Low-cost, disposable colourimetric sensors for metal ions detection

Abstract In this work, two colourimetric sensors for metal ions detection are presented. The devices are obtained by fixing two classical dyes, Eriochrome Black T (EBT) and 1-(2-pyridylazo)-2-naphthol (PAN), on the commercial paper sheet "Colour Catcher®" (here named under the acronym CC) generally used in the washing machine to prevent colour run problems. The devices are optical sensors, since the indicator dye, fixed on the solid material, changes its spectral properties (colour and hence UV-vis spectrum) upon contact with the metal ion solution. We used the partial least squares (PLS) regression for obtaining the relationship between the metal ion content and the UV-vis spectrum change of each sensor

DFO@EVOH and 3,4-HP@EVOH: Towards New Polymeric Sorbents for Iron(III)

The paper presents the synthesis and preliminary characterization of two novel solid-phase sorbents for iron(III), resulting from the functionalization of ethylene-vinyl alcohol copolymer (EVOH) with deferoxamine, DFO (DFO@EVOH), and a novel tripodal 3-hydroxy-4-pyridinone, named 3,4-HP (3,4-HP@EVOH). DFO and 3,4-HP have been covalently bonded to EVOH, using carbonyldiimidazole as a coupling agent. Before their use as Fe(III) sorbents, they were warm-pressed to obtain a thin film. Polymers have been characterized by conventional physico-chemical techniques; furthermore, the sorption properties towards Fe(III) were investigated. The physico-chemical characterization of the new solid-state devices demonstrates the effective linkage of the two receptors on the polymeric support. Despite a relatively low sorption capacity for both materials, the stoichiometry and the complexation constants of Fe(III)/DFO@EVOH and Fe(III)/3,4-HP@EVOH are in pretty good agreement with those obtained for the same ligands in aqueous solutions

Hemangiomas infantis: avaliação e diagnóstico

Introduction: Hemangiomas are the most common benign tumors of the vascular endothelium in childhood, often self-limiting. Others can cause complications, such as ulceration, disfigurement, and involvement of vital organs. They can be associated with developmental anomalies. In most cases, their diagnosis is clinical, with history and physical examination. Deeper lesions without characteristic skin changes and liver lesions may be difficult to distinguish from vascular malformations or other tumors. Although imaging studies may be useful, biopsy may be necessary for definitive diagnosis and histopathological evaluation. Objective: To discuss the evaluation and diagnosis of infantile hemangiomas. Methodology: Literature review based on articles from the Scielo, PubMed, and BVS databases, from January to March 2024, with descriptors “infantile hemangiomas”, “evaluation,” and “diagnosis”. Articles from 2019 to 2024 (223 studies) were included. Other categories were removed, with 05 articles in full. Results and Discussion: Vascular lesions should be evaluated regarding the following aspects: age of onset of the lesion and subsequent behavior; results of examinations performed (imaging/biopsies); previous treatments and responses; history of respiratory distress in the first months of life if cervicofacial or mandibular hemangioma; signs of heart failure; telangiectasias/purpura/thrombocytopenia. The physical examination should include skin and mucous membranes, with documentation of morphology, location and size of the lesion; presence and severity of ulceration, bleeding and evidence of secondary infection; hepatomegaly; signs of heart failure (tachycardia, wide pulse pressure). Regarding location: periorbital, segmental (face and scalp, lower body) and multiple). Imaging by ultrasound, tomography or resonance may be an option, but not reliable if there is doubt as to malignancy, in which case a tissue biopsy is indicated. Referral to a specialist in vascular anomalies is essential for the diagnosis and therapeutic management of these children and is more appropriate when associated with other developmental anomalies or segmental lesions. If early, within four to six weeks of life, systemic therapy is considered. Conclusion: Despite its benign nature of the vascular endothelium, hemangioma requires specialist monitoring for its management and prevention of complications in the child's development.Introdução: Hemangiomas são tumores mais comuns da infância, de natureza benigna do endotélio vascular e muitas vezes autolimitado. Outros podem causar complicações, como ulceração, desfiguração e comprometimento de órgãos vitais. Podem se associar a anomalias do desenvolvimento. Na maioria dos casos, seu diagnóstico é clínico, com história e exame físico. Lesões mais profundas sem alterações características da pele e lesões hepáticas podem ser difíceis de distinguir de malformações vasculares ou outros tumores. Embora estudos por imagem possam ser úteis, a biópsia pode ser necessária para diagnóstico definitivo e avaliação histopatológica Objetivo: discutir a avaliação e diagnóstico dos hemangiomas infantis. Metodologia: Revisão de literatura a partir de artigos das bases de dados da Scielo, da PubMed e da BVS, de janeiro a março de 2024, com descritores “infantile hemangiomas”, “evaluation” e “diagnosis”. Incluíram-se artigos de 2019 a 2024 (223 estudos). Retiraram-se outras categorias, com 05 artigos na íntegra. Resultados e Discussão: A lesão vascular deve ser avaliada quanto aos aspectos: idade de aparecimento da lesão e comportamento subsequente; resultados de exames realizados (imagem/biópsias); tratamentos e respostas prévios; história de dificuldade respiratória nos primeiros meses de vida se hemangioma cervicofacial ou mandibular; sinais de insuficiência cardíaca; telangiectasias/ púrpuras/ plaquetopenia. O exame físico deve ser abranger pele e mucosas, com documentação de morfologia, localização e tamanho da lesão; presença e gravidade de ulceração, sangramento e evidência de infecção secundária; hepatomegalia; sinais de insuficiência cardíaca (taquicardia, pressão de pulso ampla). Quanto à localização: periorbitais, segmentares (face e couro cabeludo, parte inferior do corpo) e múltiplos). A imagem por ultrassonografia, tomografia ou ressonância pode ser opção, mas não confiável se dúvida quanto à malignidade, sendo indicado nesse aspecto uma biópsia tecidual. O encaminhamento para especialista em anomalias vasculares é determinante para diagnóstico e manejo terapêutico dessas crianças, bem como mais adequado quando associado com outras anomalias do desenvolvimento ou lesões segmentares. Se precoce, dentro de quatro a seis semanas de vida, a terapia sistêmica é considerada. Conclusão: Apesar de sua natureza benigna do endotélio vascular, o hemangioma precisa de acompanhamento de especialistas para seu manejo e prevenção de complicações no desenvolvimento da criança

