Interaction between a cationic bolaamphiphile and DNA: The route towards nanovectors for oligonucleotide antimicrobials.

Bacterial resistance to antimicrobials is a global threat that requires development of innovative therapeutics that circumvent its onset. The use of Transcription Factor Decoys (TFDs), DNA fragments that act by blocking essential transcription factors in microbes, represents a very promising approach. TFDs require appropriate carriers to protect them from degradation in biological fluids and transfect them through the bacterial cell wall into the cytoplasm, their site of action. Here we report on a bolaform cationic surfactant, [12-bis-THA]Cl2, with proven transfection activity in vivo. By studying the physical-chemical properties of its aqueous solutions with light scattering, cryo-TEM, ζ-potential, absorption and fluorescence spectroscopies, we prove that the bolaamphiphiles associate into transient vesicles which convert into one-dimensional elongated structures over time. These surfactant assemblies complex TFDs with extremely high efficiency, if compared to common cationic amphiphiles. At Z+/-=11, the nanoplexes are stable and have a size of 120nm, and they form independently of the original morphology of the [12-bis-THA]Cl2 aggregate. DNA is compacted in the nanoplexes, as shown through CD spectroscopy and fluorescence, but is readily released in its native form if sodium taurocholate is added.

Disc-shaped polyoxyethylene glycol glycerides gel nanoparticles as novel protein delivery vehicles.

Disc-shaped nanoparticles with high aspect ratios have been reported to show preferential cellular uptake in vitro by mammalian cells. However, engineering and producing such disc-shaped nanoparticles are often complex. This study reports for the first time the use of a single, approved pharmaceutical excipient to prepare stable disc-shaped nanoparticles with a high aspect ratio via a simple, organic solvent free process. These disc-shaped nanoparticles were formed by fragmentation of stearoyl macrogol-32 glycerides (Gelucire 50/13) hydrogels. The nanoparticles showed good physical stability as a result of their outer coating of polyethylene glycol (PEG) that is a part of Gelucire composition. Using lysozyme as a model hydrophilic protein, these nanoparticles demonstrated a good loading capacity for hydrophilic macromolecules, mainly via surface adsorption. As a result of the higher hydrophobicity of the core of the nano-discs, the loading efficiency of hydrophobic model components, such as Coumarin-6, was significantly increased in comparison to the model hydrophilic compound. These Gelucire nano-discs exhibited no cytotoxicity at the tested level of 600µg/ml for Caco-2 cells. Rapid in vitro cellular uptake of the disc-shaped nanoparticles by Caco-2 cells was observed. This rapid internalisation was attributed to the high aspect ratio of the disc-shape nanoparticles which provides a high contact surface area between the particles and cells and may lower the strain energy required for membrane deformation during uptake. The results of this study demonstrate the promising potential of Gelucire nano-discs as effective nanocarriers for drug delivery and which can be manufactured using a simple solvent-free process.

Nanostructural analysis of water distribution in hydrated multicomponent gels using thermal analysis and NMR relaxometry.

Highly complex, multicomponent gels and water-containing soft materials have varied applications in biomedical, pharmaceutical, and food sciences, but the characterization of these nanostructured materials is extremely challenging. The aim of this study was to use stearoyl macrogol-32 glycerides (Gelucire 50/13) gels containing seven different species of glycerides, PEG, and PEG-esters, as model, complex, multicomponent gels, to investigate the effect of water content on the micro- and nanoarchitecture of the gel interior. Thermal analysis and NMR relaxometry were used to probe the thermal and diffusional behavior of water molecules within the gel network. For the highly concentrated gels (low water content), the water activity was significantly lowered due to entrapment in the dense gel network. For the gels with intermediate water content, multiple populations of water molecules with different thermal responses and diffusion behavior were detected, indicating the presence of water in different microenvironments. This correlated with the network architecture of the freeze-dried gels observed using SEM. For the gels with high water content, increased quantities of water with similar diffusion characteristics as free water could be detected, indicating the presence of large water pockets in these gels. The results of this study provide new insights into structure of Gelucire gels, which have not been reported before because of the complexity of the material. They also demonstrate that the combination of thermal analysis and NMR relaxometry offers insights into the structure of soft materials not available by the use of each technique alone. However, we also note that in some instances the results of these measurements are overinterpreted and we suggest limitations of the methods that must be considered when using them.

Moisture uptake of polyoxyethylene glycol glycerides used as matrices for drug delivery: kinetic modelling and practical implications.

PURPOSE: Gelucire 50/13, a polyoxyethylene glycol glyceride mixture, has been widely used in drug delivery, but its moisture uptake behaviour is still poorly understood. In this study, the effects of relative humidity, temperature, and drug incorporation on the moisture uptake of Gelucire are reported in relation to their practical implications for preparation of solid dispersions using this material. METHODS: DVS combined with kinetics modelling was used as the main experimental method to study the moisture uptake behaviour of Gelucire. Thermal and microscopic methods were employed to investigate the effect of moisture uptake on the physical properties of the material and drug loaded solid dispersions. RESULTS: The moisture uptake by Gelucire 50/13 is temperature and relative humidity dependent. At low temperatures and low relative humidities, moisture sorption follows a GAB model. The model fitting indicated that at high relative humidities the sorption is a complex process, potentially involving PEG being dissolved and the PEG solution acting as solvent to dissolve other components. CONCLUSION: Careful control of the storage and processing environmental conditions are required when using Gelucire 50/13. The incorporation of model drugs not only influences the moisture uptake capacity of Gelucire 50/13 but also the solidification behaviour.