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•IPEC particles were prepared with positive and negative net charges.•Sorption of sodium chromoglycate and tetracycline hydrochloride was carried out.•Tetracyline adsorbed both on ...positive and negatively charged IPECs.•Protonation by the tetracyline resulted in disruption of IPEC structure.
Interpolyelectrolyte complexes of chitosan and poly(sodium 4-styrenesulfonate) NaPSS were synthesized and obtained in the form of solid particles, with two different sulfonate to aminium molar ratios: 0.7, resulting in particles with positive zeta potential (IPEC+), and 1.4, yielding particles with negative zeta potential (IPEC−). Both particles were characterized as potential drug sorbents using differently charged drugs: sodium cromoglycate (negatively charged), and tetracycline hydrochloride (positively charged). The adsorption isotherm for cromoglycate and tetracycline on IPEC+ was adequately described by the Langmuir model, while the IPEC− sorption of tetracycline followed the Redlich-Peterson isotherm without the occurrence of cromoglycate sorption. The sorption kinetics consisted of two processes, one fast and the other slow, which were correlated to purely surface-related interactions and processes that resulted in diffusion and/or destruction/rearrangement on the particle surface and subsurface, respectively. Charge build up equilibrium and kinetics were also monitored via zeta potential measurements, and the differences between mass drug uptake and particle charging were used to propose adsorption mechanisms for the systems studied in this work.
Species from Pavonia genus (Malvaceae) are traditionally used as antioxidant, n‑anti‑inflammatory and antimicrobial remedies. Previous studies have revealed their diversity of specialized metabolites ...widely used in the development of new medicines. This is the first study on Pavonia glazioviana Gurke, a Brazilian species known as “Malva‑da‑Chapada”. The research led to identify fifteen compounds: 132‑(S)‑hydroxy‑pheophytin a; and 132(S)‑hydroxy‑173‑ethoxyphaeophorbide, n‑decanol, cycloart‑23Z‑ene‑3β,25‑diol, cycloart‑24S‑25‑ene‑3β,24‑diol, sitosterol‑3‑O‑β‑D‑glucopyranoside, stigmasterol‑3‑O‑β‑D‑glucopyr anoside, quercetin, acacetin, kaempferol, tiliroside, 5‑hydroxy‑3,7,8,4’‑tetramethoxyflavone, 5,7‑dihydroxy‑3,8,4’‑trimethoxyflavone, 5,7‑dihydroxy‑4’‑methoxyflavone, 5,7,4’‑trihydroxy‑3,8‑dimethoxyflavone and 5,7,4’‑trihydroxy‑3‑methoxyflavone. The major flavonoids were tested for their antimicrobial activity, and the compound 5,7‑dihydroxy‑3,8,4’‑trimethoxyflavone showed strong activity against Escherichia coli (MIC = 512 μg mL‑1), Pseudomonas aeruginosa (MIC = 512 μg mL‑1), Candida albicans (MIC = 512 μg mL‑1), Candida tropicalis (MIC = 512 μg mL‑1), Candida parapsilosis (MIC = 512 μg mL‑1), Aspergillus flavus (MIC = 512 μg mL‑1) and A. fumigantus (MIC = 512 μg mL‑1). The total phenolic content, flavonoid content, and radical scavenging potential were determined showing its great production of phenolics and flavonoids, along with interesting radical scavenging potential (DPPH EC50 = 6.36 ± 0.029 mg mL‑1). Our findings contributed to characterize P. glazioviana as a source of methoxylated flavonoids with antimicrobial potential.
Multi-Walled Carbon Nanotubes (MWCNT) have been functionalized with rutin through three steps (i. reaction step; ii. purification step; iii. drying step) and their physicochemical properties ...investigated with respect to morphological structure, thermal analysis, Fourier Transform Infrared Spectroscopy (FTIR), and cytotoxicity. The molecular docking suggested the rutin-functionalized MWCNT occurred by hydrogen bonds, which was confirmed by FTIR assays, corroborating the results obtained by thermal analyses. A tubular shape, arranged in a three-dimensional structure, could be observed. Mild cytotoxicity observed in 3T3 fibroblasts suggested a dose–effect relationship after exposure. These findings suggest the formation of aggregates of filamentous structures on the cells favoring the cell penetration.
.
In this work we use single molecule force spectroscopy performed with optical tweezers in order to characterize the complexes formed between the anticancer drug Pixantrone (PIX) and the DNA ...molecule, at two very different ionic strengths. Firstly, the changes of the mechanical properties of the DNA-PIX complexes were studied as a function of the drug concentration in the sample. Then, a quenched-disorder statistical model of ligand binding was used in order to determine the physicochemical (binding) parameters of the DNA-PIX interaction. In particular, we have found that the PIX molecular mechanism of action involves intercalation into the double helix, followed by a significant compaction of the DNA molecule due to partial neutralization of the phosphate backbone. Finally, this scenario of interaction was quantitatively compared to that found for the related drug Mitoxantrone (MTX), which binds to DNA with a considerably higher equilibrium binding constant and promotes a much stronger DNA compaction. The comparison performed between the two drugs can bring clues to the development of new (and more efficient) related compounds.
Graphical abstract
Scheme with proposed mechanism of sorption of tetracycline on chitosan particles.
