Self-Assembly and Electrical Conductivity of a New [1]benzothieno[3,2-b][1]-benzothiophene (BTBT)-Peptide Hydrogel.

The conjugation of small-molecule semiconductors with self-assembling peptides is a powerful tool for the fabrication of supramolecular soft materials for organic electronics and bioelectronics. Herein, we introduced the benchmark organic semiconductor [1]benzothieno[3,2-b][1]-benzothiophene (BTBT) within the structure of a self-assembling amphipathic peptide. The molecular structure of the conjugate was rationally designed to favour π-π stacking between BTBT cores and π-delocalization within the self-assembled architectures. Hydrogels with fibrillar structure were obtained upon self-assembly. Spectroscopic studies confirmed that both hydrogen bonding between peptide segments and π-π stacking between BTBT chromophores are responsible for the formation of the 3D fibrillar network observed by transmission electron microscopy. The hydrogel was successfully deposited on gold interdigitated electrodes and a conductivity up to 1.6 (±0.1) × 10-5 S cm-1 was measured.

Insecticidal activity in vitro of the essential oil of Pogostemon cablin against Ctenocephalides felis felis.

The aim of this study was to evaluate the in vitro insecticidal activity of the essential oil (EO) of P. cablin against immature and adult stages of C. felis. The chemical composition of P. cablin EO was determined by gas chromatography (GC). To evaluate the insecticidal activity, the egg, larva, pupa, and adult stages of C. felis were exposed to different concentrations of P. cablin EO diluted in acetone and impregnated in filter paper in a concentration range of 25 to 200 µg.cm-2. After exposure, the material was incubated in climatized chambers and mortality assessment was performed after 24 h for the larval and adult stages, 72 h for the egg stage and 15 days for the pupal stage. After GC analysis, the major constituents of the EO of P. cablin were found to be patchoulol (27.4%), α-bulnesene (19.7%) and α-guayene (15.0%). The of mortality percentage was 100% at the concentration of 200 µg.cm-2 for all stages. The LCs50 values were 46.1, 49.2, 60.6 and 62.7 µg.cm-2, respectively for the pupal, egg, larva and adult stages. Based on the results obtained, we can conclude that the EO of P. cablin contained patchoulol, α-bulnesene, and α-guayene as major constituents and had insecticidal activity against the immature and adult stages of C. felis.

O objetivo deste estudo foi avaliar a atividade inseticida in vitro do óleo essencial (OE) de Pogostemon cablin frente estágios imaturos e adultos de Ctenocephalides felis. A composição química do OE de P. cablin foi determinada por cromatografia gasosa (CG). Para a avaliação da atividade inseticida os estágios de ovo, larva, pupa e adultos de C. felis foram expostos a diferentes concentrações do OE de P. cablin diluídos em acetona e impregnados em papel filtro com a faixa de concentração de 25 a 200 µg.cm-2. Após a exposição, o material foi incubado em câmaras climatizadas e a avaliação da mortalidade foi realizada após 24 h para os estágios de larvas e adultos, 72 h para o estágio de ovo e 15 dias para o estágio de pupa. Após análise cromatográfica, os constituintes majoritários para o OE de P. cablin foram: patchoulol (27,4%), α-bulneseno (19,7%) e α-guaieno (15%). Foi obtido 100% de mortalidade na concentração de 200 µg.cm-2 para todos os estágios. As CLs50 foram de 46,1; 49,2; 60,6 e 62,7 µg.cm-2, respectivamente para os estágios de pupa, ovo, larva e adultos. Com base nos resultados obtidos é possível concluir que o OE de P. cablin apresentou o patchoulol, α-bulneseno, e α-guaieno como constituintes majoritários e atividade inseticida frente aos estágios imaturos e adultos de C. felis.

A Peptide-Based Hydrogel for Adsorption of Dyes and Pharmaceuticals in Water Remediation.

