Synthesis and properties of novel block copolymers containing poly(lactic-glycolic acid) and poly(ethyleneglycol) segments

A synthetic process for obtaining high-molecular-weight block copolymers containing poly(lacticglycolic acid) and poly(ethylene glycol) segments has been established. This process involves the reaction of poly(ethylene glycols) with phosgene, followed by polycondensation of the resulting ,ω-bis (chloroformates) with poly(lactic-glycolic acid) oligomers. The copolymers have been characterized for their molecular weight, solubility properties, water absorption and preliminarily thermal behaviour. All evidence points to the conclusion that the process described is a general one, enabling biodegradable polymers to be obtained tailor-made according to specific requirements.     

A geometric reappraisal of proximal landing zones for thoracic endovascular aortic repair according to aortic arch types

Objective

This study assessed whether the additional use of the aortic arch classification in type I, II, and III may complement Ishimaru's aortic arch map and provide valuable information on the geometry and suitability of proximal landing zones for thoracic endovascular aortic repair.

Polymer substrate topography actively regulates the multicellular organization and liver-specific functions of cultured hepatocytes

This study examines the role of topography of porous synthetic polymer substrates in regulating the tissue-specific morphogenesis of cultured hepatocytes. Porous foams of amorphous 50/50 poly(D,L glycolic-co-lactic acid) (PGLA) with a wide range of controlled pore-size distributions ( approximately 1 to 100 microm) were used as culture model surfaces. We found that the induction of microporosity in PGLA substrates significantly improved cell attachment and viability in comparison to those observed on non-porous PGLA films. A detailed evaluation of cellular morphogenesis on the microporous matrices showed that hepatocellular organization was sensitively dependent on the topographical feature size of the foam surfaces. Foams with subcellular size voids ( approximately 3 microm) induced kinetics of two-dimensional hepatocyte reorganization, yet limited the extent of three-dimensional aggregation. In contrast, foams with supercellular size voids ( approximately 67-microm) restricted hepatocyte motility, thereby promoting the kinetics of 3D aggregation. At intermediate void sizes ( approximately 17 microm), both 2D and 3D reorganization kinetics were promoted. Albumin secretory kinetics progressively increased on all void size configurations, the most rapid and sustained kinetics observed in supercellular sized voids, which may serve to minimize cell-polymer contacts and maximize cell-cell contacts in 3D. Overall, these studies demonstrate that void topography of porous polymer substrates is a critical textural feature to induce short-term cell adhesion and viability, and to also selectively regulate the kinetics and extent of multicellular spreading versus 3D aggregation. By virtue of its effects on cell adhesion and morphogenesis, the void topography of nonphysiological polymer scaffolds also is a powerful variable to microengineer hepatospecific activity of tissue analogs.     

Biological performance of a novel biodegradable polyamidoamine hydrogel as guide for peripheral nerve regeneration

Polyamidoamines (PAAs) are a well-known family of synthetic biocompatible and biodegradable polymers, which can be prepared as soft hydrogels characterized by low interfacial tension and tunable elasticity. For the first time we report here on the in vivo performance of a PAA hydrogel implant as scaffold for tissue engineering. In particular, an amphoteric agmatine-deriving PAA hydrogel shaped as small tubing was obtained by radical polymerization of a soluble functional oligomeric precursor and used as conduit for nerve regeneration in a rat sciatic nerve cut model. The animals were analyzed at 30, 90, and 180 days post-surgery. PAA tubing proved to facilitate nerve regeneration. Good surgical outcomes were achieved with no signs of inflammation or neuroma. Moreover, nerve regeneration was morphologically sound and the quality of functional recovery satisfactory. In conclusion, PAA hydrogel scaffolds may represent a novel and promising material for peripheral nerve regeneration.     

Hyperlactatemia during cardiopulmonary bypass: determinants and impact on postoperative outcome

Introduction  

Hyperlactatemia during cardiopulmonary bypass is relatively frequent and is associated with an increased postoperative morbidity. The aim of this study was to determine which perfusion-related factors may be responsible for hyperlactatemia, with specific respect to hemodilution and oxygen delivery, and to verify the clinical impact of hyperlactatemia during cardiopulmonary bypass in terms of postoperative morbidity and mortality rate.