Coating for preventing nonspecific adhesion mediated biofouling in salty systems: Effect of the electrostatic and van der waals interactions

Development of anti-biofouling coating has attracted immense attention for reducing the massively detrimental effects of biofouling in systems ranging from ship hulls and surgical instruments to catheters, implants, and stents. In this paper, we propose a model to quantify the role of electrostatic and van der Waals (vdW) forces in dictating the efficacy of dielectric coating for preventing the nonspecific adhesion mediated biofouling in salty systems. The model considers a generic charged lipid-bilayer encapsulated vesicle-like structure representing the bio-organism. Also, we consider the fouling caused by the nonspecific adhesion of the bio-organism on the substrate, without accounting for the explicit structures (e.g., pili, appendages) or conditions (e.g., surface adhesins secreted by the organisms) involved in the adhesion of specific microorganism. The model is tested by considering the properties of actual coating materials and biofouling causing microorganisms (bacteria, fungi, algae). Results show that while the electrostatic-vdW effect can be significant in anti-biofouling action for cases where the salt concentration is relatively low (e.g., saline solution for surgical instruments), it might not be effective for marine environment where the salt concentration is much higher. The findings, therefore, point to a hitherto unexplored driving mechanism of anti-biofouling action of the coating. Such an identification will also enable the appropriate choices of the coating materials (e.g., possible dielectric material with volume charge) and other system parameters (e.g., salinity of the solution for storing the surgical instruments) that will significantly improve the efficiency of the coatings in preventing the nonspecific adhesion mediated biofouling.     

Inclusion complexes of sulphanilamide drugs and β-cyclodextrin: a theoretical approach

PM3 theoretical methodology was used to access and compare the relative stability of inclusion complexes formed by sulphadiazene, sulphisomidine, sulphamethazine and sulphanilamide with β-cyclodextrin (β-CD). The study predicted that (i) the heterocyclic ring is encapsulated in the hydrophobic part and aniline ring is present in the hydrophilic part of the β-CD cavity and (ii) intermolecular hydrogen bonds were formed between host and guest molecules. The negative free energy and enthalpy changes indicated that all the four inclusion complexation processes were spontaneous and enthalpy driven process. HOMO and LUMO orbital investigation confirmed that the stability increased in the inclusion complexes and also proved no significant change in the electronic structure of the guest and host molecules after complexation.     

Vocal Folds Detect Ionic Perturbations on the Luminal Surface: An In Vitro Investigation

The homeostasis of fluid bathing the luminal surface of the vocal folds is important for phonation and laryngeal defense. Dehydration of the respiratory tract during mouth breathing can perturb the concentration of sodium and chloride ions in surface fluid. Exposure to dry air also increases the osmolarity of airway surface fluid. We hypothesized that viable vocal fold epithelium would detect changes in the ionic and osmotic composition of fluid on the luminal surface. Therefore, we examined bioelectric responses of vocal folds exposed to physiologically real, luminal ionic and osmotic challenges in vitro. The study used randomized factorial design with experimental and sham control groups. Fifty native ovine vocal folds were exposed to five challenges (ionic, osmotic, combined ionic-osmotic, and sham) on the luminal surface. Bioelectric measures of potential difference (PD), short-circuit current (I(SC)), and tissue resistance were assessed at prechallenge baseline, during challenge, and after removal of challenge. Ionic and combined ionic-osmotic challenges reduced PD and I(SC) (P<0.01). These reductions depended on the nature of the ionic challenge, were observed within 10 minutes, lasted for the duration of exposure, and were reversible after removal of the challenge. Conversely, sham or osmotic challenge did not alter bioelectric parameters over time (P>0.05). Viable ovine vocal fold epithelia detect ionic perturbations to the luminal surface. This sensitivity to luminal ionic challenge may be necessary to maintain the homeostasis of surface fluid.