Arsenic and fluoride in groundwater triggering a high risk: Probabilistic results using Monte Carlo simulation and species sensitivity distribution.

The widespread presence of arsenic (As) and fluoride (F-) in groundwater poses substantial risks to human health on a global scale. These elements have been identified as the most prevalent geogenic contaminants in groundwater in northern Mexico. Consequently, this study aimed to evaluate the human health and ecological risks associated with the content of As and F- in the Meoqui-Delicias aquifer, which is in one of Mexico's most emblematic irrigation districts. Concentrations of As and F- were measured in 38 groundwater samples using ICP-MS and ion chromatography, respectively. Overall, these elements showed a similar trend across the aquifer, revealing a positive correlation between them and pH. The concentration of As and F- in the groundwater ranged from 5.3 µg/L to 303 µg/L and from 0.5 mg/L to 8.8 mg/L, respectively. Additionally, the levels of As and F- surpassed the established national standards for safe drinking water in 92% and 97% of samples, respectively. Given that groundwater is used for both agricultural purposes and human activities, this study also assessed the associated human health and ecological risks posed by these elements using Monte Carlo simulation and Species Sensitivity Distribution. The findings disclosed a significant noncarcinogenic health risk associated with exposure to As and F-, as well as an unacceptable carcinogenic health risk to As through water consumption for both adults and children. Furthermore, a high ecological risk to aquatic species was identified for F- and high to medium risks for As in the sampling sites. Therefore, the findings in this study provide valuable information for Mexican authorities and international organizations (e.g., WHO) about the adverse effects that any exposure without treatment to groundwater from this region represents for human health.

Detection of Acetaminophen in Groundwater by Laccase-Based Amperometric Biosensors Using MoS2 Modified Carbon Paper Electrodes.

The use of enzyme-based biosensors for the detection and quantification of analytes of interest such as contaminants of emerging concern, including over-the-counter medication, provides an attractive alternative compared to more established techniques. However, their direct application to real environmental matrices is still under investigation due to the various drawbacks in their implementation. Here, we report the development of bioelectrodes using laccase enzymes immobilized onto carbon paper electrodes modified with nanostructured molybdenum disulfide (MoS2). The laccase enzymes were two isoforms (LacI and LacII) produced and purified from the fungus Pycnoporus sanguineus CS43 that is native to Mexico. A commercial purified enzyme from the fungus Trametes versicolor (TvL) was also evaluated to compare their performance. The developed bioelectrodes were used in the biosensing of acetaminophen, a drug widely used to relieve fever and pain, and of which there is recent concern about its effect on the environment after its final disposal. The use of MoS2 as a transducer modifier was evaluated, and it was found that the best detection was achieved using a concentration of 1 mg/mL. Moreover, it was found that the laccase with the best biosensing efficiency was LacII, which achieved an LOD of 0.2 µM and a sensitivity of 0.108 µA/µM cm2 in the buffer matrix. Moreover, the performance of the bioelectrodes in a composite groundwater sample from Northeast Mexico was analyzed, achieving an LOD of 0.5 µM and a sensitivity of 0.015 µA/µM cm2. The LOD values found are among the lowest reported for biosensors based on the use of oxidoreductase enzymes, while the sensitivity is the highest currently reported.

Development of a surface plasmon resonance based immunosensor for diclofenac quantification in water.

