Polyglutamate copolymers as a tissue-engineering platform: Polymer scaffold modification through aminolysis of poly(γ-benzyl-l-glutamate-co-2,2,2-γ-trichlorethyl-l-glutamate)

Homopolymers of γ-benzyl-l-glutamate (BLG) and its copolymers with more reactive 2,2,2-γ-trichlorethyl-l-glutamate (TCEG), poly(γ-benzyl-l-glutamate-co-2,2,2-γ-trichlorethyl-l-glutamate) (poly(BLG-co-TCEG)), were synthesized by ring opening polymerization of respective N-carboxyanhydrides (NCA). The copolymerization parameters of N-carboxyanhydrides were determined according to the Fineman-Ross and Kelen-Tüdõs methods. To be studied as potential material for fabrication of tissue engineering scaffolds, polyglutamates were processed into solid films by casting from solution in dichloroethane as well as to fibres by solution-spinning method. The feasibility of functional modification of polyglutamate films and fibres through aminolysis of glutamate ester side chains with 2-aminoethanol or with a 2-aminoethanol/1,6-diaminohexane mixture under various conditions was studied. The progress and extent of polymer side chain modification and the resulting surface modification of PBLG or poly(BLG-co-TCEG) films and fibres were analyzed by following methods: (a) the conversion of aminolysis of BLG units alone was determined from the amount of released benzyl alcohol extracted into hexane and followed by HPLC analysis, (b) the conversion of aminolysis of TCEG units in poly(BLG-co-TCEG) was calculated from elemental analysis, (c) the depth and extend of films surface modification was evaluated from the change of ester-amide ratio at the surface, as obtained from ATR IR measurements and (d) the amount of reactive free amino groups, created by aminolysis with 1,6-diaminohexane, was quantified by reaction with 2,4,6-trinitrobenzenesulfonic acid (TNBS).