Percorrer por autor "Aguiar, Juliana I. S."
A mostrar 1 - 10 de 11
Resultados por página
Opções de ordenação
- Design and development of a μPAD device for magnesium determination in salivaPublication . Aguiar, Juliana I. S.; Mesquita, Raquel B. R.; Rangel, António O. S. S.
- Development of a microfluidic paper-based analytical device (µPAD) for iron determination in waterPublication . Aguiar, Juliana I. S.; Ribeiro, Susana O.; Leite, Andreia; Rangel, Maria; Rangel, António O. S. S.; Mesquita, Raquel B. R.Ingestion of waters with high iron concentration can cause several risks to human health. In this work, a new microfluidic paper-based analytical device (µPAD) was developed to quantify iron in surface and waste waters using a new fluorescent 3-hydroxy-4-pyridione ligand. Under optimal conditions, a linear calibration curve was obtained in the concentration range of 0.25 – 2.00 mg/L with a limit detection of 0.11 mg/L. The proposed µPAD method was successfully applied to the determination of iron in surface and waste water samples with no need for sample pre-treatment, and its accuracy evaluated by comparing to the AAS standard method (RD < 10%). The developed µPAD is simple, economical, sensitive and present low analysis time. Each µPAD uses low amounts of reagents, approximately 0.5 mg of ligand and 17 mg of sodium hydrogenocarbonate and sample consumption of 100 µL.
- Development of a microfluidic paper-based analytical device for magnesium determination in saliva samplesPublication . Aguiar, Juliana I. S.; Silva, Mafalda T. S.; Ferreira, Helena A. G.; Pinto, Elisabete C. B.; Vasconcelos, Marta W.; Rangel, António O. S. S.; Mesquita, Raquel B. R.In this work, a microfluidic paper-based analytical device (μPAD) was developed for magnesium determination in saliva samples. The idea was to develop a fast and simple method for biological magnesium quantification targeting saliva as an easy to collect and non-invasive alternative to blood or urine samples. The μPAD approach was chosen due to its advantages, namely ideally suited to conduct on-location determinations, and not requiring trained operators or specialized laboratory equipment. The developed μPAD was based on the colorimetric reaction between eriochrome cyanine and magnesium to form an intense orange/reddish colour product. The colour intensity was determined by image processing after digital scanning, made within 10 to 90 min after sample loading. Under optimal conditions, the dynamic concentration range was 82–247 μM, with detection and quantification limits of 62 μM and 81 μM, respectively. The device is stable for up to 3 months when stored in vacuum or in a modified nitrogen atmosphere. An accuracy assessment was made by comparing the results obtained using the developed μPAD with those from atomic absorption spectrometry (AAS). The relative difference between the two sets of results was below 5%.
- Development of a microfluidic paper-based device for aluminium quantification in urine: potential implications for Alzheimer’s disease monitoringPublication . Aguiar, Juliana I. S.; Montenegro, Tomás; Presta, Tommaso; Rangel, António O. S. S.; Mesquita, Raquel B. R.In this work, the development of a simple and low-cost microfluidic paper-based analytical device (mPAD) for the colorimetric detection and quantification of aluminium in urine samples is presented. Aluminium exposure is an increasing public health concern due to its potential neurotoxic effects and its association with disorders such as Alzheimer’s disease and autism spectrum disorder. In this context, it may be highly advantageous to have a simple fast quantification method to evaluate aluminium exposure. The developed device relies on the colorimetric reaction of Al(III) ions through complexation with Chrome Azurol S (CAS) in a paper-based platform. The formed blue-coloured complex is measurable via scanner-based image analysis using a free image-processing software, such as ImageJ. The colour intensity of the product and convert it into pseudo-absorbance values and a linear relationship with the aluminium concentration is established. The microfluidc paper-based device (mPAD) assembly consists of two layers of paper, enabling vertical fluid transport with simple fabrication. The top layer, composed of Whatman Grade 3 filter paper, acts as a physical barrier to mitigate potential interferences from macromolecules in the urine matrix and as protective barrier for the reagents in the bottom layer. The bottom layer, composed of Whatman Grade 1 filter paper, contains the CAS reagent and an acetate buffer solution. Several chemical and physical optimization studies were carried out to improve the performance of the device. One of the major challenges was matrix interferences, particularly phosphate ions, which can form stable complexes with aluminium, hindering the Al-CAS reaction. To address this, AgNO3 was successfully used as a masking agent, precipitating phosphate and significantly improving the method’s selectivity. The mPAD enabled the quantification of aluminium within the concentration range of 0.20 to 2.0 mg/L of Al(III), which covers the levels of interest for exposure monitoring. The limit of detection and limit of quantification were 0.08 and 0.20 mg/L, respectively. The device demonstrated reliable performance for aluminium determination in real urine samples, without requiring complex sample pretreatment. Its simplicity, portability, and selectivity make it a promising tool for rapid and accessible monitoring of aluminium exposure in clinical and environmental settings.
- Development of a microfluidic paper-based device for aluminium quantification in urine: potential implications for Alzheimer’s disease monitoringPublication . Aguiar, Juliana I. S.; Montenegro, Tomás; Presta, Tommaso; Rangel, António O. S. S.; Mesquita, Raquel B. R.
