electrochemical detection

Carvacrol (Carv) and thymol (TOH), components of essential oils, are known by their antimicrobial and antioxidant activity. However, Carv but not TOH seems to be the responsible of anti-inflammatory and inhibition of Cu corrosion properties. Since Carv and TOH are positional isomers, their identification is tricky and GC-MS is usually required. To find simple and inexpensive methods that allow the detection of Carv in presence of TOH (e.g. essential oils), cyclic voltammetry and chronoamperometry tests using Pt and Cu as electrodes in TOH and Carv containing mixtures and essential oils were made. Electrochemical and ATR-FTIR results show that pure phytocompounds and mixtures lead to the formation of polymeric layers on both metallic surfaces. Results show that only Cu is suitable for Carv detection. Potentiostatic and potentiodynamic detection is simple and conclusive in Carv þ TOH mixtures and in essential oils due to the formation of a homogeneous blocking Carv electropolymeric layer on Cu.

Rapid, selective detection of metals in complex samples remains an elusive goal that could provide critical analytical information for biological and environmental sciences and industrial waste management. Fast-scan cyclic voltammetry (FSCV) using carbon-fiber microelectrodes (CFMs) is an emerging technique for metal analysis with broad potential applicability because of its rapid response to changes in analyte concentration and minimal disturbance to the analysis medium. In this communication, we report the first effective application of covalently modified CFMs to achieve highly selective, subsecond Cu(II) measurements using FSCV. A two-part strategy is employed for maximum selectivity: Cu(II) binding is augmented by a covalently grafted ionophore, while binding of other metals is prevented by chemical blocking of nonselective surface adsorption sites. The resulting electrodes selectively detect Cu(II) in a complex medium comprising several interfering metals. Overall, this strate...

A escolha errada do sistema cimentante pode levar ao fracasso clínico na cimentação de coroas e próteses parciais fixas. Este trabalho teve como objetivo estudar "in vitro" a espessura de película de seis cimentos odontológicos para fixação de peças protéticas, de três grupos distintos, sendo eles: dois cimentos de fosfato de zinco, dois cimentos de ionômero de vidro convencional e dois cimentos resinosos. Foi realizado a manipulação dos cimentos de acordo com as instruções dos fabricantes e após, interposto 1g de material entre duas placas de vidro polidas e sobre as mesmas um peso de 3 Kg, durante 10 minutos. Estas placas foram medidas com um paquímetro digital antes e após a presa dos materiais. Foi realizada a análise estatística com o teste T Student e com o Teste de Variância ANOVA e foi observado uma menor espessura de película de um cimento de ionômero de vidro perante os outros cimentos testados, com diferenças estatísticas ao nível de 5%. Os autores concluíram que o cimento de ionômero de vidro obteve a menor espessura de película, sendo apropriado para cimentação de coroas e pontes fixas.

Objetivo: Identificar os principais materiais restauradores que apresentam bons desempenhos frente à fratura em reabilitação com endocrown. Método: Trata-se de uma revisão integrativa da literatura, realizada com os descritores: Endocrown, Fracture e Restorative Material combinados com operador booleano and nas bases de dados Pubmed, Scopus e Web Of Science. Foram incluídos estudos in vitro disponíveis na íntegra e publicados no idioma inglês. Foram excluídos os artigos duplicados e não condizentes com a temática do estudo. Resultouse em 10 artigos analisados para responder a questão do estudo. Resultados e Discussão: Destacou-se o dissilicato de lítio com melhores resultados entre os materiais com adequada resistência à fratura abordados nos estudos. Justificado pelo sua utilização no padrão de comparação com excelente desempenho causado pelo alto volume de preenchimento de cristais produzindo uma distribuição de forma fortemente interligada, que neutraliza a propagação de possíveis trincas. A utilização de compostos resinosos também foi descrita, principalmente as resinas nanocerâmicas com resistência semelhante ao dissilicato pelo seu módulo de elasticidade semelhante aos tecidos dentinários. Conclusão: O dissilicato de lítio e a resina nanocerâmica apresentam-se com resultados satisfatórios com relação a resistência à fratura para materiais utilizados na produção de endocrown.

Objetivo: Identificar os principais materiais restauradores que apresentam bons desempenhos frente à fratura em reabilitação com endocrown. Método: Trata-se de uma revisão integrativa da literatura, realizada com os descritores: Endocrown, Fracture e Restorative Material combinados com operador booleano and nas bases de dados Pubmed, Scopus e Web Of Science. Foram incluídos estudos in vitro disponíveis na íntegra e publicados no idioma inglês. Foram excluídos os artigos duplicados e não condizentes com a temática do estudo. Resultouse em 10 artigos analisados para responder a questão do estudo. Resultados e Discussão: Destacou-se o dissilicato de lítio com melhores resultados entre os materiais com adequada resistência à fratura abordados nos estudos. Justificado pelo sua utilização no padrão de comparação com excelente desempenho causado pelo alto volume de preenchimento de cristais produzindo uma distribuição de forma fortemente interligada, que neutraliza a propagação de possíveis trincas. A utilização de compostos resinosos também foi descrita, principalmente as resinas nanocerâmicas com resistência semelhante ao dissilicato pelo seu módulo de elasticidade semelhante aos tecidos dentinários. Conclusão: O dissilicato de lítio e a resina nanocerâmica apresentam-se com resultados satisfatórios com relação a resistência à fratura para materiais utilizados na produção de endocrown.

