Bridged EGFET Design for the Rapid Screening of Sorbents as Sensitisers in Water-Pollution Sensors.

We further simplify the most 'user-friendly' potentiometric sensor for waterborne analytes, the 'extended-gate field effect transistor' (EGFET). This is accomplished using a 'bridge' design, that links two separate water pools, a 'control gate' (CG) pool and a 'floating gate' (FG) pool, by a bridge filled with agar-agar hydrogel. We show electric communication between electrodes in the pools across the gel bridge to the gate of an LND150 FET. When loading the gel bridge with a sorbent that is known to act as a sensitiser for Cu2+ water pollution, namely, the ion exchanging zeolite 'clinoptilolite', the bridged EGFET acts as a potentiometric sensor to waterborne Cu2+. We then introduce novel sensitisers into the gel bridge, the commercially available resins PurometTM MTS9140 and MTS9200, which are sorbents for the extraction of mercury (Hg2+) pollution from water. We find a response of the bridged EGFET to Hg2+ water pollution, setting a template for the rapid screening of ion exchange resins that are readily available for a wide range of harmful (or precious) metal ions. We fit the potentiometric sensor response vs. pollutant concentration characteristics to the Langmuir-Freundlich (LF) model which is discussed in context with other ion-sensor characteristics.

Durability of Antibody Responses to SARS-CoV-2 Infection and Its Relationship to Disease Severity Assessed Using a Commercially Available Assay.

Background: Assessing the humoral immune response to SARS-CoV-2 is crucial for inferring protective immunity from reinfection and for assessing vaccine efficacy. Data regarding the durability and sustainability of SARS-CoV-2 antibodies are conflicting. In this study, we aimed to determine the seroconversion rate of SARS-CoV-2 infection in a cohort of reverse-transcriptase polymerase chain reaction (RT-PCR)-confirmed SARS-CoV-2 infections and the antibody dynamics, durability, and the correlation of antibody titers with disease severity using the commercially available SARS-CoV-2 anti-spike (S1/S2) protein. Methods: A total of 342 subjects with PCR-confirmed COVID-19 were enrolled. A total of 395 samples were collected at different time points (0-204) after the onset of symptoms or from the day of positive PCR in asymptomatic patients. Demographics, clinical presentation and the date of PCR were collected. All samples were tested using the automated commercial chemiluminescent system (DiaSorin SARS-CoV-2 S1/S2 IgG) on the LIAISONXL® platform (LIAISON). Results: The seroconversion rate for samples collected 14 days after the onset of infection was much higher than that for samples collected before 14 days (79.4% vs. 39.4%). The rate of seroconversion in symptomatic participants (62.1%) was similar to that of asymptomatic participants (56.1%) (p = 0.496). The IgG titer distribution was also similar across both groups (p = 0.142), with a median IgG level of 27.86 AU/ml (3.8-85.5) and 15 AU/ml (3.8-58.85) in symptomatic and asymptomatic participants, respectively. However, IgG titers were significantly higher in ICU patients, with a median of 104 AU/ml (3.8-179) compared to 34 AU/ml (3.8-70) in the non-ICU participants (p < 0.0001). Furthermore, the median time to seroconversion occurred significantly faster in ICU patients than in non-ICU participants (19 versus 47 days) (P < 0.0001). IgG titers were also higher in subjects ≥50 years compared to those <50 years (p < 0.009), male compared to female (p < 0.054) and non-Saudi compared to Saudi (p < 0.003). Approximately 74% of all samples tested beyond 120 days were positive. Conclusion: Antibodies can persist in circulation for longer than 4 months after COVID-19 infection. The majority of patients with COVID-19 mounted humoral immune responses to SARS-CoV-2 infection that strongly correlated with disease severity, older age and male gender. However, the population of individuals who tested negative should be further evaluated.

Parallel Potentiometric and Capacitive Response in a Water-Gate Thin Film Transistor Biosensor at High Ionic Strength.

We show that an SnO2-based water-gate thin film transistor (WGTFT) biosensor responds to a waterborne analyte, the spike protein of the SARS-CoV-2 virus, by a parallel potentiometric and capacitive mechanism. We draw our conclusion from an analysis of transistor output characteristics, which avoids the known ambiguities of the common analysis based on transfer characteristics. Our findings contrast with reports on organic WGTFT biosensors claiming a purely capacitive response due to screening effects in high ionic strength electrolytes, but are consistent with prior work that clearly shows a potentiometric response even in strong electrolytes. We provide a detailed critique of prior WGTFT analysis and screening reasoning. Empirically, both potentiometric and capacitive responses can be modelled quantitatively by a Langmuir‒Freundlich (LF) law, which is mathematically equivalent to the Hill equation that is frequently used for biosensor response characteristics. However, potentiometric and capacitive model parameters disagree. Instead, the potentiometric response follows the Nikolsky-Eisenman law, treating the analyte 'RBD spike protein' as an ion carrying two elementary charges. These insights are uniquely possible thanks to the parallel presence of two response mechanisms, as well as their reliable delineation, as presented here.

