOF) derived porous carbon. Thanks to the 100% single-atom active Fe dispersion and the large surface area of the porous support, the Fe-N-C SAN provided a specific activity of 57.76 U mg-1, which was almost at the same level as natural horseradish peroxidase (HRP). Attractively, the SAN presented much better storage stability and robustness against harsh environments. As a proof-of-concept application, highly sensitive biosensing of butyrylcholinesterase (BChE) activity using the Fe-N-C SAN as a substitute for natural HRP was further verified.

Monitoring concerned activities and identifying activity types usually require sensors and corresponding data processing circuits, which are often restricted by the limited power supply in wireless sensor networks (WSNs). This study presents a self-powered smart WSN for passively monitoring and distinguishing different vibration events. In the proposed WSN, the sensing function is performed by vibration-threshold-triggered energy harvesters (VTT-EHs). The output power of the VTT-EH dramatically increases when an input vibration exceeds the pre-set vibration-threshold of the harvester, indicating the occurrence of specific concerned events. On the basis of this principle, two VTT-EHs with different thresholds were designed to detect and distinguish vibration events with different vibration characteristics. Meanwhile, electromagnetic EHs were applied to generate sufficient power for wirelessly transmitting the alarm signals within several seconds. The prototype of the proposed WSN was developed and evaluated. The sensor node was able to identify two types of intrusive activities: weak shake and strong knock. The alarming signals were first sent to a router node and then transmitted to a mobile phone through the global system of mobile communication network. The mobile phone received the alarming text messages with correct event type within 2 s after the excitation occurred.

In this paper, an immunosensor using CdTe@SiO2 core-shell nanoparticles as labels was constructed for highly sensitive detection of prostate-specific antigen (PSA). In this approach, CdTe@SiO2 core-shell nanoparticles were synthesized using the sol-gel method. The additional Cd ions and sulfur source in SiO2 shell can greatly enhance the fluorescence intensity of CdTe nanocrystals. The reason is the formation of CdS-like cluster in SiO2 shell, which reduced the quantum size effect. The obtained CdTe@SiO2 nanoparticles also exhibited excellent biocompatibility, which was ideal for applying in biomarker detection. Furthermore, PSA capture antibodies functionalized magnetic Fe3O4 nanoparticles (Fe3O4-Ab1) were utilized in the proposed immunosensor to capture and enrich the PSA. The captured PSA was then immuno-recognized by CdTe@SiO2 labeled with PSA detection antibodies (CdTe@SiO2-Ab2) by forming the sandwich complex Fe3O4-Ab1/PSA/Ab2-CdTe@SiO2. The construction of this immunosensor was confirmed by fluorescence spectroscopy. The proposed immunosensor showed a good linear relationship between the fluorescent intensity and the target PSA concentration ranging from 0.01 to 5 ng/mL, and a detection limit as low as 0.003 ng/mL was achieved. The sensor also exhibited good specificity to PSA. This highly sensitive and specific immunosensor has great potential to be used in other biological detection.

为了实现便携化测试,将传统的多线圈检测结构简化为单线圈,采用脉冲激励单线圈,并检测线圈输出信号,通过数字信号处理器(DSP)构成检测电路,达到简捷方便的测试目的.结合快速傅里叶变换(FFT)和线性调频Z变换(CZT)算法,提高了毫米级磁致伸缩传感器的检测精度,并完成了两种不同尺寸传感器(长度为4 mm和5 mm)的同时检测.实验测试结果表明:长度为4 mm的传感器灵敏度为0.3841kHz/μgn,长度为5mm的传感器灵敏度为0.2198kHz/μgn.设计的传感器在便携式生化检测仪器中具有广泛的应用价值.

The design, implementation and characterization of a micro acceleration measurement system based on highly-sensitive tunnel magneto-resistance (TMR) sensor is presented in this paper. The proposed micro-system provides a new way to develop high-precision accelerometer. The measurement system was constructed with a “force-magnetic-electric” coupling structure and fabricated using MEMS based micro-fabrication process. The basic structure of the micro-system was designed based a silicon micro-cantilever, which could convert the acceleration force to the change of the magnetic field. A TMR sensor was used to precisely measure the magnetic field. The whole system was fabricated and packaged into a micro-chip to improve measurement resolution. The experimental results show that this micro-system could achieve measurement resolution of \pmb17.35μg/√{H}z at 1Hz within \pmb±1.6g range.

