Desenvolvimento, caracteriza??o e liofiliza??o de nanopart?culas e encapsulamento de antibi?tico de uso veterin?rio.

Na primeira parte deste trabalho foi avaliado o processo de liofiliza??o de nanoesferas e nanoc?psulas, utilizando-se v?rios crioprotetores e duas condi??es de congelamento, tendo como par?metro de investiga??o a efici?ncia do m?todo na manuten??o da distribui??o de tamanho inicial. Diferentes crioprotetores como glicose, sacarose, manitol e polidextrose, e concentra??es foram utilizadas. A distribui??o de tamanho das nanopart?culas e o ?ndice de polidispers?o foram determinados por espectroscopia de correla??o de f?tons e a morfologia por microscopia de for?a at?mica e eletr?nica de varredura. As nanopart?culas preparadas apresentaram-se com tamanho inferior a 300 nm e monodispersas. As amostras liofilizadas em presen?a de 5% (p/v) de sacarose forneceram como resultados de rela??o tamanho final/inicial valores de Tf/Ti=0,981 e Tf/Ti=0,995 a -80?C e a -196?C, respe ctivamente. Estudos por calorimetria diferencial explorat?ria confirmaram o efeito da sacarose sobre a intera??o entre tensioativos e pol?meros na estrutura das nanoesferas. O uso da polidextrose, como novo crioprotetor forneceu valores adequados de Tf/Ti=1,006, possibilitando a produ??o de nanoesferas liofilizadas na aus?ncia de mono e dissacar?deos. O uso de sacarose a 10% (p/v) forneceu resultados adequados Tf/Ti=1,059 para nanoc?psulas. Formula??es nanoestruturadas contendo cloxacilina benzatina, um antimicrobiano de uso veterin?rio, foram desenvolvidas e caracterizadas. Uma nova metodologia de doseamento da cloxacilina benzatina por cromatografia l?quida de alta efici?ncia foi desenvolvida e utilizada para determina??o do f?rmaco em amostras contendo nanopart?culas e outros componentes. A porcentagem de encapsula??o foi de 37 e 87% para nanoc?psulas de policaprolactona e de policaprolactona revestida com quitosana, respectivamente. O potencial zeta foi significativamente alterado pela presen?a de concentra??es crescentes do f?rmaco evidenciando sua adsor??o ? superf?cie das nanopart?culas. O perfil de libera??o da cloxacilina benzatina a partir dos carreadores em condi??es sink, indicou uma maior efici?ncia na reten??o do f?rmaco pelas nanoc?psulas de policaprolactona e um perfil de libera??o prolongado nas primeiras 6 horas, seguido de reten??o por mais 42 horas. As nanoc?psulas de policaprolactona revestidas com quitosana liberaram mais rapidamente a cloxacilina benzatina em meio contendo leite em rela??o ?s nanoc?psulas de policaprolactona.In this work, the process of freeze-drying of nanocapsules and nanospheres was evaluated using a range of cryoprotectors and two freezing conditions, evaluating their efficiency by the ability of maintaining the initial size distribution. The cryoprotectors, glucose, sucrose, mannitol and polydextrose, and different concentrations were used. The size distribution of poly-e-caprolactone nanoparticles was determined by photon correlation spectroscopy and the morphology by atomic force microscopy and scanning electron microscopy. Their sizes were consistently lower than 300 nm and the populations were monodispersed. The sucrose at 5% (w/v) was considered the best cryoprotector providing final to initial sizes ratio as efficient as 0,981 and 0,995, at -80 and - 196?C, respectively. Differential scanning calorimetry studies indicated that sucrose influenced the interactions between polymer and surfactants in nanoparticles during freeze-drying. The use of polydextrose as a new cryoprotector at -196?C provided also good size data Sf/Si=1,006 and allow the production of ?sugar-free? nanoparticulate formulations. In respect to nanocapsules the best result was obtained with 10% (w/v) of sucrose with Tf/Ti=1,059. In the second part, nanocapsules containing cloxacillin benzathine (CLOXB), an antibiotic for veterinary use, were prepared. A new assay method of CLOXB based in high liquid chromatography was developed and used for the determination of the loading yield, loading efficiency and release kinetic of the drug from nanocapsules. The results showed that the percentage of CLOXB entrapment in polycaprolactone nanocapsules (PCL NC) and nanocapsules of polycaprolactone and chitosan (PCL-QUIT NC) was 37 and 87%, respectively. Zeta potential of nanocapsules changed after drug association, indicating a strong influency of CLOXB on the particle surface. The release kinetic results of CLOXB from NC showed linear release profile up to 6 hours for NC and a plateau until 48h with incomplete release, indicating the retention of CLOXB entrapped for longer time in nanocapsules compared with the fast diffusion of free drug to the media. CLOXB release from PCL-QUIT NC was higher in saline with milk than PCL NC