Tannic acid incorporation in chitosan-based microparticles and in vitro controlled release

Chitosan, a natural polycationic polysaccharide, was coupled with two polyanionic polymers: Na-alginate and carboxymethylcellulose (CMC) and with tannic acid (TA) obtaining three species of self-assembled complexes: chitosan/alginate/TA (sample 1), chitosan/TA (sample 2) and chitosan/CMC/TA (sample 3). The microparticle formation was achieved by dropwise addition of one solution into other by using a coaxial airflow sprayer. These systems were characterized with regard to particle size distribution, thermal stability, tannic acid entrapment efficiency. Sample 2 showed quite a different behavior compared to the other two samples; the particle diameter is located in the nanometric region, the quantity of incorporated tannic acid is higher than in the other two samples and the material shows better thermal stability. The release of tannic acid from these complexes was studied in water (pH = 5.89), phosphates buffer (pH = 7.04) and acetate buffer (pH = 4.11). These studies revealed two distinct periods in tannic acid delivery process: an initial period, varying between 4 and 10 h, characterized by a high release rate with a delivered tannic acid amount of approximately 80% of the incorporated polyphenol and a second period, which starts after 20 to 30 h of delivery and it ends after approximately 120 h, when the release process takes place with low and constant rate and the kinetic curve is linear—characteristic for a zero order kinetic.     

Enterotoxigenic and genetic profiles of Bacillus cereus strains of food origin in Brazil

In Brazil, the incidence of Bacillus cereus outbreaks is unknown, and there is little information about B. cereus occurrence in food. In addition, data on toxin production and genetic characterization of the B. cereus isolates cannot be found. This pathogen causes two distinct types of toxin-mediated foodborne illnesses known as diarrheal and emetic syndromes. Diarrheal syndrome has been linked to three different enterotoxins: two protein complexes, hemolysin BL (HBL) and nonhemolytic enterotoxin (NHE); and an enterotoxic protein, cytotoxin K (cytK). Emetic syndrome is related to cereulide, a toxin encoded by the ces gene. In this study, NHE and HBL production capacities of 155 strains of B. cereus isolated from Brazilian food products were evaluated with an immunoassay. Strains were also tested for the presence of the genes of the HBL and NHE complexes, cytK, cytK-1, cytK-2, and ces, using PCR. HBL was detected in 105 (67.7%) strains and NHE in 154 (99.4%) strains. All the strains harbored at least one gene of the NHE complex, while 96.1% of them were positive for at least one of those of the HBL complex. Genes cytK1 and ces were not detected. All strains showed toxigenic capacity and could represent a risk for consumers if good practices are not followed. This is the first report on toxigenic and genetic profiles of B. cereus strains isolated in Brazil.     

A mitochondrial mechanism is involved in apoptosis of Robertsonian mouse male germ cells

The aim of this study was to determine whether the intrinsic mechanism of apoptosis is involved in the death of germ cells in Robertsonian (Rb) heterozygous adult male mice. Testes from 5-month-old Rb heterozygous CD1 x Milano II mice were obtained and compared with those from homozygous CD1 (2n=40) and Milano II (2n=24) mice. For histological evaluation of apoptosis, TUNEL labelling and immunohistochemistry were used to localise Bax and cytochrome c. Expression of calbindin D(28k) (CB), an anti-apoptotic molecule, was also analysed by immunohistochemistry and immunoblotting. Testicular ultrastructure was visualised by electron microscopy. Morphology and cell associations were abnormal in the Rb heterozygous seminiferous epithelium. An intense apoptotic process was observed in tubules at stage XII, mainly in metaphase spermatocytes. Metaphase spermatocytes also showed Bax and cytochrome c redistributions. Mitochondria relocated close to the paranuclear region of spermatocytes. CB was mainly expressed in metaphase spermatocytes, but also in pachytene spermatocytes, spermatids and Sertoli cells at stage XII. The co-localisation of CB and TUNEL labelling was very limited. Sixty per cent of metaphase spermatocytes were apoptotic and calbindin negative, while 40% were calbindin positive without signs of apoptosis. Ten per cent of the Bax- and cytochrome c-positive cells were also calbindin positive. These data suggest that apoptosis of the germ cells in heterozygous mice occurs, at least in part, through a mitochondrial-dependent mechanism. Calbindin overexpression might prevent or reduce the apoptosis of germ cells caused by Rb heterozygosity, which could partially explain the subfertility of these mice.     

