bluuebunny/crossref_metadata_2025_split huggingface dataset:
DNA-Based Electrochemical Biosensor for Microrna-155 Detection By Exonuclease III -Aided Cascade Target Recycling
Authors: Yang Xiao , Feng Ming hui , Zhang Fei fei , Wang Zong hua 
Published: May 2020

MicroRNAs (miRNAs) are important biomarkers for early diagnosis and prognosis of genetic diseases including human cancers and neurological diseases, etc. They are a class of small (about 22 nucleotides) single-stranded non-protein-encoding RNAs, whose abnormal expressions are closely related to the pathogenesis of many malignant tumors. However, they have intrinsic characteristics such as low abundance, short length and sequence homology, so accurate and rapid analysis of miRNAs is of great significance for biological research, diagnosis and treatment of diseases. In this study, based on exonuclease III (Exo III) -aided cascade target recycling, a simple and sensitive electrochemical biosensor is developed for miRNA-155 detection, which is of an important biomarker for the diagnosis of breast cancer. At the same time, Ti3C2 MXene was synthesized and used as a support due to its special layered structure and metallic property. Noble metal nanoparticles were used to enlarge the electro-active surface area and facilitate the electron mobility of electrochemical biosensors. Moreover, MXene nanosheets embedded with noble metal nanoparticles (such as Au NPs, Ag NPs, Pt NPs) could totally ensure MXene nanosheets with improved conductivity and enhanced electrochemical properties. Therefor AuNPs/Ti3C2 MXene three-dimensional composite was selected as substrate for immobilizing capture DNA (cDNA) by Au-S chemical bonds. The whole sensing system is named as cDNA/AuNPs/ Ti3C2 Mxene /Au E. The cDNA was modified with methylene blue (MB) at the end of 3', resulting in a large initial electrochemical signal. In the presence of miRNA-155, Exo III cleaved the 3' end of the cDNA in the double strands, caused the electrochemical signal molecule MB to be released from the electrode surface, thereby reduced the electrochemical signal. The concentrations of miRNA-155 could be monitored simply and effectively by measuring the peak current difference of MB redox (ΔI=Ic﹣Ih, Ic represents the DPV peak current value obtained in the absence of miRNA-155, Ih represents the peak current value recorded in the presence of miRNA-155, and ΔI represents the change in peak current value). Under the optimal experimental conditions, the electrochemical sensor achieved a detection limit of 0.35 fM (S/N =3) with a linear range from 1.00 fM to 100 pM. This method also shows desirable stability, reproducibility and specificity. In conclusion, with its excellent analytical performance, the biosensor may have the potential to be used in the clinical diagnosis of breast cancer.
Keywords: Exonuclease III; miRNA-155; Au NPs; Ti3C2 Mxene; Electrochemical biosensor;

Figure 1
Oxide Coated Nano-Porous Ag Thin Film for Chemical Sensing By Gas Flow Sputtering
Authors: Hwang Sehoon , Park Young Min , Kim Hyun-Jong , Son Seong Ho , Yun Sungho , Lee Ho-Nyun 
Published: May 2020

