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Our study demonstrates that poly(ester amine) may be applied as an useful gene carrier.

IntroductionPolymers that show phase transition in water upon raising the temperature above a critical point, termed lower critical solution temperature (LCST), have attracted much attention in many areas of modern science and engineering. Among these polymers, poly(N-isopropylacrylamide) (PNIPAAm) is the most popular temperature-sensitive polymer due to its dramatic and reversible transition behavior at around 32 8C. [1,2] Most work on the phase transition of PNIPAAm has so far been limited to the measurements on the macroscopic quantities, although many methods including cloud point measurement, [3] light scattering, [2] DSC, [4] and fluorescence [5] have been used.NMR relaxation times, i.e., spin-lattice relaxation time (T 1 ) and spin-spin relaxation time (T 2 ), and a linewidth give useful information on the microscopic molecular motion of water and polymer in solutions. [6][7][8] Applying NMR technique to study the phase transition of PNIPAAm, Tokuhiro et al. [9] measured T 1 of nonionic and ionic PNIPAAm gels in D 2 O and made a complete interpretation on the dynamics of the side and backbone chains through the phase transition process. In addition, a few researchers reported on the dynamics of PNIPAAm gel, polymer, and water molecules Summary: Core-shell-type nanoparticles composed of PBLG and PNIPAAm were prepared in an attempt to study the effects of temperature on the dynamic behavior of temperature-sensitive polymeric shell, PNIPAAm, in the nanoparticles by 1 H NMR spectroscopy. Spin-lattice relaxation time (T 1 ) and line halfwidth in D 2 O and CDCl 3 were measured to monitor the change of the chain mobility of PNIPAAm in the GN nanoparticles within the temperature range encompassing its LCST. The molecular motion of PBLG segment in GN nanoparticles in CDCl 3 was also examined and compared with that of the PNIPAAm. The morphology, size distribution, and effect of temperature on the sizes of the GN nanoparticles were also investigated. The temperature dependence of T 1 and line halfwidth suggests that the N-isopropyl group turns gradually into the solid-like aggregates at temperatures higher than the LCST of PNIPAAm due to the collapsed coil-globule transition. T 1 values of N-isopropyl groups decreased with increasing PBLG content in GN diblock copolymer, suggesting the mobility of PNIPAAm chain, as the shell, becomes more restricted at higher PBLG core content.Changes in the mobility of PNIPAAm shell in the core-shelltype nanoparticles composed of PBLG and PNIPAAm.

Purpose: Intussusception is one of the most common causes of an acute abdomen in infancy. The majority of pediatric cases of intussusception are of the ileocolic type and usually idiopathic. Small bowel intussusception is rarely diagnosed in children, and few cases have been reported. The purpose of this study was to determine the clinical features and causes of small bowel intussusception in children. Methods: We retrospectively reviewed the clinical and radiologic findings of 21 children with small bowel intussusception who were admitted to Seoul National University Children's Hospital between March 2005 and January 2010. Results:The clinical presentation of small bowel intussusception included abdominal pain or irritability (85%), vomiting (23%), fever (14%), bloody stools (14%), and abdominal masses (4%). Six patients required surgical management. Ultrasonography showed that the mean diameter of the lesions and mean thickness of the outer rims were 1.6±0.7 and 1.7±1.8 mm, respectively. Eleven lesions were located in the left abdominal or paraumbilical regions. Children who underwent surgical management were older than children with transient small bowel intussusception (mean age, 51 vs. 109 months). The mean diameter of the lesions and mean thickness of the outer rims were greater in the surgically-managed group. The location of intussusception was not significantly different between the two groups. Conclusion: Small bowel intussusception was spontaneously reduced in a large number of pediatric patients. However, sonographic demonstration of larger size, older age, and pathologic lead point warrant surgical intervention. (Korean J Pediatr Gastroenterol Nutr 2010; 13: 128∼133)