Fabrication of electrospun fibers from a waterborne soy-based polyurethane employing polyethylene oxide as a coformer

The fabrication of electrospun fibers made from aqueous dispersions of polyurethane obtained from renewable sources is an eco-friendly method to produce porous membranes for different applications. Polyethylene oxide (PEO) has been already employed in formulations for allowing fiber formation, but its role was not yet completely understood. In this work the fabrication of electrospun fibers made from biobased polyurethane aqueous dispersion with PEO in order to obtain regular fibers is performed. The role of PEO was studied by thermal analysis, infrared and Raman spectroscopy, rheology, and fiber morphology. Polyurethane fibers were obtained only when PEO was added, otherwise the dispersion is electrosprayed and particles are formed. It was observed that PEO modifies the rheology of dispersion and assists coalescence of polyurethane particles. On the other hand, polyurethane fibers conserved their diameter and their homogeneous structure after removal of PEO by immersion in water, which indicates that the distribution of both polymers was even within the fibers. This work provides both an insight on the role of PEO and a route for the fabrication of eco-friendly biobased polyurethane microfibers from aqueous dispersions.     

Direct,Late-Stage Mono-N-arylation of Pentamidine: Method Development,Mechanistic Insight,and Expedient Access to Novel Antiparastitics against Diamidine-Resistant Parasites

A selective mono-N-arylation strategy of amidines under Chan-Lam conditions is described. During the reaction optimization phase, the isolation of a mononuclear Cu(II) complex provided unique mechanistic insight into the operation of Chan-Lam mono-N-arylation. The scope of the process is demonstrated, and then applied to access the first mono-N-arylated analogues of pentamidine. Sub-micromolar activity against kinetoplastid parasites was observed for several analogues with no cross-resistance in pentamidine and diminazene-resistant trypanosome strains and against Leishmania mexicana. A fluorescent mono-N-arylated pentamidine analogue revealed rapid cellular uptake, accumulating in parasite nuclei and the kinetoplasts. The DNA binding capability of the mono-N-arylated pentamidine series was confirmed by UV-melt measurements using AT-rich DNA. This work highlights the potential to use Chan-Lam mono-N-arylation to develop therapeutic leads against diamidine-resistant trypanosomiasis and leishmaniasis.     

Elucidating the interactions between carbon nanotubes and carbon black with styrene butadiene rubber

The reinforcement mechanism of carbon nanotubes (CNT) on styrene butadiene rubber is studied through dynamic and swelling tests. Compounds containing carbon black (CB) and an unfilled one were prepared for comparison purposes. The dynamic properties are interpreted through the Maier-Göritz model to distinguish the contributions of stable and unstable crosslinks to the storage modulus, finding that the unstable ones become more relevant in samples containing a CNT concentration higher than 5 phr. In addition, the crosslinks density estimated by swelling and the stable contribution obtained with dynamical properties present the same tendency with the CNT amount. The former presents lower values, which can be explained considering that only stable crosslinks remain in the equilibrium-swollen state, while in the second one both stable and unstable are considered. In addition, differences in the filler-polymer interaction mechanisms are observed according to the morphology and aspect ratio of CNT in contrast to CB.     

The sanitizing action of essential oil-based solutions against Salmonella enterica serotype Enteritidis S64 biofilm formation on AISI 304 stainless steel

Bacterial adhesion and biofilm formation by Salmonella enterica serovar Enteritidis is a serious concern in the food processing industry; organism persistence in biofilms represents a continual source of contamination. Due to unsuccessful disinfection processes and emerging resistance, conventional control methods are rapidly becoming ineffective, necessitating the development of new control strategies. The following study evaluated the anti-biofilm effect of disinfectant solutions formulated with essential oils (EOs) of peppermint (Mentha piperita) and lemongrass (Cymbopogon citratus) against biofilm formation by S. enterica serotype Enteritidis S64 on stainless steel surface AISI 304 (#4) after 10, 20 and 40 min of contact. A minimum inhibitory concentration (MIC) of 7.8 μL/mL was found for both EOs and disinfectant solutions were formulated based on these MIC values. Ten minutes of sanitizing solution contact significantly reduced (p ≤ 0.05) adhered bacterial populations for both EOs tested. After 20 and 40 min of treatment, cell counts were not detected. Thus, M. piperita and C. citratus EOs can be considered convenient, quality alternatives to the application of conventional sanitizing agents in the food industry; further, use of these EOs addresses the increasing consumer demand for natural products.