Fluorescent paper-based sensor integrated with headspace thin-film microextraction for the detection of acyclic N-nitrosamines following in situ photocatalytic decomposition

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGBackground: In this work, a novel analytical approach based on the photocatalytic decomposition of N-nitrosamines combined with headspace thin-film microextraction of the generated nitrogen oxides such as NO has been developed for the determination of the acyclic N-nitrosamine fraction in drinking water samples. A hydrophilic cellulose substrate modified with fluorescent silver nanoclusters (Ag NCs) was used both as extractant and sensing platform. A quenching effect of Ag NCs fluorescence occurs as the concentration of N-nitrosamines increases. Front-face fluorescence spectroscopy with a solid sample holder was employed for directly measuring the fluorescence quenching onto the cellulose substrate. Results: In order to achieve an optimal analytical response, different parameters involved in the photocatalytic reaction as well as those concerning the microextraction step were fully investigated. It is demonstrated that the photodegradation rate of cyclic N-nitrosamines at acidic pH is much lower than that of acyclic ones, which can be the basis for the determination of the later fraction in waters. Under optimal conditions, a detection limit for the acyclic N-nitrosamine fraction around 0.08 μg L−1 using N-nitrosodimethylamine (NDMA) as model compound for calibration was obtained. Several drinking waters were spiked with acyclic N-nitrosamines showing recoveries in the range of 98–102% with a relative standard deviation of 3–4% (N = 3). Significance and novelty: N-nitrosamines generated as by-products during disinfection processes applied to water cause multiple adverse effects on human health being classified as potential human carcinogens. This study highlights the suitability of a fluorescent paper-based sensor for the rapid analysis of the acyclic N-nitrosamine fraction (i.e. the most abundant fraction) as a total index in drinking water, being useful as screening tool before exhaustive chromatographic analysis, which saves costs, time and reduces waste generation.Agencia Estatal de Investigacion | Ref. RTI2018- 093697-B-I00Xunta de Galicia | Ref. ED481D-2021-02

Silver nanocluster-based colorimetric/fluorimetric dual-mode sensor for the detection of bromide and sulfite in waters and wastewaters

In this work, the development of a fluorimetric/colorimetric dual-mode nanosensor for the determination of sulfite and fluorimetric determination of bromide involving silver nanoclusters (AgNCs) is reported. SO2 and Br2 were found to significantly modify the optical properties of AgNCs. Particularly, both volatiles weakened the fluorescence of AgNCs, whereas a color change from nearly colorless to yellowish/brown occurred upon exposure of AgNCs to SO2. Accordingly, three smartphone-based optical assays were devised for sulfite and bromide determination, involving in situ volatile generation and enrichment/trapping of the selectively formed volatiles by AgNCs confined in a droplet and exposed to the headspace above the sample. A hydrophobized cellulose substrate acting as drop holder enabled integrating both the enrichment and the subsequent smartphone-based optical detection in a straightforward manner. Smartphone-based digitization of the enriched AgNCs microdrops and subsequent image processing using a smartphone and its integrated App, respectively, were used for quantitative purposes. Under optimal conditions, limits of detection (LODs) of 1.1 μM and 1.5 μM were achieved for the fluorimetric determination of sulfite and bromide, respectively, whereas sulfite was alternatively determined by colorimetric readout, yielding a LOD of 37.0 μM. The repeatability, expressed as relative standard deviation, was found to be in the range of 5.1–5.9 % in all cases (N = 8). The applicability of the method was demonstrated in aqueous samples of increasing complexity, with recoveries in the range 91–109 %. In addition, the responsiveness of AgNCs to SO2 and Br2 rendered them suitable for the monitoring of bromide and sulfite in increasingly relevant advanced reduction processes such as the UV/sulfite system, as demonstrated in this work.Agencia Estatal de Investigación | Ref. PID2022-136337OB-I00Universidade de Vigo/CISU

Droplet-based luminescent sensor supported onto hydrophobic cellulose substrate for assessing fish freshness following smartphone readout

In this work, two sensitive droplet-based luminescent assays with smartphone readout for the determination of trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) are reported. Both assays exploit the luminescence quenching of copper nanoclusters (CuNCs) produced when exposed to volatile nitrogen bases. In addition, hydrophobic-based cellulose substrates demonstrated their suitability as holders for both in-drop volatile enrichment and subsequent smartphone-based digitization of the enriched colloidal solution of CuNCs. Under optimal conditions, enrichment factors of 181 and 153 were obtained with the reported assays for TMA-N and TVB-N, respectively, leading to methodological LODs of 0.11 mg/100 g and 0.27 mg/100 g for TMA-N and TVB-N, respectively. The repeatability, expressed as RSD, was 5.2% and 5.6% for TMA-N and TVB-N, respectively (N = 8). The reported luminescent assays were successfully applied to the analysis of fish samples, showing statistically comparable results to those obtained with the reference methods of analysis.Agencia Estatal de Investigación | Ref. RTI2018-093697-B-I00Universidade de Vigo/CISU

