Polymeric nanoparticles have received great attention as potential controlled drug delivery systems. Biodegradable polymers has been extensively used in the development of these drug carriers, and the polyesters such as polylactic acid, polyglycolic acid and their copolymers as poly-lactide-co-glycolide are the most used, considering its biocompatibility and biodegradability. Thermal analysis techniques have been used for pharmaceutical substances for more than 30 years and are routine methods for screening drugexcipient interactions. The aim of this work is to use thermal analysis to characterize PLGA nanoparticles containing a hydrophobic drug, praziquantel. The results show that the drug is in an amorphous
INTRODUCTIONNanoparticles are considered one of the most promising dosage forms as potential formulations for sitespecific drug delivery system including drug targeting (Mainardes, Silva, 2004;Hans, Lowman, 2002). Colloidal polymeric particles used as drug carriers can be made of artificial or natural polymers, which must be biocompatible (Soppimath et al., 2001; Gorner et al., 1999). In the past two decades, many works have been carried out in order to apply biocompatible and/or biodegradable polymers in drug delivery systems (Jain, 2000).Nanoparticles are a collective name for nanospheres and nanocapsules. Nanospheres have a matrix type structure, where active compounds can be adsorbed on their surface, entrapped or dissolved into the matrix. Nanocapsules have a polymeric shell and an inner core. In this case, the active substances are usually dissolved in the core, but may also be adsorbed on their surface (Allemann et al., 1998;Panyam, Labhasetwar, 2003).Although a number of different polymers have been investigated for formulating biodegradable nanoparticles, polymers of poly(L-lactic-acid) (PLA) and their copolymers with glycolic acid (PLGA) have been extensively used in controlled drug delivery systems. The lactide/glycolide polymers chains are cleaved by hydrolysis to form natural metabolites (lactic and glycolic acids), which are eliminated from the body through the citric acid cycle. PLGA provides a wide range of degradation rates, from months to years, depending on its composition and molecular weight (Mainardes, Evangelista, 2005;Uhrich et al., 1999;Vert et al., 1998;Anderson, Shive, 1997;Burkersroda et al., 2002).Aliphatic polyesters are polymers of the poly(α-hidroxy) acids class, one of the polymers families more attractive and promising, because their members are biocompatible and bioresorbable and could be used in several applications in the medicinal area (Iannace et al., 1994). The presence of the ester linkage makes these polymers hydrolytically unstable, this means that they can be degraded when in contact with the corporal fluids, resulting in products that are reabsorbed by the organism, as part of the carbohydrates metabolism (Beiser, Kanat, 1990). In the last years, the biodegradable polymers have gained a growing importance in the medical area. They have been used in a wide number ...