The removal of dyes and pharmaceuticals from water has become a major issue in recent years due to the shortage of freshwater resources. The adsorption of these pollutants through nontoxic, easy-to-make, and environmentally friendly adsorbents has become a popular topic. In this work, a tetrapeptide-pyrene conjugate was rationally designed to form hydrogels under controlled acidic conditions. The hydrogels were thoroughly characterized, and their performance in the adsorption of various dyes and pharmaceuticals from water was investigated. The supramolecular hydrogel efficiently adsorbed methylene blue (MB) and diclofenac (DCF) from water. The effect of concentration in the adsorption efficiency was studied, and results indicated that while the adsorption of MB is governed by the availability of adsorption sites, in the case of DCF, concentration is the driving force of the process. In the case of MB, the nature of the dye-hydrogel interactions and the mechanism of the adsorption process were investigated through UV-Vis absorption spectroscopy. The studies proved how this dye is first adsorbed as a monomer, probably through electrostatic interactions; successively, at increasing concentrations as the electrostatic adsorption sites are depleted, dimerization on the hydrogel surface occurs.

Mathematical modelling of the use of insecticide-treated nets for elimination of visceral leishmaniasis in Bihar, India.

Visceral leishmaniasis (VL) is a deadly neglected tropical disease caused by a parasite Leishmania donovani and spread by female sand flies Phlebotomus argentipes. There is conflicting evidence regarding the role of insecticide-treated nets (ITNs) on the prevention of VL. Numerous studies demonstrated the effectiveness of ITNs. However, KalaNet, a large trial in Nepal and India did not support those findings. The purpose of this paper is to gain insight into the situation by mathematical modelling. We expand a mathematical model of VL transmission based on the KalaNet trial and incorporate the use of ITNs explicitly into the model. One of the major contributions of this work is that we calibrate the model based on the available epidemiological data, generally independent of the KalaNet trial. We validate the model on data collected during the KalaNet trial. We conclude that in order to eliminate VL, the ITN usage would have to stay above 96%. This is higher than the 91% ITNs use at the end of the trial which may explain why the trial did not show a positive effect from ITNs. At the same time, our model indicates that asymptomatic individuals play a crucial role in VL transmission.

Metal Cation Triggered Peptide Hydrogels and Their Application in Food Freshness Monitoring and Dye Adsorption.

Metal-ligand interactions have emerged as an important tool to trigger and modulate self-assembly, and to tune the properties of the final supramolecular materials. Herein, we report the metal-cation induced self-assembly of a pyrene-peptide conjugate to form hydrogels. The peptide has been rationally designed to favor the formation of ß-sheet 1D assemblies and metal coordination through the Glu side chains. We studied in detail the self-assembly process in the presence of H+, Li+, Na+, K+, Ca2+, Ni2+, Cu2+, Zn2+, Cd2+, Co2+, Fe3+, and Cr3+ and found that the morphology and mechanical properties of the hydrogels are ion-dependent. Moreover, thanks to the presence of the metal, new applications could be explored. Cu2+ metallogels could be used for amine sensing and meat freshness monitoring, while Zn2+ metallogels showed good selectivity for cationic dye adsorption and separation.

Graphene-Based Scaffolds for Regenerative Medicine.

Leading-edge regenerative medicine can take advantage of improved knowledge of key roles played, both in stem cell fate determination and in cell growth/differentiation, by mechano-transduction and other physicochemical stimuli from the tissue environment. This prompted advanced nanomaterials research to provide tissue engineers with next-generation scaffolds consisting of smart nanocomposites and/or hydrogels with nanofillers, where balanced combinations of specific matrices and nanomaterials can mediate and finely tune such stimuli and cues. In this review, we focus on graphene-based nanomaterials as, in addition to modulating nanotopography, elastic modulus and viscoelastic features of the scaffold, they can also regulate its conductivity. This feature is crucial to the determination and differentiation of some cell lineages and is of special interest to neural regenerative medicine. Hereafter we depict relevant properties of such nanofillers, illustrate how problems related to their eventual cytotoxicity are solved via enhanced synthesis, purification and derivatization protocols, and finally provide examples of successful applications in regenerative medicine on a number of tissues.