Bilingual Comics on the Border as Graphic Medicine: Journaling and Doodling for Dementia Caregiving during the COVID-19 Pandemic

The use of comics can be a powerful tool to expand educational outreach efforts for improving the health and well-being of people everywhere. Dr. Ian Williams coined the term graphic medicine to denote the use of comics in medical education and patient care ( Graphic Medicine ). Alzheimer\u27s disease affects approximately five million Americans and is expected to triple to 13.8 million by 2050. Hispanics and Blacks are disproportionately affected at a higher rate than other groups ( Facts and Figures ). There is a lack of culturally relevant educational materials available for these populations. To address this disparity, an interdisciplinary community engaged collaboration was initiated with the Alzheimer\u27s Association West Texas Chapter, The University of Texas at El Paso (UTEP), and Dukes Comics to produce a series of virtual workshops entitled, Journaling and Doodling for Stress Reduction and Relaxation for caregivers of people living with Alzheimer\u27s and other dementias. These sessions were live-streamed and began during the COVID-19 pandemic. Spanish sessions have also been provided to the public. Health information about the disease process and common caregiver challenges are provided in each session. A guided journaling and doodling activity are also included. Journaling has been shown to be an effective and easy tool to use for stress management (Scott). The impetus behind this project was to address the dire need for increasing access to Alzheimer\u27s disease education and resources in El Paso, Texas, a border community that is also home to Fort Bliss Army base. Hispanics comprise approximately 82% of the population and include a large Spanish-speaking segment. Language is often a barrier to health care access and education. To meet the aim of increasing accessibility, the workshops and comics are available in both English and Spanish and soon in-person. This project received a 2022 joint seed grant from Texas Tech University Health Sciences Center El Paso and UTEP to conduct research and examine data from these workshops that will be provided in-person in marginalized and multilingual Latina communities surrounding El Paso starting in the fall

A 3D microfluidic paper-based analytical device with smartphone-assisted colorimetric detection for iodine speciation in seaweed samples

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe present work reports on the development of a 3D origami microfluidic paper-based analytical device (3D µPAD) for the determination of iodide and iodate in edible seaweeds by smartphone-based colorimetric detection. In addition, a methacrylate holder was designed and fabricated to enhance interlayer contact in 3D µPADs, obtaining excellent sensitivity and precision, also allowing real-time monitoring in a straightforward and expeditious way. The reported assay, based on the formation of a blue colored triiodide-starch complex at the detection areas of the 3D µPAD, represents an affordable, fast and greener alternative for the simultaneous determination of inorganic iodine species. Under optimal conditions, the proposed method showed limits of detection and quantification of 9.8 and 32.7 µM for I- and 0.6 and 1.8 µM for IO3-, respectively. The repeatability, expressed as relative standard deviation, was 1.7% and 3.3% for I- and IO3-, respectively. The proposed 3D µPAD was applied to the determination of iodine species in extracts of edible seaweeds and related food additives, showing satisfactory recoveries (90–109%).Agencia Estatal de Investigación | Ref. RTI2018-093697-B-I0

Silver nanoparticle-cellulose composite for thin-film microextraction of Cd and Pb as dithiocarbamate derivatives followed by inductively-coupled plasma mass spectrometry determination

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGPreconcentration of Cd and Pb at ultratrace level in waters following filtration through silver nanoparticles-cellulose composites used for thin-film microextraction was performed. The new procedure was based on the formation of pyrrolidine dithiocarbamate (APDC) derivatives, which showed a large affinity toward the AgNPs. For this purpose, cellulose filters modified with AgNPs were prepared in situ upon reduction of silver ions by sodium tetrahydroborate. The effect of several experimental parameters such as the kind of derivatization agent and its concentration, sample pH, desorption conditions and volume of filtered sample was assessed. Cd and Pb were quantitated in the eluates by inductively coupled plasma-mass spectrometry (ICP-MS). Filters were characterized by scanning electron microscopy (SEM) in backscattering electron mode and combined with energy dispersive X-ray spectrometry, showing the presence of Ag and S in the cellulose filter. The repeatability expressed as relative standard deviation (RSD,%) was 1.4% for Cd and 5.8% for Pb. Methodological detection limits were 0.6 and 8.5 ng/L for Cd and Pb, respectively. The method was applied to several environmental waters.Agencia Estatal de Investigación | Ref. RTI2018-093697-B-I0

Detection of gases and organic vapors by cellulose-based sensors

The growing interest in the development of cost-effective, straightforward, and rapid analytical systems has found cellulose-based materials, including cellulose derivatives, cellulose-based gels, nanocellulosic materials, and the corresponding (nano)cellulose-based composites, to be valuable platforms for sensor development. The present work presents recent advances in the development of cellulose-based sensors for the determination of volatile analytes and derivatives of analytical relevance. In particular, strategies described in the literature for the fabrication and modification of cellulose-based substrates with responsive materials are summarized. In addition, selected contributions reported in the field of paper-based volatile sensors are discussed, with a particular emphasis on quick response (QR) code paper-based platforms, intelligent films for food freshness monitoring, and sensor arrays for volatile discrimination purposes. Furthermore, analytical strategies devised for the determination of ionic species by in situ generation of volatile derivatives in both paper-based analytical devices (PADs) and microfluidic PADs will also be described.Universidade de Vigo/CISUGAgencia Estatal de Investigación | Ref. RTI2018-093697-B-I0

