Antifouling zwitterionic pSBMA‐MSN particles for biomedical applications

Mesoporous silica nanoparticles (MSNs) are one of the most promising nanocarriers in biomedicine. Nonetheless, surface modification has been pointed out as a condition necessary for drug delivery applications, where stability and biocompatibility are extremely important for the vehicle performance. Likewise, zwitterionic polymers are outstanding candidates in biological fields, where poly(sulfobetaine methacrylate) (pSBMA) has been widely studied. These polymers, known as antifouling materials, are able to render a surface capacity to avoid protein adhesion. In this work, a core‐shell nanocarrier was created, where pSBMA was covalently grafted by atom transfer radical polymerization (ATRP) onto a previously functionalized MSN surface. Brush morphologies with different chain lengths ( , between 6500 and 32 300) and graft densities (σ_pSBMA, between 0.15 and 0.51 molecules of pSBMA per nm² of MSN) were obtained. Protein adhesion resistance was evaluated with two proteins: fibronectin (FN) and bovine serum albumin (BSA). The best nanocarrier synthesized allowed a reduction of 96% of FN and 76% of BSA adhesion (compared with an adsorption of 100% assigned to the native material). Since the influence of the brush morphology is seldom studied or reported, this work aims to comprehend how the configuration of the polymer brushes affected their antifouling capacity, in order to use this pSBMA‐MSN product for biomedical applications, notably as a possible drug delivery nanocarrier. Future work will analyze the solution behavior of the zwitterionic brushes to evaluate variations of temperature and pH values as possible mechanisms of delivery.     

Solar Water Disinfection to Produce Safe Drinking Water: A Review of Parameters,Enhancements, and Modelling Approaches to Make SODIS Faster and Safer

Solar water disinfection (SODIS) is one the cheapest and most suitable treatments to produce safe drinking water at the household level in resource-poor settings. This review introduces the main parameters that influence the SODIS process and how new enhancements and modelling approaches can overcome some of the current drawbacks that limit its widespread adoption. Increasing the container volume can decrease the recontamination risk caused by handling several 2 L bottles. Using container materials other than polyethylene terephthalate (PET) significantly increases the efficiency of inactivation of viruses and protozoa. In addition, an overestimation of the solar exposure time is usually recommended since the process success is often influenced by many factors beyond the control of the SODIS-user. The development of accurate kinetic models is crucial for ensuring the production of safe drinking water. This work attempts to review the relevant knowledge about the impact of the SODIS variables and the techniques used to develop kinetic models described in the literature. In addition to the type and concentration of pathogens in the untreated water, an ideal kinetic model should consider all critical factors affecting the efficiency of the process, such as intensity, spectral distribution of the solar radiation, container-wall transmission spectra, ageing of the SODIS reactor material, and chemical composition of the water, since the substances in the water can play a critical role as radiation attenuators and/or sensitisers triggering the inactivation process.     

Chemical composition and in vitro antibacterial and antiproliferative activities of the essential oil from the leaves of Psidium myrtoides O. Berg (Myrtaceae)

In this study, the chemical composition and antibacterial and antiproliferative potential of the essential oil obtained from fresh leaves of Psidium myrtoides (PM-EO) against oral pathogens and human tumour cell lines were investigated for the first time. GC-FID and GC-MS analyses showed that trans-β-caryophyllene (30.9%), α-humulene (15.9%), α-copaene (7.8%), caryophyllene oxide (7.3%) and α-bisabolol (5.3%) are the major constituents of PM-EO. The antibacterial activity of PM-EO against a panel of oral pathogens was investigated in terms of their minimal inhibitory concentrations (MIC) using the broth microdilution method. PM-EO displayed moderate activity against Streptococcus mitis (MIC = 100 μg/mL), S. sanguinis (MIC = 100 μg/mL), S. sobrinus (MIC = 250 μg/mL), and S. salivarius (MIC = 250 μg/mL), and strong activity against S. mutans (MIC = 62.5 μg/mL). The antiproliferative activity in normal (GM07492A, lung fibroblasts) and tumour cell lines (MCF-7, HeLa, and M059 J) was performed using the XTT assay. PM-EO showed 50% inhibition of normal cell growth at 359.8 ± 6.3 μg/mL. Antiproliferative activity was observed against human tumour cell lines, with IC₅₀ values significantly lower than that obtained for the normal cell line, demonstrating IC₅₀ values for MCF-7 cells (254.5 ± 1.6 μg/mL), HeLa cells (324.2 ± 41.4 μg/mL) and M059 J cells (289.3 ± 10.9 μg/mL). Therefore, the cytotoxicity of PM-EO had little influence on the antibacterial effect, since it showed antibacterial activity at lower concentrations. Our results suggest that PM-EO is a promising source of new antibacterial and antitumour agents.     

What to sacrifice? Fusions of cofactor regenerating enzymes with Baeyer-Villiger monooxygenases and alcohol dehydrogenases for self-sufficient redox biocatalysis

A collection of fusion biocatalysts has been generated that can be used for self-sufficient oxygenations or ketone reductions. These biocatalysts were created by fusing a Baeyer-Villiger monooxygenase (cyclohexanone monooxygenase from Thermocrispum municipale: TmCHMO) or an alcohol dehydrogenase (alcohol dehydrogenase from Lactobacillus brevis: LbADH) with three different cofactor regeneration enzymes (formate dehydrogenase from Burkholderia stabilis: BsFDH; glucose dehydrogenase from Sulfolobus tokodaii: StGDH, and phosphite dehydrogenase from Pseudomonas stutzeri: PsPTDH). Their tolerance against various organic solvents, including a deep eutectic solvent, and their activity and selectivity with a variety of substrates have been studied. Excellent conversions and enantioselectivities were obtained, demonstrating that these engineered fusion enzymes can be used as biocatalysts for the synthesis of (chiral) valuable compounds.     

