Wireless Wearable Ultrasound Sensor to Characterize Respiratory Behavior.

A wireless wearable sensor on a paper substrate was used to continuously monitor respiratory behavior that can extract and deliver clinically relevant respiratory parameters to a smartphone. Intended to be placed horizontally at the midpoint of the costal margin and the xiphoid process as determined through anatomical analysis and experimental test, the wearable sensor is compact at only 40 × 35 × 6 mm3 in size and 6.5 g weight including a 2.7 g lithium battery. The wearable sensor, consisting of an ultrasound emitter, an ultrasound receiver, wireless transmission system, and associated data acquisition, measures the linear change in circumference at the attachment location by recording and analyzing the changes in ultrasound pressure as the distance between the emitter and the receiver changes. Changes in ultrasound pressure corresponding to linear strain are converted to temporal lung volume data and are wirelessly transmitted to an associated custom-designed smartphone app. Processing the received data, the mobile app is able to display the temporal volume trace and the flow rate vs. volume loop graphs, which are standard plots used to analyze respiration. From the plots, the app is able to extract and display clinically relevant respiration parameters, including forced expiratory volume delivered in the first second of expiration (FEV1) and forced vital capacity (FVC). The sensor was evaluated with eight volunteers, showing a mean difference of the FEV1/FVC ratio as bounded by 0.00-4.25% when compared to the industry-standard spirometer results. By enabling continuous tracking of respiratory behavioral parameters, the wireless wearable sensor helps monitor the progression of chronic respiratory illnesses, including providing warnings to asthma patients and caregivers to pursue necessary medical assistance.

Wireless Wearable Ultrasound Sensor on a Paper Substrate to Characterize Respiratory Behavior.

Respiratory behavior contains crucial parameters to feature lung functionality, including respiratory rate, profile, and volume. The current well-adopted method to characterize respiratory behavior is spirometry using a spirometer, which is bulky, heavy, expensive, requires a trained provider to operate, and is incapable of continuous monitoring of respiratory behavior, which is often critical to assess chronic respiratory diseases. This work presents a wireless wearable sensor on a paper substrate that is capable of continuous monitoring of respiratory behavior and delivering the clinically relevant respiratory information to a smartphone. The wireless wearable sensor was attached on the midway of the xiphoid process and the costal margin, corresponding to the abdomen-apposed rib cage, based on the anatomical and experimental analysis. The sensor, with a footprint of 40 × 35 × 6 mm3 and weighing 6.5 g, including a 2.7 g battery, consists of three subsystems, (i) ultrasound emitter, (ii) ultrasound receiver, and (iii) data acquisition and wireless transmitter. The sensor converts the linear strain at the wearing site to the lung volume change by measuring the change in ultrasound pressure as a function of the distance between the emitter and the receiver. The temporal lung volume change data, directly converted from the ultrasound pressure, is wirelessly transmitted to a smartphone where a custom-designed app computes to show volume-time and flow rate-volume loop graphs, standard respiratory analysis plots. The app analyzes the plots to show the clinically relevant respiratory behavioral parameters, such as forced vital capacity (FVC) and forced expiratory volume delivered in the first second (FEV1). Potential user-induced error on sensor placement and temperature sensitivity were studied to demonstrate the sensor maintains its performance within a reasonable range of those variables. Eight volunteers were recruited to evaluate the sensor, which showed the mean deviation of the FEV1/FVC ratio in the range of 0.00-4.25% when benchmarked by the spirometer. The continuous measurement of respiratory behavioral parameters helps track the progression of the respiratory diseases, including asthma progression to provide alerts to relevant caregivers to seek needed timely treatment.

Transition metal dichalcogenide quantum dots: synthesis, photoluminescence and biological applications.

The unique electronic, physical and chemical properties of nanostructured transition metal dichalcogenide (TMD) materials have received great attention, specifically, with the decrease of size to several nanometers, particles named TMD quantum dots (QDs). The inherent properties of TMD QDs make them promising for a variety of applications, including catalytic, luminescence and biomedical. In this review, we first briefly introduce the controlled synthesis of TMD QDs using mechanical exfoliation, ion intercalation-assisted liquid exfoliation, free radical and electrochemical shear and hydrothermal/solvothermal reaction. We then summarize recent progress on chemical and biological applications of TMD QDs in detail.

Construction of a Graphene/Au-Nanoparticles/Cucurbit[7]uril-Based Sensor for Pb(2+) Sensing.