The application of a quinoprotein glucose dehydrogenase modified thick-film sensor as label detector in a capillary immunoassay (CIA) for xenoestrogens is presented. The detection of the alkylphenols and their ethoxylates is based on the competition between the analyte and tracer molecules for the binding sites of anti-alkylphenol ethoxylate antibodies. This assay is performed off-line in small disposable PVC capillaries coated with immobilized antibodies. This format allows the combination of the assay with a small portable device potentially useful for on-site environmental monitoring. Beside high amplification the utilization of b-galactosidase as enzyme label allows the direct combination with a GDH biosensor at optimal pH conditions. The bioelectrocatalytic properties of this biosensor offer an additional amplification and thus allow a very sensitive quantification of 4-aminophenol, generated by the bgalactosidase. Detection limits of the analytes in the mg/l range were obtained, while other phenolics and surfactants showed no or very little cross reactivity.

Paper has shown potential as an ubiquitous material for fabricating micro analytical devices for diagnostic and drinking water screening applications for resource-limited regions; paper-based sensing technology has become a hot research field since 2007. Intensive research in the past decade has accumulated a large number of scientific publications. However, commercialization of microfluidic paper-based analytical devices (µPADs) for real applications is noticeably lagging behind. The "ASSURED" criteria (i.e. Affordable, Sensitive, Specific, User-friendly, Rapid and robust, Equipment-free, Deliver to the users who need them), set by the World Health Organization specified the whole spectrum of requirements for a low-cost sensor designed for use in developing countries; they define the technical capabilities (i.e. "ASSR") and user acceptance (i.e. "UED") of low-cost sensing technology. While "ASSR" should be taken as the basic requirements of any sensor, "UED" determines whether or not the sensor could potentially be commercialized and gain user acceptance. This review presents a perspective on these two critical aspects of paper-based diagnostics by revisiting the original motivation of the paper-based analytical platform. It is our opinion that "UED" are important requirements that deserve more research to increase the commercialization of paper-based analytical devices.

coordenador e também chefe do departamento de Materiais Odontológicos e Prótese, Prof. Associado Wirley Gonçalves Assunção e seus membros, pela competência e afinco na condução da nossa pós-graduação. À Coordenação de Aperfeiçoamento Pessoal de Nível Superior (CAPES), pela concessão da Bolsa de Mestrado durante todo o primeiro ano do curso (Código de Financiamento 001). Meus sinceros agradecimentos por promover o apoio financeiro. Ao meu orientador, Prof. Ass. Dr. Aldiéris Alves Pesqueira, primeiramente pela confiança em mim depositada. Obrigada por me aconselhar e por sempre alegrar o departamento e nossas vidas, por sempre estar de portas abertas pra me receber e por despender parte do seu tempo a mim. Pelo exemplo de ética, empatia, honestidade, competência e tranquilidade. Agradeço também por todos os ensinamentos compartilhados de forma admirável, e por me guiar nos primeiros passos da pós-graduação, com paciência, carinho e dedicação, com os quais me conduziu neste momento impar em minha vida... Muito obrigada por tudo! Aos professores que compõem a banca de avaliação, Prof. Ass. Dr. Valentim Adelino Ricardo Barão e ao Prof. Ass. Dr. Leonardo Perez Faverani, por colaborarem e dedicarem seu tempo a examinarem esse trabalho. Obrigada por aceitarem o convite, pela oportunidade de aprender e por serem exemplos de caráter e dedicação à pesquisa odontológica.

The number of patients suffering from Inflammatory Bowel Disease (IBD) is increasing worldwide. The development of noninvasive tests that are rapid, sensitive, specific and simple would allow preventing patient discomfort, delay in diagnosis, and the follow-up of the status of the disease. Herein, we show the interest of vertically aligned nitrogen-doped carbon nanotube (VA-NCNTs) electrodes for the required sensitive electrochemical detection of lysozyme in serum, a protein that is up-regulated in IBD. To achieve selective lysozyme detection, biotinylated lysozyme aptamer were covalently integrated onto the VA-NCNTs. Detection of lysozyme concentrations in serum was achieved by measuring the decrease in the peak current of the Fe(CN)63-/4- redox couple by differential pulse voltammetry upon addition of the analyte. A detection limit as low as 100 fM with a linear range up to 7 pM could be achieved, in line with required demands for the determination of lysozyme level in patients su...

