Significant Increase In Permeation Research Articles

Lipid nanoconstructs for superior hepatoprotection: In vitro assessments as predictive tool for in vivo translation.

To investigate comparative in vitro and in vivo performance of lipid vesicular and particulate systems in escalating oral bioavailability for superior hepatoprotection. Systems were fabricated using easy to scale up process and novel excipients to deliver Silibinin. In vitro characterization followed by pharmacokinetic and pharmacodynamic evaluation in rats was conducted to establish a correlation. Nanoformulations resulted in 20 fold increase in solubilisation and significant increase in permeation. 2.5 fold increase in bioavailability was evident in vivo. Vesicles demonstrated greatest hepatoprotective potential in efficacy study. The findings establish a link between in vitro and in vivo performance to rank order lipid nanoartchitects. Concurrently, a significant potential in therapeutic intervention of hepatotoxicity is envisaged as elucidated.

Understanding the poor iontophoretic transport of lysozyme across the skin: When high charge and high electrophoretic mobility are not enough

The original aim of the study was to investigate the transdermal iontophoretic delivery of lysozyme and to gain further insight into the factors controlling protein electrotransport. Initial experiments were done using porcine skin. Lysozyme transport was quantified by using an activity assay based on the lysis of Micrococcus lysodeikticus and was corrected for the release of endogenous enzyme from the skin during current application. Cumulative iontophoretic permeation of lysozyme during 8h at 0.5mA/cm2 (0.7mM; pH6) was surprisingly low (5.37±3.46μg/cm2 in 8h) as compared to electrotransport of cytochrome c (Cyt c) and ribonuclease A (RNase A) under similar conditions (923.0±496.1 and 170.71±92.13μg/cm2, respectively) — despite its having a higher electrophoretic mobility. The focus of the study then became to understand and explain the causes of its poor iontophoretic transport. Lowering formulation pH to 5 increased histidine protonation in the protein and decreased the ionisation of fixed negative charges in the skin (pI ~4.5) and resulted in a small but statistically significant increase in permeation. Co-iontophoresis of acetaminophen revealed a significant inhibition of electroosmosis; inhibition factors of 12–16 were indicative of strong lysozyme binding to skin. Intriguingly, lidocaine electrotransport, which is due almost exclusively to electromigration, was also decreased (approximately 2.7-fold) following skin pre-treatment by lysozyme iontophoresis (cf. iontophoresis of buffer solution) — suggesting that lysozyme was also able to influence subsequent cation electromigration. In order to elucidate the site of skin binding, different porcine skin models were tested (dermatomed skin with thicknesses of 250 and 750μm, tape-stripped skin and heat-separated dermis). Although no difference was seen between permeation across 250 and 750μm dermatomed skin (13.57±12.20 and 5.37±3.46μg/cm2, respectively), there was a statistically significant increase across tape-stripped skin and heat-separated dermis (36.86±7.48 and 43.42±13.11μg/cm2, respectively) — although transport was still much less than that seen across intact skin for Cyt c or RNase A. Furthermore, electroosmotic inhibition factors fell to 2.2 and 1.0 for tape-stripped skin and heat-separated dermis — indicating that lysozyme affected convective solvent flow through interactions with the epidermis and predominantly the stratum corneum. Finally, cation exchange and hydrophobic interaction chromatography confirmed that although lysozyme had greater positive charge than Cyt c or RNase A under the conditions used for iontophoresis, it also possessed the highest surface hydrophobicity, which may have facilitated the interactions with the transport pathways and encouraged aggregation in the skin microenvironment. Thus, high charge and electrophoretic mobility seem to be inadequate descriptors to predict the transdermal iontophoretic transport of proteins whose complex three dimensional structures can facilitate interactions with cutaneous transport pathways.

Alteration of fibrin clot properties by ultrafine particulate matter

Both long- and short-term (1-2 hours) exposure to particulate matter (PM) are associated with morbidity and mortality caused by cardiovascular diseases. One of the underlying mechanisms may be due to changes to blood coagulability upon exposure to PM. We investigated this possibility by measuring differences in blood clots formed in the presence of particulate matter in vitro. Total (T)PM increased the permeation of clots in a dose-dependant manner. Filtered (F)PM (17 microg/ml) also produced a significant increase in permeation. Turbidity measured as maximum optical density (ODmax) was increased in a dose-dependant manner with increasing concentration of TPM and FPM. Turbidity measurements also showed a significantly faster rate of polymerisation in the presence of 68 microg/ml FPM. Laser scanning confocal microscopy (LSCM) showed a decrease in fibre density without a significant increase in fibre diameter. However, LSCM showed increased clot heterogeneity due to fibre clustering, creating areas of denser fibrin network surrounded by looser network. The presence of reactive oxygen species (ROS) scavenger mannitol inhibited the effects on fibre clustering. Our data show that TPM and FPM cause alterations in fibrin clot structure, likely through the formation of ROS. These changes in fibrin clot structure may play a role in thromboembolic events upon PM exposure.

Influence of Ultrasound on the Percutaneous Absorption of Ketorolac Tromethamine In Vitro Across Rat Skin

The influence of ultrasound on percutaneous absorption of ketorolac tromethamine was studied in vitro across rat skin. Sonication was carried out with a continuous mode, at an intensity of 1–3 W/cm2 and a frequency of 1 MHz for 30 min. A significant increase in permeation of ketorolac through rat skin was observed with the applied sonication at 3 W/cm2 when compared with permeation at 1 and 2 W/cm2. Enhanced ketorolac penetration at 3 W/cm2 can be explained by the mechanical and/or thermal action of ultrasound waves. The distance of the ultrasound probe from the skin surface did not influence the flux of the drug. Pretreatment of skin by 5% d-limonene in ethanol for 2 hr followed by sonication at 3 W/cm2 (30 min) significantly enhanced the permeation of ketorolac when compared with passive flux with or without enhancer pretreatment.

Measurement of blood-brain barrier permeation in rats during exposure to 2450-MHz microwaves.

Adult rats anesthesized with pentobarbital and injected intravenously with a mixture of [14C] sucrose and [3H] insulin were exposed for 30 min to an environment at an ambient temperature of 22, 30, or 40 degrees C, or were exposed at 22 degrees C to 2450-MHz CW microwave radiation at power densities of 0, 10, 20, or 30 mW/cm2. Following exposure, the brain was perfused and sectioned into eight regions, and the radioactivity in each region was counted. The data were analyzed by two methods. First, the data for each of the eight regions and for each of the two radioactive tracers were analyzed by regression analysis for a total of 16 analyses and Bonferroni's Inequality was applied to prevent false positive results from numerous analyses. By this conservative test, no statistically significant increase in permeation was found for either tracer in any brain region of rats exposed to microwaves. Second, a profile analysis was used for a general change in tracer uptake across all brain regions. Using this statistical method, a significant increase in permeation was found for sucrose but not for inulin. A correction factor was then derived from the warm-air experiments to correct for the increase in permeation of the brain associated with change in body temperature. This correction factor was applied to the data for the irradiated animals. After correcting the data for thermal effects of the microwave radiation, no significant increase in permeation was found.