The development of highly sensitive and selective methods for the detection of lead ion (Pb(2+)) is of great scientific importance. In this work, we develop a new surface-enhanced Raman scattering (SERS)-based sensor for the selective trace measurement of Pb(2+). The SERS-based sensor is assembled from gold nanoparticles (AuNPs) and graphene using cucurbit[7]uril (CB[7]) as a precise molecular glue and a local SERS reporter. Upon the addition of Pb(2+), CB[7] forms stronger complexes with Pb(2+) and desorbs from AuNPs, resulting in a sensitive "turn-off" of SERS signals. This SERS-based assay shows a limit of detection (LOD) of 0.3 nm and a linear detection range from 1 nm to 0.3 µm for Pb(2+). The feasibility of the assay is further demonstrated by probing Pb(2+) in real water samples. This SERS-based analytical method is highly sensitive and selective, and therefore holds promising applications in environmental analysis.

In situ regulation nanoarchitecture of Au nanoparticles/reduced graphene oxide colloid for sensitive and selective SERS detection of lead ions.

In this work, the colloid of Au nanoparticles (AuNPs)/reduced graphene oxide (rGO) was synthesized by growth AuNPs on rGO via the reduction of HAuCl4 on graphene oxide (GO) nanosheets. The nanoarchitecture of the colloid could be controllably regulated through in-situ Pb(2+)-enhanced gold leaching reaction, which made the colloid be a flexible surface-enhanced Raman scattering (SERS) platform for Pb(2+) detection. Upon the addition of Pb(2+), the Raman signal of graphene underwent significant descent due to the decrease of the amount of the "hot spots", which was originated from Pb(2+)-accelerated dissolution of AuNPs on the graphene surface in the present of thiosulfate (S2O3(2-)). Based on the change of SERS signal through in situ regulation the nanoarchitecture of the colloid, a sensitive and selective strategy for Pb(2+) measurement was developed with a linear range from 5nM to 4µM as well as a low detection limit of 1nM. Furthermore, the SERS-based method was applied for the determination of Pb(2+) in water samples with satisfactory results.

A label-free colorimetric sensor for Pb2+ detection based on the acceleration of gold leaching by graphene oxide.

In this work, we developed a novel, label-free, colorimetric sensor for Pb(2+) detection based on the acceleration of gold leaching by graphene oxide (GO) at room temperature. Gold nanoparticles (AuNPs) can be dissolved in a thiosulfate (S2O3(2-)) aqueous environment in the presence of oxygen; however, the leaching rate is very slow due to the high activation energy (27.99 kJ mol(-1)). In order to enhance the reaction rate, some accelerators should be added. In comparison with the traditional accelerators (metal ions or middle ligands), we found that GO could efficiently accelerate the gold leaching reaction. Kinetic data demonstrate that the dissolution rate of gold in the Pb(2+)-S2O3(2-)-GO system is 5 times faster than that without GO at room temperature. In addition, the effects of surface modification and the nanoparticle size on the etching of AuNPs were investigated. Based on the GO-accelerated concentration-dependent colour changes of AuNPs, a colorimetric sensor for Pb(2+) detection was developed with a linear range from 0.1 to 20 µM and the limit of detection (LOD) was evaluated to be 0.05 µM. This colorimetric assay is simple, low-cost, label-free, and has numerous potential applications in the field of environmental chemistry.

Recyclable removal of bisphenol A from aqueous solution by reduced graphene oxide-magnetic nanoparticles: adsorption and desorption.

Reduced graphene oxide (rGO) nanosheets decorated with tunable magnetic nanoparticles (MNPs) were synthesized by a simple co-precipitation method and employed for recyclable removal of bisphenol A (BPA) from aqueous solution. The morphological characterization shows that Fe3O4 nanoparticles are uniformly deposited on rGO sheets. The magnetic characterization demonstrates that composites with various amounts of Fe3O4 nanoparticles are superparamagnetic. Due to the superparamagnetism, rGO-MNPs were used as recyclable adsorbents for BPA removal in aqueous solution. The kinetics of the adsorption process and the adsorption isotherm were investigated. The results indicate that the adsorption process is fitted to Langmuir model and the composites with lower density of MNPs represent better adsorption ability. In addition, its kinetics follows pseudo-second-order rate equation. Moreover, the adsorbents could be recovered conveniently by magnetic separation and recyclable used because of the easy desorption of BPA.

Sensitive Pb(2+) probe based on the fluorescence quenching by graphene oxide and enhancement of the leaching of gold nanoparticles.

