Large molecules as anti-adhesive compounds against pathogens.

Anti-adhesive compounds are potential prophylactic tools in alternative treatment regimes against bacterial infection, as bacterial adhesion is commonly mediated by carbohydrate-protein interactions between surface adhesions of microorganisms and the host cell. The use of exogenous polyvalent, high-molecular carbohydrates and tannin-like plant-derived compounds should antagonize the adhesive interaction. A range of carbohydrates and carbohydrate- and proanthocyanidin-enriched plant extracts were screened for potential anti-adhesive effects against Helicobacter pylori, Campylobacter jejuni, Porphyromonas gingivalis and Candida albicans in different in-situ assays on primary tissue. The adhesion of H. pylori on human stomach tissue was effectively blocked by glucuronic acid-enriched polysaccharides from immature okra fruits (Abelmoschus esculentus). These compounds also had strong in-vitro effects against C. jejuni (inhibition up to 80%), but were ineffective in an in-vivo study in infected chicken broilers due to metabolism in the gastrointestinal system. Polysaccharides from Glycyrrhizia glabra, also enriched with glucuronic acid, showed strong anti-adhesive properties against H. pylori and P. gingivalis (inhibition 60-70%). Pelargonium sidoides extract, containing mainly polymeric proanthocyanidins, was effective against H. pylori in a dose-dependent manner. Due to the multifunctional adhesive strategy of C. albicans, no effective compounds were detected against this yeast. Structure-activity relationships are presented and the potential in-vivo use of carbohydrate-based anti-adhesives is discussed.

DNA acts as a nucleation site for transient cavitation in the ultrasonic nebulizer.

Several new technologies based upon ultrasound technology have been proposed as a method to enhance the delivery of genetic therapeutics. Using ultrasonic nebulization and a well-established method to quantitatively monitor transient cavitation, this study investigates the extent and factors influencing the degradation of DNA. Results from our studies show that the presence of DNA greatly enhances cavitation, and that the number of transient cavitation events also increases with the hydrodynamic diameter and number of DNA molecules in solution. More importantly, removing saturated gases from the plasmid DNA solutions resulted in a decrease in transient cavitation events but not degradation rate, suggesting that the cavitation event responsible for degradation occurs locally at the DNA molecule. Finally, complexing plasmid DNA with the cationic polymer polyethylenimine protected the native structure by reducing the molecule's potential to act as a heterogeneous nucleation site for transient cavitation.

High molecular weight polysaccharides from black currant seeds inhibit adhesion of Helicobacter pylori to human gastric mucosa.

Several crude and purified polysaccharides from black currant seeds (Ribes nigrum L.) have been isolated, analysed and examined on their effects against Helicobacter pylori in in situ adhesion studies on sections of human gastric mucosa. After pre-treatment of Helicobacter pylori with 0.01 to 0.1 % solutions of the isolated raw polysaccharide (RPS), the epithelial binding of the bacteria was considerably reduced in a concentration-dependent manner, as compared with a non-treated control suspension. Preincubation of the mucosal sections with 0.1 % solutions did not result in a reduced binding of non-treated bacteria. An anion-exchange fraction of RPS eluted with 0.1 M phosphate buffer exhibited a comparable, concentration-dependent reduction of adhesion, whereas the water-eluted fraction was ineffective at the respective concentrations. Both subfractions consisted of similar 1,3-linked galactans, decorated with side chains possessing 1,4-galacturonic acid, galactose and arabinose residues. Molecular weight profiling by GPC revealed that the antiadhesive activity of the buffer eluate correlated with high molecular weight components ranging from about 1000 Da to 340 kDa, whereas the ones of the inactive water eluate had molecular weights of about 100 and 25 kDa, respectively. None of the active fractions revealed inhibitory effects on bacterial growth in vitro. We conclude that acidic, high molecular weight galactans are responsible for the antiadhesive qualities of black currant seed extracts and that these polymers are able to block Helicobacter surface receptors, thus inhibiting their interaction with specific binding factors located on human gastric epithelia.

Dissolution and partitioning behavior of hydrophobic ion-paired compounds.

PURPOSE: This study was conducted to determine the effects of counterion hydrophobicity on organic/aqueous partition coefficients for hydrophobic ion paired (HIP) complexes. Furthermore, the coupled dissolution and reverse ion-exchange kinetics for dissolution of HIP complexes into aqueous electrolyte solutions were measured and mathematically modeled. METHODS: HIP complexes of model drugs tacrine and l-phenylephrine were formed using linear sodium alkylsulfates and bis (2-ethylhexyl sodium sulfosuccinate). Equilibrium partition coefficients between chloroform and aqueous solutions for the complexes and the kinetics of dissolution of the complexes in buffered aqueous solutions were measured. RESULTS: The chloroform/aqueous partition coefficients for l-phenylephrine/bis (2-ethylhexyl sodium sulfosuccinate) complexes decrease with increasing molar surface tension increment of salts added to the aqueous solution. The logarithm of the partition coefficient for a homologous series of alkyl sulfate complexes decreases as the hydrophilic-lipophilic balance number increases. Dissolution of HIP complexes in deionized water shows first order kinetics, whereas dissolution in aqueous electrolyte solutions shows biphasic kinetics. A kinetic model explains these dissolution rates. CONCLUSIONS: Solubility and dissolution rates for HIP complexes depend on the hydrophobic-lipophilic balance number of the organic counter ion as well as on the electrolyte composition of aqueous solutions. Reverse ion-exchange kinetics are sufficiently slow to allow HIP complexes to be considered simple prodrugs.

Shear-induced degradation of plasmid DNA.

The majority of gene therapy clinical trials use plasmid DNA that is susceptible to shear-induced degradation. Many processing steps in the extraction, purification, and preparation of plasmid-based therapeutics can impart significant shear stress that can fracture the phosphodiester backbone of polynucleotides, and reduce biological activity. Much of the mechanistic work on shear degradation of DNA was conducted over 30 years ago, and we rely heavily on this early work in an attempt to explain the empirical observations of more recent investigations concerning the aerosolization of plasmids. Unfortunately, the sporadic reports of shear degradation in the literature use different experimental systems, making it difficult to quantitatively compare results and reach definitive mechanistic conclusions. In this review, we describe the forces imparted to DNA during shear stress, and use published data to quantitatively evaluate their relative effects. In addition, we discuss the effects of molecular weight, strain rate, particle size, flexibility, ionic strength, gas-liquid interfaces, and turbulence on the fluid flow degradation of supercoiled plasmid DNA. Finally, we speculate on computational methods that might allow degradation rates in different experimental systems to be predicted.