Publications by authors named "Aleksandr Simonian"

In partnership with the Air Force Office of Scientific Research (AFOSR), the National Science Foundation's (NSF) Emerging Frontiers and Multidisciplinary Activities (EFMA) office of the Directorate for Engineering (ENG) launched an Emerging Frontiers in Research and Innovation (EFRI) topic for the fiscal years FY22 and FY23 entitled "Brain-inspired Dynamics for Engineering Energy-Efficient Circuits and Artificial Intelligence" (BRAID) [...

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The emergence of the COVID-19 pandemic has starkly exposed our significantly limited ability to promptly identify and respond to emergent biological threats. Consequently, there is an urgent need to advance biotechnological methods for addressing both known and unforeseen biological hazards. Recently, the CRISPR/Cas system has revolutionized genetic engineering, enabling precise and efficient synthetic biology applications.

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Understanding the chemical composition and morphology of interfaces plays a vital role in the development of sensors, drug delivery systems, coatings for biomedical implants, and so forth. In many cases, the interface characterization can be performed by a combination of electrochemical and one of the optical techniques. In this study, we further enhanced capabilities in probing interfaces by combining electrochemical characterization with multiple optical techniques, that is, surface plasmon resonance (SPR) and fluorescence spectroscopy.

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  • Researchers developed a method to renew biocatalysts for biosensors, specifically focusing on layer-by-layer (LbL) self-assembly of enzymes on multiwalled carbon nanotube (MWCNT) interfaces.
  • The study utilized surface plasmon resonance (SPR) to confirm the successful buildup of multiple layers, which enhanced the biosensor’s functionality.
  • A desorption strategy was established to remove inhibited enzyme layers while preserving the cushion layers, allowing for multiple regenerations and maintaining sensor stability during acetylcholine determination.
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Organophosphate compounds are heavily used in agriculture and military activities, while non-organophosphate pesticides are mostly used in agriculture and home defense. Discriminative detection of such toxic compounds is very challenging and requires sophisticated and bulky instrumentation. Meanwhile, multi-enzyme biosensors may offer an effective solution to the problem and may become a versatile analytical tool for discriminative detection of different neurotoxins.

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  • Type I collagen is crucial for the structure and strength of connective tissues, but its triple-helical forms are unstable at body temperature, prompting studies on its stability at the fibril level.* -
  • Experiments show that heating collagen fibrils causes a decrease in stiffness (Young's modulus) until 58°C, after which stabilization occurs due to intermolecular interactions, alongside water absorption and increased internal friction.* -
  • The findings suggest a new intermolecular mechanism for collagen stability, which could enhance our understanding of how these proteins maintain their function in biological tissues.*
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Biosensors are of great significance because of their capability to resolve a potentially large number of analytical problems and challenges in very diverse areas such as defense, homeland security, agriculture and food safety, environmental monitoring, medicine, pharmacology, industry, etc. The expanding role of biosensing in society and a real-world environment has led to an exponential growth of the R&D efforts around the world. The world market for biosensor devices, according to Global Industry Analysts, Inc.

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Campylobacter spp. are an important cause of acute bacterial diseases in humans worldwide. Many bacterial species in the Campylobacter genus are considered harmful and may cause several infectious diseases.

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We develop a framework for optimizing a novel approach to extending the linear range of bioanalytical systems and biosensors by utilizing two enzymes with different kinetic responses to the input chemical as their substrate. Data for the flow injection amperometric system devised for detection of lysine based on the function of L-lysine-alpha-oxidase and lysine-2-monooxygenase are analyzed. Lysine is a homotropic substrate for the latter enzyme.

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The applications of biosensors range from environmental testing and biowarfare agent detection to clinical testing and cell analysis. In recent years, biosensors have become increasingly prevalent in clinical testing and point-of-care testing. This is driven in part by the desire to decrease the cost of health care, to shift some of the analytical tests from centralized facilities to "frontline" physicians and nurses, and to obtain more precise information more quickly about the health status of a patient.

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  • The paper discusses integrating miniature gold electrodes with immune cells (macrophages) to detect hydrogen peroxide (H2O2) released by these cells, which is important for analyzing cellular responses.
  • The researchers used photopatterning techniques to create specific areas for cell attachment near the sensing electrodes while ensuring that the surrounding surface was non-fouling, allowing for effective cell interaction.
  • The developed microdevice demonstrated sensitivity to H2O2 detection with a significant limit of detection, enabling real-time monitoring of macrophage responses, which could be useful for examining immune reactions and inflammation in future studies.
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  • - A new nanocomposite interface using carbon nanotubes and biopolymers is created, where layers of oxidized carbon nanotubes alternately hold a cationic enzyme and an anionic DNA, optimizing stability and electron transfer.
  • - Techniques like thermogravimetric analysis and Raman spectroscopy were used to confirm the properties of the carbon nanotubes and the successful attachment of the enzyme and DNA.
  • - The fabricated multilayer structure shows promising performance for biosensing, with high sensitivity, consistent calibration, and a stable electrochemical response, while being easily renewable.
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Current bacterial detection methods require the collection of samples followed by preparation and analysis in the laboratory, both time and labour consuming steps. More importantly, because of cost, only a limited number of samples can be taken and analyzed. This paper presents the results of an investigation to directly detect Salmonella typhimurium on fresh tomato surfaces using phage-based magnetoelastic (ME) biosensors.

