Synthesis and Properties of Bioresorbable Block Copolymers of l-Lactide, Glycolide, Butyl Succinate and Butyl Citrate.

Natalia Śmigiel-Gac,Małgorzata Krok-Borkowicz,Elżbieta Pamuła,Piotr Dobrzyński,Anna Smola-Dmochowska

doi:10.3390/polym12010214

Natalia Śmigiel-Gac, Małgorzata Krok-Borkowicz + Show 3 more

Open Access

https://doi.org/10.3390/polym12010214

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Abstract

The paper presents the course of synthesis and properties of a series of block copolymers intended for biomedical applications, mainly as a material for forming scaffolds for tissue engineering. These materials were obtained in the polymerization of l-lactide and copolymerization of l-lactide with glycolide carried out using a number of macroinitiators previously obtained in the reaction of polytransesterification of succinic diester, citric triester and 1,4-butanediol. NMR, FTIR and DSC were used to characterize the materials obtained; wettability and surface free energy were assessed too. Moreover, biological tests, i.e., viability and metabolic activity of MG-63 osteoblast-like cells in contact with synthesized polymers were performed. Properties of obtained block copolymers were controlled by the composition of the polymerization mixture and by the composition of the macroinitiator. The copolymers contained active side hydroxyl groups derived from citrate units present in the polymer chain. During the polymerization of l-lactide in the presence of polyesters with butylene citrate units in the chain, obtained products of the reaction held a fraction of highly branched copolymers with ultrahigh molecular weight. The reason for this observed phenomenon was strong intermolecular transesterification directed to lactidyl side chains, formed as a result of chain growth on hydroxyl groups related to the quaternary carbons of the citrate units. Based on the physicochemical properties and results of biological tests it was found that the most promising materials for scaffolds formation were poly(l-lactide–co–glycolide)–block–poly(butylene succinate–co–butylene citrate)s, especially those copolymers containing more than 60 mol % of lactidyl units.

Highlights

Regenerative medicine and tissue engineering are presumably the most exciting scientific activities, giving hope for our aging society to extend life span and its quality
The macroinitiators were obtained by the polytransesterification reaction of succinic and citric acid esters and 1,4-butandiol
During the polymerization of l-lactide conducted with presence of polyesters containing butylene citrate units in the chain, obtained product held a fraction of very highly branched copolymers of very high molecular weight

Summary

Introduction

Regenerative medicine and tissue engineering are presumably the most exciting scientific activities, giving hope for our aging society to extend life span and its quality. Biocompatible and biodegradable supporting structures (scaffolds) playing a role of natural extracellular matrix, in conjunction with human cells and signaling molecules are used to restore or improve tissues functions Aliphatic polyesters such as homopolymers and copolymers of lactides, glycolide and ε-caprolactone are the most commonly used polymeric biomaterials for scaffold manufacturing, mainly due to their well-known and proven biocompatibility and defined biodegradation course. Pendant carboxyl and hydroxyl groups of citric acid derivatives can be partially preserved to provide inherent functionality in the bulk of the material for the conjugation of bioactive molecules [5] As it has been shown, that these polymers exhibit excellent cytocompatibility and provoke only minimal inflammation in different tissues. This effect occurs in contact with other biodegradable materials—aliphatic polyester carbonates containing high amount of carboxyl side groups [10]

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