A Surface Plasmon Resonance (SPR) biosensor based on an inhibition immunoassay was developed for the detection of diclofenac (DCF) in aqueous solution. Due to the small size of DCF, an hapten-protein conjugate was produced by coupling DCF to bovine serum albumin (BSA). DCF-BSA conjugate formation was confirmed via MALDI-TOF mass spectrometry. The resulting conjugate was immobilized onto the surface of a sensor fabricated via e-beam deposition of a 2 nm chromium adhesion layer followed by a 50 nm gold layer onto precleaned BK7 glass slides. Immobilization onto the nano thin gold surface was accomplished by covalent amide linkage through a self-assembled monolayer. Samples were composed of a mixture of antibody at a fixed concentration and DCF at different known concentrations in deionized water, causing the inhibition of anti-DCF on the sensor. The DCF-BSA was obtained with a ratio of 3 DCF molecules per BSA. A calibration curve was performed using concentrations between 2 and 32 µg L-1. The curve was fitted using the Boltzmann equation, reaching a limit of detection (LOD) of 3.15 µg L-1 and limit of quantification (LOQ) of 10.52 µg L-1, the inter-day precision was calculated and an RSD value of 1.96% was obtained; and analysis time of 10 min. The developed biosensor is a preliminary approach to the detection of DCF in environmental water samples, and the first SPR biosensor developed for DCF detection using a hapten-protein conjugate.

Optical Biosensors and Their Applications for the Detection of Water Pollutants.

The correct detection and quantification of pollutants in water is key to regulating their presence in the environment. Biosensors offer several advantages, such as minimal sample preparation, short measurement times, high specificity and sensibility and low detection limits. The purpose of this review is to explore the different types of optical biosensors, focusing on their biological elements and their principle of operation, as well as recent applications in the detection of pollutants in water. According to our literature review, 33% of the publications used fluorescence-based biosensors, followed by surface plasmon resonance (SPR) with 28%. So far, SPR biosensors have achieved the best results in terms of detection limits. Although less common (22%), interferometers and resonators (4%) are also highly promising due to the low detection limits that can be reached using these techniques. In terms of biological recognition elements, 43% of the published works focused on antibodies due to their high affinity and stability, although they could be replaced with molecularly imprinted polymers. This review offers a unique compilation of the most recent work in the specific area of optical biosensing for water monitoring, focusing on both the biological element and the transducer used, as well as the type of target contaminant. Recent technological advances are discussed.

Novel Magnetic Polymeric Filters with Laccase-Based Nanoparticles for Improving Congo Red Decolorization in Bioreactors.

In this work, five different magnetic biofilters, containing magnetic nanoparticles (142 nm), immobilized laccase on nanoparticles (190 nm) and permanent magnetic elements, such as neodymium magnets and metallic meshes, were designed, manufactured and tested. The five types of filters were compared by measuring the decolorization of Congo Red dye inside bioreactors, the half-life of the filters and the amount of magnetic nanoparticle and enzyme lost during multiple cycles of operation. Filters containing laccase immobilized on magnetite (Laccase-magnetite), permanent magnets and metallic mesh presented the highest Congo Red decolorization (27%) and the largest half-life among all types of filters (seven cycles). The overall dye decolorization efficiencies were 5%, 13%, 17%, 23%, and 27% for the paper filter, paper filter with magnetite, paper filter with Laccase-magnetite, paper filter with Laccase-magnetite with magnets and paper filter with Laccase-magnetite with magnets and metallic mesh, respectively. Although the highest losses of magnetite occurred when using the filters containing magnets (57 mg), the use of permanent magnetic elements in the filters increased the half-life of the filter three-fold compared to the filters without enzymatic properties and two-fold compared to the filters with Laccase-magnetite. Results indicate that the novel use of permanent magnetic elements improved the nanoparticle retention in the filters and promoted the mass transfer between the dye and the biocatalyst to enhance wastewater treatment.

Treatment of Wastewater, Phenols and Dyes Using Novel Magnetic Torus Microreactors and Laccase Immobilized on Magnetite Nanoparticles.

