RAMAN AND INFRARED SPECTROSCOPIC STUDY OF THE MOLECULAR CHARACTERIZATION OF THE BIOCOMPATIBILITY OF PROSTHETIC BIOMATERIALS

Raman spectra were obtained directly in a non-destructive and non-invasive way from the biomaterials PMMA [poly(methyl methacrylate)], HDPE (high-density polyethylene), alpha-Al2O3 (alumina) and HA (hydroxyapatite) constituting the components (bone cement, acetabular cup, ball and stem coated with ceramic) of a hip prosthesis. The aim was to give an objective contribution at a molecular level to predict their biocompatibility. In particular, Raman spectra of explanted PMMA bone cements do not show the 1640 cm-1 band due to the stretching mode of C=C unsaturated centres. Moreover, conformational changes of PMMA following the implant appear in the spectra in the range 1100-500 cm-1, where conformational marker bands at 985, 968, 601 and 565 cm-1 are present. The limited number of HDPE explanted acetabular cups did not allow unequivocal Raman results to be obtained, by means of band deconvolution in the region between 1500 and 1000 cm-1, regarding the changes in the crystalline, amorphous and interfacial contents of the acetabular cup surfaces following the implant. Alpha-Al2O3 proved to be a ceramic with good biocompatibility as a biomaterial constituting a hip prosthesis. As regards the stem coating, Raman and Fourier transform IR spectra of HA pre-coating and HA coating on metal implants show spectroscopic modifications due to structural and chemical changes with formation of other calcium phosphates. The development of new bioactive coatings containing precursors of bone growth and able to promote osteogenesis is outlined.