A completely non-destructive analytical method is one of the great advantages of Raman spectroscopy. However, low efficiency of Raman signals should be improved to be widely used for detecting less than ppm of chemicals. Surface enhanced Raman scattering (SERS), which is a valuable technique for detecting the target substance very sensitively, is a method of amplifying Raman signals by the plasmon coupling effect at the gap between the nanoparticles. For this reason, materials and the nano-structure such as particle size, shape, gap and density were major factors for determining the performance of the SERS substrate.
In this study, gas flow sputtering (GFS) was used for fabricating SERS substrates. The nano-porous structure was observed using scanning electron microscope (SEM) and crystal structures were also analyzed by X-ray diffraction (XRD). The density of the nano-porous structure was calculated using the thickness of the film and the mass difference before and after deposition.
Silver (Ag) was widely studied as SERS substrate, due to excellent SERS effect and lower price than that of other noble metals. However, Ag has a significant degradation in SERS effect with time which appears to be a problem caused by oxidation of the Ag surface. Owing to this problem, fabricating a highly reproducible SERS substrate is a challenging issue and many researchers are conducting study.
To solve this problem, Ag dense film and oxide film were sequentially deposited. Then, Ag nano-porous thin film was deposited on the oxide film to form a dielectric nano-gap between Ag dense film and Ag nano-porous thin film. Also, to protect from oxidation, Ag nano-porous thin film was coated with a thin oxide film using in-situ co-sputtering. The structure of nano-porous thin film was controlled by varying the sputtering power, time, process pressure.
As a result, rhodamine 6G of less than 0.5 uM was successfully detected and it showed much improved Raman signal compared with single Ag nano-porous thin film. In addition, the aging problem, which was the most important issue, also reduced noticeably.
Insights into the Kinetics of Electrostatic Denaturation of Surface-Bound DNA
Authors: Taylor Jeffrey K , Raghu Gayatri , West Ryan M 
Published: May 2020

Electrostatic denaturation of double-stranded DNA (dsDNA), i.e. electrochemical melting, can be used to interrogate duplex stability, allowing discrimination of dsDNA based on the presence of mismatches, deletions, and other mutations (1). More recently, electrochemical melting has allowed examination of DNA-small molecule interactions, e.g. DNA-cisplatin adducts (2). Denaturation of dsDNA in self-assembled monolayers (SAMs) occurs when a sufficiently negative potential is applied to the DNA-modified working electrode, presumably due to strong electrostatic repulsion of the phosphate background in the presence of the high electric field in the electrical double-layer (109 V/m). In our work, we use a purely electrochemical approach for monitoring the electric field-induced melting of dsDNA SAMs. Application of moderate negative potentials (-500 mV vs. Ag/AgCl) is sufficient to melt DNA without substantial thiol reduction (1). Here we present the dependence of electrochemical melting on the temperature of the buffer and the frequency of applied potential in an effort to better understand the complex interplay of DNA stability, backbone charge screening, and double-layer structure. Previous studies have shown that electrochemical melting depends on temperature in the range 10 – 18 °C while no effect of temperature was found above this 18 °C (3). Here, we explore the temperature dependence in more detail to better understand how temperature effects the electric field effects. In particular, we examine the kinetics of the melting process at different temperatures. Additionally, the formation of the high electric fields necessary for melting depends on the screening of electrode charge by counterions from solution. Rant et al. reported that the responsiveness of the immobilized DNA is directly related to the formation of the electrical double-layer (4). By applying fast potentials pulses to melt the DNA, we determine the frequency at which the rate of melting drastically decreases due to insufficient time for the strong field to develop. Together, the temperature and frequency dependence of electrochemical melting shines new light on the role of electrical fields on DNA stability.

References

1. S. Mahajan, J. Richardson, T. Brown and P. N. Bartlett, Journal of the American Chemical Society, 130, 15589 (2008).
2. E. Madrigal, G. Raghu, J. Taylor and R. M. West, Cross-linking of DNA Monolayers by Cisplatin Examined Using Electrochemical Melting Analysis, The Journal of Electroanalytical Chemistry, Submitted (2019).
3. E. Papadopoulou, M. Meneghello, P. Marafini, R. P. Johnson, T. Brown and P. N. Bartlett, Bioelectrochemistry, 106, 353 (2015).
4. C. Sendner, Y. W. Kim, U. Rant, K. Arinaga, M. Tornow and R. Netz, physica status solidi (a), 203, 3476 (2006).
(Plenary) Wearable Sensors for Monitoring Chemical Markers: Beyond Steps and Vitals
Authors: Wang Joseph 
Published: May 2020

