Fabrication and In Situ Cross-Linking of Carboxylic-Acid-Functionalized Poly(Ester Amide) Scaffolds for Tissue Engineering

Abstract

Three-dimensional (3D) scaffolds are important tools for tissue engineering and should ideally provide both biochemical cues and biomechanical support for cells. Poly(ester amide)s (PEAs) have emerged as promising materials for the preparation of tissue engineering scaffolds, and the pendant side chains of residues, such as l-lysine and l-aspartic acid, can provide sites for the conjugation of biochemical signals. However, it has been challenging to combine scaffold morphological stability with the presentation of reactive groups on PEA scaffolds. We describe here a new approach involving the functionalization of a l-lysine-containing PEA with maleic anhydride to simultaneously introduce cross-linkable alkenes and carboxylic acid conjugation sites. Maleic-acid-functionalized PEA was processed to form 3D scaffolds using a salt leaching method and the scaffolds were cross-linked in situ using a poly(ethylene glycol) dimethacrylate cross-linking agent by thermal free radical curing. Microcomputed tomography analysis indicated that the cross-linked scaffolds had higher polymer volume fraction, lower porosity, and smaller pore size than the non-cross-linked scaffolds, but both scaffolds exhibited high morphological stability and negligible mass loss upon incubation in phosphate-buffered saline for 5 days. The Young’s moduli of the cross-linked and non-cross-linked scaffolds were 28 and 9 kPa, respectively. Fluorescein-labeled bovine serum albumin was successfully conjugated to the scaffolds using a carbodiimide-based coupling. Finally, it was shown that the scaffolds supported the attachment and proliferation of mouse embryonic mesenchymal multipotent cells, showing their promise as platforms for tissue engineering applications.