Browsing by Author "Fortunato, Elvira"
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- A biomimetic sensor for monitoring oxidative stress biomarker in point-of-carePublication . Martins, Gabriela V.; Fortunato, Elvira; Fernandes, Helena R.; Sales, M. Goreti F.Free radicals and other reactive species are constantly generated in vivo and can cause oxidative damage to biomolecules, a process that seems to play an important role at the origin of cancer. 8-Hydroxy-2'-deoxyguanosine (8-OHdG) is a major product of DNA hydroxylation and is considered a biomarker of damage caused by oxidative stress (OS). Thus, early diagnosis of OS biomarkers may be used as a fundamental tool in cancer prevention and in more efficient therapeutic strategies. For this purpose, a biomimetic sensor for 8-OHdG detection and quantification by Electrochemical Impedance Spectroscopy (EIS) is proposed herein. The biomimetic sensor was obtained by modifying a clean gold (Au) electrode with a OH-terminal thiol compound, followed by direct electropolymerization of phenol in the presence of 8-OHdG. The biomimetic/Au acted as working electrode, while glassy carbon and Ag/AgCl were used as counter and reference electrodes, respectively. Electropolymerization of phenol was performed by Cyclic Voltammetry (CV) over the potential range 0.2 to 0.9 V in pH 7.0 PBS buffer, enabling the formation of a non-conductive layer. Non-imprinted materials (NIM) were also performed by removing the template from the procedure and, then, the ability of the polymer to interact non-specifically with the template was measured. Preliminary results showed the development of a direct and label-free biomimetic sensor with good performance, stability and sensibility. In particular, only MIP material was able to rebind to the target molecule and produce a linear response against EIS on the range 0.010 to 10ng/ml. Overall, the biosensor described herein is simple, precise and may allow routine use for biological samples on-site.
- Electrochromic Device Composed of a Di-Urethanesil Electrolyte Incorporating Lithium Triflate and 1-Butyl-3-Methylimidazolium ChloridePublication . Gonçalves, Maria Cristina; Pereira, Rui F. P.; Alves, Raquel; Nunes, Sílvia C.; Fernandes, Mariana; Gonçalves, Helena M R; Pereira, Sónia; Silva, M. Manuela; Fortunato, Elvira; Rego, Rosa; Zea Bermudez, Verónica deA di-urethane cross-linked poly(oxyethylene)/silica hybrid matrix [di-urethanesil, d-Ut(600)], synthesized by the sol-gel process, was doped with lithium triflate (LiCF3SO3) and the 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) ionic liquid. The as-produced xerogel film is amorphous, transparent, flexible, homogeneous, hydrophilic, and has low nanoscale surface roughness. It exhibits an ionic conductivity of 3.64 × 10–6 and 5.00 × 10–4 S cm–1 at 21 and 100°C, respectively. This material was successfully tested as electrolyte in an electrochromic device (ECD) with the glass/ITO/a-WO3/d-Ut(600)10LiCF3SO3[Bmim]Cl/c-NiO/ITO/glass configuration, where a-WO3 and c-NiO stand for amorphous tungsten oxide and crystalline nickel oxide, respectively. The device demonstrated attractive electro-optical performance: fast response times (1–2 s for coloring and 50 s for bleaching), good optical memory [loss of transmittance (T) of only 41% after 3 months, at 555 nm], four mode modulation [bright mode (+3.0 V, T = 77% at 555 nm), semi-bright mode (−1.0 V, T = 60% at 555 nm), dark mode (−1.5 V, T = 38 % at 555 nm), and very dark mode (−2.0 V, T = 11% and −2.5 V, T = 7% at 555 nm)], excellent cycling stability denoting improvement with time, and high coloration efficiency [CEin = −6727 cm2 C–1 (32th cycle) and CEout = +2794 cm2 C–1 (480th cycle), at 555 nm].
- Molecular Imprinting on Nanozymes for Sensing ApplicationsPublication . Cardoso, Ana Rita; Frasco, Manuela F.; Serrano, Verónica; Fortunato, Elvira; Sales, Maria Goreti FerreiraAs part of the biomimetic enzyme field, nanomaterial-based artificial enzymes, or nanozymes, have been recognized as highly stable and low-cost alternatives to their natural counterparts. The discovery of enzyme-like activities in nanomaterials triggered a broad range of designs with various composition, size, and shape. An overview of the properties of nanozymes is given, including some examples of enzyme mimics for multiple biosensing approaches. The limitations of nanozymes regarding lack of selectivity and low catalytic efficiency may be surpassed by their easy surface modification, and it is possible to tune specific properties. From this perspective, molecularly imprinted polymers have been successfully combined with nanozymes as biomimetic receptors conferring selectivity and improving catalytic performance. Compelling works on constructing imprinted polymer layers on nanozymes to achieve enhanced catalytic efficiency and selective recognition, requisites for broad implementation in biosensing devices, are reviewed. Multimodal biomimetic enzyme-like biosensing platforms can offer additional advantages concerning responsiveness to different microenvironments and external stimuli. Ultimately, progress in biomimetic imprinted nanozymes may open new horizons in a wide range of biosensing applications.