Excessive use of herbicide and insecticide causes bioaccumulation in the environment and increases potential toxicity for people and animals. Portable systems for rapid assays of herbicide and insecticide residues have attracted prominent interests. Here, we developed a two-dimensional (2D) Pt-Ni(OH)(2) nanosheets (NSs) amplified two-way lateral flow immunoassay (LFI) with a smartphone-based readout for simultaneous detection of acetochlor and fenpropathrin. The 2D Pt-Ni(OH)(2) NSs were synthesized and used as the enhanced signal label in the immunoassay due to their high peroxidase-like activity and low migration speed. The two-way LFI was designed to eliminate potential cross-reaction between two targets. Portable detection system was developed based on a smartphone-based readout, which scans the LFI and provides the accurate testing result. The universal use of smartphones makes the developed platform suitable for cheap and on-site applications. Using the integrated platform, detection of acetochlor and fenpropathrin simultaneously was successfully achieved with the detection limits of 0.63 ng/mL and 0.24 ng/mL, respectively. To confirm the performance of the on-site application, we detected 10 non-spiked samples and 3 spiked samples. The obtained detection results were consistent with the data from gas chromatography analysis. The estimated recoveries ranged from 97.12% to 111.46%, indicating the practical reliability of our developed assay. The developed smartphone-based platform exhibits enhanced sensitivity, which provides a promising technique for on-site, multiplex, highly sensitive detection of pesticides.

Carbon dots (CDs) synthesized from natural organic precursors, such as glucose, citric acid, glycerol, and chitosan, have attracted great interest since natural organic precursors provide abundant carbon sources, a variety of heteroatoms for doping (such as N, S, and P) and good biocompatibility. However, previous approaches utilized organic solvents during synthesis procedures, which limited their widespread development in biomedical applications. Herein, the facile synthesis of a new type of bright CDs through an eco-friendly method that employs linseed as a natural precursor has been reported. The as-obtained CDs possessed high quantum yield of 14.2%, excellent solubility and photostability as well as excitation-dependent photoluminescence (PL). In addition, the as-prepared CDs exhibited great potential in cell imaging owing to negligible cytotoxicity as well as excellent biocompatibility and great resistance to photobleaching. Subsequently, the as-prepared CDs were also applied in the fabrication of a biosensor for sensitive detection of butyrylcholinesterase (BChE) based on the fluorescence quenching mechanism, which could be used as an indicator for detecting pesticides and nerve gases. By monitoring the change in the fluorescence intensity of the CDs, the activity of BChE was sensitively analyzed. The limit of detection (LOD) of BChE was 0.035 mU mL-1. The as-prepared CDs have potential applications in both biosensors and bio-imaging.

Polymeric nanoparticles have been investigated as biocompatible and promising nano-carriers to deliver drugs across the blood-brain barrier (BBB). However, most of the polymeric nanoparticles cannot be observed without attaching them with fluorescent dyes. Generally complex synthesis process is required to attach fluorescent dye tracing molecules with drug carrier nanoparticles. In this paper, we synthesized a novel fluorescent polymer based on poly [Triphenylamine-4-vinyl-(P-methoxy-benzene)] (TEB). This polymer was prepared from TEB polymer through coprecipitation. Furthermore, three types of ligands, transferrin (TfR), lactoferrin (LfR) and lipoprotein (LRP), were covalently attached on the nanoparticle surface to improve the BBB transport efficiency. All of prepared TEB-based nanoparticles were biocompatible, exhibited excellent fluorescence properties and could be observed in vivo. The transcellular transportation of these TEB-based nanoparticles across the BBB was evaluated by observing the fluorescent intensity. The translocation study was performed in an in vitro BBB model that were constructed based on mouse cerebral endothelial cells (bEnd.3). The results showed that ligand-coated TEB nanoparticles can be transported across BBB with high efficiencies (up to 29.02%). This is the first time that the fluorescent TEB nanoparticles were applied as nano-carriers for transport across the BBB. Such fluorescent polymeric nanoparticles have the potential applications in brain imaging or drug delivery.

