Evaluation of Oleic Acid-Modified Hydroxyapatite Polymer Nanocomposites for Regenerative Medicine Applications

Biomaterials are a key element of bone tissue engineering, where they can act as scaffolds for tissue regeneration. The goal of presented research is to evaluate the influence of oleic acid (OA) on the structure and properties of poly(ɛ-caprolactone), or PCL, (with molar masses: 45 000 and 80 000 g/mol), hydroxyapatite (HAp) composites and to determine the optimal OA to HAp ratio ensuring optimal material properties. Visual assessment as well as light and scanning electron microscopy revealed improved dispersion of HAp in the PCL matrix due to its amphiphilic character and, therefore, stabilisation of HAp by OA. However, excessive OA caused deterioration of the PCL45k membrane as cracks were observed. Moreover, the mechanical performance also decreased when the OA to HAp ratio was greater than 1:3 (by weight). Raman spectra confirmed that such effects were due to the increasing amorphous nature of the membranes with increasing OA concentration. Two-dimensional correlation spectroscopy (2D-COS) revealed clear differences in the response of the PCL-HAp system to increasing OA content depending on the molar mass of PCL. Considering the obtained data, the OA:HAp ratio in the PCL matrix ensuring a homogeneous structure and the highest mechanical performance is 1:6 by weight.