In this work, the design, manufacture, and testing of three different magnetic microreactors based on torus geometries (i.e., one-loop, two-horizontal-loop, and two-vertical-loop) is explored to increase the enzyme-based transformation of dyes by laccase bio-nanocomposites, improve the particle suspension, and promote the interaction of reagents. The laccase enzyme was covalently immobilized on amino-terminated silanized magnetite nanoparticles (laccase-magnetite). The optimal configuration for the torus microreactor and the applied magnetic field was evaluated in silico with the aid of the CFD and particle tracing modules of Comsol Multiphysics®. Eriochrome Black T (EBt) dye was tested as a biotransformation model at three different concentrations, i.e., 5 mg/L, 10 mg/L, and 20 mg/L. Phenol oxidation/removal was evaluated on artificial wastewater and real wastewater. The optimal catalytic performance of the bionanocomposite was achieved in the range of pH 4 to 4.5. A parabolic movement on the particles along the microchannels was induced by the magnetic field, which led to breaking the stability of the laminar flow and improving the mixing processes. Based on the simulation and experiments conducted with the three geometries, the two-vertical-loop microreactor demonstrated a better performance mainly due to larger dead zones and a longer residence time. Additionally, the overall dye removal efficiencies for this microreactor and the laccase-magnetite bionanocomposite were 98.05%, 93.87%, and 92.74% for the three evaluated concentrations. The maximum phenol oxidation with the laccase-magnetite treatment at low concentration for the artificial wastewater was 79.89%, while its phenol removal efficiency for a large volume of real wastewater was 17.86%. Treatments with real wastewater were carried out with a larger volume, equivalent to 200 biotransformation (oxidation) operating cycles of those carried out with dyes or phenol. Taken together, our results indicate that the novel microreactors introduced here have the potential to process wastewaters rich in contaminant dyes in continuous mode with efficiencies that are attractive for a potential large-scale operation. In this regard, future work will focus on finding the requirements for scaling-up the processes and evaluating the involved environmental impact indexes, economic performance, and different device geometries and processing schemes.

Comparison of Acetaminophen Degradation by Laccases Immobilized by Two Different Methods via a Continuous Flow Microreactor Process Scheme.

The presence of micropollutants in wastewater is one of the most significant environmental challenges. Particularly, pollutants such as pharmaceutical residues present high stability and resistance to conventional physicochemical and biological degradation processes. Thus, we aimed at immobilizing a laccase enzyme by two different methods: the first one was based on producing alginate-laccase microcapsules through a droplet-based microfluidic system; the second one was based on covalent binding of the laccase molecules on aluminum oxide (Al2O3) pellets. Immobilization efficiencies approached 92.18% and 98.22%, respectively. Laccase immobilized by the two different methods were packed into continuous flow microreactors to evaluate the degradation efficiency of acetaminophen present in artificial wastewater. After cyclic operation, enzyme losses were found to be up to 75 µg/mL and 66 µg/mL per operation cycle, with a maximum acetaminophen removal of 72% and 15% and a retention time of 30 min, for the laccase-alginate microcapsules and laccase-Al2O3 pellets, respectively. The superior catalytic performance of laccase-alginate microcapsules was attributed to their higher porosity, which enhances retention and, consequently, increased the chances for more substrate-enzyme interactions. Finally, phytotoxicity of the treated water was lower than that of the untreated wastewater, especially when using laccase immobilized in alginate microcapsules. Future work will be dedicated to elucidating the routes for scaling-up and optimizing the process to assure profitability.

Microplastics in Latin America and the Caribbean: A review on current status and perspectives.

A literature review was carried out to analyze the current status of microplastic research in Latin America and the Caribbean (LAC). Specifically, this work focused on publications pertaining to (1) occurrence and distribution of microplastics in the environment, including water, sediments, and soil and (2) the environmental impact of MPs, particularly their presence and effects on aquatic and terrestrial organisms. The review included peer-reviewed articles from Scopus, Science Direct, Web of Science, Google Scholar and two iberoamerican open access databases (Redalyc and SciELO). It was found that LAC has only contributed to 5% of the global scientific output on microplastics, and overall the highest contributor within the region was Brazil (52%), followed by Chile (16%) and Mexico (13%). An additional section analyzing the barriers to conducting microplastic research in LAC and their exacerbation by the current COVID-19 pandemic was included to provide additional context behind the relatively low scientific production and improve recommendations encouraging research in this region.

Tracking nitrate and sulfate sources in groundwater of an urbanized valley using a multi-tracer approach combined with a Bayesian isotope mixing model.