Hydrogen sulfide as a gas indicator molecule plays an important role in various human physiological processes. However, due to the high volatility and diffusivity of H2S in biological systems, it is very difficult to implement a precise assay for H2S detection. Compared with the destructive instrumental methods, assays based on fluorescence probes provide noninvasive and real-time detections of H2S in living cells. In this work, we presented a fluorescent nanoprobe based on dye-functionalized Au nanorods (NRs)@silica for sensitive and selective detection of H2S in vitro and living cells. With the metal enhanced fluorescence effect, the fluorescence turn-on and turn-off were controlled by the formation and disassembly of coordination compound between dyes and copper ions. Silica matrix was used to coat the Au NRs to prevent them from the biological cytotoxicity. The effects of the different distances between Au NRs and fluorophores on fluorescent enhancement were explored and approximately 5-fold fluorescence enhancement was obtained with a distance of 22 nm. A detection of limit of 17 nM was achieved. In addition, visualization of exogenous and endogenous H2S in living cells was validated.

Intracellular miRNA detection is vitally important for diagnosing severe diseases like cancer and for resolving the ensemble of gene products that orchestrate the living state of cells. Recent advances in the design, synthesis, and application of biocompatible nanomaterials as platforms for probing miRNAs have enabled widespread efforts to mobilize new compounds in biomedical research. Two-dimensional graphene-like nanomaterials exhibit desirable physical properties such as convenient quantum size and dynamic interface functionality. Because miRNAs regulate gene expression in the cytoplasm, it is imperative that nanomaterials targeting them are properly delivered. Unloading of nanomaterials into the cytosol using the cellular endocytic transport pathway is often hindered by an inability to cross the endosomal membrane. To address this challenge, we designed a strategy to deliver functionalized WSe2 nanosheets (FWNs) to the cytosol using perfluorinated surface functionalization. Perfluorinated compounds are both hydrophobic and lipophobic, exhibiting excellent phase-separation tendency in both polar and nonpolar environments. FWNs are ∼120 nm in diameter, feature low toxicity, and exhibit excellent stability in serum. The fluorinated nanostructure of FWNs enabled efficient cytosolic delivery from the endomembrane system. The fidelity of this approach was confirmed through intracellular delivery of two DNA probes (ssDNA-21 and ssDNA-210), which resulted in specific labeling of cytosolic miRNA and demonstrated the utility of this system for direct cytosolic biosensing.

The design and synthesis of biocompatible nanomaterials as cargoes for the intracellular delivery of therapeutic proteins or genes have attracted intense attention because of their potential for use in therapeutics. Despite the advances in this area, very few nanomaterials can be efficiently delivered to the cytosol. To address these challenges, crystalline nanoflower-like particles are designed and synthesized from fluorinated sequence-defined peptoids; the crystallinity and fluorination of these particles enable highly efficient cytosolic delivery with minimal cytotoxicity. A cytosol delivery rate of 80% has been achieved for the fluorinated peptoid nanoflowers. Furthermore, these nanocrystals can carry therapeutic genes, such as mRNA and effectively deliver the payload into the cytosol, demonstrating the universal delivery capability of the nanocrystals. The results indicate that self-assembly of crystalline nanomaterials from fluorinated peptoids paves a new way toward development of nanocargoes with efficient cytosolic gene delivery capability.

