An in vitro test of the efficacy of silver-containing wound dressings against Staphylococcus aureus and Pseudomonas aeruginosa in simulated wound fluid

An isothermal microcalorimetric assay was used to quantify the efficacy of a silver-containing wound dressing against two common wound pathogens, Pseudomonas aeruginosa and Staphylococcus aureus. The growth patterns of the two species were unique and varied depending on the environment in which the organisms were grown. Addition of non-silver-containing dressing altered the growth kinetics while addition of silver (contained either in a dressing or as AgNO3 solution) was seen to elicit inhibition and/or kill depending on concentration. Tests were conducted in nutrient broth and simulated wound fluid. It was found that minimum inhibitory and minimum bactericidal concentration values were higher in simulated wound fluid and under anaerobic conditions. Bioavailability of silver from the wound dressing was 35% against S. aureus in nutrient broth and 68% against both species in simulated wound fluid. The data highlight the importance of developing and conducting in vitro assays in biorelevant media

An acrylic ampoule represents a denture surface in a microcalorimetric biofilm problem

An acrylic microcalorimetric ampoule with inserts represented a denture surface in a Streptococcus mutans biofilm study. The biofilm of micro-organisms did not contain as many micro-organisms as those previously studied in planktonic suspension. A more sensitive microcalorimeter (Thermometric's thermal activity monitor) was required to detect the metabolism of S. mutans adhered to an engineered acrylic flow-through ampoule. Biofilm heat outputs were obtained in the acrylic ampoule following standardized procedures with cryopreserved aliquots of a homogeneous suspension of S. mutans

QSAR based on biological microcalorimetry - The interaction of Saccharomyces cerivisiae with hydrazides (vol 328, pg 91, 1999)

Calorimetry has been used as a rapid method for the determination of bioactivity. Some previous studies have been concerned with its applicability to derive structure activity relationships (SARs), which can in turn guide the synthetic chemisty through the synthesis of new chemical entities with improved antimicrobial potencies. However, earlier studies do not point out the use and importance of calorimetry in deriving quantitative structure activity relationships (QSARs), a field where it is possible not only to get information on SARs, but insight into modes of action can also be envisaged. In this paper we describe a QSAR based on biological microcalorimetry for a set of antimicrobial hydrazides acting against Saccharomyces cerivisiae. Results show that an extrathermodynamic relationship can be drawn based upon microcalorimetrically measured biopotencies and partitioning (log PTA) using the same cell system

The importance of chain-length on the wettability and solubility of organic homologs

The solubilities of an homologous series of compounds (alkyl p-hydroxybenzoates) were measured in hexane and water at 298 K. The hexane solubilities followed a trend that could be predicted by the melting points, but the aqueous solubilities showed a linear decrease with increasing alkyl chain length, until the chain was over 4 carbon units long, then the effect of adding extra methylene groups was significantly lower. With both solvents the effect on solubility was small after the chain exceeded 5 (+/- 1) carbon units in length. This phenomenon is explained on the basis that the side chain has greater rotational freedom about C-C bonds as it extends beyond five carbons. The freedom of movement will potentially influence the crystal packing (due to the increased possibility for different orientations and conformations) and hence the hexane solubility results, and the orientation of the molecules that are to be dispersed in the solvent (thus the aqueous solubility). Chain lengths of 2-5 showed no significant variation in aqueous contact angle for the powders. The contact angle did increase slightly above a chain length of 6 carbons. The results indicate that the crystal packing is influenced by chain length and that for chain lengths up to five carbons, the chain is not all present in the crystal surface (no increase in contact angles). For wettability and solubility there is a critical point at a chain length of 5 (+/- 1) carbons where the physical properties of the alkyl p-hydroxybenzoates change. Although molecular structure affects both solubility and wettability, there is no direct correlation between these two properties, wettability of the powder being influenced only by the proportions of chemical groupings that are present at the surface of the crystal

Thermochemical investigation of possible interactions between urea and some sparingly soluble solutes in aqueous solution

The interaction of alkyl-p-hydroxybenzoates and of beta-phenylalanine with urea in dilute aqueous solution which has been proposed by some workers, has been investigated by microcalorimetry. The derived enthalpies are all less than -50 J mol(-1) and hence are too small to be considered as describing specific interactions between urea and the study solutes. Furthermore a linear relationship is shown to exist for a wide variety of compounds, including the study solutes, between solute size (surface area and molecular or van der Waals' volume) and Delta(trs) G, the Gibbs function for solute transfer from water to aqueous urea solution. Both these findings support the view that the effect of urea upon these solutes' aqueous solubility is an entropically controlled bulk solvent process rather than specific complex formation between urea and solute. The results are discussed in the light of recent models of the hydrophobic effect which propose displacement by urea of water solvation molecules in the solute's hydration shell

Taylor-Aris Diffusion Studies of Solute-Polymer Interactions. 1. Alkyl p-Hydroxybenzoates with an ABA Block Copolymer (Poloxamer P407) in Aqueous Solution

This paper describes the application of the Taylor-Aris dispersion technique to the study of the diffusion of an homologous series of alkyl p-hydroxybenzoates in aqueous solutions of an ABA block copolymer, Poloxamer P407. The fraction of polymer incorporated solute was calculated after correction of the diffusion coefficients for polymer obstructional effects. These fractions increase along the homologous series allowing the use of a group contribution approach to evaluate the increment in the Gibbs function per methylene group for the incorporation process. The value obtained, -1.9 kJ mol(-1), reveals that the solubilization sites provided by the polymer aggregates are similar to those reported for micelles of low molar mass surfactants. The nature of the possible interactions between these solutes and the polymer micelles is also discussed

Different immunomodulator regulated patterns of effector-target cell-interactions - a novel application of microcalorimetry

Microcalorimetric studies of target/effector cell interactions are reported. Significant changes in the observed thermal profiles are seen upon pre-incubation of the effector cells with chemical immunomodulators. The results of these latter studies indicate that the microcalorimetric technique can reveal differences in the modes of action of different groups of immunomodulators. It is proposed that the technique can be used to screen drug activities and, following further analytical work, to contribute to an understanding of modes of action

The Synthesis of Chiral Dendritic Molecules Based on the Repeat Unit L-Glutamic Acid

The convenient synthesis of a glutamate based dendrimeric molecule is reported. This chiral unsymmetrical dendrimer, contains 15 chiral centres an with identical configurations (L)

An Approach for the Rapid Synthesis of Moderately sized Dendritic Macromolecules

A general method for the synthesis of a dendrimeric series with homologous terminal groups is described. FABMS measurements confirm the molecular mass of the reported dendrimers. The result of size exclusion chromatographic (SEC) analysis correlates well with the relative molecular mass (RMM) of the early members of the series. However, deviations in measurements of molecular mass by SEC and FABMS begin to appear for larger members of the series, suggesting a more spherical conformation when the terminal group exceeds propyl