An investigation on post-fire behavior of hybrid nanocomposites under bending loads

This work focuses on residual bending properties of hybrid nanocomposites after intense heat conditions. Carbon fiber/epoxy-nanoclay and carbon fiber/epoxy-graphene nanosheets were manufactured. The nanoparticles employed were Cloisite 30B nanoclay and surface modified graphene nanosheets. The epoxy system was RemLam M/HY956. For short beam samples exposed to 800 KW/m² heat flux, for a various period of time up to 120 s, the addition of nanoparticles (nanoclay and graphene nanosheets) increased the unburned thickness from 0.16 mm (original) to 2.63 mm and 2.74 mm, respectively. When the two-dimensional (plates) samples were tested, the improvement on heat performance was reduced. The unburned thickness improved close to 10% with the presence of nanoclay. The addition of graphene nanosheets leads to a decrease in unburned thickness of 12.8%. This result can be due to the good thermal protection properties of the graphene nanosheets. Using SEM analysis, it was observed that when the hybrid nanocomposites were subjected to a large heat flux, nanoparticles remained trapped inside the char layers. Finally, the proposed model seems to overestimate the residual bending response by 8%.     

K88 Fimbrial Adhesin Targeting of Microspheres Containing Gentamicin Made with Albumin Glycated with Lactose

The formulation and characterization of gentamicin-loaded microspheres as a delivery system targeting enterotoxigenic Escherichia coli K88 (E. coli K88) was investigated. Glycated albumin with lactose (BSA-glucose-β (4-1) galactose) was used as the microsphere matrix (MS-Lac) and gentamicin included as the transported antibiotic. The proposed target strategy was that exposed galactoses of MS-Lac could be specifically recognized by E. coli K88 adhesins, and the delivery of gentamicin would inhibit bacterial growth. Lactosylated microspheres (MS-Lac1, MS-Lac2 and MS-Lac3) were obtained using a water-in-oil emulsion, containing gentamicin, followed by crosslinking with different concentrations of glutaraldehyde. Electron microscopy displayed spherical particles with a mean size of 10–17 µm. In vitro release of gentamicin from MS-Lac was best fitted to a first order model, and the antibacterial activity of encapsulated and free gentamicin was comparable. MS-Lac treatments were recognized by plant galactose-specific lectins from Ricinus communis and Sophora japonica and by E. coli K88 adhesins. Results indicate MS-Lac1, produced with 4.2 mg/mL of crosslinker, as the best treatment and that lactosylated microsphere are promising platforms to obtain an active, targeted system against E. coli K88 infections.     

Carcinogenic carbocyclic and heterocyclic aromatic amines: a DFT study concerning their mutagenic potency

The relative stability of the nitrenium ions derived from a set of 43 aromatic and heteroaromatic amines of diverse structure was evaluated by density functional theory (DFT) calculations in order to examine the role of these electrophilic intermediates on mutagenic activity. Correlations were sought between calculated properties and mutagenic potencies from the literature. Mutagenicity was found to increase with nitrenium ion stability, which was favored by negative charge development at the exocyclic nitrogen of the ion (q(N)). Distinct correlation functions were observed for the amines grouped according to their classification as aromatic (Ar), heteroaromatic (HAr), imidazocarbocyclic (ImiAr), imidazoheterocyclic (ImiH), dipyridoimidazoles (PI), and quinoxalines (Qx). The influence of the logarithm of the octanol/water partition coefficient (LogP) on the mutagenic potency of the amines selected for this study was also analyzed.     

A combined electrocoagulation-sorption process applied to mixed industrial wastewater

The removal of organic pollutants from a highly complex industrial wastewater by a aluminium electrocoagulation process coupled with biosorption was evaluated. Under optimal conditions of pH 8 and 45.45 Am(-2) current density, the electrochemical method yields a very effective reduction of all organic pollutants, this reduction was enhanced when the biosorption treatment was applied as a polishing step. Treatment reduced chemical oxygen demand (COD) by 84%, biochemical oxygen demand (BOD(5)) by 78%, color by 97%, turbidity by 98% and fecal coliforms by 99%. The chemical species formed in aqueous solution were determined. The initial and final pollutant levels in the wastewater were monitored using UV-vis spectrometry and cyclic voltammetry. Finally, the morphology and elemental composition of the biosorbent was characterized with scanning electron microscopy (SEM) and energy dispersion spectra (EDS).     

Applicability of quantitative polymerase chain reaction (qPCR) assays for common bean authentication in processed food

Food authentication by quantitative polymerase chain reaction (qPCR) methods assures food quality. The aim was to evaluate three qPCR assays for DNA quantification after heat processing of common bean grains, genus-specific FAS assay for Phaseolus, species-specific LEC assay for common bean (Phaseolus vulgaris) and genetically modified (GM) event-specific FGM assay for Embrapa 5.1 event GM common bean. FAS assay showed high stability among Phaseolus genus samples. Common bean grains were heat-treated in autoclave (at 120 °C for 15–60 min) and target DNA copy number decreased as processing time increased. Even with DNA degradation, qPCR assays were capable to detect low DNA quantity, and the limit of detection was 100 copy number. Mean efficiency value of FGM assay was 92% in the presence of background DNA. Background DNA did not cause any interference, and 0.39% of GM material can be detected. These qPCR assays are able to quantify common bean in processed food.