Overcoming Nanoparticle-Mediated Complement Activation by Surface PEG Pairing.

Many PEGylated nanoparticles activate the complement system, which is an integral component of innate immunity. This is of concern as uncontrolled complement activation is potentially detrimental and contributes to disease pathogenesis. Here, it is demonstrated that, in contrast to carboxyPEG2000-stabilized poly(lactic-co-glycolic acid) nanoparticles, surface camouflaging with appropriate combinations and proportions of carboxyPEG2000 and methoxyPEG550 can largely suppress nanoparticle-mediated complement activation through the lectin pathway. This is attributed to the ability of the short, rigid methoxyPEG550 chains to laterally compress carboxyPEG2000 molecules to become more stretched and assume an extended, random coil configuration. As supported by coarse-grained molecular dynamics simulations, these conformational attributes minimize statistical protein binding/intercalation, thereby affecting sequential dynamic processes in complement convertase assembly. Furthermore, PEG pairing has no additional effect on nanoparticle longevity in the blood and macrophage uptake. PEG pairing significantly overcomes nanoparticle-mediated complement activation without the need for surface functionalization with complement inhibitors.

Niosomes from 80s to present: the state of the art.

Efficient and safe drug delivery has always been a challenge in medicine. The use of nanotechnology, such as the development of nanocarriers for drug delivery, has received great attention owing to the potential that nanocarriers can theoretically act as "magic bullets" and selectively target affected organs and cells while sparing normal tissues. During the last decades the formulation of surfactant vesicles, as a tool to improve drug delivery, brought an ever increasing interest among the scientists working in the area of drug delivery systems. Niosomes are self assembled vesicular nanocarriers obtained by hydration of synthetic surfactants and appropriate amounts of cholesterol or other amphiphilic molecules. Just like liposomes, niosomes can be unilamellar or multilamellar, are suitable as carriers of both hydrophilic and lipophilic drugs and are able to deliver drugs to the target site. Furthermore, niosomal vesicles, that are usually non-toxic, require less production costs and are stable over a longer period of time in different conditions, so overcoming some drawbacks of liposomes. The niosome properties are specifically dictated by size, shape, and surface chemistry which are able to modify the drug's intrinsic pharmacokinetics and eventual drug targeting to the areas of pathology. This up-to-date review deals with composition, preparation, characterization/evaluation, advantages, disadvantages and application of niosomes.

Niosomes encapsulating Ibuprofen-cyclodextrin complexes: preparation and characterization.

A new delivery system based on ibuprofen-ß-cyclodextrin (ßCd) complexation and its loading into non-ionic surfactant vesicles (NSVs) was developed to improve ibuprofen therapeutic efficacy in topical formulations. The proposed strategy exploits the well known solubilizing and stabilizing properties of cyclodextrins together with the high tolerability and percutaneous absorption enhancing properties of NSVs. The complexing capacity of Cds in the presence of Ibuprofen in aqueous solution was evaluated by means of phase solubility studies. The technique used to obtain solid ibuprofen-ßCd complexes was the co-lyophilization method. The influence of the preparation method on the physicochemical properties of the final product was evaluated by means of Fourier Transform Infrared Spectroscopy and Differential scanning calorimetry studies. Ibuprofen-ßCd complexes were included in Tween 20/Cholesterol vesicles and characterized in terms of size, zeta (ζ)-potential, stability, drug entrapment efficiency and drug release. The best ibuprofen-ßCd-NSV system exhibited in vitro drug permeation properties significantly improved with respect to those of the plain drug suspension.

Polysorbate 20 vesicles as oral delivery system: in vitro characterization.

Non-phospholipid vesicles made with non-ionic surfactants represent a promising alternative to the more widely studied liposomes. The main aim of the present work is to evaluate if vesicles of polysorbate 20 may be used as delivery systems for oral administration of drugs. Then in vitro stability and mucoadhesion studies in simulated gastrointestinal fluids were carried out. The colloidal stability of the surfactant vesicles was determined by size and fluorescence-dequenching assay, while their mucoadhesive properties were evaluated by light-scattering and protein assay. The results of in vitro stability demonstrated that the pHs and enzymes (pepsin and/or pancreatin) of the gastrointestinal fluids had not influence on surfactant vesicle stability. However, in presence of bile salts the nanosize vesicles showed a release of fluorescent marker (about 11% at 2 h and 28% at 4 h), whereas they were stable in size as confirmed by the light scattering experiments. Finally, the in vitro mucoadhesive experiments showed that the capacity of nanovesicles to adsorb mucin was higher at neutral pH than at acidic pH. As a conclusion of these preliminary studies, the surfactant vesicles could be considered a versatile tool for the oral delivery of drugs with poor stability in gastrointestinal tract and low permeability. Nevertheless, further work is required in order to examine the interaction with and/or the transport route through the epithelial cells of the gastrointestinal wall.