Wearable sensors have received a major recent attention owing to their considerable promise for monitoring the wearer’s health and wellness. The medical interest for wearable systems arises from the need for monitoring patients over long periods of time. These devices have the potential to continuously collect vital health information from a person’s body and provide this information to them or their healthcare provider in a timely fashion. Unlike early efforts aimed at monitoring mobility and vital signs, our recent efforts aim at filling the gaps by providing continuous biochemical information. The new chemical sensing wearable platforms provide new avenues to continuously and non-invasively monitor individuals and can thus tender crucial real-time information regarding a wearer’s health. This presentation will discuss recent developments in the field of wearable electrochemical sensors integrated directly on the epidermis or within the mouth for various non-invasive biomedical monitoring applications [1-3]. Particular attention will be given to non-invasive monitoring of metabolites and electrolytes using flexible amperometric and potentiometric sensors, respectively, along with related materials, energy and integration considerations. Microneedle sensor arrays for multiplexed ISF monitoring will also be discussed also with wearable energy harvesters aimed to power these devices. The preparation and characterization of such wearable electrochemical sensors will be described, along with their current status and future prospects and challenges.
REFERENCES [1] "Wearable Chemical Sensors: Present Challenges and Future Prospects" A. J. Bandodkar, I. Jeerapan, J. Wang, ACS Sensors,
2016, 1, 464.
[2] A. J. Bandodkar and J. Wang, “Non-invasive wearable electrochemical sensors: a review”, Trends Biotechnol.,
2014, 32, 363.
[3] “Wearable biosensors for healthcare monitoring”, J. Kim, A. S. Campbell, B. Esteban-Fernández de Ávila, and J. Wang, Nature Biotechnology, 2019, 37, 389.
Raman Sensor Design for Point of Care Medical and Environmental Analysis
Authors: Charron Benjamin , Masson Jean-Francois 
Published: May 2020

Due to its ability to directly probe water containing samples as well as yielding specific signal, Raman spectroscopy is rapidly expanding to various fields. The great potential of this technique has also drawn a lot of attention on the different ways by which Raman signal can be enhanced, notably by plasmonic nanostructures. Plasmonic materials enhance Raman by generating an enhanced oscillating field. The strength of that field has a great impact on the intensity of the Raman signal obtained from analysis with these materials. This field can be optimized by various methods shown before like an optimized nanostructure, addition of a stronger plasmonic metal, or alternating layers of metal and dielectric. We report here the result of a study of a newly designed plasmonic sensor combining multiple of these previously mentioned optimizations. This sensor is designed to be used for point of care analysis of street drugs on Canadian supervised consumption or overdose prevention sites and for analysis of microalgaes secretions in the ocean. Street drugs are to be analysed in order to detect contaminants and dangerous component. A user warned about a dangerous compound in its drugs is more likely to reduce his dose or even avoid taking the drug at all, effectively preventing unfortunate consequences. On the other hand, algaes play an important role in the marine ecosystem. Their life cycles and the bio-molecules they produce correlate with the environment in which they grow. Being able to detect, identify and quantify these secretions in real time directly in the ocean would allow us to use them as sensors for global warming. As an example, the melting of the icecaps would locally dilute the nutrients which in turn would change the way the algaes survive and their secretions. The resulting sensor must therefor offer strong Raman signal and good stability, be easy to use and produce, and be cheap to produce.
To tackle these multiple challenges, we have developed a sensor produced directly on a stressed polymer sheet available in arts and craft stores. The sheets are covered with layers of metal and nanostructures before being heated in an oven. The heat causes the polymer to shrink, effectively wrinkling the metal sheets on its surface. This type of surface has first been studied with various thicknesses of silver and gold. The best surface was then studied with additional structures on its surface in order to create both a stronger and a more homogeneous surface.
Keeping the targeted analytes in mind, the sensors’ potential was evaluated both with 633 nm and 785 nm laser. Ability to choose the wavelength is important as a lower laser wavelength offers a stronger Raman intensity, but a higher wavelength limits fluorescence of the analyte or solution. Sensors were also tested both in air and in water, and compared with other Raman sensors.
Graphene Oxide Modified Electrode for DNA Amperometric Detection Using Microfluidic Electrophoresis Chip
Authors: Kim Hyo Eun , Schuck Ariadna , Kim Yong-Sang 
Published: May 2020

