The invention relates to carbon nanotube-containing composites as biosensors to detect the presence of target clinical markers, methods of their preparation and uses in the medical field. The invention is particularly suitable for the detection in patient biological specimens of bone markers and tissue markers. The biosensors of the invention include carbon nanotubes deposited on a substrate, gold nanoparticles deposited on the carbon nanotubes and, binder material and biomolecule deposited on the gold-coated carbon nanotubes. The biomolecule is selected to interact with the target clinical markers. The biosensor can be used as an in-situ or an ex-situ device to detect and measure the presence of the target clinical markers.