Synergistic antimicrobial interactions of nisin A with biopolymers and solubilising agents for oral drug delivery.

In order to develop bacteriocins, like the lantibiotic nisin A, into effective alternatives to existing antibiotics, their biophysical and physicochemical properties must first be assessed, from solubility, to susceptibility and absorption. It has been well established that formulation strategies at early drug development stages can be crucial for successful outcomes during preclinical and clinical phases of development, particularly for molecules with challenging physicochemical properties. This work elucidates the physicochemical challenges of nisin A in terms of its susceptibility to digestive enzymes like pepsin, pancreatin and proteinase K and its poor solubility at physiological pHs. Low solution concentrations, below the minimum inhibitory concentration against Staphylococcus aureus, were obtained in phosphate buffered saline (PBS, pH 7.4) and in fasted state simulated intestinal fluid (FaSSIF, pH 6.5), while higher solubilities at more acidic pH's such as in a KCl/HCl buffer (pH 2) and in fasted state simulated gastric fluid (FaSSGF, pH 1.6) are observed. Tween® 80 (0.01% v/v) significantly increased the solution concentration of nisin A in PBS (pH 7.4, 24 hr). Pancreatin doubled nisin A's solution concentration at pH 7.4 (PBS) but reduced its' inhibitory activity to âˆ¼ 20%, and pepsin almost completely degraded nisin (after 24 hr), but retained activity at biologically relevant exposure times (∼15 min). Harnessing synergism between nisin A and either glycol chitosan or ε-poly lysine, combined with the solubilizing effect of Tween®, increased the antimicrobial activity of nisin A six fold in an in vitro oral administration model.

Tuning the strength and swelling of an injectable polysaccharide hydrogel and the subsequent release of a broad spectrum bacteriocin, nisin A.

Bacteriocins, which are antimicrobial peptides, are a potential alternative to current ineffective antimicrobial therapies. They can inhibit the growth of clinically relevant pathogens but their proteinaceous nature renders them susceptible to degradation and deactivation in vivo. We have designed injectable polysaccharide hydrogels for the controlled release of an incorporated bacteriocin, nisin. Nisin was encapsulated into these hydrogels which were composed of varying percentages of oxidised dextran, alginate functionalised with hydrazine groups and glycol chitosan. The nisin gels exhibited antimicrobial activity against Staphylococcus aureus up to 10 days. The incorporation of a deacetylated chitosan and the reduction of alginate-hydrazine could be used to tune the gel's swelling behaviour, strength and the subsequent release profile of nisin. Glycol chitosan also shows synergistic inhibition of S. aureus with nisin.

Estradiol attenuates mitochondrial depolarization in polyol-stressed lens epithelial cells.

PURPOSE: This study examined the state of mitochondrial physiology subsequent to exposing lens epithelium to high ambient galactose (Gal), which upon conversion to galactitol (GalOH) and resultant intracellular accumulation thereof, leads to profound destabilization of mitochondrial membrane potential (Deltapsim). Further, we determined whether the aldose reductase (AR) inhibitor, Sorbinil, or estrogen (17beta-E2, and its isomer, 17alpha-E2, which exhibits marginal binding affinity for estrogen receptor), administered prior to and concomitant with Gal exposure might prevent or delay mitochondrial membrane depolarization. METHODS: Secondary cultures of bovine lens epithelial cells (BLECs), as well as a virally-transformed human lens epithelial cell line (HLE-B3), were maintained in 40 mM galactose (Gal) for up to seven days in the presence and absence of Sorbinil, 17beta-E2 or 17alpha-E2. Endogenous accumulation of reactive oxygen species (ROS) was assessed by loading cells with H2DCF-DA, which upon oxidation in the presence of ROS transitions to the fluorescent compound, DCF. To assess Deltapsim, confocal microscopy was employed in conjunction with the potentiometric dye, JC-1. Intracellular polyol content was determined by gas chromatography. Cells were monitored for apoptosis and necrosis as determined by annexin V-propidium iodide staining and visualized by confocal fluorescence microscopy. RESULTS: BLECs, more so than HLE-B3 cells, accumulate high intracellular levels of GalOH upon exposure to high ambient Gal. BLECs were significantly depolarized while HLE-B3 cells showed little depolarization over the same course of Gal exposure. The addition of either 17alpha-E2 or 17beta-E2 to BLECs, over a dose range of 0.01 microM to 1.0 microM, prevented mitochondrial membrane depolarization as did the addition of 0.1 mM Sorbinil. The polyol content in BLECs after 3 days of exposure to Gal was 282 nmol/mg protein. Co-addition of Sorbinil during the 3-day exposure period prevented any significant accumulation of GalOH. Co-administration of either isoform of estrogen did not block GalOH synthesis and the level of attained intracellular accumulation was similar to that of Gal alone. The observed accumulation of ROS from HLE-B3 cells subsequent to 3 days of Gal exposure was negligible and consistent with that of control cells maintained in physiological medium. Intracellular accumulation of ROS with 3-day, Gal-maintained BLECs, exhibited a marginal but statistically significant increase over control cells maintained in physiological medium (5.5 mM glucose) and similar levels of ROS were generated irrespective of the presence of estrogen with Gal. Bolus addition of 100 microM hydrogen peroxide to 3-day, Gal plus Sorbinil-maintained BLECs failed to induce a change in mitochondrial membrane potential. Evidence of apoptosis or necrosis was negligible through 7 days of sustained exposure to high ambient Gal. CONCLUSIONS: Polyol accumulation promotes mitochondrial membrane depolarization and the decrease in Deltapsim is prevented by prior addition and co-administration of Sorbinil or estrogen with Gal. Unlike Sorbinil, estrogens' mode of action is not via the inhibition of aldose reductase activity. The data supports the theory that with Gal plus estradiol-treated cells, at a given intracellular polyol load, a larger portion of the mitochondrial population retains Deltapsim, and hence continues to function relative to Gal-treated cells. Results with 17alpha-E2 indicate that maintaining Deltapsim, in the face of chronic polyol accumulation, is likely to be mediated via a nuclear estrogen receptor-independent mechanism. The failure of supraphysiological levels of hydrogen peroxide added to Gal plus Sorbinil-maintained BLECs to depolarize mitochondria indicates that polyol accumulation, not ROS generation, is the causative factor responsible for the loss of mitochondrial membrane potential.

Povidone-iodine as a topical antiseptic for treating and preventing wound infection: a literature review.

With the proliferation of antibiotic and antiseptic resistant strains of bacteria around the world, attention is increasingly being focused on more 'traditional' methods of combating and preventing wound infections. This article examines the research literature pertaining to the use of povidone-iodine, a form of iodine commonly used for skin cleansing, as a prophylaxis or treatment for wound infection. The literature is discussed as it relates to the ideal characteristics of an antiseptic for use on wounds proposed by König et al (1997) and Liptak (1997). On the basis of available research, it appears that povidone-iodine should be promoted by nurses and other healthcare professionals involved in wound care as a means of preventing and treating infection in a range of acute and chronic wounds.