Amphiphilic block copolymers: synthesis, characterization and application in biomaterials

Author(s)

Lívia Mesquita Dias Loiola

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2017-02-07

Examining board members

Maria Isabel Felisberti; Maria do Carmo Gonçalves; Luiz Henrique Catalani; Angela Maria Moraes; Mathilde Julienne Gisele Champeau Ferreira

• Advisor: Maria Isabel Felisberti

Abstract

The purpose of this work is the synthesis, characterization and application of triblock and pentablock amphiphilic copolymers, based on poly(L-lactide) (PLLA) and polyethers of ethylene oxide and propylene oxide: PEO, PEO-b-PPO-b-PEO, PPO-b-PEO-b-PPO and PEO-ran-PPO, as nanocomposites and drug carrier scaffolds biomaterials. The copolymers were synthesized by ring-opening polymerization of L-lactide applying polyethers with distinct compositions and architectures as macroinitiators. These copolymers combine the antagonistic characteristics of their blocks, such as hydrophilicity/hydrophobicity and flexibility/stiffness. In addition, the end blocks of the copolymers, composed of PLLA, crystallize and prevent the central polyether blocks crystallization. The hydrophilicity of the copolymers was evaluated by water swelling and wettability tests, and it is closely related to the PEO content in the materials and can be modulated by copolymers both architecture and composition. Cytotoxicity assays revealed cell adhesion and proliferation on the copolymers films surfaces. Making use of the amphiphilic nature of these copolymers, nanocomposites were prepared by the dispersion of the hydrophilic filler nanohydroxyapatite. The filler dispersion was carried out in benzene suspensions, followed by freeze-dry and injection molding process, and cylindrical and rectangular specimens of the nanocomposites were obtained. The copolymers hydrophilic phase effectively contributed to the filler both uniform dispersion and adhesion to the polymeric matrix. The mechanical properties of the nanocomposites were determined by two antagonistic effects associated with the introduction of a rigid reinforcing filler and with the decrease of the crystallinity degree, resulting in a slight increase in elastic modulus and hardness. Finally, amphiphilic polymeric scaffolds were electrospun with and without the hydrophilic and hydrophobic model drugs addition. The amphiphilic nature of the copolymers enabled them to encapsulate both drugs; however the drugs encapsulation efficiency and release profile in aqueous medium at pH 7.4 were mainly dependent on the copolymer/drug affinity. The copolymers, as well as their nanocomposites with nanohydroxyapatite and drug carrier scaffolds, present the potential to be applied as biomaterials, whose properties can be widely modulated for a specific application (AU)

• FAPESP's process: 12/24821-0 - Biocompatible composites based on amphiphilic copolymers and hydroxyapatite
• Grantee: Lívia Mesquita Dias Loiola
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)