Sviluppo di nuovi sensori colorimetrici ed elettrochimici per applicazioni analitiche

In questo lavoro di tesi sono riportati per esteso tutti i risultati ottenuti nel progetto di dottorato dal titolo “Development of new tailored devices for analytical applications”. Lo scopo del progetto era di sviluppare sensori ottici ed elettrochimici per la determinazione di analiti di interesse ambientale e alimentare. Durante i tre anni di dottorato sono stati sviluppati sensori colorimetrici di vario tipo e, a titolo d’esempio sono stati descritti in questa tesi due dispositivi a base di carta da filtro (Paper-based Analytiical devices, PADs) per la determinazione dell’acidità di bibite commerciali e per la determinazione del Pd2+ in acque naturali. In tutti i casi per il trattamento dei dati sono state applicate tecniche chemiometriche. Inoltre sono stati sviluppati dei sensori elettrochimici basati sull’utilizzo di celle elettrochimiche stampate. Sono stati sviluppati due sensori per il Glifosato e il Fe3+ modificando la superficie degli elettrodi di lavoro d’oro con opportuni monostrati di tioli (self assembled monolayers, SAM). Sensori per la determinazione di MCPA, Atrazina, Irbesartan e Acido ascorbico sono stati ottenuti modificando la superficie dell’elettrodo di lavoro in grafite con polimeri a stampo molecolare (acrilici o elettropolimerizzati). Quando necessario sono state applicate tecniche multivariate di analisi dati.In this thesis, the results obtained during the Ph.D. project titled “Development of new tailored devices for analytical applications” are reported. The aim of the project was the development of optical and electrochemical sensors for environmental and food applications. During these three years, colorimetric sensors were realized, and as examples, two kinds of Paper-based Analytical devices (PADs) for determining the acidity of commercial drinks or Pd2+ in natural waters were described. In all cases, chemometric tools were applied for the data treatment. Furthermore, electrochemical sensors based on screen-printed cells were proposed. Sensors for Glyphosate and Fe3+ were developed by modifying the gold working electrode of the screen-printed cells with proper self-assembled monolayers. Sensors for MCPA, Atrazine, Irbesartan and Ascorbic acid were obtained by modifying the surface of the graphite working electrode of the screen-printed cells with molecularly imprinted polymers (acrylic-based or electro-synthesized). Multivariate techniques were applied for data treatment when necessary

Gold and Silver Nanoparticle-Based Colorimetric Sensors: New Trends and Applications

Gold and Silver nanoparticles (AuNPs and AgNPs) are perfect platforms for developing sensing colorimetric devices thanks to their high surface to volume ratio and distinctive optical properties, particularly sensitive to changes in the surrounding environment. These characteristics ensure high sensitivity in colorimetric devices. Au and Ag nanoparticles can be capped with suitable molecules that can act as specific analyte receptors, so highly selective sensors can be obtained. This review aims to highlight the principal strategies developed during the last decade concerning the preparation of Au and Ag nanoparticle-based colorimetric sensors, with particular attention to environmental and health monitoring applications