Over the past decades, groundwater quality has deteriorated worldwide by nitrate pollution due to the intensive use of fertilizers in agriculture, release of untreated urban sewage and industrial wastewater, and atmospheric deposition. Likewise, groundwater is increasingly polluted by sulfate due to the release of domestic, municipal and industrial wastewaters, as well as through geothermal processes, seawater intrusion, atmospheric deposition, mineral dissolution, and acid rain. The urbanized and industrialized Monterrey valley has a long record of elevated nitrate and sulfate concentrations in groundwater with multiple potential pollution sources. This study aimed to track different sources and transformation processes of nitrate and sulfate pollution in Monterrey using a suite of chemical and isotopic tracers (δ2H-H2O, δ18O-H2O, δ15N-NO3, δ18O-NO3 δ34S-SO4, δ18O-SO4) combined with a probability isotope mixing model. Soil nitrogen and sewage were found to be the most important nitrate sources, while atmospheric deposition, marine evaporites and sewage were the most prominent sulfate sources. However, the concentrations of nitrate and sulfate were controlled by denitrification and sulfate reduction processes in the transition and discharge zones. The approach followed in this study is useful for establishing effective pollution management strategies in contaminated aquifers.

Congo Red Decolorization Using Textile Filters and Laccase-Based Nanocomposites in Continuous Flow Bioreactors.

Removal of azo and diazo dye content from textile industry wastewaters is crucial due to their environmental impact. Here, we report on the use of the fungal laccase from Pycnoporus sanguineus CS43 immobilized on silica nanoparticles and entrapped in textile-based filters for the degradation of Congo Red. Laccase immobilization and synthesis of the nanocomposites were carried out by two different methods, one in the presence of acetone and the second using water as solvent. This led to a change in the hydrophobicity of the obtained biofilters. Successful preparation of the nanocomposites was confirmed via FTIR spectroscopy. Changes in the secondary structure of the enzyme were inspected through the second derivative of the FTIR spectra. Six different types of filter were fabricated and tested in a continuous flow bioreactor in terms of their decolorization capabilities of Congo Red. The results indicate removal efficiencies that approached 40% for enzymes immobilized on the more hydrophobic supports. Backscattered electron (BSE) images of the different filters were obtained before and after the decolorization process. Percentage of decolorization and activity loss were determined as a function of time until a plateau in decolorization activity was reached. Experimental data was used to recreate the decolorization process in COMSOL Multiphysics® (Stockholm, Sweden). These simulations were used to determine the proper combination of parameters to maximize decolorization. Our findings suggest that the treatment of textile-based filters with immobilized laccase in conjunction with hydrophobic nanocomposites provides a suitable avenue to achieve more efficient laccase dye decolorization (39%) than that obtained with similar filters treated only with free laccase (8%). Filters treated with silica-based nanocomposites and immobilized laccases showed an increase in their decolorization capability, probably due to changes in their wetting phenomena.

Enhanced Catalytic Dye Decolorization by Microencapsulation of Laccase from P. Sanguineus CS43 in Natural and Synthetic Polymers.

Polymeric microcapsules with the fungal laccase from Pycnoporus sanguineus CS43 may represent an attractive avenue for the removal or degradation of dyes from wastewaters. Microcapsules of alginate/chitosan (9.23 ± 0.12 µm) and poly(styrenesulfonate) (PSS) (9.25 ± 0.35 µm) were synthesized and subsequently tested for catalytic activity in the decolorization of the diazo dye Congo Red. Successful encapsulation into the materials was verified via confocal microscopy of labeled enzyme molecules. Laccase activity was measured as a function of time and the initial reaction rates were recovered for each preparation, showing up to sevenfold increase with respect to free laccase. The ability of substrates to diffuse through the pores of the microcapsules was evaluated with the aid of fluorescent dyes and confocal microscopy. pH and thermal stability were also measured for encapsulates, showing catalytic activity for pH values as low as 4 and temperatures of about 80 °C. Scanning electron microscope (SEM) analyses demonstrated the ability of PSS capsules to avoid accumulation of byproducts and, therefore, superior catalytic performance. This was corroborated by the direct observation of substrates diffusing in and out of the materials. Compared with our PSS preparation, alginate/chitosan microcapsules studied by others degrade 2.6 times more dye, albeit with a 135-fold increase in units of enzyme per mg of dye. Similarly, poly(vinyl) alcohol microcapsules from degrade 1.7 times more dye, despite an eightfold increase in units of enzyme per mg of dye. This could be potentially beneficial from the economic viewpoint as a significantly lower amount of enzyme might be needed for the same decolorization level achieved with similar encapsulated systems.