- Development of a microfluidic paper-based sensor for aluminium assessment in water for domestic consumptionPublication . Aguiar, Juliana I. S.; Rangel, António O. S. S.; Mesquita, Raquel B. R.Aluminium is one of the most abundant metal ions in soil and its leaching into groundwater is an expected consequence. Monitoring the presence of Al3+ in water sources used for domestic consumption water is crucial, considering its relationship with some neurogenetic disorders, namely Alzheimer’s and Parkinson’s diseases, autism, and multiple sclerosis. In this work, the design and development of a novel microfluidic paper-based analytical device (µPAD) specifically designed for the determination of aluminium in water sources for domestic consumption is presented (Figure 1). The proposed µPAD methodology is based on the colorimetric reaction between Al3+ and Chrome Azurol S (CAS), resulting in the formation of a blue complex. Several physical and chemical parameters aZecting the formation of the colour complex were studied to attain the best performance of the paper sensor. These parameters included the µPAD filter paper layers, in terms of number, type and porosity, reagent and buZer concentration, and sample volume. The developed paper device should enable aluminium quantification within in the analytical range of 50 – 1000 µg/L.
- Iron determination in natural waters using a synthesised 3-hydroxy-4-pyridione ligand in a newly developed microfluidic paper-based devicePublication . Aguiar, Juliana I. S.; Ribeiro, Susana O.; Leite, Andreia; Rangel, Maria; Rangel, António O. S. S.; Mesquita, Raquel B. R.This work describes the development of an iron sensor based on a microfluidic paper-based technique, to attain iron quantification in natural waters. A new water-soluble naphthalene-3-hydroxy-4-pyridione ligand was used as a colour reagent, as it formed an orange complex with iron. As a newly described ligand, several chemical and physical parameters, namely, the sample and reagent volumes and reagent concentrations, were studied related to the formation of the coloured complex. The microfluidic paper-based analytical device (μPAD) assembly, namely, the use of different types of filter paper and different numbers of layers, was developed to obtain the best performance. Under the optimal conditions, a linear correlation was obtained in the range of 0.25–2.00 mg/L of iron, with a minimum detectable value of 0.07 mg/L. The proposed μPAD method was validated by an analysis of the certified samples and by a comparison of the tested water samples with the inductively coupled plasma (ICP) results (RE < 10%). Then, the μPAD device was successfully applied to the determination of iron in tap water, well water, river water, and seawater, with no need for any prior sample pre-treatment; recovery studies were also performed (average = 100.3% with RSD = 4.2%).
- A public health tool for monitoring aluminium levels in environmental and biological samplesPublication . Aguiar, Juliana I. S.; Montenegro, Tomás; Presta, Tommaso; Rangel, António O. S. S.; Mesquita, Raquel B. R.Aluminium is an element with potential toxic effects, particularly when exposure exceeds safe limits. Drinking water is a key matrix for assessing environmental contamination and human exposure, since long-term intake of high aluminium concentrations has been associated with several health issues, including Alzheimer’s disease. Additionally, monitoring aluminium in urine provides an important measure of cumulative exposure. In this work, we report the development of a microfluidic paper-based analytical device (?PAD) for the determination of aluminium in both water and urine samples. The device relies on colorimetric detection using Chrome Azurol S (CAS), which forms a blue complex with aluminium ions. The intensity of the blue colour increases proportionally with the aluminium concentration, as illustrated in Fig. 1. Several physical and chemical parameters were optimized to achieve the best analytical performance, including the type and porosity of the filter paper, reagent volumes and concentrations, and sample volume. The final design consists of two paper layers: the top layer contains the CAS solution and acetate buffer solution, while the bottom layer is used as a reservoir to allow a higher sample volume. Aluminium determination in drinking water was successfully achieved, and the ?PAD was further adapted for urine analysis, with ongoing studies addressing potential interferences. This paper-based platform provides a simple, low-cost, and rapid analytical tool that does not require sophisticated instrumentation and shows strong potential for environmental monitoring and human biomonitoring.
- Quantification of salivary magnesium using a microfluidic paper based analytical device (μPAD)Publication . Silva, Mafalda T. S.; Aguiar, Juliana I. S.; Mesquita, Raquel B. R.; Rangel, António O. S. S.
- Salivary calcium determination with a specially developed microfluidic paper-based device for point-of-care analysisPublication . Aguiar, Juliana I. S.; Rangel, António O. S. S.; Mesquita, Raquel B. R.The calcium monitoring in the body not only anticipates several potential diseases (osteoporosis, kidney stones or high blood pressure) but also helps to improve target therapies and follow-up the patient's health status. Calcium monitoring is essential for the diagnosis of one of the most common endocrine disorders worldwide, namely hyperparathyroidism. So, in this work, a new Point-of-care test (POC-test) using a microfluidic paper-based analytical device (μPAD) for calcium quantification in saliva samples is described. The developed μPAD was based on the colorimetric reaction between calcium and cresolphthalein complexone (CPC) which forms an intense purple colour product. The developed device enabled calcium quantification in the range of 0.27–4.50 mmol/L (11.0–180 mg/L) with a detection limit of 80 µmol/L (3.2 mg/L). The accuracy of the developed μPAD was confirmed by analysing saliva samples (#10) and comparing the results obtained with the atomic absorption spectrometry reference procedure; the relative deviation between the two sets of results was below 10 %. A correlation between salivary calcium content and calcium content in blood was established and it was possible to conclude that salivary calcium concentrations above 1.55 mmol/L is an indicator of hypercalcemia. The developed device was stable for 2 weeks when stored at room temperature in vacuum conditions.