Poly(L-lactide)/multiwalled carbon nanotube composites : mechanical properties and interaction with osteoblast-like cells in vitro

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Poly(L-lactide)/multiwalled carbon nanotube composites : mechanical properties and interaction with osteoblast-like cells in vitro


Author: Pow, Yu-fung
Title: Poly(L-lactide)/multiwalled carbon nanotube composites : mechanical properties and interaction with osteoblast-like cells in vitro
Degree: M.Phil.
Year: 2008
Subject: Hong Kong Polytechnic University -- Dissertations.
Tissue engineering.
Nanostructured materials.
Department: Dept. of Health Technology and Informatics
Pages: 85 leaves : ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2239606
URI: http://theses.lib.polyu.edu.hk/handle/200/3496
Abstract: Tissue engineering is a potential solution for tissue reconstruction and function restoration. Scaffolds made by biocompatible biomaterial are important to provide guidance for cell growth and is required for tissue production. Therefore, the properties of biomaterial are important parameters to the success of tissue engineering. For bone tissue engineering, bone cell is sensitive to the mechanical environment and may be sensitive to changes of mechanical properties of scaffold. Poly (L-lactide) (PLLA) is a popular biomaterial with good mechanical properties. However, the weak mechanical property of PLLA scaffold hinders its wide application for bone tissue engineering. Reinforcing PLLA with other materials can be a good solution to address this problem. Multi-walled carbon nanotube (MWCNT), which is a novel nanomaterial with excellent mechanical properties, is a potential material for biomaterial reinforcement. However, the biocompatibility and bioactivity of this material is not clear. In this study, PLLA/MWCNT composite with different loading of MWCNT was applied for surface mechanical property reinforcement. Physical characterisation and biological study were carried out to evaluate its physical properties and biological interaction with human osteoblast-like cells (Saos2) (HOB). Multi-walled carbon nanotubes (MWCNT) were dispersed by high power ultrasound. PLLA was dissolved in chloroform. PLLA/MWCNT composite with different ratio of PLLA to MWCNT was fabricated using solvent-casting techniques. The composite was characterized by SEM, EDX and XRD. From the SEM pictures, random distribution of dispersed MWCNT was observed from the composite surface. Some tubular MWCNT was protruded from the surface. EDX spectrum showed an increase in carbon content for PLLA/MWCNT composite with more MWCNT. MWCNT was detected by XRD and showed the successful incorporation of MWCNT into PLLA. Nanoindentation was carried out and showed a higher in Young's modulus for sample reinforced with MWCNT. The composite was coated with fibronectin to study the response of HOB cell. Fixed amount of cell was cultured on composite with different PLLA/MWCNT ratio. To monitor the morphology of the cell cultured on the composite, SEM pictures were taken and found that HOB cell was successfully adhered on the composite surface. They showed good cell morphology and did not have apparent morphological differences. The cytoskeleton of HOB cell was monitored by confocal scanning microscopy. Both composites showed stressed cytoskeleton fibre and good adhesion to the surface. The viability of cell was distinguished by trypan blue staining and cytometric counting. After 2, 4, 6 and 8 days culturing, the viability of cell was evaluated. It was found that cell cultured on different samples had over 90% viability on day 2,4,6 and 8. No significant differences of cell viability were found. It was expected that there is no significant cytotoxicity of PLLA/MWCNT composite over the biocompatible control sample. The activity of mitochondrial dehydrogenase (MD) enzyme and alkaline phosphatase (ALP) enzyme was evaluated by MTT substrate and p-nitrophenyl phosphate substrate. For the result of MTT assay, it was found that both PLLA/6.25% MWCNT and PLLA/5.00% MWCNT had significant differences from the control for all four different culture days. For ALP activity, it was found that sample with higher MWCNT content had generally higher ALP activity. However, no significant differences were found statistically. It seems that the incorporation of MWCNT into PLLA can increase the MD activity, but not the ALP activity significantly. It was found that sample with more MWCNT may still have certain advantages over the control.

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