ß-Cyclodextrin-Stabilized Silver Nanoparticle Production Combined with Loop-Mediated Isothermal Amplification for the Visual Detection of Contagious Pathogens.

ß-cyclodextrin (ß-CD) is a water-soluble, non-toxic, biocompatible, and cage compound that contains six, seven, or eight α-(1-4)-attached D-glucopyranose residues. The hydroxyl group in the ß-CD is responsible for the reduction of metal ions as well as stabilizing the nanoparticles. In this study, we developed a colorimetric assay for identifying contagious pathogens such as SARS-CoV-2 and Enterococcus faecium (E. faecium) via in situ development of ß-CD-stabilized silver nanoparticles (AgNPs). In the process, the LAMP amplicons produced a complex with silver nitrate (LAMP amplicon-Ag+) which was reduced when heated at 65 °C for 5 min in the presence of ß-CD and developed a brown color. The limit of detection was determined to be approximately 101 CFU mL-1 and 10 fg µL-1 for E. faecium and SARS-CoV-2, respectively. Significantly, the colorimetric examination of contagious diseases was completed in less than 50 min, including the LAMP assay and detection process. Owing to the high sensitivity and rapid readout mechanism of the ß-CD-stabilized AgNP-based colorimetric assay, it is anticipated that the introduced method can be efficiently utilized as a versatile point-of-care testing (POCT) platform for molecular diagnostics in resource-limited areas.

Advances in deoxyribonucleic acid extraction techniques and point-of-care molecular diagnosis of foodborne pathogens.

A conventional molecular assay-based point-of-care (POC) diagnostic test involves three major stages: deoxyribonucleic acid (DNA) extraction, amplification, and amplicon detection. Among these steps, DNA extraction is costly and time-consuming. Nevertheless, it is a crucial step for the identification of sensitive and specific diseases. This review summarizes the advantages and disadvantages of DNA extraction methods over the past 10 years to effectively implement POC pathogen testing in the future. The first section briefly explains the necessity of DNA extraction and molecular assays for food pathogen detection. The second section extensively discusses DNA extraction based on liquid-liquid extraction, solid-phase extraction, and electrophoretic techniques. Molecular assay-based methods and a few commercially available POC devices for the detection of foodborne pathogens are detailed in the third and fourth sections. Finally, present challenges and future perspectives for the fabrication of integrated POC devices are highlighted.

Quercetin-Mediated Silver Nanoparticle Formation for the Colorimetric Detection of Infectious Pathogens Coupled with Loop-Mediated Isothermal Amplification.

Here, quercetin-mediated silver nanoparticle (AgNP) formation combined with loop-mediated isothermal amplification (LAMP) was introduced to colorimetrically detect two major infectious pathogens, SARS-CoV-2 and Enterococcus faecium, using a foldable PMMA microdevice. The nitrogenous bases of LAMP amplicons can readily form a complex with Ag+ ions, and the catechol moiety in quercetin, which acted as a reducing agent, could be chelated with Ag+ ions, resulting in the easy electron transfer from the oxidant to the reductant and producing brown-colored AgNPs within 5 min. The introduced method exhibited higher sensitivity than agarose gel electrophoresis due to more active redox centers in quercetin. The detection limit was attained at 101 copies µL-1 and 101 CFU mL-1 for SARS-CoV-2 RNA and E. faecium, respectively. A foldable microdevice made of two pieces of PMMA that fully integrates DNA extraction, amplification, and detection processes was fabricated to establish practical applicability. On one PMMA, DNA extraction was performed in a reaction chamber inserted with an FTA card, and then LAMP reagents were added for amplification. Silver nitrate was added to the reaction chamber after LAMP. On the other PMMA, quercetin-soaked paper discs loaded in the detection chamber were folded toward the reaction chamber for colorimetric detection. An intense brown color was produced within 5 min when heated at 65 °C. The introduced colorimetric assay, which is highly favorable for laboratory and on-site applications, could be a valuable alternative to conventional methods for detecting infectious diseases, given its unique principle, simplicity, and naked-eye detection.

Recent advances in airborne pathogen detection using optical and electrochemical biosensors.

