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Suspensões de nanocápsulas contendo melatonina foram preparadas pelo método de deposição interfacial e caracterizadas (tamanho, morfologia e eficiência de encapsulação). Foram avaliadas as influências do tipo de polímero, de óleo e de tensoativo sobre as características dos produtos. A eficiência de encapsulação da melatonina variou de 30% a 56% e a natureza do polímero foi o parâmetro de maior influência. De acordo com a maior eficiência de encapsulação, nanocápsulas preparadas com Eudragit S100 ® foram selecionadas para secagem por aspersão, objetivando-se aumentar a estabilidade física das suspensões e controlar a liberação da melatonina. O pó obtido apresentou eficiência de encapsulação de 93% e não sofreu nenhuma alteração morfológica após 12 meses de armazenamento. Este sistema apresentou perfil de liberação controlado, comparativamente ao fármaco puro, o qual foi ajustado ao modelo monoexponencial. O mecanismo de liberação da melatonina foi baseado em intumescimento e dissolução do polímero.Nanocapsule suspensions containing melatonin were prepared by interfacial deposition method and characterized (size, morphological aspect and encapsulation efficiency). The formulation parameters studied were the oil nature, the type of surfactants and the type of polymer. The melatonin-encapsulation efficiency ranged between 30% and 56% and polymer nature was the parameter that more influenced the characteristics of suspensions. According to the highest encapsulation efficiency, the nanocapsules prepared with Eudragit S100 ® were selected to be spray-dried in order to improve the physical stability of suspension and to control the release of melatonin. The melatonin-loaded nanocapsule spray-dried powder presented encapsulation efficiency of the 93% and no morphological alterations were observed after 12 months of storage. This system showed a controlled release profile in comparison to the dissolution of the pure melatonin. The release profile was fitted to monoexponential model and the melatonin release mechanism was based on swelling and dissolution of the polymer. Keywords: melatonin, nanocapsules, nanoparticles, spray-dried powders IntroductionMelatonin, N-acetyl-5-methoxytryptamine (Figure 1), is a hormone secreted at night-time by the pineal gland of mammals and it is involved in the regulation of the sleepwake cycle, as well as in several biological functions, such as the modulation of mood, the control of seasonal reproduction in animals, the circadian rhythm regulation, the normal patterns of sleep, 1 and the neuroimmunomodulation in humans.2 The administration of the exogenous melatonin has been employed for circadian rhythm disorders as jet-lag and insomnia. 1 Beyond the potent antioxidant activity, the melatonin is a free radical scavenger, 3 protects against lipid peroxidation in several models 4 and against oxidative stress observed in some neurodegenerative diseases such as Alzheimer.5 It also protects against ischemia/ reperfusion injury 6 and presents anti-tumor activities. 7However, melatonin has a v...

Nanocapsules are vesicular drug carriers constituted of an oil core, a polymeric wall, and surfactants. A general understanding about the influence of the polymeric wall of nanocapsules on the release profiles of drugs is not known. So, this work was devoted to characterize formulations prepared without polymer or containing it at different concentrations. The indomethacin ethyl ester was used as model and the strategy was based on its interfacial alkaline hydrolysis simulating a sink condition for the release. The antiedematogenic activity in rats for ester-loaded-nanocarriers was also evaluated. The nanocapsules (NC) and nanoemulsion (NE) presented particle sizes below 300 nm, polydispersity lower than 1.2 and pH around 5. SAXS analyses showed that the sorbitan monostearate is dissolved in the oil and the polymer presents regions of crystallinity independently on the PCL concentration. TEM analyses showed droplets (NE) and spherical particles (NC). The time for the total disappearance of the ester varied from 12 h to 24 h depending on the polymer concentration. The biexponential model showed that the indomethacin ester was essentially entrapped within the nanocarriers in an extension of 85 to 95%. The half-lives varied from 147 to 289 min for the sustained phases and from 3 to 6 min for the burst phases. The ester-loaded-NC showed significant antiedematogenic activity, while the ester-loaded-NE did not inhibit the carrageenin-induced paw edema. The nanocapsules promoted the absorption of the indomethacin ethyl ester and the presence of the polymer is important to achieve the pharmacological effect.

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