Functionalization and characterization of carbon black vulcan XC-72R for applications on inhibition based enzymatic biosensors

In this work, carbon black Vulcan XC-72R was functionalized using five different treatments, the oxidizing agents employed were: nitric acid, sulfuric acid and hydrogen peroxide. The physical characterization of functionalized samples was carried out using scanning electron microscopy (SEM) and Raman spectroscopy. The results suggested that the treatments did not significantly alter the morphology of the material in most cases and showed an increase in the number of defects attributed to the introduction of oxygenated functional groups. Glassy carbon electrodes (GCE) were modified with aqueous dispersions of materials in dihexadecyl hydrogen phosphate (DHP). For the electrochemical characterization of the electrodes were performed studies of cyclic voltammetry employing the probe potassium hexacyanoferrate (III). For all cases there was an increase in the electroactive area as a result of the functionalization. Subsequently, the response of the electrodes to different analytes (dopamine, catechol, paracetamol and hydroquinone) was evaluated, the electrode modified in a mixture of nitric and sulfuric acid 1:1 (CB–HNO3/H2SO41:1–DHP/GCE) showed the highest analytical signal for the different compounds tested. Calibration curves were constructed for the determination of dopamine using the GCE electrode, the electrode prepared with unmodified CB (CB–DHP/GCE) and the CB–HNO3/H2SO41:1–DHP/GCE electrode, the sensitivities of the analytical curves (angular coefficients of the analytical curves) were: 0.334, 3.65 and 6.54 A cm−2 L mol−1, respectively. These results show a significant increase in sensitivity as a result of the functionalization xvii of CB suggesting an advantage over the use of unmodified material for electroanalytical applications. Then, an analytical procedure for the determination of sodium benzoate (sodium salt of benzoic acid) based on enzyme inhibition was developed, where the tyrosinase enzyme was immobilized at the surface of the CB– HNO3/H2SO41:1–DHP/GCE electrode (biosensor). Studies of the inhibition mechanism and optimization of operating conditions were performed. The corresponding analytical curves had linear concentration ranges between 4.90 × 10−7 and 1.92 × 10−5 mol L−1 and a detection limit of 2.1 × 10−7 mol L−1.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Neste trabalho funcionalizou-se o carbon black Vulcan XC-72R utilizando-se cinco tratamentos diferentes, empregando como agentes oxidantes: ácido nítrico, ácido sulfúrico e peróxido de hidrogênio. A caracterização física das amostras funcionalizadas foi realizada empregando-se microscopia eletrônica de varredura (MEV) e espectroscopia Raman. Analisando-se os resultados obtidos tem-se que os tratamentos ácidos não alteraram significativamente a morfologia do material. Por outro lado, este tratamento proporcionou um aumento do número de defeitos atribuídos à introdução de grupos funcionais oxigenados. Foram modificados eletrodos de carbono vítreo (do inglês, glassy carbon electrode, GCE) com dispersões aquosas dos materiais em dihexadecil hidrogenofosfato (DHP). Para a caracterização eletroquímica dos eletrodos foram realizados estudos de voltametria cíclica empregando-se a sonda hexacianoferrato de potássio (III). Em todos os casos houve aumento da área eletroativa do eletrodo como consequência da funcionalização do material de carbono. Posteriormente, avaliou-se a resposta dos eletrodos frente a diferentes analitos (dopamina, catecol, paracetamol e hidroquinona), o eletrodo modificado em mistura de ácido nítrico e sulfúrico 1:1 (CB–HNO3/H2SO41:1–DHP/GCE) apresentou maior sinal analítico para os diferentes compostos investigados. Foram construídas curvas de calibração para a determinação de dopamina utilizando o eletrodo GCE, o eletrodo preparado com CB sem funcionalizar (CB–DHP/GCE) e o eletrodo CB–HNO3/H2SO41:1– DHP/GCE. As sensibilidades (coeficientes angulares das curvas analíticas) foram xv 0,334, 3,65 e 6,54 A cm−2 mol L−1, respectivamente. Estes resultados mostram um aumento significativo da sensibilidade como consequência da funcionalização do CB, sugerindo uma vantagem sobre o uso do material sem modificação para aplicações eletroanalíticas. Em seguida de denvolveu-se um procedimento analítico para a determinação de benzoato de sódio (sal de sódio do ácido benzoico) baseado na inibição enzimática da tirosinase imobilizada na superfície do eletrodo CB– HNO3/H2SO41:1–DHP/GCE (biossensor). Foram realizados estudos de mecanismo de inibição e otimização das condições de operação. A curva analítica correspondente apresentou uma faixa linear de concentração de 4,90 × 10−7 a 1,92 × 10−5 mol L−1 e um limite de detecção de 2,1 × 10−7 mol L−1

