We describe a simple and affordable “Disposable electrode printed (DEP)-On-Go” sensing platform for the rapid on-site monitoring of trace heavy metal pollutants in environmental samples for early warning by developing a mobile electrochemical device composed of palm-sized potentiostat and disposable unmodified screen-printed electrode chips. We present the analytical performance of our device for the sensitive detection of major heavy metal ions, namely, mercury, cadmium, lead, arsenic, zinc, and copper with detection limits of 1.5, 2.6, 4.0, 5.0, 14.4, and, 15.5 μg·L−1, respectively. Importantly, the utility of this device is extended to detect multiple heavy metals simultaneously with well-defined voltammograms and similar sensitivity. Finally, “DEP-On-Go” was successfully applied to detect heavy metals in real environmental samples from groundwater, tap water, house dust, soil, and industry-processed rice and noodle foods. We evaluated the efficiency of this system with a linear correlation through inductively coupled plasma mass spectrometry, and the results suggested that this system can be reliable for on-site screening purposes. On-field applications using real samples of groundwater for drinking in the northern parts of India support the easy-to-detect, low-cost (<1 USD), rapid (within 5 min), and reliable detection limit (ppb levels) performance of our device for the on-site detection and monitoring of multiple heavy metals in resource-limited settings.
Simple tests of infectiousness that return results in minutes and directly from samples even with low viral loads could be a potential game-changer in the fight against COVID-19. Here, we describe an improved isothermal nucleic acid amplification assay, termed the RICCA (RNA Isothermal Co-assisted and Coupled Amplification) reaction, that consists of a simple one-pot format of ‘sample-in and result-out’ with a primary focus on the detection of low copy numbers of RNA virus directly from saliva without the need for laboratory processing. We demonstrate our assay by detecting 16S rRNA directly from E. coli cells with a sensitivity as low as 8 CFU/μL and RNA fragments from a synthetic template of SARS-CoV-2 with a sensitivity as low as 1740 copies/μL. We further demonstrate the applicability of our assay for real-time testing at the point of care by designing a closed format for paper-based lateral flow assay and detecting heat-inactivated SARS-COV-2 virus in human saliva at concentrations ranging from 28,000 to 2.8 copies/μL with a total assay time of 15–30 min.
As the currently available therapies for HIV-1 have high costs and are associated with the appearance of multi-drug resistant HIV-1 strains, the Indian traditional medicine system Ayurveda may provide useful alternatives. In this study, we screened the inhibitory activities of various extracts of five Indian plants for inhibitory effects on HIV-1 reverse transcriptase (RT). Water extracts of the leaves of Argemone mexicana strongly inhibited the DNA polymerase activity of HIV-1 RT, which indicated that they contained substances with inhibitor activity. Neither heat treatment at 100ºC nor proteinase K treatment of the extracts abolished the inhibitory activity, suggesting that the inhibitory substance was an organic compound rather than a protein.
A newly designed handheld one-inch gel electrophoresis-based detection system and recombinase polymerase amplification (RPA) can revolutionize nucleic acid-based molecular diagnostics for people in settings with poor healthcare infrastructure.
Alzheimer’s disease is associated with the aggregation
of
the misfolded neuronal peptide, amyloid-β42 (Aβ42). Evidence
has suggested that several reasons are responsible for the toxicity
caused by the aggregation of Aβ42, including the conformational
restriction of Aβ42. In this study, one of the toxic conformers
of Aβ42, which contains a Glu-to-Pro substitution (E22P-Aβ42),
was explored using atomic force microscopy and molecular docking to
study the aggregation dynamics. We proposed a systematic model of
fibril formation to better understand the molecular basis of conformational
transitions in the Aβ42 species. Our results demonstrated the
formation of amorphous aggregates in E22P-Aβ42 that are stem-based,
network-like structures, while the formation of mature fibrils occurred
in the less toxic conformer of Aβ42, E22-Aβ42, that are
sphere-like flexible structures. A comparison was made between the
biophysical properties of E22P-Aβ42 and E22-Aβ42 that
revealed that E22P-Aβ42 had greater stiffness, dihedral angle,
number of β sheets involved, and elasticity, compared with E22-Aβ42.
These findings will have considerable implications toward our understanding
of the structural basis of the toxicity caused by conformational diversity
in Aβ42 species.
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