This work explores the transformative role of graphene in enhancing the performance of surface plasmon resonance (SPR)-based biosensors. The motivation for this review stems from the growing interest in the unique properties of graphene, such as high surface area, excellent electrical conductivity, and versatile functionalization capabilities, which offer significant potential to improve the sensitivity, specificity, and stability of SPR biosensors. This review systematically analyzes studies published between 2010 and 2023, covering key metrics of biosensor performance. The findings reveal that the integration of graphene consistently enhances sensitivity. Specificity, although less frequently reported numerically, showed promising results, with high specificity achieved at sub-nanomolar concentrations. Stability enhancements are also significant, attributed to the protective properties of graphene and improved biomolecule adsorption. Future research should focus on mechanistic insights, optimization of integration techniques, practical application testing, scalable fabrication methods, and comprehensive comparative studies. Our findings provide a foundation for future research, aiming to further optimize and harness the unique physical properties of graphene to meet the demands of sensitive, specific, stable, and rapid biosensing in various practical applications.

Artisanal and small-scale gold mining (ASGM) plays a crucial role in global gold production. However, the adoption of poor mining practices or the use of mercury (Hg) in gold recovery processes has generated serious environmental contamination events. The focus of this study is assessing the concentration of Hg in surface waters within the coastal region of Ecuador. The results are used to conduct a human health risk assessment applying deterministic and probabilistic methods, specifically targeting groups vulnerable to exposure in affected mining environments. Between April and June 2022, 54 water samples were collected from rivers and streams adjacent to mining areas to determine Hg levels. In the health risk assessment, exposure routes through water ingestion and dermal contact were considered for both adults and children, following the model structures outlined by the U.S. Environmental Protection Agency. The results indicate elevated Hg concentrations in two of the five provinces studied, El Oro and Esmeraldas, where at least 88% and 75% of the samples, respectively, exceeded the maximum permissible limit (MPL) set by Ecuadorian regulations for the preservation of aquatic life. Furthermore, in El Oro province, 28% of the samples exceeded the MPL established for drinking water quality. The high concentrations of Hg could be related to illegal mining activity that uses Hg for gold recovery. Regarding the human health risk assessment, risk values above the safe exposure limit were estimated. Children were identified as the most vulnerable receptor. Therefore, there is an urgent need to establish effective regulations that guarantee the protection of river users in potentially contaminated areas. Finally, it is important to continue investigating the contamination caused by human practices in the coastal region.

Gold mining activity is a source of supply in many areas of the world, and especially in developing countries, it is practiced illegally and by applying unsafe techniques. Particularly in Ecuador, artisanal and small-scale gold mining (ASGM) is widespread, and it is based on the use of toxic substances, such as mercury (Hg), in gold recovery. Hg is a heavy metal that is water-insoluble, which, once mobilized, poses a threat to both the environment and human health. This study analyzes Hg concentrations in the six provinces of Napo, Sucumbíos, Orellana, Pastaza, Morona Santiago, and Zamora Chinchipe of the Ecuadorian Amazon region to conduct a human health risk assessment. Significant differences in Hg levels were found between provinces, but concentrations were below MPL imposed by Ecuadorian regulations everywhere. Nevertheless, a worrisome picture emerges, especially with regard to the most vulnerable receptors represented by the child population. There are multiple factors of incidence that may affect the possible future development of the phenomenon, and with reference to the social, economic, and environmental context of the region, it can be concluded that it may be appropriate to plan further investigation to arrive at a more comprehensive assessment. The results of this study can be used by decision makers to plan further investigation and to implement monitoring networks, risk mitigation strategies, and groundwater protection measures.

This study presents the optimization of two SPR biosensors, Sys₃ and Sys₅, for SARS-CoV-2 detection at concentrations of 0.01–100 nM. Sys₃, with a 55 nm silver layer, a 13 nm silicon nitride layer, and a 10 nm ssDNA layer, achieved a figure of merit (FoM) of 571.24 RIU⁻¹, a signal-to-noise ratio (SNR) of 0.12, and a detection accuracy (DA) of 48.93 × 10⁻². Sys₅, incorporating a 50 nm silver layer, a 10 nm silicon nitride layer, a 10 nm ssDNA layer, and a 1.6 nm tungsten disulfide layer (L = 2), demonstrated a higher sensitivity of 305.33 °/RIU and a lower limit of detection (LoD) of 1.65 × 10⁻⁵. Sys₃ outshined in precision with low attenuation (<1%), while Sys₅ provided enhanced sensitivity and lower detection limits, crucial for early-stage viral detection. These configurations align with the refractive index ranges of clinical SARS-CoV-2 samples, showcasing their diagnostic potential. Future work will focus on experimental validation and integration into point-of-care platforms.

This paper is devoted to obtaining and studying two interior exact solutions of Einstein’s Field Equations (EFE) for spherical geometry in the context of gravitational decoupling (GD) through minimal geomentric deformation (MGD). We take the well-known Kohler–Chao–Tikekar cosmological solution as a seed in the framework of GD to first obtain an isotropic solution, which is decoupled again in order to obtain a second stellar anisotropic solution. Both resulting models turn out to be physically viable stellar models. Their stability is also being studied.

High-Andean páramo ecosystems regulate streamflow and water quality through water storage, subsurface flow, and natural hydrogeochemical buffering. However, increasing land-use pressures may generate early water-quality signals that are difficult to distinguish from natural geogenic variability in protected headwater catchments. This study evaluated the spatiotemporal variability of water quality in the Diablo Sacha River, located within the Quinllunga Water Protection Area, Ecuador. Water samples were collected at ten monitoring stations during six bimonthly campaigns from March 2024 to January 2025, generating 60 spatiotemporal observations per parameter. An integrated hydrogeochemical and multivariate framework was applied, combining Piper diagrams, Spearman correlation analysis, independent principal component analyses for hydrogeochemical and anthropogenic variables, and two-way PERMANOVA. Results showed a predominant Ca–Mg–HCO₃ hydrochemical facies, indicating that water chemistry is mainly controlled by natural mineral weathering, water–rock interaction, and longitudinal solute accumulation. The hydrogeochemical PCA explained 52.75% of the variance and identified a mineralization gradient associated with EC, HCO₃⁻, SO₄²⁻, Ca²⁺, Mg²⁺, and hydrological dilution. The anthropogenic PCA explained 61.77% of the variance and revealed secondary signals related to nutrients, organic matter, suspended solids, oils and grease, and microbiological indicators. PERMANOVA confirmed significant spatiotemporal structuring for hydrogeochemical variables and seasonal modulation for anthropogenic indicators. Overall, the Diablo Sacha River functions as a hydrogeochemically buffered high-Andean headwater system, where natural páramo processes maintain water-quality stability, while emerging anthropogenic signals act as early-warning indicators of ecosystem pressure.