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  • The study focuses on measuring cytokine secretion from leukocytes, particularly CD4 T-cells, which is crucial for understanding immune responses to diseases.
  • The researchers combined antibody-based cell separation with surface plasmon resonance (SPR) technology to capture CD4 T-cells and detect the inflammatory cytokine interferon-gamma (IFN-gamma) without labeling.
  • The results showed a correlation between the SPR signal and the actual cytokine production, suggesting this method could be useful for detecting various secreted proteins from specific cell types in the future.
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In this study, a novel system for the detection and quantification of organofluorophosphonates (OFP) has been developed by using an optical sensing polymeric membrane to detect the fluoride ions produced upon OFP hydrolysis. Diisopropyl fluorophosphate (DFP), a structural analogue of type G chemical warfare agents such as Sarin (GB) and Soman (GD), is used as the surrogate target analyte. An optical sensing fluoride ion selective polymeric film was formulated from plasticized PVC containing aluminum(III) octaethyl porphyrin and ETH 7075 chromoionophore (Al[OEP]-ETH 7075).

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This paper describes a biomaterial microfabrication approach for interfacing functional biomolecules (enzymes) with electrode arrays. Poly (ethylene glycol) (PEG) hydrogel photopatterning was employed to integrate gold electrode arrays with the enzymes glucose oxidase (GOX) and lactate oxidase (LOX). In this process, PEG diacrylate (DA)-based prepolymer containing enzyme molecules as well as redox species (vinylferrocene) was spin-coated, registered, and UV cross-linked on top of an array of gold electrodes.

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In this paper we demonstrate that SWNTs and a covalent immobilization strategy enable very sensitive sensors with excellent long term stability. Organophosphorus hydrolase (OPH) functionalized single and multi-walled carbon nanotube (CNT) conjugates were exploited for direct amperometric detection of paraoxon, a model organophosphate. The catalytic hydrolysis of paraoxon produces equimoles of p-nitrophenol; oxidation was monitored amperometrically in real time under flow-injection (FIA) mode.

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Electrode-immobilized glucose-6-phosphate dehydrogenase is used to catalyze an enzymatic reaction which carries out the AND logic gate. This logic function is considered here in the context of biocatalytic processes utilized for the biocomputing applications for "digital" (threshold) sensing/actuation. We outline the response functions desirable for such applications and report the first experimental realization of a sigmoid-shape response in one of the inputs.

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Protein immobilization on solid interfaces is a crucial aspect of their successful application in technologies such as biosensing, purification, separation, decontamination, etc. Although immobilization can improve the long-term and operational stability of proteins, this is often at the cost of significant losses in the catalytic activity of the tethered enzyme. Covalent attachment methods take advantage of reactive groups on the amino acid side chains.

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We demonstrate a rapid method for enzyme immobilization directly on a waveguide surface by encapsulation in a silica matrix. Organophosphate hydrolase (OPH), an enzyme that catalytically hydrolyzes organophosphates, was used as a model enzyme to demonstrate the utility of lysozyme-mediated silica formation for enzyme stabilization. Silica morphology and the efficiency of OPH encapsulation were directly influenced by the precursor choice used in silica formation.

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Large scale biomimetic single-walled carbon nanotube (SWNT) coatings with significant antimicrobial activity, high Young's Modulus, and controlled morphology were fabricated using layer-by-layer assembly. Thickness was controlled within 1.6 nm and SWNT orientation was controlled using a directed air stream.

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A novel detection method for organophosphate neurotoxins has been described, based on the fluorescence quenching of a Coumarin derivative. These dyes are similar in structure to some organophosphates (OPs), and they fluoresce in the blue-green region of the spectra. This methodology has been utilized for the detection of organophosphates whose hydrolysis product is p-nitrophenol by using an enzyme, organophosphorus hydrolase (OPH).

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Development of real-time sensor based on the target-specific probe that make possible sensitive, rapid and selective detection and monitoring of the particular antigen molecules could be of substantial importance to the many applications. Because of its high specificity to the target molecules, excellent temperature stability, and easy production, bacterial phage might serve as a powerful biorecognition probe in biosensor applications. Here, we report extremely sensitive and specific label-free direct detection of model antigen, beta-galactosidase (beta-gal), based on surface plasmon resonance (SPR) spectroscopy.

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The purpose of this study was to develop a biosensor based on surface plasmon resonance (SPR) for the rapid identification of C. jejuni in broiler samples. We examined the specificity and sensitivity of commercial antibodies against C.

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Article Synopsis
  • - A new, quick method for applying amorphous silica onto gold surfaces was developed, using lysozyme to create silica nanoparticles.
  • - The process involves depositing a layer of lysozyme on gold, which then facilitates the self-assembly of a silica monolayer, enhancing surface area and compatibility with detection systems.
  • - Additionally, the silica can be used to immobilize biomolecules, demonstrated by successfully encapsulating the enzyme organophosphate hydrolase (OPH), which showed effective detection limits for its substrate.
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