The world is currently facing an adverse condition due to the pandemic of airborne pathogen SARS-CoV-2. Prevention is better than cure; thus, the rapid detection of airborne pathogens is necessary because it can reduce outbreaks and save many lives. Considering the immense role of diverse detection techniques for airborne pathogens, proper summarization of these techniques would be beneficial for humans. Hence, this review explores and summarizes emerging techniques, such as optical and electrochemical biosensors used for detecting airborne bacteria (Bacillus anthracis, Mycobacterium tuberculosis, Staphylococcus aureus, and Streptococcus pneumoniae) and viruses (Influenza A, Avian influenza, Norovirus, and SARS-CoV-2). Significantly, the first section briefly focuses on various diagnostic modalities applied toward airborne pathogen detection. Next, the fabricated optical biosensors using various transducer materials involved in colorimetric and fluorescence strategies for infectious pathogen detection are extensively discussed. The third section is well documented based on electrochemical biosensors for airborne pathogen detection by differential pulse voltammetry, cyclic voltammetry, square-wave voltammetry, amperometry, and impedance spectroscopy. The unique pros and cons of these modalities and their future perspectives are addressed in the fourth and fifth sections. Overall, this review inspected 171 research articles published in the last decade and persuaded the importance of optical and electrochemical biosensors for airborne pathogen detection.

Emerging bismuth-based direct Z-scheme photocatalyst for the degradation of organic dye and antibiotic residues.

Organic dye and antibiotic residues are some of the key substances that can contaminate the environment due to their wide usage in various industries and modern medicine. The degradation of these substances present in waterbodies is essential while contemplating human health. Photocatalysts (PSs) are promising materials that develop highly reactive species instantly by simple solar energy conversion for degrading the organic dye and antibiotic residues and converting them into nontoxic products. Among numerous semiconductors, the bismuth (Bi)-containing PS has received great attention due to its strong sunlight absorption, facile preparation, and high photostability. Owing to the technology advancement and demerits of the traditional methods, a Bi-containing direct Z-scheme PS has been developed for efficient photogenerated charge carrier separation and strong redox proficiency. In this review, a synthetic Bi-based Z-scheme heterojunction that mimics natural photosynthesis is described, and its design, fabrication methods, and applications are comprehensively reviewed. Specifically, the first section briefly explains the role of various semiconductors in the environmental applications and the importance of the Bi-based materials for constructing the Z-scheme photocatalytic systems. In the successive section, overview of Z-scheme PS are concisely discussed. The fourth and fifth sections extensively explain the degradation of the organic dyes and antibiotics utilizing the Bi-based direct Z-scheme heterojunction. Eventually, the conclusions and future perspectives of this emerging research field are addressed. Overall, this review is potentially useful for the researchers involved in the environmental remediation field as a collection of up-to-date research articles for the fabrication of the Bi-containing direct Z-scheme PS.

Adsorptive removal of organic pollutant methylene blue using polysaccharide-based composite hydrogels.

Methylene blue (MB) is categorized as an organic dye (OD) released as effluents after various industrial activities and is one of the most abundant pollutants in the aquatic environment. Significantly, because of its potential toxicity, removing MB from wastewater has been a matter of necessity in recent times. Numerous analytical techniques have been applied, among which polysaccharide-based composite hydrogels appear as the most favorable for MB removal because of their large surface area, excellent mechanical properties, swelling capability, and large-scale production. In this review, the first section gives adequate information about the ODs' adverse effects on the environment and the contribution of polysaccharide-based hydrogels for OD removal, especially MB. Next, various mechanisms such as electrostatic interactions, π-π interactions, hydrogen bonding, hydrophobic interaction, van der Waals force, and coordination interaction involved in the adsorption technique are investigated. The third section extensively describes the MB removal by incorporation of various materials such as monomers, metal oxides, magnetic nanoparticles, and clay into the polysaccharide matrix to produce composite hydrogels. Finally, the current limitations and future perspectives of the polysaccharide-based composite hydrogel techniques are addressed. Overall, this review acknowledged the vital role of polysaccharide-based composite hydrogels for MB adsorption by surveying 110 research articles published in the past five years (2015-2021).

Recent progress in smartphone-based techniques for food safety and the detection of heavy metal ions in environmental water.

Emerging smartphone-based point-of-care tests (POCTs) are cost-effective, precise, and easy to implement in resource-limited areas. Thus, they are considered a potential alternative to conventional diagnostic testing. This review explores food safety and the detection of metal ions in environmental water based on unprecedented smartphone technology. Specifically, we provide an overview of various methods used for target analyte detection (antibiotics, enzymes, mycotoxins, pathogens, pesticides, small molecules, and metal ions), such as colorimetric, fluorescence, microscopic imaging, and electrochemical methods. This paper performs a comprehensive review of smartphone-based POCTs developed in the last three years (2018-2020) and evaluates their relative advantages and limitations. Moreover, we discuss the imperative role of new technology in the progress of POCTs. Sensor materials (metal nanoparticles, carbon dots, quantum dots, organic substrates, etc.) and detection techniques (paper-based, later flow assay, microfluidic platform, etc.) involved in POCTs based on smartphones, and the challenges faced by these techniques, are addressed.

