Nowadays, with the increased incidence of bone diseases in an aging population, treatment of bone defects remains one of the major challenges because bone tissue provides several important physiological and structural functions in the human body, being essential for hematopoietic maintenance and for providing support and protection of vital organs. Therefore, the development of the ideal scaffold able to guide the bone regeneration processes is a relevant target in the tissue engineering field. In this context, a bioactive composite scaffold made of a biopolymeric phase of acrylated soybean oil and a ceramic phase of calcium nitrate tetrahydrate, later converted to hydroxyapatite, was developed with the aim of mimicking the nature of bone tissue. Indeed, this latter is a natural composite material made of an organic fraction (mostly collagen) and an inorganic component (hydroxyapatite crystals). The scaffolds were 3D printed using the vat photopolymerization technique, which is becoming increasingly popular due to its simplicity in use and high printing resolution, allowing the fabrication of complex shape objects and permitting customization, which is very important in the biomedical field. The scaffolds had a gyroid structure and a porosity of 90%, which plays a fundamental role in the migration and proliferation of bone tissue within the scaffold itself. Furthermore, the calcium nitrate was successfully converted into hydroxyapatite by the simple immersion of the scaffolds in a phosphatizing bath (aqueous solution of sodium phosphate dibasic) kept at 80 °C for 14 days. Scaffolds immersed in phosphatizing solutions with different molar concentrations were investigated: microstructural, X-ray diffraction and mechanical analyses were carried out to determine at which concentration the best hydroxyapatite production and the optimal mechanical properties were obtained. Moreover, scaffolds were submitted to an additional heat treatment (at 60 °C for 48 hours) with the aim of increasing their strength-to-density ratio and obtaining properties more similar to those of bone tissue. Finally, cell culture tests were performed to verify biological properties, such as biocompatibility.
Al giorno d'oggi, con l'aumento dell'incidenza delle malattie ossee in una popolazione che invecchia, il trattamento dei difetti ossei è una delle sfide principali poiché il tessuto osseo svolge diverse importanti funzioni fisiologiche e strutturali nel corpo umano, essendo essenziale per il mantenimento dell'emopoiesi e nel fornire supporto e protezione agli organi vitali. Pertanto, lo sviluppo di uno scaffold ideale in grado di guidare i processi di rigenerazione ossea è un obiettivo rilevante nel campo dell’ingegneria tissutale. In questo contesto, è stato sviluppato uno scaffold composito bioattivo costituito da una fase biopolimerica di olio di soia acrilato e da una fase ceramica di nitrato di calcio tetraidrato, successivamente convertito in idrossiapatite, con l'obiettivo di imitare la natura del tessuto osseo. Quest'ultimo, infatti, è un materiale composito naturale costituito da una frazione organica (principalmente collagene) e da una componente inorganica (cristalli di idrossiapatite). Gli scaffold sono stati stampati in 3D utilizzando la stereolitografia mascherata, la quale sta diventando sempre più popolare grazie alla sua semplicità d'utilizzo e all'alta risoluzione di stampa, consentendo la fabbricazione di oggetti di forma complessa e permettendone la personalizzazione, aspetto fondamentale in campo biomedico. Gli scaffold hanno una struttura a giroide e una porosità del 90%, che gioca un ruolo fondamentale nella migrazione e nella proliferazione del tessuto osseo all'interno dello scaffold stesso. Il nitrato di calcio è stato convertito con successo in idrossiapatite attraverso la semplice immersione degli scaffold in un bagno fosfatizzante (una soluzione acquosa di sodio fosfato bibasico) mantenuto a 80 °C per 14 giorni. Gli scaffold sono stati immersi in soluzioni fosfatizzanti con diversa concentrazione molare e si sono svolte analisi microstrutturali, di diffrazione a raggi X e meccaniche al fine di determinare la concentrazione che permette di ottenere la migliore produzione di idrossiapatite e le proprietà meccaniche ottimali. Inoltre, gli scaffold sono stati sottoposti a un ulteriore trattamento termico (a 60 °C per 48 ore) con l'obiettivo di aumentarne il rapporto resistenza-densità e ottenere proprietà maggiormente simili a quelle del tessuto osseo. Infine, sono stati svolti dei test di coltura cellulare sugli scaffold per verificarne le proprietà biologiche, tra cui la biocompatibilità.
Phosphatized biopolymer - calcium nitrate composite 3D printed scaffolds for bone substitution
ZAMENGO, ELISA
2022/2023
Abstract
Nowadays, with the increased incidence of bone diseases in an aging population, treatment of bone defects remains one of the major challenges because bone tissue provides several important physiological and structural functions in the human body, being essential for hematopoietic maintenance and for providing support and protection of vital organs. Therefore, the development of the ideal scaffold able to guide the bone regeneration processes is a relevant target in the tissue engineering field. In this context, a bioactive composite scaffold made of a biopolymeric phase of acrylated soybean oil and a ceramic phase of calcium nitrate tetrahydrate, later converted to hydroxyapatite, was developed with the aim of mimicking the nature of bone tissue. Indeed, this latter is a natural composite material made of an organic fraction (mostly collagen) and an inorganic component (hydroxyapatite crystals). The scaffolds were 3D printed using the vat photopolymerization technique, which is becoming increasingly popular due to its simplicity in use and high printing resolution, allowing the fabrication of complex shape objects and permitting customization, which is very important in the biomedical field. The scaffolds had a gyroid structure and a porosity of 90%, which plays a fundamental role in the migration and proliferation of bone tissue within the scaffold itself. Furthermore, the calcium nitrate was successfully converted into hydroxyapatite by the simple immersion of the scaffolds in a phosphatizing bath (aqueous solution of sodium phosphate dibasic) kept at 80 °C for 14 days. Scaffolds immersed in phosphatizing solutions with different molar concentrations were investigated: microstructural, X-ray diffraction and mechanical analyses were carried out to determine at which concentration the best hydroxyapatite production and the optimal mechanical properties were obtained. Moreover, scaffolds were submitted to an additional heat treatment (at 60 °C for 48 hours) with the aim of increasing their strength-to-density ratio and obtaining properties more similar to those of bone tissue. Finally, cell culture tests were performed to verify biological properties, such as biocompatibility.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/58025