bluuebunny/crossref_metadata_2025_split huggingface dataset:
Probing DNA Stability in High Electric Fields: Electrochemical Melting Analysis
Authors: West Ryan 
Published: July 2021

Here we present our results on the electric field-induced melting of surface-bound DNA (i.e. electrochemical melting). In particular, we examine the effects of the DNA-binding compound cisplatin on the stability of DNA within high electric fields. Cisplatin is an anticancer drug that has been used to successfully treat testicular, ovarian, and bladder cancers, among others (1). It crosslinks DNA between the N7 atoms of purine bases, resulting in changes in structure and stability, ultimately interfering with vital cellular processes in vivo.
Self-assembled monolayers (SAMs) of thiol-modified oligonucleotides on gold electrodes provide selective and sensitive interfaces for the development of chemical and biological sensors (2). While many transduction mechanisms have been utilized (including electrochemical, optical, and gravimetric) and many analytes targeted (e.g. small DNA-binding molecules, heavy metals, and specific DNA sequences), the unique steric and electrostatic environment of the crowded DNA in the electrical double-layer complicates the behavior of these biosensors (3). Electrical potentials applied at the DNA-SAM have been shown to modulate the behavior of these monolayers (4). Here, we utilize the electric field-effect to induce melting of the bound doublestranded DNA, and we monitor the kinetics of the melting process using square wave voltammetry (5).
We find that the effect of cisplatin on the melting behavior depends on the method used to the prepare the monolayer, in particular the melting depends on surface-coverage and heterogeneity of the resulting layers. Under some conditions, cisplatin results in an apparent stabilization of the DNA-SAM, and a destabilization in others. Significant differences in the resulting melting curves suggest that the mode of cisplatin-DNA binding varies depending on the SAM preparation method. The methodology presented here has the potential of (1) providing an electrochemical approach for studying the interaction between DNA and small molecules, and (2) providing a method for indirectly assessing the heterogeneity of DNA-SAMs via electrochemical melting in the presence of cross-linking agents.
1. R. A. Alderden, M. D. Hall and T. W. Hambley, Journal of chemical education, 83, 728 (2006).
2. J. J. Gooding and N. Darwish, The Chemical Record, 12, 92 (2012).
3. P. Gong and R. Levicky, Proceedings of the National Academy of Sciences, 105, 5301 (2008).
4. U. Rant, K. Arinaga, S. Fujita, N. Yokoyama, G. Abstreiter and M. Tornow, Organic & biomolecular chemistry, 4, 3448 (2006).
5. D. Ho, W. Hetrick, N. Le, A. Chin and R. M. West, Journal of The Electrochemical Society, 166, B236 (2019).
(Invited) Barcode-Based Biorecognition for Electrochemical and Photoelectrochemical Biosensing
Authors: Soleymani Leyla , Pandey Richa , Traynor Sarah , Victorious Amanda , Saha Sudip 
Published: July 2021

Biosensors are devices that combine biorecognition with signal transduction to analyze biologically-relevant targets. In order for these devices to be used in disease management, clinical decision making, and health monitoring, they must deliver sufficient sensitivity, specificity, and speed at the point-of-care and rely on minimal sample processing. This work is focused on developing integrated biorecognition and signal transduction strategies for enhancing the performance metrics of biosensors.
Barcode-based biorecognition systems translate analyte capture to the release of specific signal transducing barcodes. We have focused on developing barcode-based systems that are compatible with photoelectrochemical and electrochemical readout for targeting proteins and nucleic acids. These systems translate molecular recognition elements using functional nucleic acids and antibody-DNA complexes for releasing an electroactive or a photoelectrochemical DNA barcode. We have combined these barcode-based systems with nanostructured electrochemical transducers for increased signal-to-noise-ratio and sensitivity.
By combining barcode-based biorecognition with electrochemical readout, we have developed handheld biosensors for clinical analysis of urinary tract infections. We have also used these strategies for detecting prostate cancer biomarkers. Integration of barcode-based biorecognition with photoelectrochemical readout presents a new modality for biosensing and opens the route for ultrasensitive and programmable biosensing.
(Invited) Development of Electrochemical 6-Well Plate for Immunosensors
Authors: Cui Feiyun , Zhou Zhiru , Zhou Hong 
Published: July 2021