The evolution of 1st to 3rd generation electrochemical biosensors reflects a simplification and enhancement of the transduction pathway. However, in recent years, modification of the transducer with nanomaterials has become increasingly studied and imparts many advantages. The sensitivity and overall performance of enzymatic biosensors has improved tremendously as a result of incorporating nanomaterials in their fabrication. Given the unique and favorable qualities of gold nanoparticles, graphene and carbon nanotubes as applied to electrochemical biosensors, a consolidated survey of the different methods of nanomaterial immobilization on transducer surfaces and enzyme immobilization on these species is beneficial and timely. This review encompasses modification of enzymatic biosensors with gold nanoparticles, carbon nanotubes, and graphene.

Rapid detection of pathogenic bacteria present in patient samples is of utmost importance for the clinical management of bacterial-induced diseases. Herein, we describe an efficient and direct electrochemical approach for the detection of 2-heptyl-3-hydroxy-4-quinolone (PQS), 2-heptyl-4hydroxyquinoline (HHQ), and pyocyanin (PYO) as three molecular signatures of Pseudomonas aeruginosa (PA), a frequently infecting pathogen with high antibiotic resistance. The cationic surfactant hexadecyltrimethylammonium bromide (CTAB) enhances the effectiveness of an unmodified thin-film boron-doped diamond (BDD) electrode for the direct detection of PYO, HHQ, and PQS in bacterial cultures of PAO1 and PA14. Differential pulse voltammetry (DPV) is then used for monitoring the production of these microbial metabolites in bacterial cultures of PAO1 over 10 h without any sample pretreatment. A proposed mechanism for the interaction of CTAB with bacteria cells is examined by zeta (ζ) potential measurements. Furthermore, the detection method is successfully extended to a clinical fluid matrix and applied to PA spiked cystic fibrosis (CF) sputum samples.

In this paper, reduced graphene oxide-ZnO (RGO-ZnO) nanorods composite was prepared via a simple one-pot hydrothermal approach. The synthesized RGO-ZnO nanorods composite has been successfully applied for glassy carbon electrode (GCE) surface modification. The RGO-ZnO nanorods composite-modified GCE was applied for sensitive and selective determination of uric acid (UA). The biosensor exhibited a linear dependence on UA concentration ranging from 1 to 800 μM with a detection limit of 0.312 μM (S/N = 3). The proposed UA sensor also showed an excellent stability, reproducibility and anti-interference property.

Apesar dos avanços apresentados pelos materiais, fraturas de restaurações metalo-cerâmicas ocorrem. Estas são freqüentemente relacionadas às tensões ou traumas. O reparo pode aumentar a longevidade clínica das restaurações. Descrição do caso: Paciente L.A.P. compareceu à clínica de prótese(FOSJC-UNESP) queixando-se de desconforto na prótese. Após anamnese, exames clínicos e complementares, foi constatada a presença de fratura passível de reparo(dente 21). Foi observada a presença de hábito parafuncional(apertemento)

The wide use of biotechnology applications in bioprocesses such as the food and beverages industry, pharmaceuticals, and medical diagnostics has led to not only the invention of innovative products but also resulted in consumer and environmental concerns over the safety of biotechnology-derived products. Controlling and monitoring the quality and reliability of biotechnology-derived products is a challenge. Current tracking and tracing systems such as barcode labels and radio frequency identification systems track the location of products from primary manufactures and/or producers throughout globalised distribution channels. However, when it comes to product authentication and tracing, simply knowing the location of the product in the supply chain is not sufficient. DNA hybridisation sensors allows for a holistic approach into product authentication and tracing in that they enable the attribution of active ingredients in biotechnology-derived products to their source. In this article, the state-of-the-art of DNA hybridisation sensors, with a focus on the application of graphene as the backbone, for product authentication and tracing is reviewed. Candidate DNA biocompatible materials, properties and transduction schemes that enable detection of DNA are covered in the discussion. Limitations and challenges of the use of DNA biosensing technologies in real-life environmental, biomedical and industrial fields as opposed to clean-cut laboratory conditions are also enumerated. By considering experimental research versus reality, this article outlines and highlights research needed to overcome commercialisation barriers faced by DNA biosensing technologies. In addition, the content is thought-provoking to facilitate development of cutting edge research activities in the field.

A method is described here for the simultaneous determination of retinol,α-tocopherol, lycopene, andβ-carotene in human plasma. The effectiveness of various protein precipitants and extraction solvents was tested. After adequate sample preparation, the samples were injected directly into the HPLC system. The separation was realized on an analytical reversed-phase column with a UV-Vis detection. The analytical performance of this method was satisfactory. The intraassay and interassay coefficients of variation were below 10%. The recoveries were as follows: 97.0% (CV 2.4%) for retinol, 94.6% (CV 1.7%) forα-tocopherol, 91.9% (CV 3.6%) for lycopene, and 93.9% (CV 4.2%) forβ-carotene. The levels of selected fat-soluble vitamins in plasma of patients with cardiovascular disease were measured and discussed.