Violacein/β-Cyclodextrin Inclusion Complex Formation Studied by Measurements of Diffusion Coefficient and Circular Dichroism

The formation of inclusion compounds between violacein and-cyclodextrin was studied by diffusion and circulardichroism measurements. The present work was undertaken to explore the feasibilityof the -cyclodextrin in reducing the toxicity and enhancing the antitumoral efficacy ofviolacein by forming an inclusion complex. The results of the two experimentsare in good agreement, suggesting the formation of 1 : 1 and 1 : 2 complexes.The diffusion coefficient measurements enabled estimates of the sizes of the complexesinvolved. From the circular dichroism and computational calculations it was possibleto view a preference for inclusion of the most polar part of the molecule to form a1 : 2 inclusion complex. We expect that this work proves the potential of thesetechniques to determining complex stoichiometry.     

Purification of the seven tetranortriterpenoids in neem (Azadirachta indica) seed by counter-current chromatography sequentially followed by isocratic preparative reversed-phase high-performance liquid chromatography

Counter-current chromatography (CCC) sequentially followed by isocratic preparative reversed-phase high-performance liquid chromatography was used to isolate the seven bio-actives (azadirachtin A, azadirachtin B, azadirachtin H, desacetylnimbin, desacetylsalannin, nimbin and salannin) from the seed concentrate (NSC) of the neem tree (Azadirachta indica A. Juss). Reproducible, narrow polarity range, high purity fractions were obtained from repeated injections of the NSC (700 mg loadings/injection), on to a relatively small volume CCC coil (116 mL). The CCC biphasic solvent system chosen was hexane:butanol:methanol:water (1:0.9:1:0.9, v/v). A mass balance of injected material showed that 95+% were recovered.     

A water-soluble perylene dye functionalised with a 17β-estradiol: a new fluorescent tool for steroid hormones

We have successfully been able to synthesise a specific estrogen receptor-directed biolabel based on a fluorescent water-soluble perylenebisimide, thus offering great potential for determining the presence of estrogen receptors in any kind of cell. Moreover, this synthetic strategy allows the preparation of other conjugates involved in the study of any kind of receptor, simply by selecting the appropriate agonist or antagonist.     

Asymptotic behaviour of a closed‐loop thermosyphon with linear friction and viscoelastic binary fluid

Viscoelastic fluids represent a major challenge both from an engineering and from a mathematical point of view. Recently, we have shown that viscoelasticity induces chaos in closed‐loop thermosyphons even when we consider binary fluids, this is, when we consider a solute in the fluid, as water and antifreezes, for example. In this work, we consider a linear friction law, and we show that in this case with the addition of a solute to the fluid we can prove, under some conditions, chaotic asymptotic behavior for suitable geometry of the circuit and heat flux or ambient temperature functions.     

Inhibition of Candida albicans CC biofilms formation in polystyrene plate surfaces by biosurfactant produced by Trichosporon montevideense CLOA72

This study evaluated the effects of glycolipid-type biosurfactant produced by Trichosporon montevideense CLOA72 in the formation of biofilms in polystyrene plate surfaces by Candida albicans CC isolated from the apical tooth canal. Biofilm formation was reduced up to 87.4% with use of biosurfactant at 16 mg/ml concentration. It has been suggested that the interaction with the cell or polystyrene plate surface could ultimately be responsible for these actions. Therefore, the interaction of C. albicans CC cells with the biosurfactant, as well as the corresponding thermodynamic parameters, have been determined by isothermal titration calorimetry and zeta potential measurements. This process is endothermic (((int)H°=+1284±5 cal/mg OD(600)) occurring with a high increase of entropy (T((int)S°=+10635 cal/mg OD(600)). The caloric energy rate data released during the titulation indicates saturation of the cell-biosurfactant at 1.28 mg/ml OD(600). Also, the zeta potential of the cell surface was monitored as a function of the biosurfactant concentration added to cell suspension showing partial neutralization of net surface charge, since the value of zeta potential ranged from -16 mV to -6 mV during the titration. The changes of cell surface characteristics can contribute to the inhibition of initial adherence of cells of C. albicans in surface. The CMC of the purified biosurfactant produced from T. montevideense CLOA72 is 2.2 mg/ml, as determined both by ITC dilution experiments and by surface tension measurements. This biomolecule did not presented any cytotoxic effect in HEK 293A cell line at concentrations of 0.25-1 mg/ml. This study suggests a possible application of the referred biosurfactant in inhibiting the formation of biofilms on plastic surfaces by C. albicans.     

How reliable are extrapolations to infinite dilution of partial molar properties using Redlich–Kister fittings?

An explicit method for uncertainty estimation associated with excess partial molar properties at infinite dilution calculated using standard uncertainties of Redlich–Kister parameters, fitted to data over the whole composition range, is presented for the first time. The application of this method to sets of accurate volumetric experimental data for aqueous water + ethanol binary mixtures, experimentally determined by different authors is made and the results are compared. A refinement of this method is also presented when, in very-diluted regions, Redlich–Kister lines deviate from experimental points more than their standard uncertainties. The procedure of uncertainty calculation is based on the Guide to the Expression of Uncertainty in Measurements (GUM).