Quantification of a COVID-19 Antibody Assay Using a Lateral Flow Test and a Cell Phone

Although several biomedical assays have been developed to screen for antibodies against SARS-CoV-2, very few can be completed without drawing blood. We developed a rapid lateral flow screening tool that used saliva samples and yielded rapid results that could be quantified using a cell phone. This assay provided the sensitive detection of IgG antibodies against SARS-CoV-2 within 10 min. We started by synthesising, modifying, and characterising gold nanoparticles. Using these particles as a coloured label, we developed a lateral flow strip made of nitrocellulose, glass fibre, and cellulose material. We quantified our visual results using pictures acquired with a cell phone and calculated a limit of detection of 4 ng/mL of antibodies against the SARS-CoV-2 spike protein

Quantification of a COVID-19 Antibody Assay Using a Lateral Flow Test and a Cell Phone

Although several biomedical assays have been developed to screen for antibodies against SARS-CoV-2, very few can be completed without drawing blood. We developed a rapid lateral flow screening tool that used saliva samples and yielded rapid results that could be quantified using a cell phone. This assay provided the sensitive detection of IgG antibodies against SARS-CoV-2 within 10 min. We started by synthesising, modifying, and characterising gold nanoparticles. Using these particles as a coloured label, we developed a lateral flow strip made of nitrocellulose, glass fibre, and cellulose material. We quantified our visual results using pictures acquired with a cell phone and calculated a limit of detection of 4 ng/mL of antibodies against the SARS-CoV-2 spike protein

An open-source advanced maskless synthesizer for light-directed chemical synthesis of large nucleic acid libraries and microarrays

Large- to ultra-large-scale synthesis of nucleic acids is becoming an increasingly important tool for understanding and manipulating biological systems, as well as for developing new technologies based on engineered biological materials, including DNA-based nanofabrication, aptamers and writing digital data at the molecular level. Several technologies for large-scale synthesis have been developed over the years, but all of them remain inaccessible to most researchers due to their complexity and/or use of proprietary technologies. Here, we present a fully open source, benchtop device for ultra-large scale nucleic acid synthesis that is also highly flexible and adaptable, able to accommodate a wide range of monomers and chemistries, while providing unrestricted access to synthesis parameter space

Screen-printed interdigitated electrodes modified with nanostructured carbon nano-onion films for detecting the cancer biomarker CA19-9

Nanostructured capacitive biosensors, combined with inexpensive fabrication technologies, may provide simple, sensitive devices for detecting clinically relevant cancer biomarkers. Herein, we report a novel platform for detecting the pancreatic cancer biomarker CA19-9 using low-cost screen-printed interdigitated electrodes (SPIDEs). The SPIDEs were modified by carbon nano-onions (CNOs) and graphene oxide (GO) films, on which a layer of anti-CA19-9 antibodies was immobilized. The modification with CNOs and GO significantly improved the analytical performance of the biosensor, which displayed superior results to those prepared only with GO. The biossensor exhibited high reproducibility and a relatively low limit of detection of 0.12 U mL-1. Using these devices in combination with information visualization methods we were able to detect CA19-9 in whole cell lysates of colorectal adenocarcinoma. The fabrication of these low-cost, disposable immunosensors is a successful attempt to explore CNOs in capacitive biosensors, which may be extended for detection of different cancer biomarkers.CAPES (001), CNPq, INEO and FAPESP (2012/15543-7, 2013/14262-7, 2015/01770-0, 2016/00991-5 and 2017/12096-3). M.N.C is grateful for the economic support from Vicerrectoria de Investigaciones and the Centro de Excelencia en Nuevos Materiales (CENM) from the Universidad del Valle