Polyacrylamide (PA) based hydrogels are used in several applications including polyacrylamide gel electrophoresis and sensing devices. Homogeneous and compact PA films can be prepared based on chemical or photopolymerization processes. However, the accurate and reproducible coating of substrates with nanohydrogel patterns is challenging due to the in situ polymerization and deposition requirements. Herein, we report an inkjet printing (IJP) concept with simultaneously performed UV photopolymerization of a specifically prepared acrylamide/N,N′-methylenebis(acrylamide) containing ink. A prepolymerization step of the hydrogel precursor molecules was implemented in the ink formulation protocol to adjust the viscosity of the ink and to enhance the rate of polymerization during printing. After the optimization of the printing parameters, a nanometer thin PA hydrogel coating with well distributed nanopores was achieved on top of a stand-alone carbon nanotubes (CNTs) pattern. Batches of fully inkjet printed PA/CNT modified electrodes were prepared that showed outstanding improvements for the electrochemical detection of antioxidants in complex matrices such as untreated orange juice and red wine samples thanks to the properties of the PA coating.

O objetivo desse estudo foi avaliar a influencia de diferentes monomeros funcionais fosfatados em primers e sistemas de cimentacao na resistencia de uniao da zirconia a dentina. Cento e oitenta coroas de dentes bovinos tiveram a dentina da face vestibular exposta apos o desgaste com lixas (#200,400,600) em politriz. 180 cilindros (O: 3.4mm; altura: 4 mm) de zirconia (Vita In-Ceram 2000) sinterizada foram divididos em 18 grupos (n=10) de acordo com fatores: “Sistema de Cimentacao” (Panavia F –PAN; RelyX Ultimate – ULT, Multilink N - MULT) e “envelhecimento” (armazenamento 37°C/24h – C (controle), 30 dias - D ou 6 meses- M; e 5.000, 10.000 ou 20.000 mil ciclos de termociclagem - TC, 5/55°C, 30s). Apos a cimentacao e envelhecimento dos especimes, foi realizado o ensaio de cisalhamento (v=1 mm/min), grau de conversao (GC) e analise de falhas. Foi feito teste de Kruskall –Wallis, seguido do teste de Dunn (α=5%). Os cimentos Multilink N (8,00)A e RelyX Ultimate (5,30)AB foram semelhantes ...

O objetivo deste relato de caso foi avaliar o desempenho clinico de lentes de contato em zirconia ultra-translucida cimentadas adesivamente ao esmalte. Paciente do genero feminino, A.T.T.S., 27 anos, procurou atendimento odontologico da Universidade Federal do Rio Grande do Norte (Natal, RN) queixando-se do tamanho e cor dos dentes. Foi realizado o planejamento digital do sorriso e observou-se a necessidade de melhora na forma, contorno e tamanho dos elementos 13 ao 23. Apos enceramento de diagnostico e mock-up (Systemp/Ivoclar Vivadent), os preparos minimamente invasivos em esmalte foram realizados e em seguida moldados com silicone de adicao (Express XT/ 3M ESPE). As lentes de contato foram confeccionadas em zirconia monolitica ultra-translucida (Prettau Anterior, Zirkonzahn). Para a cimentacao, condicionou-se o substrato com acido fosforico a 35% (Ultra-Etch/ Ultradent - 20 segundos) nas superficies internas das cerâmicas, jateamento (CoJet, 3M ESPE) por 20 segundos e aplicacao d...

We have designed a dual-aptamer complex specific to both prostate-specific membrane antigens (PSMA) (þ) and (À) prostate cancer cells. In the complex, an A10 RNA aptamer targeting PSMA (þ) cells and a DUP-1 peptide aptamer specific to PSMA (À) cells were conjugated through streptavidin. Doxorubicinloaded onto the stem region of the A10 aptamer was delivered not only to PSMA (þ) cells but to PSMA (À) cells, and eventually induced apoptosis in both types of prostate cancer cells. Cell death was monitored by measuring guanine concentration in cells using differential pulse voltammetry (DPV), a simple and rapid electrochemical method, and was further confirmed by directly observing cell morphologies cultured on the transparent indium tin oxide (ITO) glass electrode and checking their viabilities using a trypan blue assay. To investigate the in vivo application of the dual-aptamer system, both A10 and DUP-1 aptamers were immobilized on the surface of thermally cross-linked superparamagnetic iron oxide nanoparticles (TCL-SPION). Selective cell uptakes and effective drug delivery action of these probes were verified by Prussian blue staining and trypan blue staining, respectively.

We have designed a dual-aptamer complex specific to both prostate-specific membrane antigens (PSMA) (þ) and (À) prostate cancer cells. In the complex, an A10 RNA aptamer targeting PSMA (þ) cells and a DUP-1 peptide aptamer specific to PSMA (À) cells were conjugated through streptavidin. Doxorubicinloaded onto the stem region of the A10 aptamer was delivered not only to PSMA (þ) cells but to PSMA (À) cells, and eventually induced apoptosis in both types of prostate cancer cells. Cell death was monitored by measuring guanine concentration in cells using differential pulse voltammetry (DPV), a simple and rapid electrochemical method, and was further confirmed by directly observing cell morphologies cultured on the transparent indium tin oxide (ITO) glass electrode and checking their viabilities using a trypan blue assay. To investigate the in vivo application of the dual-aptamer system, both A10 and DUP-1 aptamers were immobilized on the surface of thermally cross-linked superparamagnetic iron oxide nanoparticles (TCL-SPION). Selective cell uptakes and effective drug delivery action of these probes were verified by Prussian blue staining and trypan blue staining, respectively.

