Percorrer por autor "Mesquita, Raquel"
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- An uplifting avenue upon mealworm chitosan for hemodialysis applicationPublication . Martingo, Maria; Baptista-Silva, Sara; Mesquita, Raquel; Ferreira, João Paulo; Borges, Sandra; Pintado, ManuelaChronic kidney disease (CKD) is characterized by a continuous decline in kidney function, often persisting for years or even a lifetime. This study presents a new exploration into the extraction and application of insect chitosan (Tenebrio molitor) targeting hemodialysis (HD). Initially, the potential of insect-derived chitosan as a sustainable and effective alternative to traditional sources (i.e. crustaceans) is demonstrated. Efficient extraction methods were developed (totaling between 6 h and 12 h), producing chitosan. Firstly, chitin was efficiently isolated from T. molitor through deproteinization and demineralization, with yields of approximately 5% (w/w). Subsequently, chitosan was obtained from the extracted chitin resulting in yields of between 65.0 ± 0.8% (w/w) and 79.3 ± 0.8% (w/w). Characterization using Fourier Transform Infrared Spectroscopy (FTIR) confirmed structural similarities with commercial chitosan and degrees of deacetylation in the 73 - 75% range. The bioactive properties of chitosan obtained from T. molitor, including antimicrobial and antioxidant activities, were evaluated. All the microorganisms tested were inhibited, exhibiting minimum lethal concentrations between 2 and 8 mg/mL, confirming the antimicrobial activity of the extracted chitosan. In addition, chitosan showed antioxidant activity in the range of 60 to 65 µmol Trolox equivalent/g, suggesting its viability for various medical applications. This study also developed a chitosan-based membrane (CH - M) culminating in a proof-of-concept phase for hemodialysis. The permeation characteristics of CH-M for urea and albumin were studied in vitro to assess their suitability as HD membranes. Urea was permeable to values of over 70% and albumin was retained.
- Biomarkers monitoring with specially-designed microfluidic paper-based devices as disposable, on-hand, real-time analysisPublication . Mesquita, Raquel; Rangel, António O. S. S.
- Combination of SPE and pH adjustment for the simultaneous spectrophotometric determination of copper, zinc and manganese in waterPublication . Ferreira, Francisca; Ribas, Tânia; Mesquita, Raquel; Rangel, AntónioCopper, zinc, and manganese are commonly found in both natural and treated water sources. Although these metals are essential micronutrients, their accumulation, even at low concentrations, can lead to serious health issues. Therefore, continuous and accurate monitoring of these elements in environmental and drinking water is crucial to ensure public safety. Solid Phase Extraction (SPE) is a widely used sample preparation technique that relies on sorbent materials to separate and concentrate specific analytes from complex matrices. In heavy metal analysis, SPE offers several advantages, such as enhanced sensitivity, selectivity, and compatibility with automated systems. Ion-exchange resins selectively bind to ions based on their charge and therefore are one of the most effective sorbents for metal ion separation. While cation-exchange resins retain positively charged metal ions like Cu²⁺, Zn²⁺, and Mn²⁺, anion-exchange resins bind to negatively charged species. This selectivity allows for cleaner separation and more accurate quantification in multi-parametric analysis. The objective of this work was to develop an automatic sequential injection analysis (SIA) system integrated with an in-line cation-exchange resin column (Toyopearl) for the simultaneous determination of copper (II), zinc, and manganese in water samples. This system employs a cationic resin coupled with a colorimetric reagent (Zincon) whose selectivity varies with pH, enabling the separation of target metal ions and consequent individual quantification. This method presents a reliable and reagent-efficient alternative to conventional techniques, with strong potential for real-time or on-site monitoring applications.
- Corrigendum to "Use of solid phase extraction for the sequential injection determination of alkaline phosphatase activity in dynamic water systems"Publication . Santos, Inês C.; Mesquita, Raquel; Bordalo, Adriano A.; Rangel, António O.S.S.
- Determination of urinary iron by colorimetric detection with a novel microfluidic paper-based analytical devicePublication . Ferreira, Francisca T.S.M.; Catalão, Karina A.; Mesquita, Raquel; Rangel, António O.S.S.
- Development of a µsi -lov system for the spectrophotometric determination of cadmium and lead: preliminary studiesPublication . Santos, Inês C.; Mesquita, Raquel; Rangel, António O.S.S.
- Evaluation of some of the main inorganic ions in brine solutions used for sea salt production by flow injection analysis and fourier-mid infrared spectroscopyPublication . Galvis-Sánchez, Andrea C.; Santos, Inês; Mesquita, Raquel; Lopes, João; Delgadillo, Ivonne; Rangel, António O. S. S.
- Exploiting the lab-on-valve concept to study the 3,4-HPO chelator as non-toxc reagent for the determination of iron in costal and inland bathing watersPublication . Mesquita, Raquel; Suarez, Ruth; Rangel, Maria; Bordalo, Adriano A.; Cerdà, Víctor; Rangel, António O. S. S.
- Exploring 3-hydroxy-4-pyridinone chelators synthetic versatility to attain tailor made low toxicity chromogenic reagents for iron speciation in water samplesPublication . Rangel, António O. S. S.; Mesquita, Raquel; Rangel, M.
- Exploring the potential of mealworm chitosan for hemodialysis applicationsPublication . Martingo, Maria; Baptista-Silva, Sara; Mesquita, Raquel; Ferreira, João Paulo; Borges, Sandra; Pintado, ManuelaThis study introduces a sustainable and efficient alternative to traditional chitosan sources derived from crustaceans, exploring the extraction and application of insect-derived chitosan from Tenebrio molitor for hemodialysis (HD) membranes design. Efficient extraction and deacetylation methods were tested and developed between 6 h and 12 h to obtain chitosan. Chitin was isolated from T. molitor through deproteinization and demineralization, with yields of approximately 5 % (w/w). Chitosan was obtained from the extracted chitin resulting in yields of between 65.0 and 79.3 (w/w). Characterization using FTIR confirmed structural similarities with commercial chitosan and degrees of deacetylation in the 73–75 % range. The bioactive properties of chitosan obtained from T. molitor, including antimicrobial and antioxidant activities, were evaluated. All the microorganisms tested were inhibited, exhibiting minimum lethal concentrations between 2 and 8 mg/mL. In addition, chitosan showed antioxidant activity in the range of 60–65 μmol Trolox equivalent/g, suggesting its viability for various medical applications. This study additionally allowed the design of sustainable hybrid chitosan membrane (CH-M) tailored for HD applications. The permeation characteristics of CH-M for urea and albumin were studied in vitro to assess their suitability as HD membranes. Urea was permeable to values of over 70 % and albumin was retained. Also, cytotoxicity assays against L929 fibroblast cells demonstrated that the CH-M samples exhibit low metabolic inhibition (around 15 %) The application of CH-M in HD represents a significant advance, offering the potential for enhanced therapeutic outcomes for chronic kidney disease (CKD).