Tailoring surface properties of carbon nanofibers via oxidation and its influence on dental pulp stem cell viability of PCL/CNF composites

Abstract

The effect of oxidation time on the surface chemical and morphological properties of carbon nanofibers (CNFs) and their suitability for use as a reinforcement agent in the development of bone scaffolds was assessed. The CNFs were modified using a 3:1 v/v mixture of concentrated sulfuric (H2SO4) and nitric acid (HNO3) for different periods of time. Several analytical techniques were used to characterize the oxidized CNF surface properties. Photoacoustic Fourier transform infrared spectroscopy (PAS-FTIR) showed the creation of carboxylic groups due to the acid treatments. Scanning electron microscopy images revealed differences in the nanofibers before and after acid treatment. The relationship between the CNF crystals and their defects when varying the oxidation time were determined by Raman spectroscopy. The CNF FTIR results, contact angle measurements, and dispersion tests showed the formation of carboxylic groups due to the oxidative treatment. The results confirmed the presence of microstructures with defects, as well as chemically active functional surface groups, such as carboxyls and hydroxyls. Furthermore, a composite was prepared using polycaprolactone (PCL) as a matrix and the CNF as the reinforcement. The storage module of the oxidized CNFs was improved with respect to the nonoxidized CNFs. Furthermore, the scaffolds of PCL with oxidized CNFs enhanced the cell proliferation.