An electrochemical sensor based on reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) modified electrode was utilized for determination of trace iron in coastal waters with the aid of the iron complexing ligand 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). 5-Br-PADAP reacted with iron in short chelating reaction time (<3 min). rGO as a support provided large specific surface area for AuNPs, which would facilitate the electrochemical reduction of Fe(III)-5-Br-PADAP. Under the optimized conditions, the response of Fe(III) at this resulting sensor was linear in the range of 30 nM to 3 M with a detection limit of 3.5 nM. This sensor also had excellent reproducibility and repeatability. Additionally, the modified electrode had been successfully applied to the determination of Fe(III) in real coastal waters.

The SARS-CoV-2 virus is still causing a dramatic loss of human lives worldwide, constituting an unprecedented challenge for the society, public health and economy, to overcome. The up-to-date diagnostic tests, PCR, antibody ELISA and Rapid Antigen, require special equipment, hours of analysis and special staff. For this reason, many research groups have focused recently on the design and development of electrochemical biosensors for the SARS-CoV-2 detection, indicating that they can play a significant role in controlling COVID disease. In this review we thoroughly discuss the transducer electrode nanomaterials investigated in order to improve the sensitivity, specificity and response time of the as-developed SARS-CoV-2 electrochemical biosensors. Particularly, we mainly focus on the results appeard on Au-based and carbon or graphene-based electrodes, which are the main material groups recently investigated worldwidely. Additionally, the adopted electrochemical detection techniques are also discussed, highlighting their pros and cos. The nanomaterial-based electrochemical biosensors could enable a fast, accurate and without special cost, virus detection. However, further research is required in terms of new nanomaterials and synthesis strategies in order the SARS-CoV-2 electrochemical biosensors to be commercialized.

Nanotechnology has gained much attention over the last decades, as it offers unique opportunities for the advancement of the next generation of sensing tools. Point-of-care (POC) devices for the selective detection of biomolecules using engineered nanoparticles have become a main research thrust in the diagnostic field. This review presents an overview on how the POC-associated nanotechnology, currently applied for the identification of nucleic acids, proteins and antibodies, might be further exploited for the detection of infectious pathogens: although still premature, future integrations of nanoparticles with biological markers that target specific microorganisms will enable timely therapeutic intervention against life-threatening infectious diseases.

Nanotechnology has gained much attention over the last decades, as it offers unique opportunities for the advancement of the next generation of sensing tools. Point-of-care (POC) devices for the selective detection of biomolecules using engineered nanoparticles have become a main research thrust in the diagnostic field. This review presents an overview on how the POC-associated nanotechnology, currently applied for the identification of nucleic acids, proteins and antibodies, might be further exploited for the detection of infectious pathogens: although still premature, future integrations of nanoparticles with biological markers that target specific microorganisms will enable timely therapeutic intervention against life-threatening infectious diseases.

Encontro do Grupo Brasileiro de Reciclagem em Prótese e Implante 05 a 07 de abril de 2013-Campos do Jordão, Brasil Avaliação topográfica da superfície de pinos de fibra de vidro submetidos a diferentes tratamentos de superfície Marina Caldeira Belini,

The wide use of biotechnology applications in bioprocesses such as the food and beverages industry, pharmaceuticals, and medical diagnostics has led to not only the invention of innovative products but also resulted in consumer and environmental concerns over the safety of biotechnology-derived products. Controlling and monitoring the quality and reliability of biotechnology-derived products is a challenge. Current tracking and tracing systems such as barcode labels and radio frequency identification systems track the location of products from primary manufactures and/or producers throughout globalised distribution channels. However, when it comes to product authentication and tracing, simply knowing the location of the product in the supply chain is not sufficient. DNA hybridisation sensors allows for a holistic approach into product authentication and tracing in that they enable the attribution of active ingredients in biotechnology-derived products to their source. In this article, the state-of-the-art of DNA hybridisation sensors, with a focus on the application of graphene as the backbone, for product authentication and tracing is reviewed. Candidate DNA biocompatible materials, properties and transduction schemes that enable detection of DNA are covered in the discussion. Limitations and challenges of the use of DNA biosensing technologies in real-life environmental, biomedical and industrial fields as opposed to clean-cut laboratory conditions are also enumerated. By considering experimental research versus reality, this article outlines and highlights research needed to overcome commercialisation barriers faced by DNA biosensing technologies. In addition, the content is thought-provoking to facilitate development of cutting edge research activities in the field.

