Abstract
Polyurethane (PU) is a promising polymer to support bone–matrix producing cells due to its durability and mechanical resistance. In this study two types of medical grade poly-ether urethanes Z3A1 and Z9A1 and PU-Hydroxyapatite (PU–HA) composites were investigated for their ability to act as a scaffold for tissue engineered bone. PU dissolved in varying concentrations of dimethylformamide (DMF) and tetrahydrofuran (THF) solvents were electrospun to attain scaffolds with randomly orientated non-woven fibres.Bioactive polymeric composite scaffolds were created using 15wt% Z3A1 in a 70/30 DMF/THF PU solution and incorporating micro- or nano-sized HA particles in a ratio of 3:1 respectively, whilst a 25wt% Z9A1 PU solution was doped in ratio of 5:1. Chemical properties of the resulting composites were evaluated by FTIR and physical properties by SEM. Tensile mechanical testing was carried out on all electrospun scaffolds. MLO-A5 osteoblastic mouse cells and human embryonic mesenchymal progenitor cells, hES-MPs were seeded on the scaffolds to test their biocompatibility and ability to support mineralised matrix production over a 28 day culture period. Cell viability was assayed by MTT and calcium and collagen deposition by Sirius red and alizarin red respectively.SEM images of both electrospun PU scaffolds and PU–HA composite scaffolds showed differences in fibre morphology with changes in solvent combinations and size of HA particles. Inclusion of THF eliminated the presence of beads in fibres that were present in scaffolds fabricated with 100% DMF solvent, and resulted in fibres with a more uniform morphology and thicker diameters. Mechanical testing demonstrated that the Young׳s Modulus and yield strength was lower at higher THF concentrations. Inclusion of both sizes of HA particles in PU–HA solutions reinforced the scaffolds leading to higher mechanical properties, whilst FTIR characterisation confirmed the presence of HA in all composite scaffolds.Although all scaffolds supported proliferation of both cell types and deposition of calcified matrix, PU–HA composite fibres containing nano-HA enabled the highest cell viability and collagen deposition. These scaffolds have the potential to support bone matrix formation for bone tissue engineering.
Highlights
Bone tissue engineering aims at improving musculoskeletal health by providing a living bone graft substitute to fill and aid in the repair of bone defects caused by trauma, disease, or congenital malformations or to augment bone stock around an implant site
We investigated the effect of including nano and micro size HA particles on fibre morphology, mechanical properties, biocompatibility, extracellular and calcified matrix production over a 28 day period using MLO-A5 osteoblastic mouse cells and human embryonic mesenchymal progenitor cells
Polyurethane remains a popular choice amongst polymers for its advantageous properties of biocompatibility, biodegradability, mechanical flexibility and versatile chemistry allowing it to be tailor-made for specific applications
Summary
Bone tissue engineering aims at improving musculoskeletal health by providing a living bone graft substitute to fill and aid in the repair of bone defects caused by trauma, disease, or congenital malformations or to augment bone stock around an implant site. Bone tissue engineering involves the use of materials to either induce formation of bone from the surrounding tissue or to act as a carrier or template for implanted bone cells. Later bone implant materials were engineered to be bioactive or bioresorbable to enhance tissue growth (‘second generation’), a development which coincided with the development of tissue engineering scaffolds as cell supports for multiple tissue types. Bone implant materials are designed to induce bone formation (Bose et al, 2012) and many bone graft substitute materials are used as experimental scaffolds to support cells for bone tissue engineering
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