Synthesis and characterization of novel chitosan nanocomposite hydrogels for drug delivery and bone tissue engineering

Biodegradable materials for drug delivery and bone tissue engineering are currently intensively developing and improving, but there are still a lot of problems to solve related with bioactivity, biocompatibility, release profile etc. Osteosarcoma is an aggressive malignant neoplasm arising from primitive transformed cells of mesenchymal origin that exhibit osteoblastic differentiation and produce malignant osteoid. It is the most common histological form of primary bone cancer [1,2]. Treatment is most destinations and made up for: intensive multidrug short induction chemotherapy, amputation or tumor resection within the limits of normal tissue and in the last phase again chemotherapy. This kind of neoplasm is most recently detected in young male till 25 age, therefore improving methods of treatment is so important. Chitosan is a natural-based polymer obtained by alkaline deacetylation of chitin received from powdered shrimp shells was purchased from Acros Organics. Its main advantages are non-toxic, non-immunogenic, non-carcinogenic degradation products, biocompatible, bioactive and biodegradable. These properties cause chitosan a very good candidate for novel hydrogel drug delivery systems. Chitosan easily forms hydrogel particles and entraps biomolecules through a number of mechanisms, including chemical crosslinking, ionic crosslinking, and ionic complexation [3,4]. A possible alternative of chitosan by the chemical modification also has been useful for the association of bioactive molecules to polymer and controlling the drug release profile. There are few methods of modification, or example.: copolimerization, grafting, chemical and ionic crosslinking, polyelectrolyte complexes, etc [5]. Previous studies demonstrated that chitosan could promote the proliferation and osteogenesis but only with moderate swelling ratio of composite, too high ability of entrapment water solutions are not recommended. There are a lot of advantages in chitosan properties that can be used in research work to obtain the material of the best expected properties. Laponite® (LA) is a plate-like synthetic clay hectoritetype belongs to a family of phyllosolicates type 2:1 [6]. Its structure represent empirical formula: Na0.7+[Si8Mg5.5Li0.3 O20(OH)4]0.7-. The plates size is about 25 nm x 0,92 nm. LA has a large surface area, anionic surface charges and exchangeable Na+ cations in hydrated interlayers. Presence of sodium cations causes better adsorption properties for cationic drug molecules. Moreover, the exfoliated LA particles may act as multifunctional crosslinkers in forming the nanocomposite hydrogels, and the polymer chains were anchored to the particles and entangled to form a network [7]. Used synthetic clay has got the same type structure and but better sorption properties to montmorillonite but it has got serious advantage - as a synthetic compound shows low heavy metal content. The initial results indicate that the incorporation of clay improved the swelling behavior in contrast to the pure chitosan beads. There also had been revealed significant disproportion of viscosity received hydrogels according to different type of LA or different concentration. Increasing content causes telling rise of viscosity, especially reported in higher content of used crosslinker. The aim of research is to develop a bioactive system biopolymer/layered silicate intelligent nanocomposite based on chitosan and synthetic clay by a cross-linking reaction using sodium tripolyphosphate as the gel factor. The resultant composite were characterized by Fourier transform infrared spectroscopy, scanning electronic microscope and X-ray diffraction analysis. The bioactivity in physiological pH solution (SBF pH=7.40) [8], drug encapsulation efficiency and controlled release behaviour were also investigated by using the model drug to reveal the effects of introduced LA.