Ultraviolet-induced in situ gold nanoparticles for point-of-care testing of infectious diseases in loop-mediated isothermal amplification.

The present study investigated ultraviolet-induced in situ gold nanoparticles (AuNPs) coupled with loop-mediated isothermal amplification (LAMP) for the point-of-care testing (POCT) of two major infectious pathogens, namely, Coronavirus (COVID-19) and Enterococcus faecium (E. faecium spp.). In the process, gold ions in a gold chloride (HAuCl4) solution were reduced using trisodium citrate (Na3Ct), a reducing agent, and upon UV illumination, red-colored AuNPs were produced in the presence of LAMP amplicons. The nitrogenous bases of the target deoxyribonucleic acid (DNA) acted as a physical support for capturing gold ions dissolved in the sample. The high affinity of gold with the nitrogenous bases enabled facile detection within 10 min, and the detection limit of COVID-19 plasmid DNA was as low as 42 fg µL-1. To ensure POCT, we designed a portable device that contained arrays of reagent chambers and detection chambers. In the portable device, colorimetric reagents such as HAuCl4 and Na3Ct were contained in the reagent chambers; these reagents were subsequently transferred to the detection chambers where LAMP amplicons were present and thus allowed convenient sample delivery and multiplex detection. Owing to the high sensitivity of the in situ AuNPs, simplicity of portable device fabrication, and rapid colorimetric detection, we strongly believe that the fabricated portable device could serve as a kit for rapid POCT for instantaneous detection of infectious diseases, and could be readily usable at the bedside.

Chemically robust succinimide-group-assisted irreversible bonding of poly(dimethylsiloxane)-thermoplastic microfluidic devices at room temperature.

This study investigates surface chemical modification using anhydride silane and amino silane reagents at room temperature (RT) to realize bonding between silicon-based PDMS and non-silicon thermoplastics. The anhydride silane shows vigorous activity against water, forming a terminal dicarboxylic acid in the plasma-activated elastomeric poly(dimethylsiloxane) (PDMS) surface, and it can readily react with amino-silane-modified thermoplastic surfaces, resulting in a permanent bond via the formation of a stable succinimide group without the requirement for high temperature or additional pressure to initiate the bonding. The modified surfaces of PDMS and thermoplastics were successfully characterized by water contact angle measurement, fluorescence measurement, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The bond strength values of PDMS-thermoplastic assemblies, measured by the tensile test for PDMS-polystyrene (PS), PDMS-poly(methyl methacrylate) (PMMA), PDMS-polycarbonate (PC), and PDMS-poly(ethyl terephthalate) (PET) assemblies, were found to be approximately 519.5 ± 6, 259 ± 15, 476.6 ± 8, and 458.2 ± 27 kPa, respectively. Moreover, the bond strength was further examined by performing a burst test for PDMS-PMMA, PDMS-PS, PDMS-PC, and PDMS-PET microfluidic devices, which were found to have the maximum pressure values at approximately 344.73, 448.15, 413.68, and 379.21 kPa, respectively. Based on these results, the hybrid microfluidic devices can be used for high-pressure experiments such as blood plasma separation and continuous-flow polymerase chain reaction (CF-PCR). We have also performed the large area bonding of the PDMS-PC assembly (10 × 10 cm2), ensuring the high robustness and reliability of the proposed surface chemical bonding method.

Microfluidic device fabrication mediated by surface chemical bonding.

This review discusses various bonding strategies for fabricating microfluidic devices, with a special emphasis on the modification of the surface assisted by the use of chemicals to assemble microfluidic devices under mild conditions such as room temperature and atmospheric pressure. The paper includes an overview of the wide ranges of bonding methods used in the fabrication of microfluidic systems, such as anodic bonding, fusion bonding, thermal bonding, solvent bonding, and surface chemical bonding. Among these, surface chemical bonding plays a crucial role between the polydimethylsiloxane (PDMS) and thermoplastics in order to assemble a microfluidic device in a simple and facile manner. The first section reviews relevant research on the sealing for microfluidic devices; in the second section, the materials used for device fabrication are reviewed. The third section discusses the different sealing processes used in the fabrication of microfluidic devices on silicon, glass, thermoplastic, and elastomer. Overall, this review concludes with a discussion on the importance of the surface chemical modification for bonding an elastomer - PDMS - with rigid materials at room temperature under atmospheric pressure and detailed discussions on their bond strengths.

