Browsing by Author "Ferreira, Francisca T. S. M."
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- Design and assembly of microfluidic paper-based analytical devices (µPAD) for the quantification of nitrite and nitrate in salivaPublication . Ferreira, Francisca T. S. M.; Mesquita, Raquel B. R.; Rangel, António O. S. S.
- Design and assembly of microfluidic paper-based analytical devices (μPAD) for the quantification of nitrite and nitrate in salivaPublication . Ferreira, Francisca T. S. M.; Mesquita, Raquel B. R.; Rangel, António O. S. S.
- Design and functionalization of a µpad for the enzymatic determination of nitrate in urinePublication . Ferreira, Francisca T. S. M.; Mesquita, Raquel B. R.; Rangel, António O. S. S.In this work, the design of a microfluidic paper-based analytical device (µPAD) for the quantification of nitrate in urine samples was described. Nitrate monitoring is highly relevant due to its association to some diseases and health conditions. The nitrate determination was achieved by combining the selectivity of the nitrate reductase enzymatic reaction with the colorimetric detection of nitrite by the well-known Griess reagent. For the optimization of the nitrate determination µPAD, several variables associated with the design and construction of the device were studied. Furthermore, the interference of the urine matrix was evaluated, and stability studies were performed, under different conditions. The developed µPAD enabled us to obtain a limit of detection of 0.04 mM, a limit of quantification of 0.14 mM and a dynamic concentration range of 0.14–1.0 mM. The designed µPAD proved to be stable for 24 h when stored at room temperature in air or vacuum atmosphere, and 60 days when stored in vacuum at −20◦C. The accuracy of the nitrate µPAD measurements was confirmed by analyzing four certified samples (prepared in synthetic urine) and performing recovery studies using urine samples.
- Design of paper-based analytical devices for chemical and biochemical assays of biomarkers in biological fluids of non-invasive collectionPublication . Ferreira, Francisca T. S. M.; Rangel, António O. S. S.; Mesquita, Raquel B. R.Microfluidic paper-based analytical devices (μPADs) are innovative diagnostic tools that combine microfluidic principles with paper substrates to offer simple, portable, and cost-effective solutions. Because they use capillary action, μPADs do not require external pumps or power sources. Colorimetric reactions can be performed directly on paper, allowing for the immediate visual detection and quantification of chemical and biochemical parameters, as health biomarkers. The coloured product can be scanned and quantified through digital image processing, converting colour intensity into absorbance units. These measurements then correlate with the concentration of the individual biomarkers, like glucose and urea, among others, enabling real-time, quantitative analysis with no need for complex equipment. These features make μPADs ideal for point-of-care applications as low cost, portable, ease to use and disposable devices. Recently there also has been an increased interest in the use of saliva and urine as a biological sample for diagnosis and monitorization of several health conditions, since they are more convenient and reduce patient discomfort compared to traditional blood sampling. Non-invasive sample collection is also easier to handle in field settings. It lowers infection risk, making it highly valuable for low- resource environments, remote areas, and situations where rapid, on-site diagnosis is crucial. This work aimed to combine μPADs' strengths and the benefits of non-invasive sample collection to develop disposable microfluidic devices for rapid, real-time diagnosis of biomarkers in saliva and urine. The designed devices are intended to be an alternative diagnosis tool to complement, not replace, conventional blood analysis. The developed work, focused on optimizing these devices to cover the dynamic concentration ranges of target analytes and minimize matrix interferences in the diagnostic fluids, aiming for high accuracy and reproducibility. Such innovations could significantly improve personalized medicine, early disease detection, and preventive healthcare by making diagnostics more accessible and efficient, especially where traditional laboratory facilities are unavailable or impractical.
- Determination of nitrate and nitrite in human saliva with a specially designed microfluidic paper-based analytical device (μPAD)Publication . Ferreira, Francisca T. S. M.; Mesquita, Raquel B. R.; Rangel, António O. S. S.For many years, the concentration of nitrite and nitrate anions in human saliva was believed to be correlated with disfunctions and infections in the mouth. However, recent studies have reported some benefits to the presence of these ions in the oral cavity. In any case, there is a connection between the NOX salivary concentration and the human health and therefore it has become more and more relevant to understand this connection. Nowadays, there are several methods that allow this determination for a number of concentration ranges and types of samples, but these methods have limitations like requiring high volume of reagents and sample, the time of analysis, the use of complex lab equipment, the need of constant power, specialized technicians, the production of toxic waste, among others.
- Determination of nitrate and nitrite in human saliva with a specially designed microfluidic paper-based analytical device (μPAD)Publication . Ferreira, Francisca T. S. M.; Mesquita, Raquel B. R.; Rangel, António O. S. S.
- Exploiting solid phase extraction in a sequential injection system for phosphate determination in fertilized soil leachatesPublication . Ferreira, Francisca T. S. M.; Mesquita, Letícia S.; Mesquita, Raquel B. R.; Rangel, António O. S. S.
- Exploiting solid phase extraction in a sequential injection system for phosphate determination in fertilized soil leachatesPublication . Ferreira, Francisca T. S. M.; Mesquita, Letícia S.; Mesquita, Raquel B. R.; Rangel, António O. S. S.
- Microfluidic paper-based analytical devices for the determination of salivary NOxPublication . Ferreira, Francisca T. S. M.; Mesquita, Raquel B. R.; Rangel, António O. S. S.
- A microfluidic paper-based device for monitoring urease activity in salivaPublication . Ferreira, Francisca T. S. M.; Rangel, António O. S. S.; Mesquita, Raquel B. R.Chronic Kidney Disease (CKD) is a disorder that affects over 10% of the global population, and that would benefit from innovative methodologies that would provide early detection. Since it has been reported that there are high levels of urease in CKD patients’ saliva, this sample is a promising non-invasive alternative to blood for CKD detection and monitoring. This work introduces a novel 3D µPAD for quantifying urease activity in saliva in a range of 0.041–0.750 U/mL, with limits of detection and quantification of 0.012 and 0.041 U/mL, respectively. The device uses the urease in the sample to convert urea into ammonia, causing a colorimetric change in the bromothymol blue. The accuracy of the developed device was evaluated by comparing the measurements of several saliva samples (#13) obtained with the μPAD and with a commercially available kit. Stability studies were also performed to assess its functionality as a point-of-care methodology, and the device was stable for 4 months when stored in a vacuum. After the sample placement, it could be scanned within 40 min without providing significantly different results. The developed device quantifies urease activity in saliva within 30 min, providing a simple, portable, lab-free alternative to existing methodologies.