Determination of the sanitary quality of unpasteurized fresh cheeses for human consumption in Sinaloa, Mexico

Fresh cheese represents a staple food of great importance for some communities, as well as an income from its commercialization; however, in some cases, the way it is processed could represent a risk to human health. Therefore, the objective of this study was to determine the sanitary quality of unpasteurized fresh cheeses intended for human consumption in Sinaloa. A total of 15, 20, 10, and 15 cheese samples were taken from Mazatlán, Culiacán, Guasave, and Los Mochis in the state of Sinaloa, México, respectively. The microbiological analysis was performed based on the Official Mexican Standard NOM-210-SSA1-2014. In accordance with the standard, the content of Escherichia coli, Staphylococcus aureus and Salmonella spp. was estimated. Of the total samples analyzed, 97% showed Escherichia coli, 57% S. aureus, and 13% Salmonella spp., above the reference values. The presence of indicator microorganisms and pathogens represents a risk factor for acquiring foodborne diseases, and also makes evident the need to improve hygienic practices in the preparation and preservation of these products. El queso fresco representa un alimento básico de gran importancia para algunas comunidades, así como un ingreso por su comercialización; sin embargo, en algunos casos, la forma en que se procesa podría representar un riesgo para la salud humana. Por tanto, el objetivo de este estudio fue determinar la calidad sanitaria de quesos frescos sin pasteurizar destinados al consumo humano en Sinaloa. Se tomaron un total de 15, 20, 10 y 15 muestras de queso de Mazatlán, Culiacán, Guasave y Los Mochis en el estado de Sinaloa, México, respectivamente. El análisis microbiológico se realizó con base en la Norma Oficial Mexicana NOM-210-SSA1-2014. De acuerdo con la norma, el contenido de Escherichia coli, Staphylococcus aureus y Salmonella spp., fue estimado. Del total de muestras analizadas, el 97% presentó Escherichia coli, el 57% S. aureus y el 13% Salmonella spp., por encima de los valores de referencia. La presencia de microorganismos indicadores y patógenos representa un factor de riesgo para adquirir enfermedades transmitidas por los alimentos, y también hace evidente la necesidad de mejorar las prácticas higiénicas en la elaboración y conservación de estos productos

A Simple Way to Produce Gold Nanoshells for Cancer Therapy

Gold nanoshells (GNSs), formed by a silica core surrounded by a gold shell, present a shift on their surface plasmon resonance (SPR) to the near-infrared (NIR) part of the electromagnetic spectrum when synthesized with specific dimensions. This chapter presents a simple method to prepare the nanoshells, a step-by-step characterization, as well as their absorbance spectrum. For the synthesis, silica spheres, with approximately 190 ± 5 nm in diameter, were prepared using the Stöber method and then functionalized with 3-aminopropyltriethoxysilane (APTES). The gold nanoparticles (GNPs), with a diameter of 7 ± 3 nm, were produced by the reduction of chloroauric acid. Then, the silica was seeded with the GNPs to later grow a gold shell with the help of Au(OH)4¯ ions and formaldehyde. UV-Vis spectroscopy results showed an increase of absorbance starting at 520 nm. It reached its maximum around 600 nm and kept absorbing all through 1200 nm. Transmission electron microscope (TEM) and scanning electron microscope (SEM) images suggest that the absorption peak movement coincided with the completion of the shell. Furthermore, when the sample was irradiated with an 820 nm wavelength/3.1 mW laser, its temperatures increased by 6.3°C in 2 min, showing its absorbance in the NIR

Effect of Lipophilic Bismuth Nanoparticles on Erythrocytes

Lipophilic bismuth dimercaptopropanol nanoparticles (BisBAL NPs) have a very important antimicrobial activity; however their effect on human cells or tissues has not been completely studied. Undesirable effects of bismuth include anemia which could result from suicidal erythrocyte death or eryptosis. The objective of this research was to determine the effect of bismuth dimercaptopropanol nanoparticles on blood cells. The nanoparticles are composed of 53 nm crystallites on average and have a spherical structure, agglomerating into clusters of small nanoparticles. Based on cell viability assays and optical microscopy, cytotoxicity on erythrocytes was observed after growing with 500 and 1000 µM of BisBAL NPs for 24 h. AM Calcein was retained inside erythrocytes when they were exposed to 100 µM (or lower concentrations) of BisBAL NPs for 24 h, suggesting the absence of damage in plasmatic membrane. Genotoxic assays revealed no damage to genomic DNA of blood cells after 24 h of exposition to BisBAL NPs. Finally, 100–1000 µM of bismuth nanoparticles promotes apoptosis between blood cells after 24 h of incubation. Hence BisBAL NPs at concentrations lower than 100 µM do not cause damage on blood cells; they could potentially be used by humans without affecting erythrocytes and leukocytes