This paper reports the development of a low-cost (< US$ 0.03 per device) immunosensor based on gold-modified screenprinted carbon electrodes (SPCEs). As a proof of concept, the immunosensor was tested for a fast and sensitive determination of S proteins from both SARS-CoV and SARS-CoV-2, by a single disposable device. Gold nanoparticles were electrochemically deposited via direct reduction of gold ions on the electrode using amperometry. Capture antibodies from spike (S) protein were covalently immobilized on carboxylic groups of self-assembled monolayers (SAM) of mercaptoacetic acid (MAA) attached to the gold nanoparticles. Label-free detection of S proteins from both SARS-CoV and SARS-CoV-2 was performed with electrochemical impedance spectroscopy (EIS). The immunosensor fabricated with 9 s gold deposition had a high performance in terms of selectivity, sensitivity, and low limit of detection (LOD) (3.16 pmol L −1 ), thus permitting the direct determination of the target proteins in spiked saliva samples. The complete analysis can be carried out within 35 min using a simple one-step assay protocol with small sample volumes (10 µL). With such features, the immunoplatform presented here can be deployed for mass testing in point-of-care settings.

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Recebido em 4/6/12; aceito em 14/11/12; publicado na web em 18/2/13 TRIGONELLINE, 5-CAFFEOYLQUINIC ACID, CAFEINE AND MELANOIDINS LEVELS IN COMMERCIAL BRAZILIAN INSTANT COFFEES. Commercial Brazilian regular and decaffeinated instant coffees (33 brands) were studied. The levels ranged from 0.47 to 2.15 g 100 g -1 for trigonelline, 0.38 to 2.66 g 100 g -1 for 5-caffeoylquinic acid (5-CQA), 0.24 to 4.08 g 100 g -1 for caffeine, and 0.253 to 0.476 (420 nm) for melanoidins. Variations in bioactive compound levels among batches were observed. There was no relationship between the drying process and the composition of the products. In general, Gourmet and decaffeinated coffees had higher trigonelline and 5-CQA but lower caffeine and melanoidin content than regular products.Keywords: bioactive compounds; decaffeinated coffees; HPLC. INTRODUÇÃOAtualmente o Brasil é o maior produtor mundial de café, sendo responsável por 30 % do mercado internacional, e um dos maiores exportadores de café solúvel e café torrado e moído. É também o segundo mercado consumidor, atrás somente dos Estados Unidos. 1,2 No Brasil o café é a segunda bebida mais consumida entre pessoas acima de 15 anos, atrás somente da água. 2As espécies de café mais comercializadas são Coffea arabica e Coffea canephora (robusta) constituindo 70 e 30% da produção mundial, respectivamente.1,3 O café arábica é um produto com aroma e sabor mais intenso e característico, apresentando maior valor comercial e qualidade sensorial. O café robusta, utilizado em blends com o arábica, tem a finalidade de conferir mais corpo e reduzir a acidez da bebida, ajustando-a a preferência dos consumidores. Por possuir maior teor de sólidos solúveis é amplamente utilizado na indústria de café solúvel, reduzindo o custo do produto. 1,4,5 Cuidados na colheita, secagem e composição da mistura (espécies, variedades e presença de defeitos) são decisivos para a qualidade dos produtos de café. A fabricação do produto torrado e moído engloba as etapas de composição do blend, processo de torra, moagem, embalagem e armazenamento.6 O café solúvel é o produto resultante da desidratação do extrato aquoso obtido exclusivamente do café torrado, através de métodos físicos, utilizando água como único agente extrator e dependendo do método de desidratação que pode ser classificado em granulado ou aglomerado, pó ou atomizado (spray dried) e liofilizado (freeze dried). 7Os cafés arábica e robusta apresentam diferenças no teor de diversos componentes, assim, variações nos blends empregados impactam também na composição e qualidade da bebida. 6,8 Em grãos verdes, observa-se maior teor de cafeína e ácidos clorogênicos e menor teor de trigonelina no café robusta quando comparado ao café arábica. 9Além da matéria-prima, o processo de torra também influencia na composição pela formação e degradação de compostos, sendo que uma maior intensidade de torra aumenta a concentração de produtos de reação de Maillard, como melanoidinas, e reduz os teores de compostos termolábeis, como ácidos clorogênicos e trigonelina...