The amperometric technique of capillary electrophoresis (CE) is an electrochemical detection method with various advantages that is suitable for biosensors. The amperometric detection system can be easily integrated with the CE system without the need for complicated additional equipment for optical detection. For this reason, the size of the sensor can be reduced to micro-scale, also reducing the cost of the fabrication process, enabling this system to be used in point-of-care applications [1]. The optical method depends on the detection of the fluorescence intensity of the target sample. However, amperometric detection omits the pretreatment process of the sample, such as purification extraction of samples and fluorescent staining for detection [2]. These features allow the device system to be miniaturized and having a rapid response for applications like lab-on-a-chip [3]. Modified Au electrodes integrated with PDMS based microfluidic channels were proposed as an on-chip amperometric detection of CE for DNA sensors. The graphene oxide (GO)-modified Au electrodes were fabricated via photolithography process and drop-casting deposition. First, the deposited Au electrodes were patterned with positive photoresist (PR) using the photolithography method. Next, the graphene oxide was deposited 5 layers on the bare Au using drop-casting technique. Finally, the PR was dissolved by acetone and the unwanted GO was lifted-off. The surface characterization of this the GO-modified Au electrodes is shown in Fig. 1(a) by microscopy image. It was observed that the GO was deposited on Au electrodes following the desired pattern. This treatment amplifies the current signal of amperometric detection of the CE microchip. The performance of the CE amperometric detection device has been demonstrated by sensing an amplicon lambda phage DNA. Then, 1 µL of amplified lambda phage DNA (1 ng/µL) using the conventional polymerase chain reaction (PCR) with a 30-cycle reaction was used as target sample. Figure 1(b) shows the current peak of amperometric detection before (1.9 µA) and after (6.6 µA) GO-modified on the Au electrodes which amplified the sensitivity more than 3.5 times before electrode modification. The emphasized detection of lambda phage DNA using modified electrodes gives a further possibility of biomedical applications through our developed microchip.

References

1. D. E. Scott, S. D. Willis, S. Gabbert, D. Johnson, E. Naylor, E. M. Janle, J. E. Krichevsky, C. E. Lunte and S. M. Lunte, Analyst, 2015, 140, 3820–3829.
2. N.-C. Chen, C.-H. Chen, M.-K. Chen, L.-S. Jang, M.-H. Wang, Sens. Actuators B Chem. 2014, 190, 570–577.
3. K. Ha, G. S. Joo, S. K. Jha, Y.-S. Kim, Microelectr. Eng. 2009, 86, 1407–1410.

Figure 1
Synthesis and Electrochemical Application of MxFe3-XO4 (M=Cu,Co) for the Detection and Removal of Metal Pollutants
Authors: Mohammed Soumhi 
Published: May 2020

Over the last two decades, nanomaterials (metallic nanoparticles, carbonaceous nanostructures) have triggered great interest thanks to their specific physic-chemical properties. The improvements they have made in the field of electro-analysis are numerous. Thus, a wide range of physic-chemical technologies based on the use of inorganic materials for the detection and removal of water pollutants has become a promising voice. In this context, we were interested in the design of electrodes modified by nanomaterials of the spinel type CxFe3-xO4 for the detection and quantification of metallic micro pollutants in water. The phases of the spinel system were synthesized by the sol-gel method, and physic-chemical characterization was performed by ATD-TG, DRX and MEB. The methods used for the electrochemical test are cyclic voltammetry (CV), square wave voltammetry (SWV) and impedance spectroscopy (EIS).
The results of the physic-chemical analysis of the oxides showed that the phase is obtained at a calcination temperature of 600°C, and the electrochemical tests of the elaborate electrode revealed a very high sensitivity to ions (Mn2+, cd2+, pb2+, Hg2+).

