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.

A self-assembled, modular DNA delivery system mediated by silica nanoparticles.

Due to the growing concerns over the toxicity and immunogenicity of viral DNA delivery systems, DNA delivery via non-viral routes has become more desirable and advantageous. The ideal non-viral DNA delivery system should be a synthetic system that mimics viral vectors. It should also be biocompatible, efficient, and modular so that it is tunable to various applications in both research and clinical settings. The first successful step towards this modular synthetic DNA delivery system is demonstrated: a three-component transfection system mediated by silica nanoparticles. Dense silica nanoparticles serve as an uptake-enhancing component by physical concentration at the cell surface; enhanced transfection due to the particles is seen with almost every transfection reagent tested with little toxicity. In addition, a mathematical model has been built that successfully predicts several important parameters of transfection enhancement. This three-component transfection system lays the groundwork for a future multi-component modular synthetic DNA delivery system that may be useful in non-viral gene therapy and DNA vaccination.