- A molecularly imprinted sensor for sensitive detection of 8-hydroxy-2'-deoxyguanosine (8-OHdG) oxidative stress biomarkerPublication . Martins, Gabriela V.; Fortunato, Elvira; Fernandes, Helena R.; Sales, M. Goreti F.Early diagnosis of Oxidative Stress (OS) biomarkers can be used as a crucial tool in cancer prevention, treatment and survival. In this context, 8-hydroxy-2'-deoxyguanosine (8-OHdG) is a repair product of oxidized guanine lesions and has been acknowledged as a suitable biomarker of OS1. Under this scope, a simple and sensitive molecularly imprinted (MIP)-based sensor for detection of urinary 8-OHdG has been designed via electrochemical polymerization. The biomimetic film was assembled in-situ on the gold-modified electrode through electropolymerization of phenol monomer combined with the target molecule 8-OHdG. The electropolymerization of phenol was performed by Cyclic Voltammetry (CV) over the potential range 0.1 to 0.9 V in PBS buffer at pH 7.4, enabling the formation of a non-conductive layer. Several experimental parameters, such as, the initial concentration of the monomer and the ratio template-monomer, have been carefully optimized and the electrochemical performance of the designed MIP sensor was investigated by CV and Electrochemical Impedance Spectroscopy (EIS). In parallel, RAMAN and FTIR spectroscopies comproved the formation of polyphenol films on the electrode surface by electrochemical oxidation of phenol. Our results demonstrated that 8-OHdG molecule was successfully entrapped into the polymeric matrix, enabling a three-dimensional structure with numerous imprinted cavities sites. The developed electrochemical biosensor showed high sensitivity and selectivity towards 8-OHdG over the concentration range [0.1 - 100] pg/ml. Moreover, it was employed to detect 8-OHdG in urine samples as a non-invasive approach to assess the extent of DNA oxidative damage. Overall, this label-free biosensor constitutes a promising low-cost tool to be implemented as an easy-to-use protocol for sensitive detection of 8-OHdG in biological samples.
- Nanofluid Based on Glucose‐Derived Carbon Dots Functionalized with [Bmim]Cl for the Next Generation of Smart WindowsPublication . Gonçalves, Helena M. R.; Pereira, Rui F. P.; Lepleux, Emmanuel; Carlier, Thomas; Pacheco, Louis; Pereira, Sónia; Valente, Artur J. M.; Fortunato, Elvira; Duarte, Abel J.; Zea Bermudez, Verónica deThe design of new advanced materials and technologies is essential for the development of smart windows for the next generation of energy‐efficient buildings. Here, it is demonstrated that the functionalization of glucose‐derived carbon dots with 1‐butyl‐3‐methylimidazolium chloride results in a self‐standing, water‐soluble, viscous, reusable nanofluid with self‐improving conductivity, thermotropy around 30–40 °C, and ultraviolet blocking ability. Its synthesis is straightforward, clean, fast, and cheap. At 36 °C (hot summer day), a sun‐actuated thermotropic (TT) device incorporating a 95% w/w nanofluid aqueous solution exhibits a transmittance variation (ΔT ) of 9% at 550/1000 nm, which is amplified to 47/31% via the surface plasmon resonance effect. An integrated self‐healing system enabling independent sun‐actuated TT and voltage‐actuated electrochromic (EC) operation is also produced. The low‐energy EC device offers bright hot and dark cold modes (ΔT = 68/64%), excellent cycling stability, unprecedented coloration efficiency values (−1.73 × 106/−1.67 × 106 cm2 C−1 (coloring) and +1.12 × 107/+1.08 × 107 cm2 C−1 (bleaching) at ±2.5 V), and impressive memory effect. The disruptive design and sustainable synthesis of the new nanofluid proposed here will foster the agile development of novel products with improved ecological footprint.