A novel strategy was developed for fluorescent detection of Pb(2+) in aqueous solution based on the fact that graphene oxide (GO) could quench the fluorescence of amino pyrene (AP)-grafted gold nanoparticles (AP-AuNPs) and Pb(2+) could accelerate the leaching rate of AuNPs in the presence of S2O3(2-). In this system, fluorescence reporter AP was grafted on AuNPs through the Au-N bond. In the presence of GO, the system shows fluorescence quenching because of π-π stacking between AP and GO. With the addition of Pb(2+) and S2O3(2-), the system displays fluorescence recovery, which is attributed to the fact that Pb(2+) could accelerate the leaching of the AuNPs from GO surfaces and release of AP into aqueous solution. Interestingly, the concentration of GO could control the fluorescence "turn-off" or "turn-on" for Pb(2+) detection. In addition, GO is also an excellent promoter for the acceleration of the leaching of AuNPs and shortening the analytical time to ∼15 min. Under the optimal conditions, the fluorescence Pb(2+) sensor shows a linear range from 2.0 × 10(-9) to 2.3 × 10(-7) mol/L, with a detection limit of 1.0 × 10(-10) mol/L.

Graphene based electrochemical biosensor for label-free measurement of the activity and inhibition of protein tyrosine kinase.

In this paper, we report a simple, ultrasensitive and label-free method to evaluate the activity of protein tyrosine (Tyr) kinase based on the electrochemical signal of Tyr residues at a graphene modified glassy carbon electrode. It was found that graphene could enhance the electrochemical response of Tyr through electrocatalytic oxidation reaction. After phosphorylation by kinase, the phosphorylated Tyr (pTyr) is electro-inactive and the electrochemical signal is reduced. Therefore, the electrochemical response of Tyr residues in peptides can be used as a signal reporter to assay kinase activity. In this study, using Src-catalyzed Tyr-phosphorylation as a model, the activity of kinase can be evaluated with a linear range from 0.26 to 33.79 nM and an extraordinarily low detection limit of 0.087 nM. Moreover, this electrochemical biosensor can also be utilized for monitoring the inhibition of kinase using 4-amino-5-(4-chlorophenyl)-7-(tert-butyl) pyrazolo [3,4-d] pyrimidine, a small molecule inhibitor. On the basis of the inhibitor concentration dependent Tyr oxidation signal, the IC50 value was estimated to be 99 nM.

Graphene oxide as nanocarrier for sensitive electrochemical immunoassay of clenbuterol based on labeling amplification strategy.

A novel electrochemical immunosensor for sensitive detection of clenbuterol (CLB) is fabricated using glucose oxidase (GOD)-functionalized grahene oxide (GO) nanocomposites to label CLB. The immunosensor was constructed by layer-by-layer assembly colloidal prussian blue (PB), multiwalled carbon nanotubes (MWCNTs) and CLB antibodies (Abs) on a glassy carbon electrode (GCE). In this competitive immunoassay system, PB acts as the redox mediator to reduce H2O2 originated from the catalyst cycle of GOD. The high ratio of GOD to GO effectively amplified the signal for this competitive-type immunoassay. Under optimized conditions, the immunosensor shows a wide linear range from 0.5 to 1,000 ng/mL with a low detection limit of 0.25 ng/mL. The dual signal amplification of GOD-functionalized GO nanocomposites as a label is promising to be applied to design other sensitive immunosenseors.

Electrochemical sensor for bisphenol A based on magnetic nanoparticles decorated reduced graphene oxide.

Bisphenol A (BPA), as one kind of endocrine-disrupting chemicals, has adverse impact on human health and environment. It is urgent to develop effective and simple methods for quantitative determination of BPA. In this work, an electrochemical sensor for BPA based on magnetic nanoparticles (MNPs)-reduced graphene oxide (rGO) composites and chitosan was presented for the first time. The MNPs-rGO composites were characterized by scanning electron microscopy, X-Ray diffraction and Fourier transform infrared spectroscopy. Electrochemical studies show that MNPs-rGO composites can lower the oxidation overpotential and enhance electrochemical response of BPA due to the synergetic effects of MNPs and rGO. Under the optimal experiment conditions, the oxidation peak current was proportional to the concentration of BPA over the range of 6.0×10(-8) to 1.1×10(-5)molL(-1) with the detection limit of 1.7×10(-8)molL(-1). Moreover, the MNPs-rGO based electrochemical sensor shows excellent stability, reproducibility and selectivity. The electrochemical sensor has been successfully applied to the determination of BPA in real samples with satisfactory results.