Fabrication and Characterization of a Low-Cost Microfluidic System for the Manufacture of Alginate-Lacasse Microcapsules.

The development of microfluidics-based systems in the recent years has provided a rapid and controlled method for the generation of monodisperse microencapsulates for multiple applications. Here, we explore the design, manufacture and characterization of a low-cost microsystem for the encapsulation of the fungal laccase from Pycnoporus sanguineus CS43 in alginate microcapsules. Multiphysics simulations were used to overview the fluid behavior within the device and estimate the resulting capsule size. Polymethylmethacrylate (PMMA) sheets were used for final microsystem manufacture. Different flow rates of the continuous (Qc) and discrete (Qd) phases in the ranges of 83-293 mL/h and 1-5 mL/h, respectively, were evaluated for microcapsule fabrication. Universal Serial Bus (USB) microscope and image analysis was used to measure the final particle size. Laccase encapsulation was evaluated using spectrophotometry and with the aid of fluorescent dyes and confocal microscopy. Results showed microcapsule size was in the range of 203.13-716.00 µm and Qc was found as the dominant parameter to control capsule size. There was an effective enzyme encapsulation of 65.94% with respect to the initial laccase solution.

Discrimination of radiosensitive and radioresistant murine lymphoma cells by Raman spectroscopy and SERS.

Intrinsic radiosensitivity is a biological parameter known to influence the response to radiation therapy in cancer treatment. In this study, Raman spectroscopy and surface enhanced Raman spectroscopy (SERS) were successfully used in conjunction with principal component analysis (PCA) to discriminate between radioresistant (LY-R) and radiosensitive (LY-S) murine lymphoma sublines (L5178Y). PCA results for normal Raman analysis showed a differentiation between the radioresistant and radiosensitive cell lines based on their specific spectral fingerprint. In the case of SERS with gold nanoparticles (AuNPs), greater spectral enhancements were observed in the radioresistant subline in comparison to its radiosensitive counterpart, suggesting that each subline displays different interaction with AuNPs. Our results indicate that spectroscopic and chemometric techniques could be used as complementary tools for the prediction of intrinsic radiosensitivity of lymphoma samples.

The Importance of Land Use Definition in Human Health Risk Assessment Related to Lead in Soils.

In many countries, soil contamination and lead exposure is a persistent human and environmental health issue, while in others, it is an emerging concern. Defining the extent of lead contamination and assessing human health risk allow for efficient prevention agendas. The different types of land uses delimit the exposure frequency and hence can influence the evaluation of possible threats. In this study, human health risk assessment is performed under different land use scenarios, after determining the concentration of lead in topsoil of a rehabilitated space. An analytical hybrid method was used to determine the concentrations of the heavy metal. Human health risk indicators, hazard quotient and cancer risk, were subsequently calculated and compared under such scenarios of varying population exposure by land use. Results indicate that an increasing exposure can set health risk indicators above the tolerable levels. Correctly defining the exposure frequency by land use is very important to determine the actual risk levels of a site. Local regulators should take this information into account before designing prevention plans, especially in localities where migration and urbanization are major development factors and since the land use of a public place could change over time and alter the exposure frequency to soil.

Control of Multiferroic properties in BiFeO3 nanoparticles.

