The term biomaterial, which is closely related to applications that repair or replace a part of or the whole tissue, must have favorable mechanical as well as biological properties and should play a major role in developing successful implantations by means of inducing cell adhesion, proliferation, and differentiation on the surface of the biomaterial (Sista et al. 2011). In developing new biomaterials for tissue replacement, the structure and properties of the tissue which is to be replaced, i.e., the biological template, must be taken into consideration. This is because, if properties of the new material are significantly different from those of the host tissue, the material under development will cause dynamic changes to the host tissue after implantation and thus will not achieve the goals embedded in the original conceptual design (Wang 2003). Different materials have been investigated for applications in bone tissue engineering—metals, ceramics, and polymers. As with all materials implanted into the body, the polymers for bone regeneration must be biocompatible. In addition, they should be moldable, shapeable, or polymerizable in situ to ensure good integration in the defective area (Seal et al. 2001). However, the polymer materials used for orthopedic application do not exhibit adequate mechanical properties and bioactive behavior, which are the main disadvantages for bone tissue engineering. In order to overcome these problems, polymer/bioactive ceramic composites have been developed for bone tissue engineering, which ensure the achievement of the above-mentioned properties and performance of the material (Ryszkowska et al. 2010).
It is well known that the two fundamental factors to be considered in producing polymer nanocomposites with bone-like properties are (1) good interfacial adhesion between organic polymers and inorganic hydroxyl apatite (HA) and (2) uniform dispersion of HA at the nanolevel in the polymer nanofiber (Lee et al. 2007). When such a composite is immersed in simulated body fluid (SBF), biologically active HA layers are formed on the implant due to the ion-exchange reaction between the bioactive implant and the surrounding body fluids which is chemically and crystallographically equivalent to the mineral phase of the bone (Pielichowska and Blazewicz 2010). In addition, HA is known to smartly utilize the apatite that is mineralized on their surfaces as an interface to integrate spontaneously with the living tissue (Kim et al. 2004). Nanofiber composites have certain favorable characteristics and properties, such as porosity, the surface area-to-volume ratio, pore size, pore interconnectivity, structural strength, and biocompatibility, which play a major role in the design and fabrication of polymeric materials for bone tissue engineering (Tan et al. 2003; Teoh 2004).
Although existing bioactive materials possess high compressive strength, they are unfortunately very brittle and have inherently poor tensile and torsional properties. Material selection is especially important in bone tissue engineering because a supporting substrate is critical in maintaining mechanical strength and structural support as well as providing the optimal culturing environment for bone formation during the early stages of the regenerative process (Lu et al. 2003). The large surface area-to-weight ratio of the composite material offered by electrospinning (Reneker and Chun 1996; Li and Xia 2004; Darrell et al. 2006; Ramakrishna et al. 2006; Greiner and Wendorff 2007) is achieved by means of decreasing the diameter of the fiber from the micrometer (10–100 μm) to submicron or nanometer level (10 × 10−3 to 100 × 10−3), resulting in the appearance of several amazing characteristics such as flexibility in surface functionalities and superior mechanical properties (stiffness and tensile strength) compared with any other known form of material (Huang et al. 2003).
The present study is focused on designing and developing the polymer—polyphenylene ether ether sulfone (PPEES) nanofiber composites reinforced with nanohydroxyapatite (nHA)—and evaluating its potential application as an orthopedic biomaterial. The prepared nanofiber composite was subjected to characterization and morphology studies using Fourier transform infrared (FTIR)-attenuated total reflectance spectroscopy (ATR) and scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX) to identify the presence of a structural group and morphology of the composites, respectively. Inverted fluorescence microscopy was used to identify the viability of bone-like cells over the nanofiber composite. The composite was then investigated in vitro for its multifunctional properties (mechanical and biological properties) before and after incubation in SBF in order to evaluate the compatibility of the biomaterial for orthopedic application.