(256ad) Preparation, Characterization and Comparison of Nano-Composite Scaffolds Based in Chitosan, Poly(lactic acid), Poly(lactic acid-co-glycolicacid), and Hydroxyapatite for Tissue Engineering Applications

Authors: 
Carranza Oropeza, M. V., Polytechnic School of the University of São Paulo
Giudici, R., University of São Paulo
Scaffold design and fabrication are major areas of biomaterial research, and they are also important subjects for tissue engineering and regenerative medicine research. Scaffold plays a unique role in tissue regeneration and repair. Biocompatibility, biodegradability, mechanical properties and porosity are important parameters for selection of a desirable scaffold for tissue engineering applications. For instance, scaffolds are one of the necessary components for bone tissue engineering approach. They provide 3D growth space for cells as well as for transport of nutrients and metabolites for cell expansion and tissue organization. It is not easy to define an ideal scaffold since each tissue needs a particular matrix design with well-defined material properties. Therefore, it can be said that an ideal scaffold should at least meet several requirements depending on the application region such as biocompatibility, suitable mechanical strength, interconnected porous structure, and biodegradability. Nowadays, it has being recognized that some of the widely used scaffolds do not fairly recapitulate the cell microenvironment and that the extra cellular matrix (ECM) is a dynamic and hierarchically organized nano-composite that regulates essential cellular functions such as morphogenesis, differentiation, proliferation, adhesion and migration. As a consequence, researchers developed and used existing nanotechnological tools for tissue engineering to design advanced nanocomposite scaffolds that can better mimic the ECM and eventually assemble more complex and larger functional tissues. Thus, the advancement of nanotechnologies allows for the design of a large number of hybrid and multicomponent systems. In this study nano-composite scaffolds based in chitosan (CH), poly(lactic acid) (PLA), poly(lactic acid-co-glycolic acid) (PLGA) and hydroxyapatite (HAp) were prepared by freeze drying and gas foaming techniques in order to mimic the organic/inorganic nature of the bone. Chitosan (CH) is a bioderived polysaccharide obtained mainly from shells of crustaceans, corals or jellyfish. Due of its biocompatibility and a range of interesting properties, including antimicrobial, antitumor, anti-inflammatory and immunity-enhancing ones, chitosan could serve a multifunctional purpose in biomedicine become it an attractive material for use in bone tissue engineering. On the other hand, poly(lactic acid) (PLA) and poly(lactic acid-co-glycolic acid) (PLGA) are FDA approved synthetic biodegradable polymers. Both polymers are biocompatible and their degradation products are low molecular weight compounds such as lactic acid and glycolic acid, which enter into normal metabolic pathways without causing any adverse effect. And Hydroxyapatite (HAp) [Ca10(PO4)6(OH)2], the main inorganic component of hard tissues, has a variety of applications in bone fillers and replacements because its surface is highly reactive and leads to favorable attachment and bioactivity; it has osseo conductive and osseo inductive effects. Therefore, the enhancement of the properties of HAp proceeds along two main routes: (i) manipulation of microstructure; (ii) combination with other elements and materials. The composite is expected to have improved mechanical properties compared to the polymer and better structural integrity and flexibility than brittle ceramics. In fact the combination of ceramic and polymer could provide reinforced porous structures and controlled resorption rates. A composite material would also improve biocompatibility and hard tissue integration in a way that ceramic particles. Also, the choice of the processing technique is important. The scaffolds obtained were characterized in structure, morphology, porosity, degradation, water uptake, mechanical and thermal stabilities using diverse analytical techniques, such as: spectroscopy (FTIR), microscopy (SEM), thermoporometry (using DSC), thermal analysis (TGA, DSC) and physical and chemical analysis. All formulations were compared in order to assess the influence of each component that constitute the scaffold as well as the processing technique for the potential application of those nano-composite scaffolds in hard tissue treatments.
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