Chitosan nanoparticles prepared by ionotropic gelation with the tripolyphosphate (TPP) polyanion have been widely considered for drug delivery. The stability (shelf-life) of TPP-chitosan nanoparticles is highly relevant to its potential use as a drug delivery agent as this plays an important role in the function of the nanoparticle and will determine shelf-life. In the present study, the physical stability (in terms of particle size) of TPP-chitosan nanoparticles was measured across a range of different temperature conditions: 4 ºC, 25 ºC and 40 ºC using differential sedimentation. After 12 months storage at 4 and 25 °C the size of nanoparticles remained similar to those of the freshly prepared samples, whilst after storage at 40 °C there were little or no TPP-chitosan nanoparticles remaining after only 6 months. This may be due to the decrease in molar mass of the chitosan possibly due to hydrolysis causing scission of the polymer chains, which results in a decrease in nanoparticle size and eventual disintegration. This mechanism is important in the application of TPP-chitosan as a drug delivery agent.
Chitosans of different molar masses were prepared by storing freshly prepared samples for up to 6 months at either 4 ºC, 25 ºC or 40 ºC. The weight-average molar masses, M w and intrinsic viscosities, [ ] were then measured using size exclusion chromatography coupled to multi-angle laser light scattering (SEC-MALLS) and a "rolling ball" viscometer, respectively.The solution conformation of chitosan was then estimated from:
The flexibility/ rigidity of pectins plays an important part in their structure -function relationship and therefore on their commercial applications in the food and
It was shown conclusively that chitosan nanoparticles did not improve the absorption enhancing effect of chitosan in solution or powder form and that chitosan powder was the most effective for mulation for nasal delivery of insulin in the sheep model.
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