A new type of three-electrode generator-collector sensor is described for the selective detection of any target analyte whose CV is chemically reversible in the presence of any interferent whose CV is chemically irreversible. The device consists of a layer of metallic material (Au in this work) poked by an array of cylindrical pores containing a ring-band electrode (Au in this work) placed in their middle and a disk electrode at their bottom (Au in this work). Operating the array of recessed disk electrodes to monitor the product of the stable analyte electronation while the top plane and the ring-band electrodes are poised at a potential located on the analyte and on the interferent waves allows suppressing entirely any contamination of the analyte concentration measurement by direct or indirect (EC′) involvement of the interferent. The efficiency of such devices was successfully demonstrated based on the detection of dopamine in the presence of ascorbic acid in PBS electrolyte.

In this study, we have synthesized a composite using carbon material derived from bio-inspired onion peel morphology like 2D trigona carbon nano petals (TCP) incorporated with ferrocene (FC). The FC is added with the purpose of improving the electrochemical behaviour of TCP. Further, to increase the number of electrochemically active sites in the composite, gold nanoparticles (AuNPs) were again decorated on TCP/FC, and thus derived electrochemically active TCP/FC/AuNPs nanocomposite. We have characterized the properties and surface morphology of this nanocomposite through spectroscopic and microscopic techniques. Further, using this nanocomposite for surface modification of glassy carbon electrode, we have developed an efficient GCE-TCP/FC/AuNPs electrode. The electrochemical efficiency of this electrode has been inspected through sensing and quantification of pharmaceutically valuable biomolecule dopamine through CV, DPV and square wave voltammetry techniques. The observed CV results reveals that the newly designed GCE-TCP/FC/AuNPs electrode has an ability to detect the dopamine with wide linear range of concentration from 5.96 × 10-6 to 0.1 × 10-4 M and its limit of detection was 2.9 × 10-6 M under 0.1 M phosphate buffer medium (pH 7.0). Therefore, it is important to mention here that this newly fabricated electrode can very well be used for real time sample analysis for sensing and detection of dopamine as it plays a key role in the neurotransmission and causes several diseases.

Horseradish peroxidase (HRP) was immobilised on silica gel modi®ed with titanium oxide. This material was employed to prepare modi®ed carbon paste electrode. The direct electron transfer of the hydrogen peroxide reduction by HRP was blocked when immobilised on silica±titanium. This biosensor presented a very sensitive response for phenol (1 mmol l À1) at an applied potential of 0 mV vs SCE. The best condition was achieved in phosphate buffer pH 6.8, ratio of hydrogen peroxide/phenol higher than 0.35. The biosensor showed a linear response range between 10 and 50 mmol l À1 of phenol, adjusted by the equation jÀ32.816.3 [phenol], for n5 with a correlation coef®cient of 0.9995. The response time of the biosensor was about 3 s.

The wide use of biotechnology applications in bioprocesses such as the food and beverages industry, pharmaceuticals, and medical diagnostics has led to not only the invention of innovative products but also resulted in consumer and environmental concerns over the safety of biotechnology-derived products. Controlling and monitoring the quality and reliability of biotechnology-derived products is a challenge. Current tracking and tracing systems such as barcode labels and radio frequency identification systems track the location of products from primary manufactures and/or producers throughout globalised distribution channels. However, when it comes to product authentication and tracing, simply knowing the location of the product in the supply chain is not sufficient. DNA hybridisation sensors allows for a holistic approach into product authentication and tracing in that they enable the attribution of active ingredients in biotechnology-derived products to their source. In this article, the state-of-the-art of DNA hybridisation sensors, with a focus on the application of graphene as the backbone, for product authentication and tracing is reviewed. Candidate DNA biocompatible materials, properties and transduction schemes that enable detection of DNA are covered in the discussion. Limitations and challenges of the use of DNA biosensing technologies in real-life environmental, biomedical and industrial fields as opposed to clean-cut laboratory conditions are also enumerated. By considering experimental research versus reality, this article outlines and highlights research needed to overcome commercialisation barriers faced by DNA biosensing technologies. In addition, the content is thought-provoking to facilitate development of cutting edge research activities in the field.

This paper studies the in-column detection performance for chromatography separation. Numerical modelling was performed to investigate the detection efficiency of the electrodes that are suspended within a packed chromatography column. The results show that the density of the silica beads packed within the channel does not hinder the detection ability of the electrode. The findings have been further validated with experimental works. A 8 in-column electrode array provides the full separation progress traces of the five neurotransmitters and metabolites (adrenalin, dopamine, DOPAC, serotonin and 5-HIAA) within the column. From the in-column detection, better peak resolutions are developed though the separation column as compared to the conventional post column detection. The whole progress of the separation shows that good separation (Rs > 1) can be obtained at E5 (28.7 mm from column inlet), whereas baseline separation could be obtained at E8 (last in-column electrode) with Rs ≥ 1.5 within 60 minutes. The presented results suggest the packing materials within the column does not obstruct the efficiency of the electrodes but able to produce a good baseline separation detection as compared to conventional post column detection.

