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- Alzheimer’s disease: Development of a sensitive label-free electrochemical immunosensor for detection of amyloid beta peptidePublication . Carneiro, Pedro; Loureiro, Joana; Delerue-Matos, Cristina; Morais, Simone; Pereira, Maria do CarmoIn this work, a highly sensitive label-free immunosensor for detection of the main biomarker of Alzheimer’s disease (AD), amyloid beta 1–42 (Aβ (1–42)), is presented. A gold electrode was modified with a mercaptopropionic acid (MPA) self-assembled monolayer, electrodeposited gold nanoparticles (AuNPs) and a monoclonal antibody mAb DE2B4 to recognize Aβ; all the relevant experimental variables were optimized. Antibodies were functionalized through chemical modification (thiolation) to promote the antibody immobilization on the AuNPs surface with proper orientation which enabled the direct detection of Aβ(1–42). Scanning electron microscopy, square-wave voltammetry and electrochemical impedance spectroscopy were used to characterize the construction of the biosensor. Using the proposed immunosensor, Aβ(1–42) was specifically detected within the linear range of 10–1000 pg mL−1 with a 5.2 pg mL−1 and 17.4 pg mL−1 detection and quantification limit, respectively; recovery values for the tested spiking levels ranged from 90.3 to 93.6%. The immunosensor enables rapid, accurate, precise, reproducible and highly sensitive detection (14.6%reduction mL pg−1) of Aβ with low-cost and opens the possibilities for diagnostic ex vivo applications and research-based in vivo studies.
- The simpler the better: Highly sensitive 17α-ethinylestradiol sensor based on an unmodified carbon paper transducerPublication . Torrinha, Álvaro; Carneiro, Pedro; Dias, Diana; Delerue-Matos, Cristina; Morais, SimoneThe remarkable features of a carbon fiber paper sensor (CP) were employed for detection of the estrogenic hormone 17α-ethinylestradiol (EE2), considered a contaminant of emerging concern due to its potential ecotoxicity and widespread in the aquatic ecosystems. In this work, an unpreceded CP pre-treatment study was conducted with the (Il)-hexacyanoferrate(III) ion pair, however a bare sensor without pre-treatment revealed higher efficiency on the oxidation of EE2 compared to a chemical and electrochemical pre-treated CP and a gold nanoparticles modified CP, being thus selected for EE2 determinations. The analytical conditions were thoroughly optimized in terms of electrolyte pH (pH 7), differential pulse voltammetry parameters (modulation time 0.003 s, amplitude 0.09 V, interval time 0.1 s and step potential 0.01 V), and analyte preconcentration potential (0.4 V) and time (180 s). The hormone can be determined by the CP in a wide linear range from 0.1 to 1000 nM, achieving a detection limit of 0.14 ± 0.005 nM and an outstanding sensitivity of 1636 ± 232 μA μM−1 cm−2 in the lowest linear zone (0.1–1 nM). The sensor was validated in river water and fish reaching good recoveries (91.2 ± 4.6 to 109.0 ± 7.1%), reproducibility and repeatability. Moreover, the sensor showed high selectivity to EE2 in the presence of several potential interfering compounds and frequently prescribed drugs, though it could not discriminate the similar hormone, 17β-estradiol, being the total concentration obtained in this case. CP-based sensors emerge as efficient electroanalytical tools, suggesting that modification of the surface may not always be beneficial in terms of sensitivity