Osteocompatibility of polyelectrolyte complexes scaffolds

GIMENA CORREA; M. SUSANA CORTIZO; ANTONIO MCCARTHY

Rosario

Congreso; 8vo Congreso Latinoamericano de Órganos Artificiales, Biomateriales e Ingeniería de Tejidos- 8vo COLAOB; 2014

Polyelectrolyte complexes are a particular class of macromolecules formed by the electrostatic attraction between two oppositely charged polyelectrolytes and mainly stabilized by electrostatic interactions. In recent years polyelectrolyte complexes have been extensively studied due to their wide range of applications, especially in biomedical and pharmaceutical fields. The aim of this work was to develop an osteocompatible scaffold with a polyelectrolyte complex (PC) composed by chitosan as polycation and hyaluronic acid as polyanion. In order to improve the mechanical properties of this scaffold, in some cases microwave energy was used to promote covalent bond formation (PCw). PC and PCw were analyzed and compared regarding their swelling capacity in phosphate buffer solution at 37º C, as well as their stability in 0.7M NaCl for 24 and 48 hs. PC and PCw hidrogels were lyophilized to obtain cylindrical sponges whose morphology and pore size were analysed by scanning electron microscopy (SEM). Mechanical properties of both lyophilized polymer sponges were evaluated by compression testing, while differential scanning calorimetry (DSC) was used to assess decomposition of each biomaterial as well as polymer interactions. Osteocompatibility of both hidrogels was evaluated by culturing MC3T3E1 osteoblast-like cells on previously sterilized matrices. After culturing cells for up to 10 days, the MTT assay was used to measure the viable biomass, thus determining cell growth into each scaffold. Additionally, the effect of both scaffolds on osteoblastic differentiation (collagen production) was determined by Sirius Red staining after an 8-day culture. After 300 minutes, PC showed higher maximum swelling percentage (1000%, t eq ≈ 100 min) compared to PCw (800% t eq ≈ 60 min). This behaviour suggests that PCw has a higher crosslinking density than PC, thus restricting the entry of aqueous medium into the hydrogel network. Evaluation of swelling kinetics indicates that this process could be mainly governed by a diffusive mechanism. Additionally, PCw was more stable than PC in NaCl solution (% loss of mass 48hs= 17% and 33% respectively); this is compatible with the existence of unions other than ionic bonding in PCw. SEM micro-structural evaluation of dry polymer sponges showed greater pores in PC than in PCw. In coincidence with the apparently denser network observed for PCw by SEM imaging, mechanical testing of sponges demonstrated that PCw (Young module: 10,0 kPa; total compression: 18 % )is also more resistant to compression than PC (Young module: 4,3 kPa; total compression: 45 % ). DSC evaluation in the temperature-scanning mode between -50ºC and 150ºC, showed the presence of two bands in the case of PC (possibly due to disruption into its original constituents chitosan and hyoluronic acid). However in the case of CPw no band was observed, probably because of the formation of covalent bonds that would be expected to prevent its disruption. Results of the MTT assay show that although osteoblasts are able to adhere and proliferate on both PC and PCw, cell growth was significantly greater on PCw. Additionally, both scaffolds promoted osteoblastic differentiation (as evaluated by collagen production) In conclusion, we have developed a novel polyelectrolyte complex using chitosan and hialuronic acid with potential applications as a scaffold for bone tissue engineering. In addition, we have shown that microwave-induced covalent bonding of the complex increases its capabilities (as determined by its physico-chemical, mechanical and osteocompatibility testing).