(168f) Biomineralized Cellulose Acetate Membranes with Strontium Apatite for Guided Bone Regeneration

Bone problems, such as congenital malformations, accidents, tumors, and osteoporosis, are becoming increasingly common. The replacement of compromised limbs by implants is a widely used form of treatment, however, the materials commonly used in this area present low osseointegration and great difference in the elasticity module between alloys and bone. Hybrid biomaterials, composed of an organic and an inorganic part, have proved to be strong competitors to replace traditional implants, presenting in addition to biocompatibility and osteoconduction, additional properties of interest, such as biodegradability and osteoinduction. In this context, the present work describes the production of a hybrid material composed of porous membranes of biomineralized cellulose acetate (CA) with strontium apatite (SrAp) through the biomimetic method, using a modified simulated body fluid (m-SBF) solution containing ions strontium (Sr²⁺) instead of calcium. The membranes were produced in two different immersion times (7 and 14 days) in m-SBF. The incorporation of SrAp in the membranes was evaluated quantitatively by Atomic Absorption Spectrometry (AAS) and it is possible to observe that the maximum strontium incorporation was reached in 7 days, without additional incorporation in 14 days. Fourier transform infrared spectroscopy (FTIR) was used to identify changes in the chemical structure of the material resulting from the immobilization of SrAp, which was confirmed by the peaks present in the 850 and 1570 cm^-1 ranges, which refer respectively to the elongation of the phosphate group (PO₄^3-) and the asymmetric elongation C=O of the carbonate group (CO₃^2-), both directly related to the presence of Sr²⁺ in these membranes. Scanning electron microscopy (SEM) was investigated to study the influence of SrAp biomineralization on the porosity of the analyzed membranes, showing that its morphology presents a greater organization and standardization of the pore size with the increase of days immersed in m-SBF. The cytotoxicity of the materials was studied using mouse osteoblast cells (MC3T3-E1 Subclone 14), according to ISO 10993-12, in which cell viability was measured after exposure to sample extracts (indirect method). The results showed that the cells presented high viability after exposition to both hybrid materials extracts, even at 48h of exposition. On the other hand, the cell viability decreases after 48h when exposed to AC membrane extract. The presence of SrAp decreases the membrane degradability and also seems to induce the proliferation of osteoblasts since the cell viability was over 100% when compared to cells exposed only to the culture medium. Overall, the results showed the potential of hybrid membranes based on cellulose and SrAp for bone regeneration applications.