Surface Modification of PDLLA Scaffolds with Diazonium Chemistry for Orthopedic Applications

摘要

Scaffolds are porous materials used in tissue engineering as platforms to enhance cell attachment, proliferation and activity, leading to shorter healing time of injured or missing tissue. The surface of the scaffolds is the first region cells get in contact with upon implantation, and determines their reaction to it. Since the surface of synthetic polymeric scaffolds is not ideal for cell adhesion and proliferation because of their hydrophobic nature, surface midification of these materials is crucial for enhancing implant integration in the body. When these scaffolds are used in orthopedic applications, surface midifications can help the formation of hydroxyapatite, the mineral component of bones-a process known as biomineralization. Many people have succeeded in surface midification of bi-dimensional polymer films using plasma methods, but diffusion is a major obstacle when trying to modify the surface of three-dimension scaffolds by plasma treatment. In this study, we used diazonium chemistry for the first time to functionalize poly(D, L-lactic)acid (PDLLA) scaffolds with pores in the range of 200-350 m, fabricated with the salt leaching method. By carrying out the midification in solution, we were able to modify both the outer and the inner surface of the porous scaffolds, and we introduced covalently bonded amino groups using para-phenylenediamine as precursor for in-situ generated diazonium cations (Fig 1). By changing parameters such as reaction time and reducing agent concentration we were able to tune the concentration of amino groups present on the scaffolds (Fig 2). The amino-phenyl layer formed on the scaffold surface is "self-adhesive", and can be exploited to bind other biomolecules. Here we present spectroscopic results confirming the successful surface midification of PDLLA scaffolds, and the effect of these midifications on the in-vitro biomineralization of the modified scaffolds.