Modification of tricomponent and dicomponent poly(ε-caprolactone)-co- poly(ethylene glycol) with methotrexate and folic acid

Regarding polymer-drug conjugation, the reaction and drug characteristics are of important because they reflect the possibility of conjugation. Tri- and dicomponent azido-functionalized copolymers were initially synthesized. Tricomponent copolymers consisted of caproyl, azido-substituted caproyl, and ethylene glycol repeating units, whereas dicomponent ones contained solely the last two repeating units. In parallel, the terminal alkyne derivatives of methotrexate (MTX) and folic acid (FOL) were synthesized by coupling reaction using N,N-dicyclohexylcarbodiimide and 4-dimethylaminopyridine with an additional N-hydroxysuccinimide for FOL coupling. By click reaction, MTX and FOL were successfully conjugated with tri- and dicomponent copolymers, respectively, without polymer chain degradation. The grafting efficiencies of MTX and FOL were higher than 77 and 68% by using CuI/1,8-diazabicyclo[5.4.0] undec-7-ene and CuSO₄.5H₂O/sodium ascorbate, respectively. According to the differential scanning calorimetry thermograms, MTX did not change the semicrystalline property of copolymers except for high % molar grafting, whereas the presence of FOL affected thermal properties of copolymer except at 5 molar grafting. The resultant copolymers could be further used as polymer-drug conjugate delivery system for cancer therapy.