Sirolimus has recently been introduced as a therapeutic agent for breast and prostate cancer. In the current study, conventional and Stealth liposomes were used as carriers for the encapsulation of sirolimus. The physicochemical characteristics of the sirolimus liposome nanoparticles were investigated including the particle size, zeta potential, stability and membrane integrity. In addition atomic force microscopy was used to study the morphology, surface roughness and mechanical properties such as elastic modulus deformation and deformation. Sirolimus encapsulation in Stealth liposomes showed a high degree of deformation and lower packing density especially for dipalmitoyl-phosphatidylcholine (DPPC) Stealth liposomes compared to unloaded. Similar results were obtained by differential scanning calorimetry (DSC) studies; sirolimus loaded liposomes were found to result in a distorted state of the bilayer. X-ray photon electron (XPS) analysis revealed a uniform distribution of sirolimus in multilamellar DPPC Stealth liposomes compared to a nonuniform, greater outer layer lamellar distribution in distearoylphosphatidylcholine (DSPC) Stealth liposomes.

The use of solid dispersion techniques to modify physicochemical properties and improve solubility and dissolution rate may result in alteration to electrostatic properties of particles. Particle triboelectrification, plays an important part in powder processing, affecting end product quality due to particle deposition and powder loss. This study investigates the use of glucosamine hydrochloride (GLU) in solid dispersions with indomethacin. Solvents selected for the preparation of the dispersions were acetone, acetone-water, ethanol and ethanol-water. Solid state characterizations (DSC, FTIR and XRPD) and dissolution were conducted. Dispersions were subjected to charging using a custom built device based on a shaking concept, consisting of a Faraday cup connected to an electrometer. All dispersions improved the dissolution rate of indomethacin. Analysis showed the method of preparation of the dispersion induced polymorphic forms of the drug. Indomethacin had a high propensity for charging (-411 nC/g). GLU had a very low charge (-1 nC/g). All dispersions had low charges (-1 to 14 nC/g). Acetone as a solvent, or in combination with water, produced samples with an electronegative charge in polarity. The same approach with ethanol produced electropositive charging. The results show the selection of solvents can influence powder charge thereby improving powder handling as well as dissolution properties.

The omega-3-fatty acid, docosahexaenoic acid (DHA) 22:6 n-3, is an important food component for the visual and brain development of infants. In this study two approaches have been explored for the encapsulation of DHA in the pH dependant polymer hydroxyl-propylmethyl-cellulose-acetate-succinate (HPMCAS). In the first approach Direct Spray Drying (DSD) was implemented for the microencapsulation of DHA/HPMCAS organic solutions, whilst in the second approach solid lipid nanoparticle (SLN) dispersions of DHA, were first produced by high-pressure homogenization, prior to being spray dried in HPMCAS aqueous solutions. The DSD approach resulted in significantly higher quantities of DHA being encapsulated, at 2.09 g/100 g compared to 0.60 g/100 g in the spray-dried SLNs. The DHA stability increased with the direct spray-drying approach. Release studies of DHA in the direct sprayed dried samples revealed a lag time for 2 hours in acidic media followed by rapid release in phosphate buffer (pH 6.8).

Graphical abstract

No abstract