Temperature dependence of electric conductivity of bamboo coral skeleton and glass sponge spicules, the marine origin biomaterials

Natural structural biomaterials of marine origin including corals and sponges provide an abundant source of novel bone and cartilage replacements. Even though mechanical and optical properties of these natural biocomposites have been treated extensively in the literature, there is no available data on their electric properties. In the paper electric conductivity along with enthalpy of the process of electric charge conduction process were determined. The conductivity–temperature (σ–T) characteristics of native and deproteinated spicules of marine glass sponge and the mineral phase of bamboo corals provide information on the process of water release and phase transition in collagen. Denaturation temperature for coral was found at 203 °C. The peaks at 160° and 195 °C for the native glass sponge spicules may be explained by more complicated denaturation process where probably, less ordered regions of collagen denaturated at lower temperature and regions of high crystallinity at higher temperature. The decrease in electric conductivity observed after deproteination of glass sponge spicules showed that electric charge in the native glass sponge spicules was probably transported along the paths formed by collagen. Deproteination changed also σ–T characteristics, the kink at 140 °C is caused by glass transition of collagen, whereas the peak at 175 °C was probably caused by thermal denaturation of residual collagen of perturbed structure.