BiFeO3 (BFO) nanoparticles (NPs) were synthesized using the sol-gel method at different calcination temperatures from 400 °C to 600 °C. XRD studies have confirmed that all BFO NPs show distorted rhombohedral crystals that match the R3c space group. We found evidence of local structural strain that develops with increasing particle size as suggested by TEM and Raman spectroscopy measurements. Magnetic measurements suggest that NPs have two distinct regimes: a ferromagnetic-like one at low temperatures and a superparamagnetic-like one at room temperature. The crossover temperature increases with NPs size, suggesting a size-dependent blocking magnetic regime. Similarly, local piezoelectric measurements at room temperature in single NP have confirmed a ferroelectric order with a NP size-dependent d33 coefficient. An analysis of both the ferroelectric and the magnetic results suggest that ferromagnetism and ferroelectricity coexist at room temperature in NPs. Our results lead to the possibility of tailoring the ferroic order in multifunctional materials by means of NP size.

Assessing Lead, Nickel, and Zinc Pollution in Topsoil from a Historic Shooting Range Rehabilitated into a Public Urban Park.

Soil contamination is a persistent problem in the world. The redevelopment of a site with a historical deposition of metals might conceal the threat of remaining pollution, especially when the site has become a public place. In this study, human health risk assessment is performed after defining the concentrations of Pb, Ni, and Zn in the topsoil of a former shooting range rehabilitated into a public park in the Municipality of Kesariani (Athens, Greece). A methodology that uses inductively coupled plasma mass spectrometry (ICP-MS, 13 samples), another that uses portable X-ray fluorescence (XRF) following a dense sample design (91 samples), and a hybrid approach that combines both, were used to obtain the concentrations of the trace elements. The enrichment factor and geoacummulation index were calculated to define the degree of pollution of the site. The hazard quotient and cancer risk indicators were also computed to find the risk to which the population is exposed. The present study reveals high non-carcinogenic health risk due to Pb pollution with ingestion as the main exposure pathway. The carcinogenic risk for Pb is within tolerable limits, but the definition of land use might alter such a statement. Lastly, regarding Ni and Zn, the site is unpolluted and there is insignificant carcinogenic and non-carcinogenic risks.

Enhancing internalization of silica particles in myocardial cells through surface modification.

Surface modification in nanostructured mesoporous silica particles (MSNs) can significantly increase the uptake in myocardial cells. Herein, MSNs particles were synthesized and chemically functionalized to further assess their biocompatibility in rat myocardial cell line H9c2. The surface modification resulted in particles with an enhanced cellular internallization (3-fold increase) with respect to pristine particles. Apoptosis events were not evident at all, while necrosis incidence was significant only at a higher doses (>500µg/mL). In particular, the percentage of necrotic cells decrease in a statistically significant manner for the functionalized particles at lower doses than 100µg/mL. This study concludes that the proposed surface functionalization of MSNs particles does not compromise their viability on H9c2 cells, and therefore they could potentially be used for biomedical purposes. Fourier-transform infrared, Raman, TGA/DSC, N2 adsorption-desorption, and TEM techniques were used to characterize the as-prepared materials. Confocal microscopy and flow cytometry analyses were carried out to measure the histograms of cell complexity and the half maximal inhibitory concentration, respectively. Reactive oxygen species generation was accessed using assays with MitoSOX and Amplex Red fluoroprobes.

Differential cytotoxicity and internalization of graphene family nanomaterials in myocardial cells.

