Poly(d,l-Lactic acid) Composite Foams Containing Phosphate Glass Particles Produced via Solid-State Foaming Using CO2 for Bone Tissue Engineering Applications.

Maziar Shah Mohammadi,Jason Bertram,Ehsan Rezabeigi,Martin N Bureau,Richard Gendron,Benedetto Marelli,Showan N Nazhat

doi:10.3390/polym12010231

Maziar Shah Mohammadi, Jason Bertram + Show 5 more

Open Access

https://doi.org/10.3390/polym12010231

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Journal: Polymers	Publication Date: Jan 17, 2020
Citations: 12	License type: CC BY 4.0

Affiliation: McGill University, National Research Council Canada

Abstract

This study reports on the production and characterization of highly porous (up to 91%) composite foams for potential bone tissue engineering (BTE) applications. A calcium phosphate-based glass particulate (PGP) filler of the formulation 50P2O5-40CaO-10TiO2 mol.%, was incorporated into biodegradable poly(d,l-lactic acid) (PDLLA) at 5, 10, 20, and 30 vol.%. The composites were fabricated by melt compounding (extrusion) and compression molding, and converted into porous structures through solid-state foaming (SSF) using high-pressure gaseous carbon dioxide. The morphological and mechanical properties of neat PDLLA and composites in both nonporous and porous states were examined. Scanning electron microscopy micrographs showed that the PGPs were well dispersed throughout the matrices. The highly porous composite systems exhibited improved compressive strength and Young’s modulus (up to >2-fold) and well-interconnected macropores (up to ~78% open pores at 30 vol.% PGP) compared to those of the neat PDLLA foam. The pore size of the composite foams decreased with increasing PGPs content from an average of 920 µm for neat PDLLA foam to 190 µm for PDLLA-30PGP. Furthermore, the experimental data was in line with the Gibson and Ashby model, and effective microstructural changes were confirmed to occur upon 30 vol.% PGP incorporation. Interestingly, the SSF technique allowed for a high incorporation of bioactive particles (up to 30 vol.%—equivalent to ~46 wt.%) while maintaining the morphological and mechanical criteria required for BTE scaffolds. Based on the results, the SSF technique can offer more advantages and flexibility for designing composite foams with tunable characteristics compared to other methods used for the fabrication of BTE scaffolds.

Highlights

Bone tissue engineering (BTE), which aims to use a highly porous scaffold construct to promote the regeneration of the damaged tissue, is a promising alternative to current surgical bone grafting techniques [1,2,3]
phosphate-based glass particulate (PGP) content via melt extrusion and compression molding followed by solid-state foaming using CO2
This foaming technique allowed for the incorporation of a broad range of PGP volume fraction, which can be very beneficial in BTE applications, since various particle contents may be required depending on their composition and the target application

Summary

Introduction

Bone tissue engineering (BTE), which aims to use a highly porous scaffold construct to promote the regeneration of the damaged tissue, is a promising alternative to current surgical bone grafting techniques [1,2,3]. Calcium phosphate ceramics and glasses, such as hydroxyapatite (HA) and silicate-based glasses (e.g., Bioglass®) incorporated into biodegradable polymers, e.g., poly(lactic acid) (PLA), poly(glycolic acid) (PGA), and their copolymers (PLGA) [12], as well as polycaprolactone (PCL) [13] have been extensively studied for BTE applications [12,14,15] Because of their controllable solubility in aqueous environments (e.g., physiological fluids), phosphate-based glasses (PGs) can be an alternative inorganic phase for the purpose of producing bioactive composites with controllable degradation characteristics [16,17,18]

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Discussion

Conclusion