Vancomycin Loaded Glycerol Monooleate Liquid Crystalline Phases Modified with Surfactants.

The influence of two tuning agents, polyglycerol ester (PE) and triblock copolymer (TC), on the properties of glycerol monooleate (MO) liquid crystalline phase (LCP) was investigated to achieve the therapeutic concentration of vancomycin hydrochloride (VHCl) into the eye, topically during 60 min (1 h) and intravitreally during 2880 min (48 h). Different techniques were used to elucidate the impact of surfactants on the structure of the LCP: polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), and in vitro release tests I and II (simulating local and intravitreal application in the eye). The structure analysis by SAXS depicts that the inclusion of PE into the MO LCP provided partial transition of a hexagonal phase into a lamellar phase, and TC induced a partial transition of a hexagonal phase into an LCP which identification was difficult. The LCP modulated with PE and TC demonstrated different VHCl's release patterns and were evaluated by comparing our release data with the literature data. The comparison indicated that the LCP modulated with 30% w/w PE could be a promising VHCl delivery system intravitreally during 2880 min.

Vancomycin ocular delivery systems based on glycerol monooleate reversed hexagonal and reversed cubic liquid crystalline phases.

Lyotropic bulk reversed hexagonal and reversed cubic liquid crystalline phases (hexagonal and cubic phases) composed of glycerol monooleate (GM) were used to design the vancomycin hydrochloride's (VHCl) delivery systems aiming to maintain VHCl's therapeutic concentration during 24 h in the eye, locally (as an insert) and/or intravitreally (as a bulk phase injection). Bulk VHCl's hexagonal and cubic phases were successfully prepared by melted homogenization and solvent evaporation method, and then an insert was prepared. The structural characteristics of liquid crystalline phases were studied using cross polarized light microscopy and small angle X-ray scattering technique. The presence of VHCl (1-9.5% w/w VHCl solution) did not exhibit any change in the liquid crystalline phase's structure to another liquid crystalline phase, and showed little effect on the lattice parameter of the existing liquid crystalline phase structure. In order to relate the liquid crystalline phase structure to VHCl's release rate locally into the eye, in-vitro release test of an implant has been done using a simulated tear fluid. VHCl's release in the simulated tear fluid from the cubic phase obeyed Higuchi kinetics, with linear VHCl's release versus the square root of time. The hexagonal phase released VHCl in simulated tear fluid significantly slower than the cubic phase. In order to relate the liquid phase structure to VHCl's diffusion intravitreally, in vitro release test by the Sirius' Subcutaneous Injection Site Simulator (Scissor) has been performed. Comparing the release properties by a Scissor, the VHCl's cubic phase demonstrated slower permeation through extra-cellular matrix than the VHCl solution. To evaluate the efficacy of the system investigated, the release properties of VHCl's cubic phase were compared with literature data indicating that the cubic phase could be a potential matrix system in the delivery of VHCl intravitreally during 24 h after intravitreal injection. The release data in the simulated tear fluid indicated that the cubic phase should be further optimized to achieve a therapeutic VHCl concentration locally in the eye during 24 h.

Glycerol monooleate liquid crystalline phases used in drug delivery systems.

During the last few decades, both scientific and applied research communities have shown increased attention to self-assembled lyotropic liquid crystalline phases of polar lipids, due to their remarkable structural complexity and usefulness in diverse applications. Amphiphilic properties of polar lipids in relation to water are the driving force for self-assemblies following an extraordinary polymorphism. This polymorphism is an interesting phenomenon in which lipids combine short-range disorder and long-range order. The most widely investigated liquid crystalline phases are the lamellar, the cubic and the hexagonal. Such phases have high solubilization capacity for hydrophilic, lipophilic and amphiphilic guest molecules and the ability to protect molecules against hydrolysis or oxidation. So, they can be used as an interesting drug delivery matrix for drugs, amino acids, peptides, proteins and vitamins in various food, pharmaceutical and biotechnical applications. This review presents recent progress in glycerol monooleate liquid crystalline phases used as drug delivery vehicles.

Solid lipid microparticles containing loratadine prepared using a Micromixer.

Solid lipid microparticles were investigated as a taste-masking approach for a lipophilic weak base in a suspension. The idea was that the drug concentration in the aqueous phase of a suspension might be reduced by its partitioning into the solid lipid particles. Loratadine, as a model drug, was used to prepare Precirol ATO 5 microparticles by a Micromixer. The effects of three process variables: drug loading, PVA concentration and water/lipid ratio on the microparticle size, encapsulation efficiency, surface appearance, in-vitro release and drug partitioning in a suspension were studied. Loratadine release was slow in simulated saliva and very fast at the pH of stomach. In suspension of loratadine lipid microparticles, drug was released into the aqueous phase to the same concentration as in a drug suspension. Therefore, the usefulness of these microparticles for taste-masking in liquids is limited. However, they might be useful for taste-masking in solid dosage forms.