Given the well-known physical properties of graphene oxide (GO), numerous applications for this novel nanomaterial have been recently envisioned to improve the performance of biomedical devices. However, the toxicological assessment of GO, which strongly depends on the used material and the studied cell line, is a fundamental task that needs to be performed prior to its use in biomedical applications. Therefore, the toxicological characterization of GO is still ongoing. This study contributes to this, aiming to synthesize and characterize GO particles and thus investigate their toxic effects in myocardial cells. Herein, GO particles were produced from graphite using the Tour method and subsequent mild reduction was carried out to obtain low-reduced GO (LRGO) particles. A qualitative analysis of the viability, cellular uptake, and internalization of particles was carried out using GO (~54% content of oxygen) and LRGO (~37% content of oxygen) and graphite. GO and LRGO reduce the viability of cardiac cells at IC50 of 652.1±1.2 and 129.4±1.2µg/mL, respectively. This shows that LRGO particles produce a five-fold increase in cytotoxicity when compared to GO. The cell uptake pattern of GO and LRGO particles demonstrated that cardiac cells retain a similar complexity to control cells. Morphological alterations examined with electron microscopy showed that internalization by GO and LRGO-treated cells (100µg/mL) occurred affecting the cell structure. These results suggest that the viability of H9c2 cells can be associated with the surface chemistry of GO and LRGO, as defined by the amount of oxygen functionalities, the number of graphitic domains, and the size of particles. High angle annular dark-field scanning transmission electron microscopy, dynamic light-scattering, Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopies were used to characterize the as-prepared materials.

Silica nanoparticles induce cardiotoxicity interfering with energetic status and Ca2+ handling in adult rat cardiomyocytes.

Recent evidence has shown that nanoparticles that have been used to improve or create new functional properties for common products may pose potential risks to human health. Silicon dioxide (SiO2) has emerged as a promising therapy vector for the heart. However, its potential toxicity and mechanisms of damage remain poorly understood. This study provides the first exploration of SiO2-induced toxicity in cultured cardiomyocytes exposed to 7- or 670-nm SiO2 particles. We evaluated the mechanism of cell death in isolated adult cardiomyocytes exposed to 24-h incubation. The SiO2 cell membrane association and internalization were analyzed. SiO2 showed a dose-dependent cytotoxic effect with a half-maximal inhibitory concentration for the 7 nm (99.5 ± 12.4 µg/ml) and 670 nm (>1,500 µg/ml) particles, which indicates size-dependent toxicity. We evaluated cardiomyocyte shortening and intracellular Ca2+ handling, which showed impaired contractility and intracellular Ca2+ transient amplitude during ß-adrenergic stimulation in SiO2 treatment. The time to 50% Ca2+ decay increased 39%, and the Ca2+ spark frequency and amplitude decreased by 35 and 21%, respectively, which suggest a reduction in sarcoplasmic reticulum Ca2+-ATPase (SERCA) activity. Moreover, SiO2 treatment depolarized the mitochondrial membrane potential and decreased ATP production by 55%. Notable glutathione depletion and H2O2 generation were also observed. These data indicate that SiO2 increases oxidative stress, which leads to mitochondrial dysfunction and low energy status; these underlie reduced SERCA activity, shortened Ca2+ release, and reduced cell shortening. This mechanism of SiO2 cardiotoxicity potentially plays an important role in the pathophysiology mechanism of heart failure, arrhythmias, and sudden death.NEW & NOTEWORTHY Silica particles are used as novel nanotechnology-based vehicles for diagnostics and therapeutics for the heart. However, their potential hazardous effects remain unknown. Here, the cardiotoxicity of silica nanoparticles in rat myocytes has been described for the first time, showing an impairment of mitochondrial function that interfered directly with Ca2+ handling.

Enhanced Enzymatic Activity of Laccase (from Pycnoporus sanguineus CS43) Immobilized on Sputtered Nanostructured Gold Thin Films.

Functionalization of thin films with organic ligands has been the subject of intense research due to their potential application as heterogeneous molecular nanosystems. In this work, self-assembled monolayers of thiols (16-mercaptohexadecanoic acid and 11-mercaptoundecanol) were used to bind laccase (from Pycnoporus sanguineus CS43) to nanostructured gold thin films obtained by DC sputtering. Sputtering power, sputtering pressure and substrate temperature were optimized to enhance the activity of the immobilized biomolecules. Scanning electron microscopy, confocal microscopy, X-ray diffraction and UV-vis spectroscopy were used to characterize the SAM-functionalized gold substrates. Our results demonstrate that the highest immobilized enzyme activity values can be achieved on substrates of surface roughness ˜200 nm and Au particle size of about 14 nm. The outstanding quality of the as-prepared substrates makes them particularly attractive as bionanosensors.