Investigating the transport and colloidal behavior of Fe3O4 nanoparticles in aqueous and porous media under varying solution chemistry parameters.

The possible adverse effects of engineered iron oxide nanoparticles, especially magnetite (Fe3O4 NP), on human health and the environment, have raised concerns about their transport and behavior in soil and water systems. Accumulating these NPs in the environment can substantially affect soil and water quality and the well-being of aquatic and terrestrial organisms. Therefore, it is essential to examine the factors that affect Fe3O4 NP transportation and behavior in soil and water systems to determine their possible environmental fate. In this work, experiments were conducted in aqueous and porous media using an environmentally relevant range of pH (5, 7, 9), ionic strength (IS) (10, 50, 100 mM), and humic acid (HA) (0.1, 1, 10 mg L-1) concentrations. Fe3O4 NPs exhibited severe colloidal instability at pH 7 (⁓ = pHPZC) and showed an improvement in apparent colloidal stability at pH 5 and 9 in aquatic and terrestrial environments. HA in the background solutions promoted the overall transport of Fe3O4 NPs by enhancing the colloidal stability. The increased ionic strength in aqueous media hindered the transport by electron double-layer compression and electrostatic repulsion; however, in porous media, the transport was hindered by ionic compression. Furthermore, the transport behavior of Fe3O4 NPs was investigated in different natural waters such as rivers, lakes, taps, and groundwater. The interaction energy pattern in aquatic systems was estimated using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. This study showed the effects of various physical-chemical conditions on Fe3O4 NP transport in aqueous and porous (sand) media.

Nano-diagnostics as an emerging platform for oral cancer detection: Current and emerging trends.

Globally, oral cancer kills an estimated 150,000 individuals per year, with 300,000 new cases being diagnosed annually. The high incidence rate of oral cancer among the South-Asian and American populations is majorly due to overuse of tobacco, alcohol, and poor dental hygiene. Additionally, socio-economic issues and lack of general awareness delay the primary screening of the disease. The availability of early screening techniques for oral cancer can help in carving out a niche for accurate disease prognosis and also its prevention. However, conventional diagnostic approaches and therapeutics are still far from optimal. Thus, enhancing the analytical performance of diagnostic platforms in terms of specificity and precision can help in understanding the disease progression paradigm. Fabrication of efficient nanoprobes that are sensitive, noninvasive, cost-effective, and less labor-intensive can reduce the global cancer burden. Recent advances in optical, electrochemical, and spectroscopy-based nano biosensors that employ noble and superparamagnetic nanoparticles, have been proven to be extremely efficient. Further, these sensitive nanoprobes can also be employed for predicting disease relapse after chemotherapy, when the majority of the biomarker load is eliminated. Herein, we provide the readers with a brief summary of conventional and new-age oral cancer detection techniques. A comprehensive understanding of the inherent challenges associated with conventional oral cancer detection techniques is discussed. We also elaborate on how nanoparticles have shown tremendous promise and effectiveness in radically transforming the approach toward oral cancer detection. This article is categorized under: Diagnostic Tools > Biosensing Diagnostic Tools > Diagnostic Nanodevices Diagnostic Tools > In Vitro Nanoparticle-Based Sensing.

No magic bullet: Limiting in-school transmission in the face of variable SARS-CoV-2 viral loads.

In the face of a long-running pandemic, understanding the drivers of ongoing SARS-CoV-2 transmission is crucial for the rational management of COVID-19 disease burden. Keeping schools open has emerged as a vital societal imperative during the pandemic, but in-school transmission of SARS-CoV-2 can contribute to further prolonging the pandemic. In this context, the role of schools in driving SARS-CoV-2 transmission acquires critical importance. Here we model in-school transmission from first principles to investigate the effectiveness of layered mitigation strategies on limiting in-school spread. We examined the effect of masks and air quality (ventilation, filtration and ionizers) on steady-state viral load in classrooms, as well as on the number of particles inhaled by an uninfected person. The effectiveness of these measures in limiting viral transmission was assessed for variants with different levels of mean viral load (ancestral, Delta, Omicron). Our results suggest that a layered mitigation strategy can be used effectively to limit in-school transmission, with certain limitations. First, poorly designed strategies (insufficient ventilation, no masks, staying open under high levels of community transmission) will permit in-school spread even if some level of mitigation is present. Second, for viral variants that are sufficiently contagious, it may be difficult to construct any set of interventions capable of blocking transmission once an infected individual is present, underscoring the importance of other measures. Our findings provide practical recommendations; in particular, the use of a layered mitigation strategy that is designed to limit transmission, with other measures such as frequent surveillance testing and smaller class sizes (such as by offering remote schooling options to those who prefer it) as needed.

Nano-SiO2 transport and retention in saturated porous medium: Influence of pH, ionic strength, and natural organics.

