Introduction:The synthesis of bone-like mineralized composite materials is a promising strategy for bone engineering applications. Hydrogels can be mineralized with calcium phosphate crystals to mimic the composition of natural bone[1]. Combining xanthan and chitosan hydrogels it is possible to form complex polyelectrolytes from the interactions between opposite charged functional groups: protonated amine from chitosan and carboxylate from xanthan. This hydrogels network formed by ionic interactions between groups with opposite charges shows pH-sensitive swelling. Hydrogels are insoluble due to the interaction between polysaccharide or between polysaccharide and a chemistry crosslinking[2]. In this work mineralized films were prepared by dip-coating and layer-by-layer methods.
Experimental: The films were prepared over a glass substrate by successively dipping in xanthan hydrogel, CaHPO4 solution and chitosan hydrogel. Some films were prepared by exposed in NH3 gas to precipitate calcium phosphate, these steps were doing after dipping in chitosan hydrogel. The films obtained were characterization by Scanning Electron Microscopy (SEM) and by mapping by SEM-EDS to evaluate films morphology and Ca element distribution in the films. Beyond those studies were also made analyses by swelling determinations for studying the interactions between the opposite charged polysaccharides.
Results and Discussion: Flexible thin films with thickness around 45 µm were obtained and SEM-EDS Ca element mapping shows Ca dispersed throughout the film but near the xanthan layer the mapping indicates higher Ca concentration. The swelling test, after 24 hours immersion, showed a swelling degree about 30-50 %. These results indicate that Ca2+ can be crosslinking the xanthan and then promoting the network interpenetration between xanthan and chitosan polysaccharides. The interaction between Ca/xanthan and xanthan/chitosan allows the swelling of the film and hinders its dissolution.
Conclusions: In this study was possible to produce mineralized films of polysaccharides xanthan and chitosan. It was observed the interactions between the opposite charged polysaccharides and that there is a network interpenetration between them avoiding their dissolution, and therefore it was not necessary to use an additional crosslinking agent.
Acknowledgement: This work was supported by CNPQ.
References:
[1] C. Zhong, C. C. Chu, Journal Material Chemistry, 22 (2012) 6080-6087
[2] N. Kulkarni, P. Wakte, J. Naik, International Journal Pharmaceutical Investigation, 5 (2015) 73–80