Xuesong Ye

Direct electron transfer glucose biosensor based on glucose oxidase self-assembled on electrochemically reduced carboxyl graphene

A glucose biosensor based on direct electron transfer of glucose oxidase (GOD) self-assembled on the surface of the electrochemically reduced carboxyl graphene (ERCGr) modified glassy carbon electrode has been reported. X-ray photoelectron spectroscopy (XPS) analyses of ERCGr indicate most of the oxygen-containing groups such as epoxy/ether groups and hydroxyl groups in the carboxyl graphene were eliminated, while carboxylic acid groups remained. GOD was immobilized on the ERCGr modified glassy carbon electrode via self-assembly. The cyclic voltammetric result of the electrode shows a pair of well-defined and quasi-reversible redox peaks with a formal potential of -0.467 V and a peak to peak separation of 49 mV, revealing that the direct electron transfer between GOD and the electrode has been achieved. The proposed biosensor exhibits a linear response to glucose concentrations ranging from 2 to 18 mM with a detection limit of 0.02 mM. Moreover, this facile, fast, environment-friendly and economical preparation strategy of ERCGr may be extended for the preparation of other graphene based enzyme electrode biosensors.

The fabrication of an olfactory receptor neuron chip based on planar multi-electrode array and its odor-response analysis.

A novel olfactory neurochip based on olfactory receptor neurons (ORNs) cultivated on the surface of the 60-channel planar multi-electrode array (MEA) devices was developed in this study. In order to investigate the odor-response characteristics of ORNs, two types of odorants at different concentrations were quantitatively pumped into the neurochip by a customized gas intake system, and the extracellular electrical activities of multiple ORNs were simultaneously recorded in vitro. Accordingly, the odor-response features of ORNs such as firing amplitude, firing threshold, firing rate as well as firing channels were analyzed qualitatively and quantitatively in terms of ORN spike trains. Especially, after introducing the classification algorithm based on the spike threshold, the odor-response maps from the multiple sites could be used to identify dl-limonene (LIM) and isoamyle acetate (ISO) odorants. These preliminary studies indicate that the ORN-based biosensor developed here has a potential capability of distinguishing different odorants as a true bionic electronic nose.

The fabrication of superlow protein absorption zwitterionic coating by electrochemically mediated atom transfer radical polymerization and its application

A well-controllable electrochemically mediated surface-initiated atom transfer radical polymerization (e-siATRP) method for the fabrication of superlow protein absorption zwitterionic hydrogel coatings based on poly(sulbetaine methacrylate) (pSBMA) was developed in this work. The effects of the electric condition on polymerization as well as its antifouling performances both in vitro and in vivo were also investigated. Different potentials (-0.08 V, -0.15 V and -0.22 V) and polymerization times (from 8 to 48 h) were chosen to study the polymerization procedure. X-ray photoelectron spectroscopy, atomic force microscopy and ellipsometry measurements were used to characterize the properties of the polymer layers. Ellipsometry measurements showed that a higher potential provided faster polymerization and thicker polymer layers; however, the protein absorption experiments showed that the best polymerization condition was under a constant potential of -0.15 V and 32 h, under which the protein absorption was 0.8% in an enzyme-linked immunosorbent assay (compared to a bare gold electrode). The electrodes with a pSBMA coating effectively deduced the current sensitivity decay both in undiluted serum and in vivo. The usage of the commercially available polymerization monomer of SBMA, the simple convenient synthesis process regardless of the presence of oxygen and the excellent controllability of e-siATRP make it a very promising and universal technique in the preparation of zwitterionic polymer coatings, especially in the development of biocompatible material for implantable devices such as neural and biosensor electrodes.

A low-power, wireless, wrist-worn device for long time heart rate monitoring and fall detection

A new low-power wrist-worn miniature device used for real-time wireless heart rate (HR) monitoring and fall detection is presented here. This device consists of sensors, signal condition circuits, microcontroller, and system communication module. Power management and algorithms are applied to achieve low power function. Using PASW Statistics 18.0(SPSS Statistics) software to analyze the 54 HR date gotten from Six subjects, we find that the average and standard deviation of the proposed device are 60.83 and 9.705 while they are 61.96 and 9.317 by using POLAR RS100(Polar Electro). The Pearson correlation coefficient is 0.975(p<;0.01). Results show that proposed device has good consistency as compared to the POLAR RS100. A low-power, low-cost MEMS accelerometer is used to detect the fall. Results show that we can detect the occurrence of a fall according to the threshold which is significant different from stationary, walking and standing up from sitting situations. When people worn the device fall down, an interrupt will be generated and sent to the microcontroller for further process immediately. 245 samples are tested, and the fall forwards detection accuracy is 93.75%. The device is useful to detect heartbeat problems in long-term vital sign monitoring such as combat medics, mountain climbers, etc. And also it is useful to detect health condition of elderly people.

