Investigation of liposome formulation effects on rivastigmine transport through human colonic adenocarcinoma cell line (CACO-2).

Transportations of rivastigmine containing liposomes across Caco-2 cells were studied and in vitro test results were compared with in vivo results. MTT test was used for cell viability studies. Series of formulations were prepared containing rivastigmine which is used for the treatment of Alzheimer's disease. Characterization and stability studies for liposome formulations were performed. Encapsulation efficiencies of liposomes were 35.4%, 25.2% and 29.9% for rivastigmine, rivastigmine-sodium taurocholate, rivastigmine-dimethyl-beta-CD liposomes, respectively. In stability studies, particle size and size distribution, zeta potential, rivastigmine amounts were determined and shelf lives of liposomes were calculated. Penetration properties of rivastigmine through Caco-2 cells, dialysis membrane and kinetics of release from liposomes were determined. Permeability coefficients were calculated after diffusion studies. The highest value of % cumulative amount of rivastigmine passed through caco-2 cell cultures was found to be 87.2% for rivastigmine-sodium taurocholate solution and 12.8% for rivastigmine-sodium taurocholate liposome. The highest permeability coefficient value was obtained with sodium taurocholate liposomes for -0.75. Rivastigmine liposomes and solutions were also applied to animals. Acetyl choline esterase (AChE) activity was determined by the Ellman method on mice. %AChE inhibition values were calculated using blood and brain tissue samples. The physical appearances of the brains were investigated by TEM microscope. The highest value of AChE inhibition was observed for rivastigmine and sodium taurocholate liposomes. The histological investigations and observations also supported these results.

Transport evaluation of alendronate across Caco-2 cell monolayers.

The transport of alendronate through Caco-2 monolayers in the absence and presence of absorption enhancers (sodium taurocholate-STC and dimethyl-beta-cyclodextrin-DM-beta-CD) was studied. The viability of Caco-2 cells was determined by MTT assay. The effects of the experiment period and serum existence in Dubelco's Modified Eagle's Medium (DMEM) on cell viability were examined. The least toxic concentrations of alendronate, STC and DM-beta-CD were found as 0.2% (w/v), 5 mM and 0.3% (w/v), respectively. Transport experiments were performed with these concentrations in DMEM supplemented with serum for an 8 h period. DM-beta-CD increased the transport of alendronate through Caco-2 monolayers significantly. No significance was observed with STC. Cell integrity was determined by measuring the electrical resistance values at the end of the transport experiments and found to be decreased to a greater extent with DM-beta-CD. These results indicate that DM-beta-CD is a promising agent for improving the transport of alendronate.

An investigation on skin wound healing in mice with a taurine-chitosan gel formulation.

The process of wound healing begins immediately following surface lesions or just after exposure to radiation, chemical agents or extreme temperatures. Taurine (2-aminoethane sulfonic acid), an amino acid containing sulfur, is found in almost all tissues in mammals, playing various important physio-logical roles in each organ. Taurine exhibits an antioxidant effect and is also known to have effects on cell proliferation, inflammation and collagenogenesis. Many antioxidants have been used to eliminate the negative effects of oxygen free radicals on wound healing. The objective of the present study was to examine the wound healing effect in mice of taurine-chitosan gel, which releases taurine slowly over a long time period. Fifty mM of taurine in 1.5% chitosan polymer (TAU-GEL) and 1.5% chitosan polymer (CHI-GEL) were applied to full thickness skin wounds of mice once a day for seven days. After seven days of treatment, lipid peroxide formation-malondialdehyde (MDA) and hydroxyproline (HPX) levels and the tensile strength of wound tissues were measured. All results were compared with those of the untreated control group (CONT). The structural alterations in the skin layers were also histologically investigated. It was found that locally administered TAU-GEL form significantly increased wound tensile strength by decreasing the MDA and increasing HPX levels. These results were supported by histological findings. All observations suggest that taurine gel may be effective in wound healing.

Determination of intracellular concentrations of free and two types of liposome-encapsulated enrofloxacin in anatolian shepherd dog monocytes.

In this study, it was evaluated the accumulation of free and two types of liposome-encapsulated enrofloxacin (LEE) at the doses of 0.25, 0.5 and 1 microg/ml, which were clinically relevant concentrations into monocytes of healthy Anatolian shepherd dogs. Enrofloxacin was encapsulated with two different types of liposome in multilamellar large vesicles (MLV). Type A MLV composed of 15 mg egg phosphatidylcholine and 35 mg cholesterol, Type B MLV composed of phosphatidylcholine (PC), cholesterol and enrofloxacin, in a molar ratio of 1 : 1 : 1. The mean sizes of Type A and Type B liposome were found to be 7.65 and 4.27 microm, respectively. However, the mean encapsulation rate determined of Type A (13 +/- 2%) was found lower than Type B liposome (44 +/- 3%). The amounts of intracellular enrofloxacin concentrations were determined by high performance liquid chromatography. Type B LEE accumulated significantly higher level into monocytes when compared to free drug or Type A liposome. This study showed that Type B LEE markedly concentrated within monocytes and may improve the antibacterial efficacy of the antibiotic.

pH-Metric log K calculations of famotidine, naproxen, nizatidine, ranitidine and salicylic acid.

The octanol/water partition coefficient (log K) is one of the most commonly used parameters in structure-activity relationships in many areas such as drug design (including pesticides), pharmacokinetics, anesthesiology, environmental sciences, toxicology, bioaccumulation and predicting skin permeability as a predictive parameter. log K is generally determined using shake flask method, but the possibility of calculating log K using pH-metric titrations and half neutralization points is demonstrated in this study. The potentiometric pH titration technique has been developed as an automatic technique for log K determination but it can be achieved by manual titrations. This technique uses the pKa of the substance. The pKa of the substance shifts pK'a when the titration is repeated in the presence of octanol. log K value of the substance can be determined using pKa, pK'a values and relevant equation. The aim of the study was to determine the log K values of a series of compounds using pH-metric titrations and to compare pH-metric log K determination results with the other methods. The log K values of famotidine, naproxen, nizatidine, ranitidine and salicylic acid were determined using both shake flask method and potentiometric titrations. Their log K values were also calculated theoretically using computer program and all results were compared. The pH-metric log K values were found to be close to the shake flask method results. This method was found to be useful for the determination of log K values as it provides a high degree of accuracy even in the presence of titratable impurities in the solution.