Keywords:
nanoparticles, spinals, metal pollutants, modified electrode, electrochemical tests.
Preparation of Nanopore-Containing Metal Oxide Particles and Their Gas Sensing Characteristics
Authors: Akamatsu Takafumi , Itoh Toshio , Masuda Yoshitake 
Published: May 2020

We reported the successful formation of nanopores within core-shell type metal oxide particles using the shell layer as a template. Using the polyol method, core-shell type metal oxide particles such as cerium oxide, zinc oxide, and cobalt oxide with primary particles of ~10 nm and secondary particle sizes between 20 and 300 nm were prepared, where the polymer shells comprised 10-20 wt% of the total mass. These particles were easily dispersed in water and organic solvents without the use of dispersants. In addition, the core-shell type metal oxide particles were composed of an agglomeration of several tens of nanometer-sized core-shell primary particles, with sintering at 400 °C generating the desired nanopore-containing metal oxide particles. It was reported that in the SnO2 gas sensor for H2S sensing, nanopore manipulation in the sensor response layer leads to an increased response and selectivity toward H2S compared to the smaller and more reactive hydrogen gas. We therefore expected that an increase in the specific surface area of sensing films through the formation of nanopores in the secondary particles could result in additional reaction sites to lead to a higher gas responsiveness. Indeed, this was assumed to account for the high selectivities of high specific surface area cobalt nanofiber and nanosheet gas sensors toward acetone gas and ethanol gas. In this work, metal oxide particles with nanopores were prepared by a polyol method and sintering. The gas sensor characteristics of the particles with nanopores were compared with those of the particles without nanopores, and the effectiveness of 3D-nanostructure for gas sensing was also examined.
Figure. Schematic representation of the strategy used to prepare the 3D nanostructure of metal oxide particles with nanopores.

Figure 1
Ultra-High-Sensitive Detection Using Pulse-Heating of MEMS-Type Oxide Semiconductor Gas Sensor: (1) Detection of Toluene in Ppt Level
Authors: Shimanoe Kengo , Suematsu Koichi , Watanabe Ken 
Published: May 2020

Ultra-High-Sensitive gas detection in ppt level has been proposed by using pulse-heating of MEMS-device based on SnO2. My group reported three important factors, receptor, transducer functions and utility factor, for gas sensor material designs and their integration in 2003 (1) and 2006 (2), respectively. In 2014, based on the integration of the above factors, the gas sensor using Pd-SnO2 clusters prepared by hydrothermal treatment could successfully detect toluene in ppb level (3). To enhance the sensor response more, we investigated the combination of utility factor and pulse-heating of MEMS. In 2018, we reported that such sensor responded to toluene in 0.1 ppb (4). To enhance the sensor response, we paid attention to oxygen adsorption species and the amounts. In the case of Pd-SnO2, oxygen adsorbed as mainly O2- on the surface, but the amounts become smaller with decreasing in temperature. To overcome such oxygen adsorption state, we investigated the preheating and waiting-time before pulse-heating for measurement. Finally, the gas response was found to increase as shown in Fig. 1. It is found that the sensor response depends on the waiting-time between pre-heating and measure-heating. In the presentation, I will show the details of UHS (Ultra-High Sensitive) gas sensor.
References
(1) N. Yamazoe, G. Sakai, K. Shimanoe, Catalysis Surveys from Asia, 7(1), 63-75 (2003).
(2) K. Shimanoe, N. Yamazoe, Proc. The 4th AIST International Workshop on Chemical Sensors, pp. 43-51 (2006).
(3) K. Suematsu, Y. Shin, Z. Hua, K. Yoshida, M. Yuasa, T. Kida, K. Shimanoe, ACS Appl. Mater., 6, 5319−5326 (2014).
(4) K. Suematsu, W. Harano, T. Oyama, Y. Shin, K. Watanabe, K. Shimanoe, Anal. Chem., 90(19), 11219-11223 (2018).

Figure 1