While developing low-cost and multiplexing electrochemical (EC) devices for bioassay is very attractive, the miniaturization of reference electrodes (RE) is a critical issue for fabricating EC devices. Herein, a polymer-based EC device, named EC 6-well plate, is proposed and fabricated using a non-photolithography method. Polyethylene terephthalate glycol (PETG) is used as a substrate and laser-cut polyester (PET) film is used as a mask for patterning the electrodes. Acrylic mold with wells (60 μL) was bonded to the PETG substrate. Schematic diagrams (Figure 1) are used to illustrate the preparation of electrochemical 6-well plates. The diameter of the working electrode (WE) is 900 μm, and each WE-modifying step only requires 1 μL of reagent.
Both electrochemical (HCl method) and chemical methods (FeCl3 method) were proposed to prepare the solid-state Ag/AgCl RE. Precise time control is critical for the preparation procedure. It is hard to control the time in 1 s or under 1 s using the chemical method. Hence, the electrochemical method was selected for continued work since the reaction time can be precisely controlled. The stability of solid-state Ag/AgCl and drift of open circuit potential (OCP) can be affected by anions present in the background electrolyte. Herein, 0.1 M KCl, 1 M KCl, and 0.1 M KNO3 containing 5 mM K3[Fe(CN)6]/K4 [Fe(CN)6] were compared as the electrolytes. Considering that 0.01 M PBS is the most commonly used buffer solution for bioassay, 0.01 M PBS containing 5 mM K3[Fe(CN)6]/K4 [Fe(CN)6] was also included. OCP was recorded in these electrolytes for 1 hour. These results revealed that 0.1 M KCl is the best choice for the background electrolyte. The solid-state Ag/AgCl RE-based three-electrode system, the all Au three-electrode system (3E), and all Au two-electrode system (2E) were used to develop the immunosensor forClostridium difficile toxin B detection. Differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were applied to test the stability of the EC immunosensor. The three Au electrodes system showed just a minor DPV peak position shift and the standard deviation (SD) of OCP is about 0.0026 mV. The two Au electrodes system showed no DPV peak position shift and the SD of OCP is 0.32 mV. The solid-state Ag/AgCl RE-based three-electrode system showed a relatively large DPV peak position shift and the SD of OCP is about 4.6 mV. It is demonstrated that the all Au three-electrode system is superior to the solid-state Ag/AgCl RE-based three-electrode system for developing an immunosensor.

Figure 1
Simultaneous Electrochemical Determination of L-Dopa and Melatonin Using RGO-Spinel Nanocomposite Decorated Pt Electrode
Authors: R Leena , Madhavan Arya Sethu , Kunjappan Lineesh M 
Published: July 2021

Melatonin(N-acetyl-5-methoxy tryptamine) is a paracrine hormone secreted by pineal gland in the brain. This endogenous hormone has the ability to maintain the body circadian rhythm.1 3,4-dihydroxy-L-phenylalanine (L-Dopa) is the intermediate precursor of the Neurotransmitter dopamine. L-dopa, as one of catecholamines, is widely used as a source of dopamine in the treatment of Parkinson’s disease and epilepsy.2

Here, we report a sensor based on Platinum electrode modified with hydrothermally synthesized RGO and spinel nanoferrate for the simultaneous determination of L-Dopa and Melatonin.
Graphene oxide (GO)is a graphene derived material with oxygen containing functional groups. Graphene is a material with honey comb like structure of carbon atoms having sp2 bonding character. It exhibits high electrical conductivity, thermal conductivity and mechanical strength. GO containing functional groups like –OH, -COOH etc., acts as the site for the nucleation of metal oxide nanoparticles. It improves direct electron transfer between the electrode and the redox species by accelerating the electron transfer and enlarging the effective surface area.3 GO was synthesized by modified Hummers method. Chemically converted graphene RGO has been prepared by various reduction methods such as chemical, microwave, electrochemical, thermal, solvothermal/hydrothermal, by reducing its oxygen content.4 Green synthetic pathway of hydrothermal method was adopted for RGO synthesis to avoid hazardous chemical species and vigorous reaction conditions. Spinel ferrate like Copper Cobalt ferrate (CuCoFe2O4) was synthesized by sol-gel method and RGO/Spinel nanocomposite was prepared by physical mixing.5 The synthesized materials were characterized using various techniques like FTIR, XRD, FESEM etc. The electro catalytic activity of RGO/Spinel nanocomposite anchored platinum electrode for the simultaneous determination of melatonin and L-Dopa was studied using several voltammetric techniques. Bare platinum electrode was able to sense melatonin and L-Dopa both individually, but not simultaneously. Compared to RGO modified Platinum electrode, RGO-Spinel ferrate/Pt electrode exhibited good response in terms of lower potential of electrooxidation of L-Dopa and Melatonin with enhanced catalytic current with a peak separation of 0.48V. This enhancement in electrochemical performance is due to the increase in surface area as well as conductivity of the electrode upon modification with RGO-spinel nanocomposite which act as an excellent electrochemical oxidant for L-Dopa and melatonin.