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A product of easy preparation and high added value, soluble/instant coffee is obtained by drying the aqueous extract of roasted coffee and presents a high amount of bioactive compounds. The aim of the study was to evaluate the antioxidant activity of 33 Brazilian commercial soluble coffees considering the radical scavenging activity (via the ABTS method) and the reducing capacity (via the Folin-Ciocalteu method). Soluble coffees of several brands and types (regular, gourmet, and decaffeinated), subjected to different drying processes (agglomeration, atomization, and freeze-drying) (n = 85), were evaluated. In general, regular and decaffeinated soluble coffees presented high antioxidant activity. The reducing capacity ranged from 9.9 to 15.4 g of gallic acid per 100 g, while the radical scavenging activity ranged from 20.4 to 37.0 g of Trolox per 100 g. Good repeatability-with coefficients of variation of 2.4% for Folin-Ciocalteu and of 5.2% for ABTS-and high correlations between the values of antioxidant activity obtained by both methods (r = 0.66) were observed. Gourmet coffees presented less antioxidant activity compared to the regular samples. No correlation was verified between drying processes and antioxidant activity.

Low-cost, instrument-free colorimetric tests were developed to detect SARS-CoV-2 using plasmonic biosensors with Au nanoparticles functionalized with polyclonal antibodies (f-AuNPs). Intense color changes were noted with the naked eye owing to plasmon coupling when f-AuNPs form clusters on the virus, with high sensitivity and a detection limit of 0.28 PFU mL −1 (PFU stands for plaque-forming units) in human saliva. Plasmon coupling was corroborated with computer simulations using the finite-difference time-domain (FDTD) method. The strategies based on preparing plasmonic biosensors with f-AuNPs are robust to permit SARS-CoV-2 detection via dynamic light scattering and UV−vis spectroscopy without interference from other viruses, such as influenza and dengue viruses. The diagnosis was made with a smartphone app after processing the images collected from the smartphone camera, measuring the concentration of SARS-CoV-2. Both image processing and machine learning algorithms were found to provide COVID-19 diagnosis with 100% accuracy for saliva samples. In subsidiary experiments, we observed that the biosensor could be used to detect the virus in river waters without pretreatment. With fast responses and requiring small sample amounts (only 20 μL), these colorimetric tests can be deployed in any location within the point-of-care diagnosis paradigm for epidemiological control.

The coronavirus disease 2019 (Covid-19), which caused respiratory problems in many patients worldwide, led to more than 5 million deaths by the end of 2021. Experienced symptoms vary from mild to severe illness. Understanding the infection severity to reach a better prognosis could be useful to the clinics, and one study area to fulfill one piece of this biological puzzle is metabolomics. The metabolite profile and/or levels being monitored can help predict phenotype properties. Therefore, this study evaluated plasma metabolomes of 110 individual samples, 57 from control patients and 53 from recent positive cases of Covid-19 (IgM 98% reagent), representing mild to severe symptoms, before any clinical intervention. Polar metabolites from plasma samples were analyzed by quantitative 1 H NMR. Glycerol, 3-aminoisobutyrate, formate, and glucuronate levels showed alterations in Covid-19 patients compared to those in the control group (Tukey’s HSD p -value cutoff = 0.05), affecting the lactate, phenylalanine, tyrosine, and tryptophan biosynthesis and d -glutamine, d -glutamate, and glycerolipid metabolisms. These metabolic alterations show that SARS-CoV-2 infection led to disturbance in the energetic system, supporting the viral replication and corroborating with the severe clinical conditions of patients. Six polar metabolites (glycerol, acetate, 3-aminoisobutyrate, formate, glucuronate, and lactate) were revealed by PLS-DA and predicted by ROC curves and ANOVA to be potential prognostic metabolite panels for Covid-19 and considered clinically relevant for predicting infection severity due to their straight roles in the lipid and energy metabolism. Thus, metabolomics from samples of Covid-19 patients is a powerful tool for a better understanding of the disease mechanism of action and metabolic consequences of the infection in the human body and may corroborate allowing clinicians to intervene quickly according to the needs of Covid-19 patients.