Iodine is a micronutrient of high importance for the health and good development of individuals. It is contained in many foods, but it is also part of the chemical component of oceans and soil. Its deficiency is still a problem of humanity, which has a serious repercussion on our health. It is therefore important to have specific, fast and cost effective methods of iodine detection from different samples. This work aims to identify optimal parameters for potassium iodide (KI) detection from different media, to be further applied to real samples: plant extracts, water, biological fluids. Results showed a significant difference in electrochemical results, depending on the pH values of the mixture and also on the time which influences the compounds stability. Differential pulse voltammetry and cyclic voltammetry using carbon printed sensors, as well as microsensors for redox status or direct iodide detection are important analytical tools which have a wide range of applications in the ...

Lindane is a pesticide potentially harmful to environment and human health and in general, its detection involves mostly tedious, expensive and time-consuming techniques. A new strategy to detect lindane can be focused on the activity of Streptomyces strain M7 (SM7), which is capable to grow in the presence of organochlorine pesticides (OCPs) as carbon source. On this regard, the aim of this work is to present an optimized design of a microbial biosensor prototype based on a SM7 spore platform to detect and quantify lindane by electrochemical impedance spectroscopy (EIS) as the transduction method. By means of this technique, the metabolic bacterial activity was evaluated by analyzing a set of electrical parameters calculated by fitting the measured impedance spectra through an equivalent electrical circuit. Activity studies were performed by incubating the SM7 spore platform with (optimized incubation conditions) and without (to be used in a practical biosensor) shaking in the presence of lindane. In all cases, bacterial activity was measured by the impedance changes produced in the cells due to lindane removal from the culture medium. This proposed label-free impedimetric biosensor is simple, cost-effective and feasible to detect changes in the lindane concentration as low as 120 g L −1 in less than 2 days without sample pretreatment. In addition, the surface of electrodes can be reused for several different tests. This sensor prototype represents a valuable alternative for OCPs detection.

The need of dosage of glucose concentration required to develop test methods that allow rapid and accessible even at home. It is necessary to follow a simple protocol that minimizes errors and interferences using some functions of these devices. We have identified possible errors in obtaining experimental data: lower sample volume, consume of different foods in the evening and the morning of blood collection, type of sample analysed (serum/plasma, venous/capillary blood). The data obtained using commercial biosensors were compared with spectrometric methods and good report was obtained.

A cost-effective single-use sensor technology (ZentoSens) was developed in order to sensitive and selective voltammetric detection of a mycotoxin, Zearalenone (ZEN) in food products. In this context, single-use pencil graphite electrode (PGE) was used as a sensing platform and voltammetric measurements were performed via differential pulse voltammetry technique. The limit of detection was found to be 29.47 ng mL-1. The electrochemical detection of ZEN was successfully performed in food products; such as, corn flour, corn starch, malt. Additionally, the selectivity of the sensor was tested against to other similar mycotoxins such as, Deoxynivalenol, Fumonisin, Ochratoxin A.

O objetivo deste estudo foi avaliar a resistência de união (RU) de adesivos contemporâneos à dentina sadia e afetada por cárie. SE) em dentina bovina hígida e cariada. Dois cilindros de resina composta (Filtek Z-350) foram confeccionados na superfície. Os cilindros foram submetidos ao teste de cisalhamento após 24h em uma máquina Universal de Ensaios. Para cada adesivo foi espectroscopia de infravermelho por Transformada de Fourier. Os dados foram analisados por ANOVA e Mann Whitney (5%). em ambos os substratos (p0,284), falhas adesivas predominaram. Quando analisado pH, o ADHE-SE se mostrou o mais e o Single Bond o menos ácido, já para o GC o ADHE-SE foi o que apresentou menores valores, enquanto o Ambar foi o que mais converteu. quando comparado aos outros adesivos do estudo.

Bem-vindo a uma jornada fascinante e inovadora no reino da ciência
dos materiais. Este livro é um convite para explorar os intricados processos
de cristalização de vitrocerâmicas, uma área vibrante e dinâmica que tem
revolucionado a pesquisa e aplicação de materiais avançados. Em particular,
lançamos luz sobre a influência da energia de micro-ondas, uma ferramenta
poderosa que redefine a forma como compreendemos e controlamos a formação
de cristais em vitrocerâmicas.
A cristalização de vitrocerâmicas com energia de micro-ondas representa
um campo emergente que combina a complexidade da ciência dos materiais
com a eficácia tecnológica das micro-ondas. À medida que mergulhamos nas
páginas deste livro, testemunharemos o desenvolvimento de uma abordagem
única para a síntese e o controle de propriedades cruciais em vitrocerâmicas. A
habilidade de direcionar o processo de cristalização usando energia de microondas
não apenas acelera significativamente a produção, mas também abre
portas para novas possibilidades, desde aplicações em dispositivos eletrônicos
até avanços em biomateriais.

