Strategic Project - LA 6 - 2011-2012

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Publications

Chitosan-based silver nanoparticles: a study of the antibacterial, antileishmanial and cytotoxic effects

Publication . Lima, Douglas dos Santos; Gullon, Beatriz; Cardelle-Cobas, Alejandra; Brito, Lucas M.; Rodrigues, Klinger A. F.; Quelemes, Patrick V.; Ramos-Jesus, Joilson; Arcanjo, Daniel D. R.; Plácido, Alexandra; Batziou, Krystallenia; Quaresma, Pedro; Eaton, Peter; Delerue-Matos, Cristina; Carvalho, Fernando Aecio; Silva, Durcilene Alves da; Pintado, M. E.; Leite, José Roberto de Sá

Silver nanoparticles have been studied as an alternative for treatment of microbial infections and leishmaniasis, without promoting induction of microbial or parasite resistance. In this study, chitosan-based silver nanoparticles were synthesized from silver nitrate (AgNO3), sodium borohydride as a reducing agent, and the biopolymer chitosan as a capping agent. The chitosan-based silver nanoparticles were characterized by ultraviolet-visible, Fourier transform infrared, dynamic light scattering, zeta potential, atomic force microscopy, and transmission electron microscope. The antibacterial assay was performed by determination of the minimum inhibitory concentration. The antileishmanial and the cytotoxic effects induced by AgNO3, chitosan, and chitosan-based silver nanoparticles were analyzed by resazurin and MTT colorimetric assays, respectively. AgNO3, chitosan, and chitosan-based silver nanoparticles induced a marked activity against all bacterial strains and promastigote forms of Leishmania amazonensis at minimum inhibitory concentrations ranging from 1.69 to 3.38 μg Ag/mL. Interestingly, the chitosan-based silver nanoparticles presented less cytotoxicity than the AgNO3 alone and were more active against L. amazonensis than solely chitosan. Furthermore, the cytotoxic concentrations (CC50) of both chitosan and chitosan-based silver nanoparticles against macrophages were significantly higher than the IC50 against promastigotes. Thus, the chitosan-based silver nanoparticles represent a promising alternative for the treatment of microbial infections and leishmaniasis.

2017Journal article

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Study of antimicrobial activity and atomic force microscopy imaging of the action mechanism of cashew tree gum

Publication . Campos, Débora A.; Ribeiro, Alexandra C.; Costa, Eduardo M.; Fernandes, João C.; Tavaria, Freni K.; Araruna, Felipe Bastos; Eiras, Carla; Eaton, Peter; Leite, José Roberto S. A.; Pintado, M. Manuela

The aim of this work was to evaluate the antimicrobial potential of two grades of cashew tree gum (crude and purified) against eight microorganisms and to analyze the mechanism of cashew tree gum antimicrobial action via atomic force microscopy (AFM) imaging. The results indicated strong antimicrobial properties of pure cashew tree gum against all tested microorganisms, except for Candida albicans and Lactobacillus acidophilus. On the other hand crude cashew gum showed antimicrobial activity only against Gram-positive bacteria (MRSA, MSSA, Listeria innocua and Enterococcus faecium). Atomic force microscopy imaging showed that pure cashew tree gum lead to bacterial cell collapse. In conclusion cashew tree gum presented relevant antimicrobial activity against most of the studied bacteria, and the purification of the cashew gum affected its antimicrobial spectrum.

2012Journal article

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Evaluation of green coffee beans quality using near infrared spectroscopy: A quantitative approach

Publication . Santos, João Rodrigo; Sarraguça, Mafalda C.; Rangel, António O.S.S.; Lopes, João A.

Characterisation of coffee quality based on bean quality assessment is associated with the relative amount of defective beans among non-defective beans. It is therefore important to develop a methodology capable of identifying the presence of defective beans that enables a fast assessment of coffee grade and that can become an analytical tool to standardise coffee quality. In this work, a methodology for quality assessment of green coffee based on near infrared spectroscopy (NIRS) is proposed. NIRS is a green chemistry, low cost, fast response technique without the need of sample processing. The applicability of NIRS was evaluated for Arabica and Robusta varieties from different geographical locations. Partial least squares regression was used to relate the NIR spectrum to the mass fraction of defective and non-defective beans. Relative errors around 5% show that NIRS can be a valuable analytical tool to be used by coffee roasters, enabling a simple and quantitative evaluation of green coffee quality in a fast way.

2012Journal article

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Determination of total protein content in white wines by solid phase spectrometry in a SI–LOV system

Publication . Vidigal, Susana S. M. P.; Tóth, Ildikó V.; Rangel, António O. S. S.

Although present at low concentration in wine samples, proteins, have considerable technological importance, due to their capability of haze formation. The present work presents a methodology for the quantification of total protein in white wine in a sequential injection lab-on-valve system, exploiting the bead injection concept for solid phase extraction with spectrophotometric detection. The method is based on the retention of the proteins in the solid support, NTA (nitrilotriacetic acid) superflow beads, charged by Cu2+. The change in the absorbance is monitored at 500 nm at the surface of the beads after addition of the Folin–Ciocalteu’s reagent (FCr). The developed method presented a sample consumption of 400 L per assay and a consumption of FCr and Cu2+ solution of 25 L and 100 L per assay, respectively. It was possible to achieve a linear range up to 0.30 g/L with a limit of detection and quantification of 0.03 and 0.10 g/L, respectively. The proposed method was successfully applied to white wine samples.

2012Conference object

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Authenticity control of roasted coffee brands using near-infrared spectroscopy

Publication . Sarraguça, Mafalda Cruz; Santos, João Rodrigo; Rangel, António O. S. S.; Lopes, João Almeida

In this work, a methodology based on near-infrared spectroscopy (NIRS) was exploited in order to discriminate between commercial coffee brands. The main advantages of this approach compared to other strategies (e.g., wet chemistry methods) are its lower cost, less labor, and lower time per analysis. Two commercial brands were discriminated among several others present in the Portuguese market. The chemometric method used to estimate discriminant models was partial least squares discriminant analysis (PLSDA). Results show that it is possible to discriminate coffee brands using this strategy with a correct classification of 100 %. The spectral region, more favorable to discrimination of roasted coffee brands, can be related with differences in the concentrations of compounds, such as, chlorogenic acid and sucrose, and also due to differences on lipid fraction. This methodology is adequate for field implementation, namely, adopting handheld NIRS instruments.

2013Journal article

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