References:

Levent, A.J. Diam. Relat. Mater.
2012, 21, 114-119

Yan, X.; Pan, D.; Wang, H.; Bo, X.; Guo, L.J. Electroanal. Chem.
2011, 663, 36-42

Pei, S.; Zhao, J.; Du, J.; Ren, W.; Cheng, H.J. Carbon.
2010, 48, 4466-4474

Luo, D.; Zhang, G.; Liu, J.; Sun, X.J. Phys. Chem. C.
2011, 115, 11327-11335

Elkholy, A. E.; Heakal, F. E.; Allam, K. A.J. RSC Adv.
2017, 7, 51888
(Invited) Electrochemical Detection of Gases in Ionic Liquids in Different Humidity Environments
Authors: Silvester Debbie S. , Doblinger Simon , Lee Junqiao 
Published: July 2021

Amperometric gas sensors (AGSs) are widely used due to their many advantages, such as low-cost, portability, durability, wide linear range, high sensitivity and high selectivity [1]. They are available commercially from a number of companies [2], and can detect a range of redox-active gases. The sensor devices typically employ a water/sulfuric acid mixture as the electrolyte in contact with three electrodes, covered by a gas-permeable membrane. Room temperature ionic liquids (RTILs) have strong potential for use as alternative ‘designer solvents’ in membrane-free AGSs [3], which would solve the existing technological problems of commercial AGSs, including the slow diffusion through the membrane and solvent evaporation. Their non-volatility would enable the membrane to be dispensed with, and the entire sensor to be miniaturised to provide optimal functionality over a much wider range of ambient conditions and with a longer lifespan. This allows and encourages innovative designs, with the potential for gas sensors to move from single, finite devices to more sophisticated systems that exploit recent advances in portable electronics and computing.
In this talk, I will discuss some of the challenges facing ionic-liquid based sensors, such as solvent leakage, sensitivity to moisture and accumulation of electrogenerated products, and how we can innovatively design electrode materials and electrolytes to overcome these challenges. In particular, I will show that the choice of ionic liquid is crucial in high humidity gas environments, due to the structuring and layering of the ions in the electrical double layer [4]. Overall, it is clear that RTILs show tremendous promise as electrolytes in sensors, but more understanding of their long-term operation and utility in real environments is still needed.

References

[1] Stetter JR, Li J, Amperometric Gas Sensors – A Review Chem. Rev.
2008, 108, 352–366.
[2] Xiong L, Compton RG, Amperometric Gas detection: A Review Int. J. Electrochem. Sci., 2014, 9, 7152–7181
[3] Buzzeo MC, Hardacre C, Compton RG Anal. Chem. 2004, 76, 4583–4588.
[4] Doblinger S, Lee J, Silvester DS J. Phys. Chem. C
2019, 123, 10727−10737.

Figure 1
Fast Screening of Dithiocarbamate, Chloronicotinyl and Organophosphate Pesticides By Raman Spectroelectrochemistry Based on EC-SERS Effect
Authors: Weber Michael , Fanjul Pablo , Ibáñez David , González-García María Begoña , Hernández-Santos David 
Published: July 2021