This paper presents a self-powered wireless alarming sensor node (SWASN), which was designed to monitor the occurrence of concerning vibratory events. The major components of the sensor node include a vibration-threshold-triggered energy harvester (VTTEH) that powers the sensor node, a dual threshold voltage control circuit (DTVCC) for power management and a radio frequency (RF) signal transmitting module. The VTTEH generates significant electric energy only when the input vibration reaches certain amplitude. Thus, the VTTEH serves as both the power source and the vibration-event-sensing element for the sensor node. The DTVCC was specifically designed to utilize the limited power supply from the VTTEH to operate the sensor node. Constructed with only voltage detectors and MOSFETs, the DTVCC achieved low power consumption, which was 65% lower compared with the power management circuit designed in our previous work. Meanwhile, a RF transmit circuit was constructed based on the commercially available CC1110-F32 wireless transceiver chip and a compact planar antenna was designed to improve the signal transmission distance. The sensor node was fabricated and was characterized both in the laboratory and in the field. Experimental results showed that the SWASN could automatically send out alarming signals when the simulated concerning event occurred. The waiting time between two consecutive transmission periods is less than 125 s and the transmission distance can reach 1.31 km. The SWASN will have broad applications in field surveillances.

随着现代科技的发展,传感器的应用领域不断扩大,新型传感器日新月异,对相关课程的教学内容也提出了挑战.针对本三院校学生的具体情况改革教学方法,将翻转课堂的理念引入到《传感器原理及微传感》的课堂教学和实验教学过程中,提高了学生的学习积极性,取得了较好的教学效果.

This paper presents a microfluidic sensing chip for the quick, low-cost measurement of blood plasma viscosity with a microliter sample volume. This chip is comprised of a magnetoelastic (ME) sensor, a planar measurement coil and a microfluidic system. The ME sensor is a wireless resonating sensor that operates through external magnetic fields. The planar coil is used to both actuate the sensor into mechanical resonance and detect the resonant frequency of the sensor. Due to the planar configuration of the measurement coil, the sensing chip can be fabricated by using a simple integration process (i.e., stacking and bonding) at a low cost. The sample volume required is 100 mu L. The sensing chip was first characterized by testing glycerol/water solutions with wide ranges of densities and viscosities. Next, to make a calibration plot correlating the sensor response with liquid viscosity, glycerol/water solutions with finely adjusted viscosities varying from 1.0 cP to 3.0 cP were tested, which covers the viscosity range of human blood plasma. Finally, the sensing chip was used to test various dilutions of human blood plasma samples. The results verify that the proposed sensing chip is capable of quickly measuring viscosity changes in blood plasma of small volume. (C) 2017 The Electrochemical Society. All rights reserved.

A self-powered event-triggered wireless sensor network was developed for monitoring sabotage activities. The network has the capability of identifying suspicious activities and automatically sending out alarming signals. The sensor network consists of self-powered wireless alarming sensor nodes (SWASNs), router nodes, receiver nodes, GSM network and PC terminal. The SWASN is powered by a novel vibration-threshold triggered energy harvester (VTT-EH), which generates significant electric energy to power the sensor node only when the input vibration amplitude excesses a certain threshold. With the event identification capability, the SWASN sends out alarming signals to router node if sabotage activity occurs. The alarming signal is then transmitted to the receiver node and the control center through GSM network. The GSM network is used in the proposed network to achieve long distance transmission and the capability of handling large amount of sensor nodes over large areas. The developed sensor network was tested. The results show that the designed function was realized. The proposed sensor network can be used in various applications of activity monitoring in the field.

This paper presents a novel lab-on-a-chip type biosensing system that is comprised of magnetoelastic (ME) biosensor, planar coil, and microfluidic system. The novelty of this system is to integrate planar coil to wirelessly actuate and detect the ME biosensor. Compared with solenoid coil that is traditionally used to measure ME sensors, the two-dimensional planar coil made by micro-fabrication process shows advantages of easy miniaturization and integration. The ME-sensor based microfluidic-chip was fabricated. By assembling poly-L-lysine coated ME biosensors into the chip, real-time in-liquid detection of yeast cells at different concentrations was successfully performed. The results showed that continuous decrease in the resonant frequency of the ME biosensor was observed as yeast cells were attaching on the sensor surface. Significant frequency shifts were obtained when the cell binding reached equilibrium. With the in situ real-time bio-sensing capability, this highly integratable system shows great potential of being used for rapid and low-cost bio-analysis.