No abstract

Incorporation of sunscreens into lipid carriers with an increased sun protection factor (SPF) has not yet been fully accomplished. In the present paper, the effectiveness of a sunscreen mixture, incorporated into the novel topical delivery systems, i.e. solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC), used as ultraviolet (UV) protector enhancers with a distinctly higher loading capacity has been developed and evaluated. SLN and NLC were produced by hot high pressure homogenization technique in lab scale production. Size distribution and storage stability of formulations were investigated by laser diffractometry and photon correlation spectroscopy. Nanoparticles were characterized by their melting and recrystallization behaviour recorded by differential scanning calorimetry. Lipid nanoparticles produced with a solid matrix (SLN and NLC) were established as a UV protection system. The loading capacities for molecular sunscreens reported before now were in the range of 10-15%. It was possible to load NLC with up to 70% with molecular sunscreen, which is appropriate to obtain high SPFs with this novel UV protection system. The developed formulations provide a beneficial alternative to conventional sunscreen formulations. The UV protective efficacy of the lipid particles varied with the nature of lipid and UV wavelength.

In this work the potential of chitosan nanoparticles (CNP) and thermosensitive chitosan hydrogels as particulate and sustained release vaccine delivery systems was investigated. CNP and chitosan hydrogels were prepared, loaded with the model protein antigen ovalbumin (OVA) and characterised. The immunostimulatory capacity of these vaccine delivery systems was assessed in-vitro and in-vivo. Particle sizing measurements and SEM images showed that optimised OVA-loaded CNP had a size of approximately 200 nm, a polydispersity index < 0.2, and a positive zeta-potential of approximately 18 mV. The amount of OVA adsorbed onto CNP was high with an adsorption efficacy of greater than 96%. Raman spectroscopy indicated conformational changes of OVA when adsorbed onto the surface of CNP. Uptake of the dispersions and immunological activation of murine dendritic cells in-vitro could be demonstrated. Investigation of the release of fluorescently-labelled OVA (FITC-OVA) from CNP and chitosan hydrogels in-vitro showed that approximately 50% of the total protein was released from CNP within a period of ten days; release of antigen from chitosan gel occurred in a more sustained manner, with < 10% of total protein being released after 10 days. The slow release from gel formulations may be explained by the strong interactions of the protein with chitosan. While OVA-loaded CNP showed no significant immunogenicity, formulations of OVA in chitosan gel were able to stimulate both cell-mediated and humoral immunity in-vivo.

Cancer vaccine delivery is a multidisciplinary scientific field that is currently undergoing rapid development. An important component of cancer vaccines is the development of novel vaccine delivery strategies, such as colloidal immunostimulatory delivery systems. The importance of formulation strategies for cancer vaccines can be explained by the poor immunogenicity of tumour antigens. Colloidal vaccine delivery systems modify the kinetics, body distribution, uptake and release of the vaccine. This review explores recent research that is directed towards more targeted treatments of cancer through to colloidal vaccine delivery systems. Widely investigated carrier systems include polymeric micro- and nanoparticles, liposomes, archaeal lipid liposomes (archaeosomes), immune-stimulating complexes and virus-like particles. These systems are evaluated in terms of their formulation techniques, immunological mechanisms of action as well as the potential and limitations of such colloidal systems in the field of cancer vaccines.

In this work the potential of chitosan nanoparticles (CNP) and thermosensitive chitosan hydrogels as particulate and sustained release vaccine delivery systems was investigated. CNP and chitosan hydrogels were prepared, loaded with the model protein antigen ovalbumin (OVA) and characterised. The immunostimulatory capacity of these vaccine delivery systems was assessed in-vitro and in-vivo. Particle sizing measurements and SEM images showed that optimised OVA-loaded CNP had a size of approximately 200 nm, a polydispersity index < 0.2, and a positive zeta-potential of approximately 18 mV. The amount of OVA adsorbed onto CNP was high with an adsorption efficacy of greater than 96%. Raman spectroscopy indicated conformational changes of OVA when adsorbed onto the surface of CNP. Uptake of the dispersions and immunological activation of murine dendritic cells in-vitro could be demonstrated. Investigation of the release of fluorescently-labelled OVA (FITC-OVA) from CNP and chitosan hydrogels in-vitro showed that approximately 50% of the total protein was released from CNP within a period of ten days; release of antigen from chitosan gel occurred in a more sustained manner, with < 10% of total protein being released after 10 days. The slow release from gel formulations may be explained by the strong interactions of the protein with chitosan. While OVA-loaded CNP showed no significant immunogenicity, formulations of OVA in chitosan gel were able to stimulate both cell-mediated and humoral immunity in-vivo.