A three dimensional polymeric network obtained by the sol-gel process was applied to develop disposable, sensitive, selective and stable electrochemical biosensors for detection and quantification of Escherichia coli. This biosensor is based on the integration of a thiolated capture probe sequence from Escherichia coli and gold nanoparticles (AuNPs) into a sol-gel 3D polymeric network derived from (3-mercaptopropyl)-trimethoxysilane (MPTS), formed onto a screen-printed gold electrode surface. MPTS presents the advantage of forming a 3D polymeric network containing a large number of thiol tail groups distributed throughout its structure that enable both its anchoring onto gold surfaces and the AuNPs incorporation. Moreover, this matrix allows the incorporation of a high amount of capture probe and provides a biocompatible environment that preserves its original recognition capability after its immobilization, which is expected to improve the sensitivity of the final biosensing device. The hybridization event is detected using the ruthenium complex, [Ru(NH 3) 5 L] 2+ , where L is the ligand [3-(2-phenanthren-9-yl-vinyl)-pyridine], as redox indicator, which interacts preferentially with ds-DNA. With the use of this approach, complementary target sequences of Escherichia coli can be quantified over the range of 21 to 400 pmoles with a detection limit of 6.3 pmoles and good reproducibility (RSD=4.3%, n=4, C=10 µM). In addition, this approach is very selective allowing the detection, without the need of a hybridization suppressor, of a single mismatch. It is also quite stable under storage conditions, giving response at least for 25 days.

The SARS-CoV-2 virus is still causing a dramatic loss of human lives worldwide, constituting an unprecedented challenge for the society, public health and economy, to overcome. The up-to-date diagnostic tests, PCR, antibody ELISA and Rapid Antigen, require special equipment, hours of analysis and special staff. For this reason, many research groups have focused recently on the design and development of electrochemical biosensors for the SARS-CoV-2 detection, indicating that they can play a significant role in controlling COVID disease. In this review we thoroughly discuss the transducer electrode nanomaterials investigated in order to improve the sensitivity, specificity and response time of the as-developed SARS-CoV-2 electrochemical biosensors. Particularly, we mainly focus on the results appeard on Au-based and carbon or graphene-based electrodes, which are the main material groups recently investigated worldwidely. Additionally, the adopted electrochemical detection techniques are also discussed, highlighting their pros and cos. The nanomaterial-based electrochemical biosensors could enable a fast, accurate and without special cost, virus detection. However, further research is required in terms of new nanomaterials and synthesis strategies in order the SARS-CoV-2 electrochemical biosensors to be commercialized.

Alkanethiols are commonly used self-assembly reagents in the preparation of modified electrode. In this study, self-assembled monolayers (SAMs) of alkanethiols with different chain lengths formed on gold electrode were mainly investigated by electrochemical impedance spectroscopy (EIS) in addition to cyclic voltammetry (CV). Two types of immobilization strategies applied to the electrode were also examined. The interfacial properties of all self-assembled electrodes were evaluated in the presence of Fe(CN) 6 3−/4− redox probe. A simple equivalent circuit model with a constant phase element was used to interpret the obtained impedance spectra. The results of cyclic voltammetry revealed that the voltammetric behavior of the redox probe was influenced by the electrode surface modification. The EIS data indicated that the formation of saturated SAMs on gold required at least 30 min and more apparent differences occurred with immobilization time compared to that obtained by CV. Depending on the alkyl chain length of the SAMs, the electron-transfer resistance increased and the capacitance decreased. It was found a good linear relationship between inverse capacitance and chain length for carboxyl-terminated SAMs. To achieve a defect-free structure and/or close packing, the direct application method may provide a more effective, rapid, and facile self-assembly immobilization than immersion method from the viewpoint of the electron-transfer resistance.

Devido aos padrões estéticos atuais, que visam um sorriso branco e alinhado e um aumento da valorização e enfoque desses atributos pela mídia e pela sociedade, ocorreu nos últimos anos uma rápida evolução no que se diz respeito às próteses livres de metal. Por outro lado, juntamente com o ganho estético decorrido desse material, houve também a perda de resistência e aumento de friabilidade devido à redução de fase cristalina. Para evitar fracassos decorrentes de falhas técnicas, pesquisas são desenvolvidas, a fim de proporcionar melhor adaptação e adesão à superfície dental, bem como a obtenção de materiais mais estéticos e resistentes. O objetivo desse trabalho foi realizar revisão de literatura e reunir informações atuais sobre as cerâmicas utilizadas na confecção de próteses livres de metal e aprofundar o entendimento do uso das porcelanas, em cada situação clínica. Foram analisados artigos publicados sobre o assunto, no Pubmed e Medline, nos últimos vinte anos. Por meio dos estudos selecionados foi possível concluir que existem diversos tipos de cerâmicas utilizadas em próteses livres de metal; que o uso de cada material vai depender da estética, resistência desejada e localização da prótese em boca e que a tecnologia CAD/CAM elevou o nível das próteses dependendo de seu material, podendo ter esta a resistência semelhante às metalocerâmicas.