Experiments to monitor and characterize the kinetics of adsorption of tetracycline on chitosan particles are reported ...in this work. The same pseudo-order kinetics that has been widely used for describing the adsorption in systems related to wastewater purification and drug loading was used to treat the present data. As some unexpected results came out from the experiments, it was necessary a detailed deduction for this sort of kinetics to be carried out, so that approximations related to short and long times were obtained. Firstly it was shown that an apparently linear
t/
q(
t) versus
t relationship did not imply a pseudo-second-order sorption kinetics, differently of what has been repeatedly reported in the literature. It was found that this misinterpretation could be avoided by using non-linear regression. Finally, the adsorption of tetracycline on chitosan particles was analyzed, using the insights obtained from theoretical analysis, and the parameters generated were used to analyze to adsorption kinetics and to propose an adsorption mechanism.
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► Tetracycline sorption on chitosan may occur by diffusion (absorption) or adsorption. ► A discontinuity in sorption isotherm indicates the point that absorption prevails. ► Zeta ...potential may be used to follow chitosan surface charging during adsorption. ► Influences of protonated and nonprotonated tetracycline can be separately analyzed. ► Equilibrium and kinetic expressions using depletion method confirm the results.
Adsorption phenomena occurring at the solid/liquid interface of chitosan particles are of extreme importance in the kinetics of drug release/upload as well as in effluent treatment by adsorption. In this work, equilibrium and kinetic aspects of protonated tetracycline adsorption on chitosan are explored using classic solution depletion method and zeta potential measurements. Equilibrium experiments showed that for solutions with tetracycline initial concentration of ca. 1.2gL−1, corresponding to a pH around 3, chitosan structure disrupted, as indicated by an increase in magnitude of tetracycline sorption. Adsorption and zeta potential isotherms before disruption suggested that the process of adsorption had a Langmuir character up to a point at which subsurface was exposed to adsorption; at this point, a second mode of sorption began: zeta potential tended to an equilibrium value, following Sips isotherm and tetracycline sorption had a linear dependence on its continuous phase concentration. The kinetics of tetracycline sorption suggested that sorption of tetracycline was divided between the sorption of protonated and non-protonated tetracycline; tetracycline in its non-protonated form seemed to rule the sorption of tetracycline.
Larvicidal activities against
Aedes aegypti have been determined in the ethanolic extracts obtained from 51 Brazilian medicinal plants. Eleven of the 84 extracts studied showed significant (LC
50
<
...100
μg
mL
−1) activities against larvae, with extracts from
Annona crassiflora (root bark, LC
50
=
0.71
μg
mL
−1; root wood, LC
50
=
8.94
μg
mL
−1) and
Annona glabra (seed, LC
50
=
0.06
μg
mL
−1) showing the highest activities. The results obtained should be of value in the search for new natural larvicidal compounds.
Biomass has great potential for the production of fuels with high volatility and reactivity. In the Amazon region, biomass waste is mainly from fruits, which generate a large amount of stone and ...shell. Therefore, there is a need for technology to advance the use of renewable energy. This study aims to evaluate the combustion properties of biomass waste by using thermogravimetric analysis (TG-DTG). Five residues were used: acai stone, cocoa shell, coconut shell, cupuacu shell and Brazil nut shell. TG curves show the mass loss from room temperature to 140 °C, which is related to the removal of moisture. The second mass loss is ascribed to volatile matter in the temperature range of 140–400 °C, and the third mass loss from 400 to 600 °C is due to the decomposition of fixed carbon. By evaluating the thermal properties such as volatile matter, moisture, ignition temperature and mean reactivity index, it can be said that the coconut shell sample has combustion features that lead to its better use as fuel, while the acai stone biomass presents unsatisfactory combustion properties among the biomasses studied. The higher heating value is an important property which defines the energy content and efficient use of these fuels, and thus, for the biomass samples, the following order of higher heating value can be observed: Brazil nut shell, acai stone, cupuacu shell, cocoa shell and coconut shell.
The exploration of unconventional hydrocarbons may be very effective in promoting economic development and confronting energy crisis around the world. However, the environmental risks associated with ...this practice might be an impediment if not adequately dimensioned. In this context, naturally occurring radioactive materials and ionizing radiation are sensitive aspects in the unconventional gas industry that may compromise the environmental sustainability of gas production and they should be properly monitored. This paper provides a radioecological assessment of the São Francisco Basin (Brazil) as part of an environmental baseline evaluation regarding the Brazilian potential for exploring its unconventional gas reserves. Eleven and thirteen samples of surface waters and groundwater were analyzed for gross alpha and beta using a gas flow proportional counter. A radiological background range was proposed using the ± 2 Median Absolute Deviation method. Using geoprocessing tools, the annual equivalent doses and lifetime cancer risk indexes were spatialized. Gross alpha and beta background thresholds in surface water ranged from 0.04–0.40 Bq L
−1
to 0.17–0.46 Bq L
−
, respectively. Groundwater radiological background varies from 0.006–0.81 Bq L
−1
to 0.06–0.72 Bq L
−1
for gross alpha and beta, respectively. All environmental indexes are relatively higher in the south of the basin, probably a direct response to the local volcanic formations. Traçadal fault and local gas seepages might also influence the gross alpha and beta distribution. All samples have radiological indexes below the environmental thresholds, and should remain at acceptable levels with the development of the unconventional gas industry in Brazil.
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