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Titolo: Caratterizzazione dimensionale e morfologica di nanoparticelle lipidiche contenenti molecole farmacologicamente attive
Data di pubblicazione: 2-mar-2012
Abstract: With the advent of nanotechnology, great interest is being dedicated to the interactions of nanomaterials/nanoparticles with human beings. All the interactions occurring due to an intentional exposure are investigated by a new research field named Nanomedicine. As this name may suggest, the use of drug delivery systems, sized in the nanometric scale, may favor overcoming anatomical barriers to reach, passively or by a targeting design, the body area to be pharmacologically treated. In this thesis, we focused our attention to the morphological and dimensional characterization of pharmaceutical lipidic nanoparticles (NP). These carriers were selected because we hypothesized that they could be good candidates for potent but lipophilic drugs that cannot be systemically administered with conventional formulations (e.g., solutions, dispersions). In addition, we focused on their preparation and characterization to evaluate potential therapeutic applications based on shape and size. Specifically, we prepared two types of NP named nanocapsules (NC) and nanoemulsions (NE); the former differs from the latter for a polysaccharidic capsule. Several drugs (ibuprofen and its sodium salt, transretinoic acid, paclitaxel, AZL 6 and 38) and two fluorescently-labeled lipids (i.e.,FITC-PE, NBD) have been entrapped within both NP. We found that lipophilic molecules were completely encapsulated in both NP. In contrast, in the case of the hydrophilic drug, the polysaccharidic capsule causes ibuprofen sodium salt to be entrapped with a greater efficiency in NC than NE (i.e. 92.6 % IE in NC vs. 20.4 % IE in NE). Morphological analysis has been carried out on NP, that were not subjected to a purification treatment, by TEM, and in a few cases also by Cryo-TEM. Although the sample drying step showed to be very critical in producing artifacts, we arrived to the conclusion that particles were spherical. Dimensional analysis has been carried out with TEM and DLS on NP subjected or not-subjected to two different purification methods (i.e., centrifugal filtration, dialysis). The rational of purifica- tion is to remove molecules that, potentially, were not assembled in the NP. The DLS analyses allowed to measure dimensions (Z-Ave) at both 25° and 37°C, and to obtain the polydispersity index(PDI) and superficial charge (ZP). Results showed that NC are positively charged (ca. 45.7 mV) and sized averagely 185-230 nm at 25°C. Their PDI range is 0.145-0.198. In contrast, NE are negatively charged (ca. -58.5 mV) and sized averagely 142-153 nm at 25°C. Their PDI range is 0.111-0.135. By increasing temperature to 37°C, NC and NE dimensions are affected up to a - 10% and + 3 %, respectively. Ranges of PDI change a little, and become 0.131-0.178 and 0.120-0.133 respectively for NC and NE. It seems that temperature might give energy for a better ar- rangement of molecules and drugs. Hence, also ZP changes: in NC it was possible to observe, in almost all cases, a decrease up to 23%. In NE, we observed a correlation between PDI and ZP: e.g.,if PDI increases ZP decreases; in any case, values are not larger than +-17%. Purification by centrifugation differently affects NP. In the case of NC dimensions increase (22-53%) as well as PDI (15-108% = 0.210-0.342), whereas ZP might increase or decrease depend- ing on the entrapped drug (+- 12%). In the case of NE, dimensions stay stable (≤ 1%) but their PDI might change significantly (-2 - +64% = 0.110-0.221), and ZP decreases (0.4-20%). Dialysis is not indifferent either, and results also vary with dialysis time. After 48 h we observed the followings. In the case of NC, dimensions increase (17-52%), PDI decreases (5-46%) and ZP may increase or decrease (-8 - +17%). In the case of NE, dimensions slightly decrease (3-5%), PDI decreases (3-27%), and ZP increases (19-32%). In conclusion, these NP are suitable candidates for further developments on pharmaceutical ap- plications, however their characterization should be accurately set-up to mimic body fluids and conditions at the area to be pharmacologically treated.
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