Electrochemical surface-enhanced Raman scattering (EC-SERS) effect is an outstanding procedure that ensures the enhancement of Raman signal by the electrochemical activation of the electrode surface. In that way, activation of metallic screen-printed electrodes (SPEs) by electrochemical routes leads to the generation of reproducible nanostructures with excellent SERS properties [1,2] and opens new gates for analytical applications.
In this work, detection of thiram, imidacloprid and chlorpyrifos pesticides is achieved by the development of a new procedure. This methodology offers a quick and easy protocol which consists of three steps: (1) preconcentration of the sample, (2) electrochemical activation of SPE and (3) Raman detection of pesticides (Figure 1).
Figure 1. Raman spectrum of thiram obtained following the proposed procedure.
Analysis of tap water samples provides suitable results that demonstrate the capabilities of the proposed method. In that way, Raman spectroelectrochemistry based on EC-SERS effect avoids the complicated instrumentation, tedious pretreatment protocols or time-consuming measurement procedures used in other methods, and offers an interesting alternative in fields as environmental and food safety.
References
[1] D. Martín-Yerga, A. Junquera-Pérez, M. B. González-García, J. V. Perales-Rondon, A. Heras, A. Colina, D. Hernández-Santos, P. Fanjul-Bolado, Electrochim. Acta 264 (2018) 183-190.
[2] D. Ibáñez, A. Junquera-Pérez, M. B. González-García, D. Hernández-Santos, P. Fanjul-Bolado, Talanta 206 (2020) 120190.

Figure 1
Low Cost Wearable Multi-Gas Chemical Sensor Badges for First Responders
Authors: Jayaraman Ambalavanan , Haanstad Trevor , Haanstad Meredith , Dubovik Margarita , Chamot Matthew , Marotta Christopher 
Published: July 2021

Introduction
Toxic Industrial Chemicals (TICs) are chemical substances which produce toxic effects if encountered in sufficient quantities and/or long durations. TICs are a great concern for the U.S. Department of Homeland Security (DHS) since they would be easier for terrorists to obtain and use than Chemical Warfare Agents (CWAs). Therefore, first responders need a small, rugged, wearable, monitor that alerts them when they are facing TICs, and if so, what is present and at what levels. While there are many commercially available handheld and personal gas monitors for TICs, most are bulky (more than 0.75” in thickness) and expensive ($500 or more). These monitors are primarily used in cities having a population of 100k or more. Hence, there is a need for a low cost (less than $100) wearable multi-gas sensor. Such wearable sensors will also find use in the much bigger application of industrial worker safety monitoring.
To address this need TDA Research (TDA) has developed a simple, low cost wearable smart chemical sensor badge that has high sensitivity and selectivity to multiple TICs at trace (low parts per million) concentrations and triggers distinct alarms at permissible exposure limit (PEL), and Immediately Dangerous to Life or Health (IDLH) concentrations. Our wearable smart sensor badge uses a Lab-on-a-chip, is smaller than 2” x 2” x 0.75”, and can detect multiple TICs ( 4 to 6) of interest, and has a low rate of false alarms so that easy and widespread deployment can be achieved.
TDA's sensor
We have demonstrated the operation of the sensor in a fully integrated prototype to detect four to six TICs among the H2S, NH3, PH3, HCN, Cl2, and NO2 at ppm levels and produce an electrical signal that can be used to identify and quantify them. We then obtained performance data that included results for these TICs both separately and together and in the presence of interferents, such as diesel and bleach. The sensor response was correlated and corrected based on ambient temperature, relative humidity levels and the air flow rate through the sensor. This low cost sensor is built using commercial-off-the-shelf (COTS) components along with TDA proprietary media and detection/quantification algorithms to detect and quantify TICs, eliminating false positives and false negatives. The sensors also have the ability to generate multiple alarms (audible, visual, and vibrate) at high (IDLH) and low (PEL) concentrations for four or more of the TICs in a small wearable form factor. TDA’s sensor has the unique ability to distinguish between different volatile organic compounds (VOCs) and oxidizes (Cl2, NO2 and even ozone). The attached figure is a photo of the TDA sensor. The results from the TDA sensor development and their performance under different threats at different humidity and temperature levels will be presented at the meeting.

Figure 1
A Portable Fluorometer with Multiple Excitation LEDs
Authors: SHIN Young HO , Gutierrez-Wing Maria Teresa , Choi Jin-Woo 
Published: July 2021