Ascorbic Acid Sensing by Molecularly Imprinted Electrosynthesized Polymer (e-MIP) on Screen-Printed Electrodes

This paper presents the development of a cheap and rapid electrochemical sensor for ascorbic acid detection. In particular, the graphite ink working electrode of screen-printed cells was covered by a film of elecrosynthesized molecularly imprinted polypyrrole (e-MIP); differential pulse voltammetry (DPV) was the selected method for the analyte detection. The ascorbic acid molecules were successfully entrapped in the polypyrrole film, creating the recognition sites. The best results were obtained after polypyrrole overoxidation and performing the measurements in phosphate buffer solution 0.05 M/KCl 0.1 M at pH 7.5. A comparison with the bare and the not-imprinted polypyrrole-modified electrodes showed that the e-MIP-based sensor had the highest selectivity and reproducibility. The developed method was applied to assess ascorbic acid in farmaceutical products, obtaining values not significantly different from the declared content

Disposable and Low-Cost Colorimetric Sensors for Environmental Analysis

Environmental contamination affects human health and reduces the quality of life. Therefore, the monitoring of water and air quality is important, ensuring that all areas are acquiescent with the current legislation. Colorimetric sensors deliver quick, naked-eye detection, low-cost, and adequate determination of environmental analytes. In particular, disposable sensors are cheap and easy-to-use devices for single-shot measurements. Due to increasing requests for in situ analysis or resource-limited zones, disposable sensors' development has increased. This review provides a brief insight into low-cost and disposable colorimetric sensors currently used for environmental analysis. The advantages and disadvantages of different colorimetric devices for environmental analysis are discussed

Chemometric-assisted eMIP-modified screen-printed sensor for robust herbicide MCPA determination

The paper describes the development and application of a screen-printed electrode cell with a graphite-ink working electrode modified by a molecularly imprinted electropolymerized polypyrrole for the voltammetric determination of the herbicide 4‑chloro-2-methylphenoxyacetic acid (MCPA). The method exploits the direct measurement of the analyte by applying the differential pulse voltammetry (DPV) technique, taking advantage of the irreversible oxidation peak at about +1.0 V vs. Ag/AgCl pseudo reference electrode. The presence of the molecularly imprinted polypyrrole enhances the sensor's selectivity and sensitivity. A chemometric approach has been crucial for quantitative analysis because of the peak's broad and not well-defined shape. Firstly, a proper pretreatment of the voltammetric signals is identified, proving the most effective is the first-derivative function transformation of the signal. The Partial Least Square regression (PLS) is the tool applied for MCPA quantification. A preliminary PLS model has been developed and validated in dihydrogen phosphate solution at pH 5.5, aiming to optimize the data treatment approach. Then, the same approach is used to develop a PLS model analyzing tap water samples fortified with MCPA and other pesticides as possible interferents to simulate contaminated natural waters. The model correctly predicted the analyte concentration in the range of 2.5–75 μM, assuring the reliability and robustness of the sensor for the possible quantification of MCPA in wastewater samples

MIP-Based Screen-Printed Potentiometric Cell for Atrazine Sensing

This work presents the development of a MIP-based screen-printed potentiometric cell for sensing the pesticide atrazine. The cell comprises three screen-printed electrodes; the working and the counter are obtained by graphite-ink and the pseudo-reference by silver/silver chloride-ink. All electrodes are printed on the support of polyester. Obviously, only the working and the pseudo-reference electrodes are connected for potentiometric measurements. The prepolymeric mixture was composed of the reagents at the following molar ratio: 1 atrazine (ATZ):5 methacrylic acids (MAA):4 ethylene glycol dimethacrylate (EGDMA). An amount of 7 µL of the prepolymeric solution was drop coated on the graphite working electrode of the cell, and the polymerization was carried out in an oven at 70 °C overnight. The specific sites obtained after polymerization and template elution can be viewed as the ionophore of a usual ISE membrane. The active ion is the atrazine in its protonated form, positively charged, so the determination was carried out in aqueous solutions at pHs1.5. At these conditions, the potential increases linearly with atrazine concentration ranging from 5 × 10−7 to 5 × 10−6 M; the limit of detection obtained is 4 × 10−7 M. The slope of the calibration curve E vs. log c (obtained as an average value of the slope of different standardization performed with several electrodes) is 40(6) mV/dec; the sub-Nernstian behavior can be ascribed to the interference of the anions present in the solution media