Isocyanate-functional adhesives for biomedical applications. Biocompatibility and feasibility study for vascular closure applications.

Biodegradable isocyanate-functional adhesives based on poly(ethylene glycol)-adipic acid esters were synthesized, characterized, and evaluated in vitro and in vivo. Two types of formulations, P2TT and P2MT, were developed by functionalization with 2,4-tolylene diisocyanate (TDI) or 4,4'-methylene-bis(phenyl isocyanate) (MDI), respectively, and branching with 1,1,1-trimethylolpropane (TMP). The biocompatibility of the synthesized adhesive formulations was evaluated as per ISO 10993. Cytotoxicity, systemic toxicity, pyrogenicity, genotoxicity (reverse mutation of Salmonella typhimurium and Escherichia coli), hemolysis, intracutaneous reactivity, and delayed-type hypersensitivity were evaluated. All formulations met the requirements of the conducted standard tests. The biological behavior and ability of the adhesive formulations to close an arteriotomy and withstand arterial pressure following partial approximation with a single suture were evaluated in a rat abdominal aorta model. Animals were evaluated at 1, 2, 3, and 4 weeks after surgery. Macroscopic and histopathologic evaluation of explanted arteries suggested that the P2TT formulation had better in vivo performance than the P2MT formulation. Additionally, the P2TT formulation resulted in less tissue reaction than P2MT formulation. To our knowledge, this is the first study demonstrating the potential of this new class of isocyanate-functional degradable adhesives for vascular applications.

Synthesis, optical, and electrochemical properties of a new family of dendritic oligothiophenes.

A new class of semi-flexible dendrimers with oligothiophene (OT) arms up to the third generation have been synthesized and investigated. The synthetic methods employed include a combination of palladium-catalyzed Stille cross-coupling reactions for oligothiophenes, Sonogashira cross-coupling reactions for building blocks, and carbodiimide-mediated esterification for building up the various dendrimers. The optical and electrochemical properties of this series of oligothiophenes-based dendrimers are shown to be strongly influenced by their morphologies as demonstrated by their pronounced solvatochromic and thermochromic responses under different environmental conditions. Introducing rigid oligothiophene arms to shape non-persistent ester-linked dendrimers causes higher generation dendrimers (G2 and G3) to exhibit solvatochromism and thermochromism, while their oligomeric counterpart (3b) and lower generation (G1) analogue do not. Spectroscopic changes due to both intramolecular and intermolecular aggregations are observed.