Fluorescent probes are widely used in biological research due to their sensitivity, selectivity, and versatility [1, 2]. Many fluorescence probes, such as fluorophores, typically have a variety of absorption and emission peaks ranging from UV to near-infrared. Therefore, a wide range of excitation wavelengths is required to simultaneously detect multiple fluorescent target analytes. Here, we propose a portable fluorometer with 13 different excitation LEDs (280 – 730 nm) that can be a viable option for simultaneously detecting multiple fluorophores. For fluorescence detection, a monochromator module was implemented to separates the color components of fluorescent emission and sequentially scan a range of wavelength (400 nm – 780 nm) with 1 nm resolution. For demonstration, fluorescein was selected as target analyte for this study. Fluorescein is an organic compound dye that is commonly used in many bioscience applications.
For the excitation light source, different LEDs were used to offer a broad range of excitation wavelengths, ranging from 280 nm to 725 nm. Each LED was coupled with a color filter and a collimator lens to carry out a narrow excitation spectrum. LEDs were controlled by an LED driver IC and a microcontroller to provide a linear output current in the range of 0 to 300 mA. A multiplexer IC was implemented to sequentially turn on and off each excitation LED. The maximum absorbance and emission wavelength of fluorescein were 485 nm and 514 nm, respectively. For excitation, 434 nm LED was chosen instead of 470 nm to minimize spectral overlap between the excitation and emission spectra. The fluorescein was dissolved in methanol at a concentration of 220 mg/ml at room temperature (25 ºC). The figure shows the spectra of the excitation LED and fluorescein fluorescence measured with a developed portable fluorometer. The spectral profile of the excitation LED and the peak fluorescence of fluorescein was well-matched with previously measured value from the laboratory-based benchtop fluorometer (Fluorolog 3 FL3-22, Horiba, Japan).
In summary, we have developed a portable fluorometer multiple LEDs covering a broad range of excitation wavelengths to simultaneously detect multiple fluorescent targets. Our compact fluorometer provides a viable option for multi-analyte detection in a variety of remote sensing applications such as point-of-care or environmental monitoring.

Figure 1
Printed-Circuit-Board (PCB) Based Multiplex Sensor for Ion Sensing
Authors: Zhang Zhehao , Papautsky Ian 
Published: July 2021

Combining electrochemical sensing with microfluidic system presents an attractive approach for in vitro study of physiology and pathophysiology (e.g. organ-on-chip platform) [1] and for inline monitoring of environmental parameters (e.g. water quality) [2]. Ion-selective electrodes (ISE) are potentiometric sensors that measure activities of ions. They offer a simpler analytical method compare to voltammetric sensors or ISFETs. Solid-state ISEs differ from conventional ISEs in that the inner filling solution is replaced by a solid contact material. The removal of liquid compartment can make such sensor more durable and flexible, enabling it to be integrated with microfluidic device. In this work, we fabricated and evaluated a multiplex ion sensing platform by modifying the printed circuit board with solid-state ISEs. The choice of PCB platform allows straightforward multiplexing of electrodes and interfacing with downstream electronics by leveraging standardized PCB technology, which can also be cost effective in terms of fabrication. ISEs for potassium (K+) and nitrate (NO3-) approximately 1.5 mm in diameter were prepared by coating polymeric membrane and mesoporous carbon layers as the solid contact on a pre-patterned transfer tape. The electrode response was significantly stabilized by casting the membrane away from the underlying metal pads. The stabilizing effect was attributed to the increase of effective surface area of mesoporous carbon between membrane and conducting metal. The multiplex sensor was further integrated with a 3D printed microchamber for onchip analysis (Figure 1A). The K+ and NO3- electrodes displayed near-Nernstian slopes of 53 and -50 mV/dec (vs. Ag/AgCl/0.01 M Cl- reference) in KNO3 solutions, respectively. Despite some noise and baseline drift, both electrodes showed reasonable stability and reversibility upon switching solution (Figure 1B). The sensor can be stored dry between measurements. The slope of K+ electrode decayed over time, while NO3- electrode maintained sensitivity for at least one week. The slope decrease was likely due to the diffusion of ion-exchanger (tetraphenylborate) into the surrounding adhesive tape. During integration with the microchamber, the K+ electrode was also found subject to the bonding adhesive between the chamber and transfer tape, where possible reaction and/or degradation of the ion exchanger has caused complete loss of electrode response. Nevertheless, with further improvement, the PCB based multiplex ISEs provides a promising tool for ion sensing in many biomedical and environmental applications.
References:
[1] Sunghee Estelle Park, Andrei Georgescu, Dongeun Huh. Organoids-on-a-chip. Science, 2019, Vol. 364, Issue 6444, pp. 960-965, DOI: 10.1126/science.aaw7894
[2] Am Jang, Zhiwei Zou, Kang Kug Lee, Chong H Ahn and Paul L Bishop. State-of-the-art lab chip sensors for environmental water monitoring. Meas. Sci. Technol., 2011, Vol. 22, 032001, doi:10.1088/0957-

Figure 1