Electrochemical and bioactive evaluation of polycaprolactone/multi-walled carbon nanotubes coatings on titanium alloy

Composite materials of polymer – carbon nanotubes have been widely studied for biomedical applications due to the versatility of polymers in this field and the excellent mechanical, thermal and electrical properties of carbon nanotubes. However, carbon nanotubes are materials which can provide some toxicity in biological systems, since they have low solubility in water and organic solvents, tend to form aggregates in solution, are bioincompatible and limited compatibility with polymeric matrices. For this reason, carbon nanotubes considered for biomedical applications must comply with this basic requirement of solubility. To improve the compatibility of the carbon nanotubes, they were exposed to treatment with HNO₃, NaOH and HCl to eliminate impurities and improve the solubility in other solvents. Polycaprolactone coatings at 2.5% w/v and multi-wall carbon nanotubes (0.5, 1.0 and 1.5 g/L) were developed to evaluate the electrochemical and bioactive properties. Techniques such as infrared spectroscopy, contact angle, scanning electron microscopy, atomic force microscopy, electrochemical impedance spectroscopy using simulated body fluid as electrolyte and the bioactivity of human osteoseosarcoma cells (HOS ATCC® CRL-1543) by alkaline phosphatase were used. From the reported characterizations, it was observed that the resistance to polarization increases according to the degree of dispersion of carbon nanotubes present in the polymer matrix, decreasing the degradation rate of the material.