Soft nanotechnology: the potential of polyelectrolyte multilayers against E. coli adhesion to surfaces

Preprečevanje adhezije bakterij na površine je najbolj učinkovit način obvladovanja rasti biofilmov. Namen te raziskave je bil analizirati anti-adhezivni potencial 5 in 50 mmol/L polielektrolitskih plasti poli(alilamin hidroklorid)/poli(natrijev 4-stirensulfonat), poli(4-vinil-N-etilpiridin bromid/ poli(natrijev 4-stirensulfonat) in poli(4-vinil-N-izobutilpiridin bromid/ poli(natrijev 4-stirensulfonat) na bakterijo E. coli. Pet zaporednih plasti polielektrolitov je bilo sestavljenih na steklenih površinah in izpostavljenih bakterijski suspenziji. Rezultati kažejo, da 50 mmol/L poli(4-vinil-N-etilpiridin bromid/ poli(natrijev 4-stirensulfonat) najbolj učinkovito prepreči adhezijo bakterij 0,4 log bakt./mm2 (60 %), sledi mu poli(4- vinil-N-izobutilpiridin bromid/ poli(natrijev 4-stirensulfonat) 0,3 log bakt. mm-2 (47 %) in poli(alilamin hidroklorid)/ poli(natrijev 4-stirensulfonat) 0,2 log bakt. mm-2 (38 %). Ta raziskava dokazuje, da polieletrolitske plasti z kvartarne amino skupinami igrajo pomembno vlogo pri preprečevanju adhezije bakterij in zato predstavljajo pomembno uporabo v živilski in farmacevtski industriji ter v medicini.Preventing bacterial attachment to surfaces is the most efficient approach to controlling biofilm proliferation. The aim of this study was to compare anti-adhesion potentials of 5 and 50 mmol/L polyelectrolyte multilayers of poly(allylamine hydrochloride)/poly(sodium 4–styrenesulfonate), poly(4-vinyl-N-ethylpyridinium bromide)/ poly(sodium 4–styrenesulfonate), and poly(4-vinyl-N-isobutylpyridinium bromide)/poly(sodium 4–styrenesulfonate) against Escherichia coli. Glass surface was covered with five polyelectrolyte layers and exposed to bacterial suspensions. Poly(4-vinyl-N-ethylpyridinium bromide)/poly(sodium 4–styrenesulfonate) was the most effective against bacterial adhesion, having reduced it by 60 %, followed by poly(4-vinyl-N-isobutylpyridinium bromide)/poly(sodium 4– styrenesulfonate) (47 %), and poly(allylamine hydrochloride)/poly(sodium 4–styrenesulfonate) (38 %). Polyelectrolyte multilayers with quaternary amine groups have a significant anti-adhesion potential and could find their place in coatings for food, pharmaceutical, and medical industry

Polyelectrolyte Multilayers on Silica Surfaces: Effect of Ionic Strength and Sodium Salt Type

The formation of polyelectrolyte multilayers on silica surfaces was investigated in the presence of binary 1:1 sodium salts (NaCl, NaBr and NaNO3) at various salt concentrations. The build-up of multilayers was monitored using electrophoretic light scattering and quartz crystal microbalance with dissipation monitoring techniques. As cationic polyelectrolyte poly(diallyldimethylammonium chloride) was used and as anionic poly(sodium 4-styrene sulfonate). The counterion specific formation of multilayers was observed at higher electrolyte concentrations and the more pronounced influence was observed in the case of nitrate and bromide than in the case of chloride salt. These results confirm that solely by adjusting the appropriate ionic strength and by choosing the electrolyte type, polyelectrolyte multilayers with various properties and structure can be obtained. This work is licensed under a Creative Commons Attribution 4.0 International License

Chemistry in Education: From Temperature Changes to Reaction Enthalpies

Objašnjena je razlika i povezanost unutrašnje energije i entalpije sustava te su dani razlozi zašto se prilikom opisa energijskih promjena tijekom kemijskih reakcija primjenjuje promjena entalpije, a ne promjena unutrašnje energije. Detaljno su analizirane energijske promjene u sustavu i promjene fizikalnih svojstava sustava do kojih dolazi uslijed kemijske reakcije. Objašnjen je način određivanja reakcijske entalpije iz rezultata kalorimetrijskog pokusa. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.The relationship between internal energy and enthalpy was analysed, stating the reasons why the energy changes accompanying chemical reactions are usually characterized by enthalpy changes instead of internal energy changes. The changes within a system during the course of a chemical reaction were analysed in detail. The calculation of reaction enthalpy from the results of calorimetric measurements were explained. This work is licensed under a Creative Commons Attribution 4.0 International License

Complexation of Oxonium and Ammonium Ions by Lower-rim Calix[4]arene Amino Acid Derivatives