Comparative study of SAW temperature sensor based on different piezoelectric materials and crystal cuts for passive wireless measurement

As widely reported substrates for surface acoustic wave (SAW) temperature sensors, YX-cut quartz, YZ-cut LiNbO3 and 128°YX-cut LiNbO3 are selected to fabricate different one-port SAW resonator temperature sensors and comprehensive comparative studies of their performance and specifications are conducted carefully in this paper. Firstly, SAW sensors of each cut with 50 different layouts were designed and fabricated according to the calculated SAW velocity, and a general wireless measurement platform was setup. Secondly, under the same test conditions, Q factor, temperature sensitivity and decaying waves of these sensors were tested, and along with the calculated temperature coefficient of frequency (TCF), these parameters were finally compared respectively. After comparison, the conclusions are as follows: LiNbO3 sensors had higher temperature sensitivity, and showed superiority without the limitation of distance in wireless measurements, while quartz sensors performed well when the distance increased, and this suggests they can be applied to long distance sensing for their high Q factor even the sensitivity is moderate.

A needle-type glucose biosensor based on PANI nanofibers and PU/E-PU membrane for long-term invasive continuous monitoring

A minimally invasive glucose biosensor capable of continuous monitoring of subcutaneous glucose has been developed in this study. This sensor was prepared using electropolymerized conductive polymer polyaniline (PANI) nanofibers as an enzyme immobilization material and polyurethane (PU)/epoxy-enhanced polyurethane (E-PU) bilayer coating as a protective membrane. The sensor showed almost the same sensitivity (63nA/mM) and linearity (0-20mM with the correlation coefficient r2 of 0.9997) in both PBS and bovine serum tests. When stored in 37°C bovine serum, the sensors sensitivity gradually increased about 30% of the initial value within the first 13 days and then remained stable for the rest of the study period of 53 days. In vivo implantation experiments using mice models showed real-time response to the variation of blood glucose with an average signal delay of about 8min. Continuous monitoring showed that the sensor response increased for the first 12 days and then entered a stable period for 14 days. The sensors baseline (530±10nA) and the total response to 1ml 50% dextrose injection were almost the same (267±15nA) in the stable period. The in vivo stable performances indicated that the sensor could be used as an implantable device for long-term invasive monitoring of blood glucose.

A novel implantable saw sensor for blood pressure monitoring

A novel implantable surface acoustic wave (SAW) sensor has been developed for blood pressure monitoring. The sensor is a wireless and batteryless microsystem composed of an SAW resonator, an oscillating circuit and an RF power converter. The total volume of the sensor is 1.9cm3 and the weight is 2.5g including its bio-compatible silicone coating. The sensitivity of the sensor is 1.75 KHz/mmHg. In vivo tests have been performed in a rat, showing the capability of the sensor for monitoring the blood pressure of small laboratory animals.

Vertically aligned PANI nanorod arrays grown on graphene oxide nanosheets for a high-performance NH3 gas sensor

In this paper, vertically aligned PANI nanorod arrays were successfully prepared on GO nanosheets at low temperature via a dilute polymerization method, in which the GO nanosheets with abundant hydrophilic groups were employed to support the heterogeneous growth of uniformly-distributed PANI nanorod arrays. The acquired nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). NH3 sensing performances of the as-prepared nanocomposite were carefully examined. With the help of the enhanced synergistic effect derived from the large number of p–n heterojunctions in the deliberately-designed microstructure, the device exhibited an enhanced response to NH3 vapor (14.63 at 50 ppm), wide dynamic range (1–6400 ppm), and fast response and recovery processes, in comparison to pure PANI nanofibers. The impact of the drop-coating amount of the sensing nanocomposite on the sensing performances was also investigated to find out the suitable amount for fabricating a high-performance ammonia sensor. Herein, the superior performances of the proposed well-organized microstructure make it an effective nanocomposite for gas sensing applications.

Progress in defining heterogeneity and modeling periglomerular cells in the olfactory bulb

In recent years the evolution of olfactory bulb periglomerular cells, as well as the function of periglomerular cells in olfactory encoding, has attracted increasing attention. Studies of neural information encoding based on the analysis of simulation and modeling have given rise to electrophysiological models of periglomerular cells, which have an important role in the understanding of the biology of these cells. In this review we provide a brief introduction to the anatomy of the olfactory system and the cell types in the olfactory bulb. We elaborate on the latest progress in the study of the heterogeneity of periglomerular cells based on different classification criteria, such as molecular markers, structure, ion channels and action potentials. Then, we discuss the several existing electrophysiological models of periglomerular cells, and we highlight the problems and defects of these models. Finally, considering our present work, we propose a future direction for electrophysiological investigations of periglomerular cells and for the modeling of periglomerular cells and olfactory information encoding.

Label-free DNA biosensor based on cladding-etched thin-core fiber modal interferometer

The fabrication and characterization of a highly sensitive DNA biosensor based on thin-core fiber modal interferometer (TCFMI) are presented. The TCFMI is made by using a thin-core fiber (TCF) with core diameter of ~3.0 μm and etched by using Hydrofluoric (HF) acid solution for sensitivity enhancement. A thin layer of polymer (PLL, poly-L-lysine) was coated on the sensor surface and experimentally demonstrated for the detection of hybridization of deoxyribonucleic acid (DNA).