Influence of chemical and physical conditions in selection of Gluconacetobacter hansenii ATCC 23769 strains with high capacity to produce bacterial cellulose for application as sustained antimicrobial drug-release supports.

AIMS: Obtain varieties of Gluconacetobacter hansenii from original strain ATCC 23729 with greater efficiency to produce bacterial cellulose (BC) membrane with better dry mass yield for application as support of sustained antimicrobials' drug release. METHODS AND RESULTS: Application of different chemical and physical conditions (pH, temperature and UV light exposure) to obtain different G. hansenii varieties with high capacity to produce BC membranes. Characterization of the G. hansenii variants was performed by scanning electron microscopy (SEM) and optical microscopy of the colony-forming units. BC membrane produced was characterized by SEM, infrared spectroscopy and X-ray diffraction. The BC produced by variants isolated after incubation at 35°C showed elevated dry mass yield and high capacity of retention and sustained release of ceftriaxone antibiotic with the produced BC by original G. hansenii ATCC 23769 strain subjected to incubation at 28°C and with commercial BC. CONCLUSION: The application of different chemical and physical conditions constitutes an important method to obtain varieties of micro-organisms with dissimilar metabolism advantageous in relation to the original strain in the BC production. SIGNIFICANCE AND IMPACT OF THE STUDY: These results demonstrate the importance of in vivo studies for the application, in medicine, of BC membranes as support for antimicrobial-sustained release for the skin wound treatment.

A novel binuclear copper complex incorporating a nalidixic acid derivative displaying a one-dimensional coordination polymeric structure.

The identification of the antibacterial action of nalidixic acid (nx) was central to the development of the quinolone antibacterial compounds. The ability of the nx naphthyridyl ring to interact with and inhibit some proteins has encouraged the investigation of similar structures in the search for more active compounds with less adverse effects. The possibility of structural modification by attachment of other biologically active moieties to the naphthyridyl ring of nx allowed the development of new active antimicrobial molecules. Hydrazone derivatives of nx can be synthesized easily based on the condensation of the hydrazide derivative of nx with the desired aldehyde or ketone. Only a few complexes with nx hydrazone derivatives have been described but for none were the crystal structures elucidated. The synthesis of a new one-dimensional Cu(II) coordination polymer, namely catena-poly[[copper(II)-di-µ-chlorido-copper(II)-{µ-1-ethyl-N'-[(1H-imidazol-4-yl)methylidene]-7-methyl-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carbohydrazidato}-[dimethanolcopper(II)]-{µ-1-ethyl-N'-[(1H-imidazol-3-yl)methylidene]-7-methyl-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carbohydrazidato}] dichloride methanol tetrasolvate], {[Cu3(C16H15N6O2)2Cl2(CH3OH)2]Cl2·4CH3OH}n, with the (1H-imidazol-4-yl)methylidene carbohydrazide derivative of nalidixic acid (denoted h4imi), is presented and its structure is compared to the density functional theory (DFT) optimized structure of free h4imi. The title structure presents an octahedral Cu(II) ion on an inversion centre alternating along a polymer chain with a square-pyramidal Cu(II) ion, with the two Cu(II) centres bridged by two chloride ligands. Hydrogen bonds involving chloride counter-ions and methanol solvent molecules mediate the three-dimensional packing of the polymer. Comparison of the geometrical results from the structure analysis with those derived from a DFT study of the free ligand reveal the differences that arise upon coordination.

Effects of coordination mode of 2-mercaptothiazoline on reactivity of Au(I) compounds with thiols and sulfur-containing proteins.

Gold(I) based drugs are interesting for their potential medical use. The relatively facile ligand substitution in linear gold(I) compounds makes the identification of active species complicated. Ligands such as PR3 and CN- are likely to be carrier ligands due to their strong trans-directing properties and will dictate the nature of substitution reactions. The 2-mercaptothiazoline (mtz) ligand is an N,S-heterocyclic compound which presents an exocyclic thiol sulfur as well as a heterocyclic nitrogen. The coordination of mtz to transition metals can be modulated by the trans ligand and complexes with metal bound through the nitrogen and/or the exocyclic sulfur are known. Therefore, the complexes [NCAu(N-mtz)] (N-coordinated) and [(Ph3P)Au(S-mtz)] (S-coordinated) were investigated to compare the influence of CN- and PR3 as well as the coordination mode of the mtz ligand on reactivity with thiols and sulfur-containing proteins. As a further comparison the compound [(Ph3P)AuCN] was also studied. Human serum albumin, egg white lysozyme and, principally, the C-terminal zinc finger (ZF2) of the nucleocapsid NCp7protein of HIV-1 were studied. Results from zinc finger studies show that the coordination structure can determine the reactivity toward biomolecules. Due to ligand scrambling, the complex [NCAu(N-mtz)] forms very reactive species in solution generating [NCyAux-biomolecule] adducts, where x,y≤3. The observation by mass spectrometry of [(CN)Au]-ZF confirms the ability of Au(I) compounds to form [(Ligand)Au] adducts on zinc fingers, in contrast to Au(III), where all ligands are lost upon reaction with the zinc finger. On the other hand, [(Ph3P)Au(S-mtz)] also generates the [(Ph3P)2Au]+ species due to ligand scrambling, that showed lower reactivity, probably due to steric hindrance. For this complex [(Ph3P)Au-biomolecule] and [Au-biomolecule] adducts are dominant. The results corroborate the hypothesis of modulation through coordination as the reactivity clearly depends on not only the ligand, but also the coordination mode.