Bacitracin-conjugated superparamagnetic iron oxide nanoparticles: synthesis, characterization and antibacterial activity.

Bacitracin-conjugated superparamagnetic iron oxide (Fe(3)O(4)) nanoparticles were prepared by click chemistry and their antibacterial activity was investigated. After functionalization with hydrophilic and biocompatible poly(acrylic acid), water-soluble Fe(3)O(4) nanoparticles were obtained. Propargylated Fe(3)O(4) nanoparticles were then synthesized by carbodiimide reaction of propargylamine with the carboxyl groups on the surface of the iron oxide nanoparticles. By further reaction with N(3)-bacitracin in a Cu(I)-catalyzed azide-alkyne cycloaddition, the magnetic Fe(3)O(4) nanoparticles were modified with the peptide bacitracin. The functionalized magnetic nanoparticles were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, TEM, zeta-potential analysis, FTIR spectroscopy and vibrating-sample magnetometry. Cell cytotoxicity tests indicate that bacitracin-conjugated Fe(3)O(4) nanoparticles show very low cytotoxicity to human fibroblast cells, even at relatively high concentrations. In view of the antibacterial activity of bacitracin, the biofunctionalized Fe(3)O(4) nanoparticles exhibit an antibacterial effect against both Gram-positive and Gram-negative organisms, which is even higher than that of bacitracin itself. The enhanced antibacterial activity of the magnetic nanocomposites allows the dosage and the side effects of the antibiotic to be reduced. Due to the antibacterial effect and magnetism, the bacitracin-functionalized magnetic nanoparticles have potential application in magnetic-targeting biomedical applications.

A colorimetric sensor based on catechol-terminated mixed self-assembled monolayers modified gold nanoparticles for ultrasensitive detections of copper ions.

A colorimetric sensor for Cu(II) ions has been developed based on mixed self-assembled monolayers (SAMs) modified gold nanoparticles (AuNPs). The AuNPs were modified with mixed SAMs consisting of mercaptosuccinic acid and the product of electrochemically triggered Michael addition reaction of 4-thiouracil and catechol. In the presence of Cu(II) ions, the coordination of Cu(2+) to catechol-terminated AuNPs leads to aggregation-induced changes of surface plasmon resonance. The cost-effective chemical sensor allows rapid, sensitive and selective detection of Cu(2+) ions, indicating its potential application in environmental field.

Fluorescent probe for Fe(III) based on pyrene grafted multiwalled carbon nanotubes by click reaction.

The attempt to decorate carbon nanotubes with organic molecules to form new functional materials has attracted broad attention in the scientific community. Here, we report the covalent functionalization of multiwalled carbon nanotubes (MWCNTs) with pyrene via Cu(I)-catalysed azide/alkyne click (CuAAC) reactions under mild conditions to afford the nanocomposites of pyrene-MWCNTs. Fourier transform infrared spectroscopy (FT-IR), ultraviolet and visible spectroscopy (UV-Vis), and fluorescence spectroscopy were used to characterize the nanocomposites of pyrene clicked MWCNTs. Experimental results indicate that the CuAAC reaction occurs in an efficient manner and the spacer linking MWCNTs and the photoactive molecule is well defined. In contrast to the noncovalent functionalization of π-π stacking, the nanocomposites of pyrene clicked MWCNTs show relatively strong fluorescence and have potential applicability in photoluminescent devices as a highly sensitive and selective fluorescence "turn-off" sensor for Fe(3+).

An electrochemical platform for acetylcholinesterase activity assay and inhibitors screening based on Michael addition reaction between thiocholine and catechol-terminated SAMs.

An electrochemical platform for acetylcholinesterase (AChE) activity assay and its inhibitors screening is developed based on the Michael addition reaction of thiocholine, the hydrolysis product of acetylthiocholine (AsCh) in the presence of AChE, with the electrogenerated o-quinone of catechol-terminated SAMs on a gold electrode. For understanding and confirming the mechanism of the reaction, the electrochemical behaviors of Michael addition reaction of two model compounds, cysteine (CYS) and glutathione (GSH), towards the catechol-terminated SAMs have been studied. The enzyme kinetics and the inhibition effects of three types of AChE inhibitors, which are tacrine, carbofuran and parathion-methyl, have been investigated using an amperometric method. Among these three inhibitors, tacrine exhibits the strongest inhibiting effect, which is reinforced by the resulting data of kinetic studies on each inhibitor's influence upon the enzyme activity.