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Candidate carbon fiber reinforced carbon (CFRC) porous implant materials were evaluated for tissue compatibility in a rat model. Six different CFRCs of constant pore size (about 30 microm) were fabricated that had 9, 12, and 17% porosity with 2-nm3 matrix crystallites and 6, 12, and 20% at 25 nm3. They were implanted as femoral transverse diaphyseal pins that were 1.5 mm in diameter. At 5 and 45 weeks, implant and bone histologic specimens were evaluated histologically and by a scanning electron microscope and an electron microprobe. Also, regional lymph nodes and spleens were examined. By 45 weeks, direct implant-bone contact was observed over most of the interface in most specimens. At the implant surface, there was partial replacement of CFRC with host tissue. However, the microprobe showed that the implant-bone interface was chemically abrupt with no cross-diffusion of ionic species. Besides the surface effects, there was partial filling of the implant pores with tissue, including bone organized de novo deep within. This was observed histologically and confirmed by microprobe. Lymph nodes and spleens were histologically normal, and no carbon particles were found. None of the results were influenced by porosity or matrix crystallite size over the ranges studied. In summary, these porous CFRCs are partially degraded when in contact with bone and appear substantially tissue compatible. They may be useful as scaffolds for regrowth of bone.

Graphene family materials (GFM) are currently considered to be one of the most interesting nanomaterials with a wide range of application. They can also be used as modifiers of polymer matrices to develop composite materials with favorable properties. In this study, hybrid nanocomposites based on chitosan (CS) and reduced graphene oxide (rGO) were fabricated for potential use in bone tissue engineering. CS/rGO hydrogels were prepared by simultaneous reduction and composite formation in acetic acid or lactic acid and crosslinked with a natural agent—tannic acid (TAc). A broad spectrum of research methods was applied in order to thoroughly characterize both the components and the composite systems, i.e., X-ray Photoelectron Spectroscopy, X-ray Diffractometry, Attenuated Total Reflection Fourier-Transform Infrared Spectroscopy, Scanning Electron Microscopy, ninhydrin assay, mechanical testing, in vitro degradation and bioactivity study, wettability, and, finally, cytocompatibility. The composites formed through the self-assembly of CS chains and exfoliated rGO sheets. Obtained results allowed also to conclude that the type of solvent used impacts the polymer structure and its ability to interact with rGO sheets and the mechanical properties of the composites. Both rGO and TAc acted as crosslinkers of the polymer chains. This study shows that the developed materials demonstrate the potential for use in bone tissue engineering. The next step should be their detailed biological examinations.