- Paper-based (bio)sensor for label-free detection of 3-nitrotyrosine in human urine samples using molecular imprinted polymerPublication . Martins, Gabriela V.; Marques, Ana C.; Fortunato, Elvira; Sales, Maria Goreti FerreiraOver the last years, paper technology has been widely spread as a more affordable, sustainable and reliable support material to be incorporated in the design of point-of-care (POC) diagnostic devices. However, the single work employing a paper-based device for 3-nitrotyrosine (3-NT), a relevant biomarker for oxidative stress (OS) that is a major origin for many diseases, is incapable of reading successfully complex samples because every species that oxidizes before ~0.75 V will also contribute to the final response. Thus, the introduction of a selective element was made into this set-up by including a molecularly-imprinted polymer (MIP) tailored in-situ. Herein, a novel MIP for 3-NT was assembled directly on a paper platform, made conductive with carbon ink and suitable for an electrochemical transduction. The biomimetic material was produced by electropolymerization of phenol after optimizing several experimental parameters, such a scan-rate, number of cycles, range of potential applied, monomer and template concentrations. Under optimal conditions, the label-free sensor was able to respond to 3-NT from 500 nM to 1 mM, yielding a limit of detection of 22.3 nM. Finally, the applicability of the (bio)sensor was tested by performing calibration assays in human urine samples and a good performance was obtained in terms of sensitivity, selectivity and reproducibility. Overall, the attributes of the herein described sensing approach can be compared to a very limited number of other electrochemical devices, that are still using a conventional three electrode system, making this paper-sustained device the first electrochemical (bio)sensor with potential to become a portable and low-cost diagnostic tool for 3-NT. In general, the incorporation of molecular imprinting technology coupled to electrochemical transduction enabled the fabrication of suitable smart sensors for wide screening approaches.
- Paper-Based Platform with an In Situ Molecularly Imprinted Polymer for β-AmyloidPublication . Pereira, Marta V.; Marques, Ana C.; Oliveira, Daniela; Martins, Rodrigo; Moreira, Felismina; Sales, Maria Goreti Ferreira; Fortunato, ElviraAlzheimer’s disease (AD) is one of the most common forms of dementia affecting millions of people worldwide. Currently, an easy and effective form of diagnosis is missing, which significantly hinders a possible improvement of the patient’s quality of life. In this context, biosensors emerge as a future solution, opening the doors for preventive medicine and allowing the premature diagnosis of numerous pathologies. This work presents a pioneering biosensor that combines a bottom-up design approach using paper as a platform for the electrochemical recognition of peptide amyloid β-42 (Aβ-42), a biomarker for AD present in blood, associated with visible differences in the brain tissue and responsible for the formation of senile plaques. The sensor layer relies on a molecularly imprinted polymer as a biorecognition element, created on the carbon ink electrode’s surface by electropolymerizing a mixture of the target analyte (Aβ-42) and a monomer (O-phenylenediamine) at neutral pH 7.2. Next, the template molecule was removed from the polymeric network by enzymatic and acidic treatments. The vacant sites so obtained preserved the shape of the imprinted protein and were able to rebind the target analyte. Morphological and chemical analyses were performed in order to control the surface modification of the materials. The analytical performance of the biosensor was evaluated by an electroanalytical technique, namely, square wave voltammetry. For this purpose, the analytical response of the biosensor was tested with standard solutions ranging from 0.1 ng/mL to 1 μg/mL of Aβ-42. The linear response of the biosensor went down to 0.1 ng/mL. Overall, the developed biosensor offered numerous benefits, such as simplicity, low cost, reproducibility, fast response, and repeatability less than 10%. All together, these features may have a strong impact in the early detection of AD.
- Passive direct methanol fuel cells acting as fully autonomous electrochemical biosensors: Application to sarcosine detectionPublication . Silva Ferreira, Nadia; Carneiro, Liliana P.T; Viezzer, Christian; Almeida, Maria J.T.; Marques, Ana C.; Pinto, Alexandra M.F.R.; Fortunato, Elvira; Ferreira Sales, Maria GoretiThis work describes an innovative electrochemical biosensor that advances its autonomy toward an equipment-free design. The biosensor is powered by a passive direct methanol fuel cell (DMFC) and signals the response via an electrochromic display. Briefly, the anode side of the DMFC power source was modified with a biosensor layer developed using molecularly imprinted polymer (MIP) technology to detect sarcosine (an amino acid derivative that is a potential cancer biomarker). The biosensor layer was anchored on the surface of the anode carbon electrode (carbon black with Pt/Ru, 40:20). This was done by bulk radical polymerization with acrylamide, bis-acrylamide, and vinyl phosphonic acid. This layer selectively interacted with sarcosine when integrated into the passive DMFC (single or multiple, in a stack of 4), which acted as a transducer element in a concentration-dependent process. Serial assembly of a stack of hybrid DMFC/biosensor devices triggered an external electrochromic cell (EC) that produced a colour change. Calibrations showed a concentration-dependent sarcosine response from 3.2 to 2000 µM, which is compatible with the concentration of sarcosine in the blood of prostate cancer patients. The final DMFC/biosensor-EC platform showed a colour change perceptible to the naked eye in the presence of increasing sarcosine concentrations. This colour change was controlled by the DMFC operation, making this approach a self-controlled and self-signalling device. Overall, this approach is a proof-of-concept for a fully autonomous biosensor powered by a chemical fuel. This simple and low-cost approach offers the potential to be deployed anywhere and is particularly suitable for point-of-care (POC) analysis.