Complexation of oxonium and ammonium cations with two calix4arene amino acid derivatives, namely 5,11,17,23-tetra-tert-butyl-26,28,25,27-tetrakis-(O-methyl-D-α-phenylglycylcarbonylmethoxy)-calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-26,28,25,27-(O-methyl-L-leucylcarbonylmethoxy)calix[4]¬arene (2), in acetonitrile and methanol was studied by means of spectrophotometric and calorimetric titrations at 25 °C. The classical molecular dynamics simulations of the macrocycles and the corresponding complexes with NH4+ and H3O+ were carried out in order to investigate their possible structures in solution. The examined calix[4]arene derivatives were shown to be rather efficient binders for H3O+ cation and moderately efficient for NH4+ in acetonitrile, whereas the complexation of these cations in methanol could not be observed. The structures of the complexes obtained by means of molecular dynamics simulations suggested the involvement of ether and carbonyl oxygen atoms in the complexation of both NH4+ and H3O+. An inclusion of an acetonitrile molecule into the hydrophobic cavity of the free and complexed ligands was observed as well. The difference in binding affinities of 1 and 2 towards NH4+ and H3O+ ions could be explained by taking into account cation solvation, difference in their size and in the strength of hydrogen bonding between cations and the ligand binding sites. (doi: 10.5562/cca2172

Complexation of Alkali Metal Cations by a Tertiary Amide Calix[4]Arene Derivative in Strongly Cation Solvating Solvents

The complexation of alkali-metal cations with calix[4]arene tertiary amide derivative (L) was studied in N-methylformamide (NMF), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) by means of microcalorimetric and UV spectrophotometric titrations. The Gibbs energies, enthalpies, and entropies for transfer of reactants and products from N-methylformamide to other solvents were determined. Favorable enthalpic contribution to overall stability was found to be the most important for all complexation reactions, especially in the case of NaL+ formation, resulting in an affinity peak of L for this cation. The complexation entropy changes were always unfavorable. The ligand dissolution was endothermic in all solvents, accompanied by positive solution entropy. The highest complex stability constants were determined in NMF, whereas in DMSO the affinity of L towards alkali metal cations was the lowest. An interesting interplay between the transfer enthalpies and entropies of the reactants and complexes was revealed and discussed in detail. This work is licensed under a Creative Commons Attribution 4.0 International License

Synthesis of Fluorescent Diphenylanthracene-Based Calix[4]arene Derivatives and their Complexation with Alkali Metal Cations

Two novel fluorescent calix[4]arenes comprising diphenylanthracene moiety at the lower rim were synthetized and their complexation with alkali metal cations in acetonitrile/dichloromethane and methanol/dichloromethane mixtures (φ = 0.5) was studied experimentally and by classical molecular dynamics and quantum chemical calculations. The monosubstituted calixarene derivative (L1) proved to be a poor cation receptor, whereas the ester-based macrocycle (L2) exhibited rather high affinity towards lithium, sodium and potassium cations, particularly in MeCN/CH2Cl2. All complexation reactions were enthalpically controlled, whereby the overall stability was the largest in the case of sodium complex. The computational investigations provided an additional insight into the complexation properties and structures of complex species. The molecular dynamics simulations indicated the occurrence of inclusion of solvent molecules in the calixarene hydrophobic cavity of the free and complexed ligand, which was found to significantly affect the complexation equilibria. This work is licensed under a Creative Commons Attribution 4.0 International License

The Role of Triazole and Glucose Moieties in Alkali Metal Cation Complexation by Lower-Rim Tertiary-Amide Calix[4]arene Derivatives

The binding of alkali metal cations with two tertiary-amide lower-rim calix[4]arenes was studied in methanol, N,N-dimethylformamide, and acetonitrile in order to explore the role of triazole and glucose functionalities in the coordination reactions. The standard thermodynamic complexation parameters were determined microcalorimetrically and spectrophotometrically. On the basis of receptor dissolution enthalpies and the literature data, the enthalpies for transfer of reactants and products between the solvents were calculated. The solvent inclusion within a calixarene hydrophobic basket was explored by means of 1H NMR spectroscopy. Classical molecular dynamics of the calixarene ligands and their complexes were carried out as well. The affinity of receptors for cations in methanol and N,N-dimethylformamide was quite similar, irrespective of whether they contained glucose subunits or not. This indicated that sugar moieties did not participate or influence the cation binding. All studied reactions were enthalpically controlled. The peak affinity of receptors for sodium cation was noticed in all complexation media. The complex stabilities were the highest in acetonitrile, followed by methanol and N,N-dimethylformamide. The solubilities of receptors were greatly affected by the presence of sugar subunits. The medium effect on the affinities of calixarene derivatives towards cations was thoroughly discussed regarding the structural properties and solvation abilities of the investigated solvents