Bioactivity and Degradation of wollastonite-poly(N- butyl-2-cyanoacrylate) composites

Quick setting cements may be a promising alternative to metallic devices for immobilization of bone fragments in several maxillofacial surgical procedures. The aim of this study was the evaluation of bioactivity and degradation of wollastonite-poly(n-butyl-2-cyanoacrylate) composite biomaterials, just to be used as surgical cements. Three formulations were prepared by mixing n-butyl-2-cyanoacrylate with natural wollastonite-W, silanized wollastonite-Ws and wollastonite, coated with 5 % acetyl tributyl citrate-Wa. Raw materials and composites were characterized by means of X-ray diffraction, Fourier transform-infrared spectroscopy, thermal gravimetric analysis and scanning electron microscopy, coupled to energy dispersive X-ray analysis. Bioactivity was tested by immersion of the material into simulated body fluid (SBF) for 21. Hydrolytic degradation was studied in distilled water at 70 °C for 2, 7 and 30. The morphological and compositional analysis of material surfaces after SBF immersion tests showed a time dependent apatite nucleation and growth, typical of bioactive materials. The apatite layer formed on Wa-BCA after 21 of soaking in SBF was denser than those on W-BCA and Ws-BCA composites. The greater degradation Lídia Ágata-de Sena, Rosa Mayelín Guerra-Bretaña*, Marcia Marie Maru, Márcia Maria Lucchese y Carlos Alberto Achete** Instituto de Metrologia e Qualidade Industrial (INMETRO), Ave. Nossa Senhora Das Graças 50, Xerém, Duque de Caxias, RJ, Brazil, CEP. 25.250-020 *Centro de Biomateriales, Universidad de La Habana, Avenida Universidad entre calles Ronda y G, Código Postal 10400, La Habana, Cuba.**Programa de Engenharia Metalúrgica e de Materiais (PEMM), Universidade Federal do Rio de Janeiro, RJ, Brazil. [email protected] Revista CENIC Ciencias Químicas, Vol. 44, pp. 39-48, 2013. 40 observed for the Wa-BCA composite and the subsequent exposition of bioactive ceramics to the environment seems to be the reason for the increased bioactivity, in comparison to the other formulations tested behavior makes these biomateriales attractive to be used as bone cements. INTRODUCTION In several maxillofacial surgical procedures, immobilization of bone fragments is necessary for an adequate healing process. These techniques often involve the utilization of screw retained rigid fixation devices such as microplates or miniplates, with excellent ability to provide three dimensional control and high biocompatibility. However, in some cases the fragile osseous structures and/or the adjacent anatomical ones may be damaged by the placement of screws. Other negative responses such as infections inflammatory reactions and bone resorption have been observed in their clinical application. Otherwise, thin bone fragments do not offer adequate support for mechanical fixation of fractures. These facts encourage the search for new bone fixation methods capable of providing similar stability, but without the complications that metal osteosynthesis devices may produce. A suitable alternative to these cases is the utilization of quick setting, non-toxic adhesives or cements, alone or in conjunction with metallic plates. Since the 60’s, alkyl-2-cyanoacrylates (CA) have been widely used in medical practice. They are highly reactive liquids with low viscosity, which can polymerize at room temperature in the presence of moisture to form strong adhesive unions. Although the main application of CA is dealing with soft tissue adhesion, prospective results for reparation of hard tissues have been published. In mixtures with inorganic materials such as calcium carbonate, glassionomer and calcium phosphates, CA based adhesives might be useful for bone bonding. In tests performed in vitro, Perry and Youngson found that n-butyl-2-cyanoacrylate adhesive and bis-GMA-glass ionomer dental resin failed at significant lower forces than the screw/plate system but still function so they are a valuable alternative to fix fractures of bones comprising the cranial vault. Gonzalez et al. reported the utilization of ethyl-2-cyanoacrylate adhesive for fixation of the cranial bone flap in one hundred craniotomies. They found that the adhesive provides adequate stability without local reaction or displacement. Saska also evaluated ethyl cyanoacrylate adhesives for fixation of bone graft in animal models. This monomer was biocompatible and fixed the grafts, providing adequate stability for new bone formation. When longer chain cyanoacrylate adhesives are used in the treatment of osseous fractures, no harmful effects in the adjacent tissue are observed. In order to obtain materials for bone augmentation and regeneration, synthetic and natural wollastonite based biocomposites with polymeric matrixes have been investigated. These materials exhibit a better bioactivity regarding the polymer component alone due to the well know biocompatibility of wollastonite, that is attributed to nucleation of hydroxyapatite on the material surface, activated by dissolution of calcium and silicate ions. The use of wollastonite-filled cyanoacrylates has not been widely investigated. The aim of the present study was to evaluate the bioactivity and degradability of some wollastonite-poly(n-butyl-2-cyanoacrylate) formulations, just to gain more insight into the potential use of this composite in osseous repair. MATERIALS AND METHODS Preparation of samples The biocomposite materials were made up of an inorganic filler and in situ polymerized n-butyl-2-cyanoacrylate (BCA, batch n. 6004, purity ≥ 99 %, Biomaterials Center, Havana University). A natural wollastonite (W) (Vansil1 W40, Vanderbilt Co., Inc.), with an average particle size of 13.2 μm and (1.056 ± 0.001) SiO2 : CaO molar ratio, was selected as inorganic filler. Three composite formulations were prepared by mixing n-butyl-2-cyanoacrylate (BCA) with natural wollastonite (W), silanized wollastonite (Ws) and wollastonite coated with 5 % acetyl tributyl citrate