Smoking Induced Hemolysis: Spectral and microscopic investigations.

Smoking is one of the major causes of lifestyle associated mortality and morbidity such as cancer of the oral cavity and lungs, and also cardiovascular diseases. In this study, we have provided evidences for the smoking-induced hemolysis using two methods: spectra of blood components and atomic force microscopic analysis of surface morphology. A total of 62 subjects (control = 31; smoker = 31: 21 male; 10 female in each set) were considered for the study. The findings indicate that smoking leads to potholes on the surface, swelling of shape, rupturing of erythrocytes, removal of hematoporphyrin and flushing into the plasma as metabolites of the erythrocyte. The overall morphology of the erythrocytes of the smoker group appears more like a Mexican hat. The mean surface roughness was 5.5 ± 3 nm for the smoker group, but 1.2 ± 0.2 nm for the control group. Such damages might help the toxins, (CO, peroxidants, aldehydes etc.,) to gain easy access and get strongly absorbed by the hemoglobin, leading to enhanced rates of hemolysis as shown by the spectral features of metabolites. This indicates that the average life span of the smoker's erythrocytes is significantly less than that of the control group.

Impact of scaling and root planing with adjunct essential-oil-based mouthwash usage on whole salivary IgG levels in patients with periodontal inflammation.

OBJECTIVE: The aim was to assess the effect of scaling and root planing (SRP) with and without adjunct use of an essential-oil-based-mouthwash (EOBM) on whole salivary immunoglobulin G (IgG) levels in patients with periodontal inflammation. METHODS: Fifty patients with periodontal inflammation were included. Treatment wise, these patients were randomly divided into two groups. In group 1, patients underwent SRP and were instructed to rinse with 10 mL of an EOBM twice daily for 30 days, whereas those in group 2 underwent SRP and were instructed to rinse with 10 mL of water twice daily for 30 days. Whole saliva samples were collected at baseline and after 40 days of treatment. P-values < 0.05 were considered statistically significant. RESULTS: At baseline, whole salivary IgG levels were comparable among patients in groups 1 (60.5 ± 5.5 mg/dL) and 2 (57.3 ± 2.4 mg/dL). After 40 days of follow-up, there is a significant decrease in whole salivary IgG levels among patients in group 1 (7.2 ± 2.4 mg/dL) as compared to those in group 2 (26.6 ± 4.6 mg/dL) (P < 0.001). CONCLUSIONS: SRP, when performed with adjunct use of an EOBM, is more effective in reducing whole salivary IgG levels as compared to when SRP is performed without adjunct use of an EOBM.

A swelling-based chemiresistor for a biogenic odour.

Escherichia coli bacteria release 1-decanol as a byproduct of their metabolism. We demonstrate the detection of 1-decanol odour at a partial pressure in the order 100 ppb by the resistance change of a swelling-based sensor, consisting of Langmuir-Schäfer deposited Au core/organic ligand shell nanoparticle films. This is an exceptionally low limit of detection for swelling-based sensors, and relies firstly, in the careful matching of the CSNPs ligands to the targeted odour, and secondly, in the very low volatility of this odour. Sensor response can be substantially increased further when films are cooled below the freezing point of 1-decanol. We observe unexpected quantitative behaviour of our sensors: response is only weakly dependent on the odour's partial pressure, and scales differently with temperature than the response of other Au-CSNP odours to more volatile odours. This may be related to their unusually strong thermal resistance drift, the difficulties in delivering very low partial pressure odour atmospheres, and the proximity to the analyte's freezing point.

Manifold sensitivity improvement of swelling-based sensors.

The sensitivity of swelling-based gold core-organic shell nanoparticle vapor sensors is improved manifold by cooling sensors below ambient temperature. This is due to the reduced volatility of the analyte. Sensitivity to a particular analyte scales with temperature like that of analyte's saturated vapor pressure, thus allowing quantitative prediction of sensitivity enhancement. We believe our conclusions apply to all swelling-based sensors.