Bone tissue engineering is a promising alternative in the treatment of non-healing bone fractures. In this field, the use of nanocomposite thermoplastic polymer - hydroxyapatite (HAp) scaffolds show encouraging results; however, challenges still exist in fabricating matrices with optimal bioactivity and suitable mechanical properties. This study investigates the fabrication of slowly biodegradable, nanocomposite polymer scaffolds made from PCL/acrylated l-lactide-co-trimethylene carbonate (aPLA-co-TMC) and HAp. The addition of acrylate groups permits the ‘in-process’ formation of crosslinks between PLA-co-TMC chains during electrospinning of the composite system. GPC and NMR analysis were conducted to assess the quality of polymer obtained. Although PCL and aPLA-co-TMC were miscible in a co-solvent, during electrospinning a ‘core-shell’ fibres structure is produced, with the core being composed of PCL, and the shell of crosslinked elastomeric aPLA-co-TMC. TEM and AFM analysis confirm this particular structure, that is conserved also with the addition of the HA particles. To solve dispersion problem of the HA particles in the polymer matrix, hence enhancing the mechanical property of the scaffolds, three different surface modification methods of HAp, with Stearic Acid (SA), Polylactide Acid (PLA) and PolyCaprolactone (PCL) were conducted: FT-IR, TGA and dispersion analysis were performed to confirm the effectiveness of these reactions. TEM and SEM analysis were used to morphologically evaluate the scaffolds; especially TEM was critical to assess the particles dispersion into the polymer fibres. Then tensile tests were performed in order to evaluate the enhancement of the mechanical properties given by the addition of low amount the modified HAp. The best properties were found with the addition of 1 wt.% of PCL-HA, improving the Young’s modulus of more than 250 %. Degradation tests were conducted over a period of 6 months to characterize the degradation dynamic of the electrospun scaffolds. This new processing methodology and resulting mechanically-improved composite scaffolds hold significant promise for bone tissue engineering applications.
L'ingegneria dei tessuti ossei è un'alternativa promettente nel trattamento delle fratture ossee non auto rigenerabili. In questo campo, l'uso di scaffold termoplastici polimero-idrossiapatite (HAp) nanocompositi mostra risultati incoraggianti; Tuttavia, esistono ancora delle difficoltà nella fabbricazione di matrici con bioattività ottimale e proprietà meccaniche appropriate. Questo studio esamina la realizzazione di scaffold nanocompositi, lentamente biodegradabili, ottenuti da PCL/aPLA-co-TMC e HAp. L'aggiunta di gruppi acrilati consente la formazione in processi di reticolazione tra le catene di PLA-co-TMC durante l'elettrospinning del sistema composito. Sono state condotte analisi GPC e NMR per valutare la qualità del polimero ottenuto. Sebbene PCL e aPLA-co-TMC siano miscibili in un co-solvente, durante l'elettrospinning viene prodotta una struttura di fibre "core shell", con il nucleo composto da PCL e il guscio di aPLA-co-TMC elastomerico reticolato. L'analisi TEM e AFM confermano questa particolare struttura, che è conservata anche con l'aggiunta delle particelle di HA. Per risolvere il problema della dispersione delle particelle HA nella matrice polimerica, migliorando così la proprietà meccanica degli scaffold, sono stati condotti tre metodi di modifica della superficie di HAp con Stearic Acid (SA), Polylactide Acid (PLA) e PolyCaprolactone (PCL). FT-IR, TGA e analisi di dispersione sono state eseguite per confermare l'efficacia di queste reazioni. Analisi TEM e SEM sono state utilizzate per valutare morfologicamente gli scaffold; Soprattutto TEM è stato fondamentale per valutare la dispersione delle particelle nelle fibre polimeriche. Quindi sono stati eseguiti test di trazione per valutare il miglioramento delle proprietà meccaniche fornite dall'aggiunta di una ridotta quantità di HAp modificato. Le migliori proprietà sono state trovate con l'aggiunta di 1% in peso di PCL-HA, migliorando il modulo di Young di oltre il 250%. I test di degradazione sono stati condotti per un periodo di 6 mesi per caratterizzare la dinamica di degradazione degli scaffold. Questa nuova metodologia di lavorazione e gli scaffold compositi ottenuti, meccanicamente migliorati, sostituiscono una significativa promessa per le applicazioni di ingegneria dei tessuti ossei.
Development of aPLA-co-TMC/PCL bionanocomposites with different modified hydroxyapatite for bone tissue engineering
DE MATTEO, MARIO
2016/2017
Abstract
Bone tissue engineering is a promising alternative in the treatment of non-healing bone fractures. In this field, the use of nanocomposite thermoplastic polymer - hydroxyapatite (HAp) scaffolds show encouraging results; however, challenges still exist in fabricating matrices with optimal bioactivity and suitable mechanical properties. This study investigates the fabrication of slowly biodegradable, nanocomposite polymer scaffolds made from PCL/acrylated l-lactide-co-trimethylene carbonate (aPLA-co-TMC) and HAp. The addition of acrylate groups permits the ‘in-process’ formation of crosslinks between PLA-co-TMC chains during electrospinning of the composite system. GPC and NMR analysis were conducted to assess the quality of polymer obtained. Although PCL and aPLA-co-TMC were miscible in a co-solvent, during electrospinning a ‘core-shell’ fibres structure is produced, with the core being composed of PCL, and the shell of crosslinked elastomeric aPLA-co-TMC. TEM and AFM analysis confirm this particular structure, that is conserved also with the addition of the HA particles. To solve dispersion problem of the HA particles in the polymer matrix, hence enhancing the mechanical property of the scaffolds, three different surface modification methods of HAp, with Stearic Acid (SA), Polylactide Acid (PLA) and PolyCaprolactone (PCL) were conducted: FT-IR, TGA and dispersion analysis were performed to confirm the effectiveness of these reactions. TEM and SEM analysis were used to morphologically evaluate the scaffolds; especially TEM was critical to assess the particles dispersion into the polymer fibres. Then tensile tests were performed in order to evaluate the enhancement of the mechanical properties given by the addition of low amount the modified HAp. The best properties were found with the addition of 1 wt.% of PCL-HA, improving the Young’s modulus of more than 250 %. Degradation tests were conducted over a period of 6 months to characterize the degradation dynamic of the electrospun scaffolds. This new processing methodology and resulting mechanically-improved composite scaffolds hold significant promise for bone tissue engineering applications.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/134961