Development and Evaluation of a Nanoemulsion Containing Ursolic Acid: a Promising Trypanocidal Agent

Over a hundred years after the discovery of Chagas disease, this ailment continues to affect thousands of people. For more than 40 years, only two drugs have been available to treat it. Ursolic acid is a naturally occurring terpene that has shown a good trypanocidal action. However, the hydrophobicity of this compound presents a challenge for the development of proper delivery systems. Nanostructured systems are a prominent in delivering lipophilic drugs. Thus, a nanoemulsion containing ursolic acid was developed and had its trypanocidal activity and cytotoxicity evaluated. Pseudo-ternary phase diagrams and hydrophilic-lipophilic balance (HLB) system were used in the development. The system was stable throughout 90 days of testing, as evidenced by turbidimetry analysis and measurements of the droplet size (57.3 nm) and polydispersity index (0.24). Fourier transform infrared spectroscopy and mass spectrometry evidenced drug’s integrity in the formulation. An in vitro dissolution profile showed 75% of ursolic acid release after 5 min from the nanoemulsion into the alkaline dissolution medium, while only 20% could be released from a physical mixture after 2 h. Trypanocidal activity and cytotoxicity were evaluated on the CL Brener strain and LLC-MK2 (monkey kidney) fibroblast by chlorophenol red-β-d-galactoside (CPRG) method. Biological studies showed that the developed formulation was nontoxic and effective against replicant forms of the parasite. A stable and efficient nanoemulsion could be developed to improve the delivery of a promising drug to treat a threatening illness such as Chagas disease.     

Optimization of Nanoemulsion Fabrication Using Microfluidization: Role of Surfactant Concentration on Formation and Stability

Nanoemulsions have some important potential advantages over conventional emulsions for certain commercial applications due to their optical clarity, high physical stability, and ability to increase the bioavailability of lipophilic bioactives. In this study, the factors influencing droplet size and stability in nanoemulsions fabricated from a hydrocarbon oil and an anionic surfactant were examined. Octadecane oil-in-water nanoemulsions were produced by a high pressure homogenizer (microfluidizer) using sodium dodecyl sulfate (SDS) as a model anionic surfactant. The influence of homogenization pressure, number of passes, and surfactant concentration was examined. The droplet size decreased with increasing homogenization pressure, number of passes, and surfactant concentration. Nanoemulsions with low turbidity and small droplet diameters (≈62 nm) could be produced under optimized conditions. Interestingly, nanoemulsions containing relatively high surfactant levels were highly susceptible to creaming when they were only passed through the homogenizer a few times, which was attributed to depletion flocculation. These results show the importance of optimizing surfactant levels to produce small droplets that are also stable to creaming.     

Enhanced Ordering in Monolayers Containing Glycosphingolipids: Impact of Carbohydrate Structure

The influence of carbohydrate structure on the ordering of glycosphingolipids (GSLs) and surrounding phospholipids was investigated in monolayers at the air-water interface. Binary mixtures composed of GSLs, chosen to span a range of carbohydrate complexity, and zwitterionic dipalmitoylphosphatidylcholine phospholipid, were studied. X-ray reflectivity was used to measure the out-of-plane structure of the monolayers and characterize the extension and conformation of the GSL carbohydrates. Using synchrotron grazing incidence x-ray diffraction, the in-plane packing of the lipid acyl chains and the area per molecule within ordered domains were characterized at different mole ratios of the two components. Our findings indicate that GSL-containing mixtures, regardless of the carbohydrate size, enhance the ordering of the surrounding lipids, resulting in a larger fraction of ordered phase of the monolayer and greater dimensions of the ordered domains. Reduction of the averaged area per molecule within the ordered domains was also observed but only in the cases where there was a size mismatch between the phospholipid headgroups and GSL components, suggesting that the condensation mechanism involves the relief of steric interactions between headgroups in mixtures.     

Study of Polymorphs of Progesterone by Novel Melt Sonocrystallization Technique: A Technical Note

A large number of pharmaceuticals exhibit polymorphism; 23% steroids, 60% sulfonamides, and 70% of barbiturates have shown this property. In this study, we have investigated and compared a new technique termed as melt sonocrystallization (MSC) with melt and sonocrystallization (SC) for induction of polymorphism in progesterone (PRG). Polymorphs were characterized by DSC, XRD, FT-IR, and FT Raman spectroscopy. Melt sonocrystallized progesterone (MSC-PRG) contained both the polymorphs, more soluble form II along with less soluble form I, whereas melt progesterone (M-PRG) and sonocrystallized progesterone (SC-PRG) contained only form I. Improvement in dissolution characteristics of both the polymorphs were compared and form II was found to be more readily soluble than form I in deionized water. Reduction in mean particle size of PRG during SC was also determined using laser diffractometer. During stability testing (40°C/75% RH) for 1 month, metastable form II of MSC-PRG was found to be transformed into its more stable state. MSC technique was thus found as a useful tool for induction of polymorphism.     

Technical Note: Modelling Soft Tissue Using Biphasic Theory - A Word of Caution

In recent years the biphasic approach initiated by Mow and coworkers, has been very popular in modelling soft, hydrated, cartilage tissues as well as other soft tissues, such as the brain. This work points out that due to the inherent inability of biphasic models in their present form to account for stress-strain rate dependence resulting from the viscoelasticity of the solid phase, the applicability of these models is limited to the loading conditions producing large relative velocities of phases.     

Dynamic CT Perfusion Imaging of the Myocardium: A Technical Note on Improvement of Image Quality

Objective

To improve image and diagnostic quality in dynamic CT myocardial perfusion imaging (MPI) by using motion compensation and a spatio-temporal filter.

Methods

Dynamic CT MPI was performed using a 256-slice multidetector computed tomography scanner (MDCT). Data from two different patients–with and without myocardial perfusion defects–were evaluated to illustrate potential improvements for MPI (institutional review board approved). Three datasets for each patient were generated: (i) original data (ii) motion compensated data and (iii) motion compensated data with spatio-temporal filtering performed. In addition to the visual assessment of the tomographic slices, noise and contrast-to-noise-ratio (CNR) were measured for all data. Perfusion analysis was performed using time-density curves with regions-of-interest (ROI) placed in normal and hypoperfused myocardium. Precision in definition of normal and hypoperfused areas was determined in corresponding coloured perfusion maps.

Results

The use of motion compensation followed by spatio-temporal filtering resulted in better alignment of the cardiac volumes over time leading to a more consistent perfusion quantification and improved detection of the extend of perfusion defects. Additionally image noise was reduced by 78.5%, with CNR improvements by a factor of 4.7. The average effective radiation dose estimate was 7.1±1.1 mSv.

Conclusion

The use of motion compensation and spatio-temporal smoothing will result in improved quantification of dynamic CT MPI using a latest generation CT scanner.