Heat and pressure-resistant room temperature irreversible sealing of hybrid PDMS-thermoplastic microfluidic devices via carbon-nitrogen covalent bonding and its application in a continuous-flow polymerase chain reaction.

In this study, we have introduced a facile room-temperature strategy for irreversibly sealing polydimethylsiloxane (PDMS) elastomers to various thermoplastics using (3-aminopropyl)triethoxysilane (APTES) and [2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane (ECTMS), which can resist heat and pressure after sealing due to the high chemical reactivity of the used chemicals. An irreversible chemical bond was realized at RT within 30 min through the initial activation of PDMS and thermoplastics using oxygen plasma, followed by surface modification using amino- and epoxy-based silane coupling reagents on either side of the substrates and then conformally contacting each other. Surface characterizations were performed using contact angle measurements, fluorescence measurements, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) to verify the successful surface modification of PDMS and thermoplastics. The tensile strengths of the bonded devices were 274.5 ± 27 (PDMS-PMMA), 591.7 ± 44 (PDMS-PS), 594.7 ± 25 (PDMS-PC), and 510 ± 47 kPa (PDMS-PET), suggesting the high stability of interfacial bonding. In addition, the results of the leakage test revealed that there was no leakage in the indigenously fabricated hybrid devices, even at high pressures, which is indicative of the robust bond strength between PDMS and thermoplastics obtained through the use of the chemical bonding method. Moreover, for the first time, the heat and pressure-resistant nature of the bonded PDMS-PC microfluidic device was assessed by performing a continuous-flow polymerase chain reaction (CF-PCR), which requires a high temperature and typically generates a high pressure inside the microchannel. The results demonstrated that the microfluidic device endured high heat and pressure during CF-PCR and successfully amplified the 210 bp gene fragment from the Shiga-toxin gene region of Escherichia coli (E. coli) O157:H7 within 30 min.

Palladium Supported on an Amphiphilic Triazine-Urea-Functionalized Porous Organic Polymer as a Highly Efficient Electrocatalyst for Electrochemical Sensing of Rutin in Human Plasma.

Metal nanoparticle-containing porous organic polymers have gained great interest in chemical and pharmaceutical applications owing to their high reactivity and good recyclability. In the present work, a palladium nanoparticle-decorated triazine-urea-based porous organic polymer (Pd@TU-POP) was designed and synthesized using 1,3-bis(4-aminophenyl)urea with cyanuric chloride and palladium acetate. The porous structure and physicochemical properties of the electrode material Pd@TU-POP were observed using a range of standard techniques. The Pd@TU-POP material on the electrode surface showed superior sensing ability for rutin (RT) because the Pd dispersion facilitated the electrocatalytic performance of TU-POP by reducing the overpotential of RT oxidation dramatically and improving the stability significantly. Furthermore, TU-POP provides excellent structural features for loading Pd nanoparticles, and the resulting Pd@TU-POP exhibited enhanced electron transfer and outstanding sensing capability in a linear range between 2 and 200 pM having a low detection value of 5.92 × 10-12 M (S/N = 3). The abundant porous structure of Pd@TU-POP not only provides electron transport channels for RT diffusion but also offers a facile route for quantification sensing of RT with satisfactory recoveries in aqueous electrolyte containing human plasma and red wine. These data reveal that the synthetic Pd@TU-POP is an excellent potential platform for the detection of RT in biological samples.

Synthesis, spectral and antimicrobial evaluation of some novel 1-methyl-3-alkyl-2,6-diphenylpiperidin-4-one oxime carbonates.

Synthesis of some novel biologically active piperidin-4-one oxime carbonates from 1-methyl-3alkyl-2,6-diphenylpiperidin-4-one oximes and substituted chloroformates was carried out in the presence of potassium carbonate as base and tetrabutylammonium bromide (TBAB) as catalyst. The newly synthesized compounds were characterized by IR, (1)H, (13)C NMR and LC-mass spectra. Based on the (1)H NMR analysis, all the compounds were found to adopt normal chair conformation with equatorial orientation of all the substituents. For all the synthesized compounds (5a-5l) antimicrobial activity has been tested against bacterial and fungal strains using Streptomycin and Amphotericin B as standards.