A low-cost carbon-based electrochemical platform for determining 2,3-dihydroxyphenol: applications in natural water and biodiesel samples.

2,3-Dihydroxyphenol (DHP) is a phenolic compound that has been used as an additive in biodiesel to avoid the auto-oxidation of biofuels and also in the production of cosmetic products. However, this substance can be released into the environment during its manufacture, transport, disposal and industrial use and can be harmful to health due to its toxicity, and hence, monitoring its presence in different samples is very important. Therefore, this work describes an electroanalytical study of DHP using different carbon-based pastes prepared to evaluate which one would be more promising to be used as an electrochemical platform for DHP quantification. The materials studied (graphite, carbon black and carbon nanotubes) in this work were characterized by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and the Boehm method. Voltammetric studies showed that pure carbon black presented a higher current density for detecting DHP than the other materials tested (graphite, carbon black + graphite, carbon nanotubes, carbon nanotubes + graphite). In studying the medium's pH, the highest currents occurred in acid media and acetate buffer solutions. After optimizing the experimental parameters, it was possible to obtain a wide range of linear responses from 0.1 to 10 000 µmol L-1 for DHP and a good limit of detection (LOD) of 0.03 µmol L-1. The selectivity of the electrode was tested for different species that may be present in samples containing DHP. Finally, the electrode was applied to determine DHP in natural water and biodiesel samples, showing recovery values between 98 and 102%, indicating good accuracy.

Characterization, antimicrobial and cytotoxic activity of polymer blends based on chitosan and fish collagen.

This study aims to produce, characterize, and assess the antimicrobial activity and cytotoxicity of polymer blends based on chitosan (CT) and fish collagen (COL) produced by different precipitation methods. Polymer blends were obtained in alkaline (NaOH), saline (NaCl), and alkaline/saline (NaOH/NaCl) solutions with different CT:COL concentration ratios (20:80, 50:50, and 80:20). The polymer blends were characterized by various physicochemical methods and subsequently evaluated in terms of their in vitro antimicrobial and cytotoxicity activity. In this study, the degree of chitosan deacetylation was 82%. The total hydroxyproline and collagen content in the fish matrix was 47.56 mg. g-1 and 394.75 mg. g-1, respectively. The highest yield was 44% and was obtained for a CT:COL (80:20) blend prepared by precipitation in NaOH. High concentrations of hydroxyproline and collagen in the blends were observed when NaOH precipitation was used. Microbiological analysis revealed that the strains used in this work were sensitive to the biomaterial; this sensitivity was dose-dependent and increased with increasing chitosan concentration in the products. The biocompatibility test showed that the blends did not reduce the viability of fibroblast cells after 48 h of culture. An analysis of the microbiological activity of the all-polymer blends showed a decrease in the values of minimal inhibitory concentration (MIC) and minimal bactericidal concentrations (MBC) for S. aureus and P. aeruginosa. The blends showed biocompatibility with NIH-3T3 murine fibroblast cells and demonstrated their potential for use in biomedical applications such as wound healing, implants, and scaffolds.

Chitosan-edible oil based materials as upgraded adsorbents for textile dyes.

Biopolymer chitosan is a low cost, abundant, environmentally friendly, very selective and efficient anionic dyes adsorbent, being a promising material for large-scale removal of dyes from wastewater. However, raw chitosan (CS) is an ineffective cationic dyes adsorbent and its performance is pH sensitive, thus, CS modifications that address these issues need to be developed. Here, we report the preparation and characterization of two new CS modifications using edible oils (soybean oil or babassu oil), and their adsorption performance for two dyes, one anionic (remazol red, RR) and one cationic (methylene blue, MB). Both modifications extended the pH range of RR adsorption. The babassu oil modification increased adsorption capacity of the cationic dye MB, whereas the soybean oil modification increased that of RR. Such improvements demonstrate the potential of these two new CS modifications as adsorbent candidates for controlling dyes pollution in effluents.