Nano silica (nSiO2), induces potential harmful effects on the living environment and human health. It is well established that SiO2 facilitates the co-transport of a variety of other contaminants, including heavy metals and pesticides. The current study focused on the systematic evaluation of the effects of multiple physicochemical parameters such as pH (5, 7, and 9), ionic strength (10, 50, and 100 mM), and humic acid (0.1, 1, and 10 mg/L) on the transport and retention of nSiO2 in saturated porous medium. Additionally, the influent concentration of nSiO2 (10, 50, and 100 mg/L) was also varied. Our experimental findings indicate that the size of nSiO2 aggregates was directly related to the pH, ionic strength, HA, and particle concentration had a significant impact on the breakthrough curves (BTCs). The stability provided by the varying concentrations of pH and humic acid had a significant effect on the size of nSiO2 aggregates and transport (C/C0 > 0.7). The presence of a greater magnitude of negative charge on the surface of both nSiO2 and quartz sand resulted in less aggregation and enhanced flow of nSiO2 through the sand column. The Electrostatic and steric repulsion forces were the primary governing mechanisms in relation to the size of nSiO2 aggregates, affecting the single-collector efficiency and attachment efficiency, which determined the maximal transport of nSiO2. Conversely, a probable increase in Van der Waals force of attraction exacerbated the particle deposition and reduced their mobility for high ionic strength, and particle concentrations (C/C0 < 0.1). The formation of large nSiO2 aggregates, in particular, was principally responsible for the enhancement of nSiO2 retention in sand columns over a broad range of IS and particle concentration. The interaction energy profiles based on the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory were determined to understand the mechanism of nSiO2 deposition. Aditionally, all the experimental BTCs were mathematically simulated and justified by the colloidal filtration theory (CFT). Considering the environmental ramifications, the transport behavior of nSiO2 was further evaluated in various natural matrices such as river, lake, ground, and tap water. The nSiO2 suspended in the river, lake, and tap water had significantly higher mobility (C/C0 > 0.7), whereas groundwater indicated higher retention (C/C0 < 0.3). The study advances our collective knowledge of physicochemical and environmental parameters that can affect particle mobility.

A comprehensive estimate of the aggregation and transport of nSiO2 in static and dynamic aqueous systems.

Silicon dioxide nanoparticles (nSiO2) are extensively used in diverse fields and are inevitably released into the natural environment. Their overall aggregation behaviour in the environmental matrix can determine their fate and ecotoxicological effect on terrestrial and aquatic life. The current study systematically evaluates multiple parameters that can influence the stability of colloidal nSiO2 (47 nm) in the natural aquatic environment. At first, the influence of several hydrochemical parameters such as pH (5, 7, and 9), ionic strength (IS) (10, 50, and 100 mM), and humic acid (HA) (0.1, 1, and 10 mg L-1) was examined to understand the overall aggregation process of nSiO2. Furthermore, the synergistic and antagonistic effects of ionic strength and humic acid on the transport of nSiO2 in the aqueous environment were examined. Our experimental findings indicate that pH, ionic strength, and humic acid all had a profound influence on the sedimentation process of nSiO2. The experimental observations were corroborated by calculating the DLVO interaction energy profile, which was shown to be congruent with the transport patterns. The present study also highlights the influence of high and low shear forces on the sedimentation process of nSiO2 in the aqueous medium. The presence of shear force altered the collision efficiency and other interactive forces between the nanoparticles in the colloidal suspension. Under the experimental stirring conditions, a higher abundance of dispersed nSiO2 in the upper layer of the aqueous medium was noted. Additionally, the transport behaviour of nSiO2 was studied in a variety of natural water systems, including rivers, lakes, ground, and tap water. The study significantly contributes to our understanding of the different physical, chemical, and environmental aspects that can critically impact the sedimentation and spatial distribution of nSiO2 in static and dynamic aquatic ecosystems.

Delayed Breaker Systems To Remove Residual Polymer Damage in Hydraulically Fractured Reservoirs.

Hydraulic fracturing is a widely used technology to enhance the productivity of low-permeability reservoirs. Fracturing fluids using guar as the rheology builder leaves aside residual polymer layers over the fractured surface, resulting in a restricted matrix to fracture flow, causing reduced well productivity and injectivity. This research developed a specialized enzyme breaker and evaluated its efficiency in breaking linear and cross-linked guar-polymer gel as a function of time, temperature, and breaker concentration targeting a high-temperature carbonate reservoir. The study began with developing a high-temperature stable galacto-mannanase enzyme using the "protein-engineering" approach, followed by the optimization of fracturing fluids and breaker concentrations measuring their rheological properties. The thermal stability of the enzyme breaker vis-à-vis viscosity reduction and the degradation pattern of the linear and cross-linked gel observed from the break tests showed that the enzyme is stable and active up to 120 °C and can reduce viscosity by more than 99%. Further studies conducted using a high-temperature high-pressure HT-HP filter press for the visual inspection of polymer cake quality, filtration loss rates, and cake dissolution efficiency showed that a 6 h enzyme treatment degrades the filter cake by 94-98% compared to 60-70% degradation in 72 h of the natural degradation process. Coreflooding studies, under simulated reservoir conditions, showed the severity of postfracture damage (up to 99%), which could be restored up to 95% on enzyme treatment depending on the treatment protocol and the type of fracturing gel used.

Development of Hybrid Drilling Fluid and Enzyme-Acid Precursor-Based Clean-Up Fluid for Wells Drilled with Calcium Carbonate-Based Drilling Fluids.

Significant formation damage can occur during drilling operations because of the invasion of drilling fluid fines and filtrates that lead to pore blocking and saturation alteration mechanisms. This study demonstrates the ways to minimize drilling fluid-related damage and the removal of the deposited filter cake in the carbonate reservoir through judicious selection of bridging particles using "ideal packing theory" and formulation of an enzyme-based clean-up fluid with an acid precursor. The polymer-based drill-in-fluid with a mixed grade of CaCO3 bridging particles resulted in a compact filter cake with reduced filtration loss preventing internal pore damage significantly. Several ester hydrolysis reaction kinetics were studied, and finally, one combination was chosen as the suitable acid precursor because of its ability to generate a required concentration of acid within the downhole condition. The return permeability of mud-damaged carbonate core plugs was higher than 95% after exposure to the clean-up solution. The corrosion rates were found to be significantly below the industry limits, and the use of acid corrosion inhibitors is eliminated.