Effect of Carbon Fibers Coated With Nanosized Hydroxyapatite on the Strength and Biocompatibility of Polymer Composites

ABSTRACT Recognizing the need for polymeric materials that combine biocompatibility, biointegration, and sufficient mechanical strength for bone applications, a PLA‐based composite reinforced with hydroxyapatite‐coated carbon fibers was examined. The three different types of inorganic fillers of various concentrations were tested. The morphology, crystallinity, and chemical composition were characterized using scanning electron microscopy (SEM), x‐ray diffraction (XRD), and Fourier transform infrared spectra (FT‐IR). The reinforcing properties of hydroxyapatite‐coated carbon fibers as composite fillers are evidenced through functional and mechanical characterization, including differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). When nHAp filler and CF reinforcement were combined, the mechanical characteristics were clearly degraded. This indicated a change in the filler‐matrix interactions compared to unmodified carbon fibers. Despite this, biological evaluation using MC3T3‐E1 and 7F2 cell lines revealed that the composites support osteoblastic cell functions. Cytocompatibility was assessed using MTT and LDH assays, as well as Live/Dead fluorescence imaging, which confirmed high cell viability (> 80%) and low cytotoxicity. Moreover, the composites promoted cell proliferation and showed excellent cell adhesion, particularly on surfaces containing nHAp, indicating enhanced bioactivity and favorable cell–material interactions. These results confirm that the developed PLLA composites, especially those with tailored nHAp surface modifications, offer a promising balance between mechanical performance and biological compatibility, making them suitable candidates for bone tissue engineering applications.