Characterization of Goldfish Scales by Vibrational Spectroscopic Analyses

Scales of bony fishes are calcified tissues that contain osteoblasts, osteoclasts, and bone matrix, all of which are similar to those found in mammalian bone. The scales are composed of hydroxylapatite (HAP) and extracellular matrix which is mainly type I collagen fibers. We investigated the scales from goldfish by Fourier transform infrared (FTIR) and Raman spectroscopic analyses to characterize the components in the scales. The attenuated total reflection (ATR)-FTIR spectrum obtained from the surface coat of the normal goldfish scale was quite different from that of the backside coat of the same scale. The former showed a strong band at 1013 cm−1, which was assignable to HAP, and weak bands at about 1643, 1415, and 870 cm−1, whereas the latter showed a typical protein profile: strong bands at about 1631, 1550, and 1240 cm−1, which were assignable to amide-I, amide-II, and amide-III of collagen, respectively. We also investigated the local structure of goldfish scales by using micro-Raman spectroscopy. The Raman spectrum of the normal scale showed the amide-I band at about 1640 cm−1 from the collagen and the PO43− symmetric stretching band at about 961 cm−1 from the HAP. We discuss the implication of Raman and FTIR profiles for normal and regenerating goldfish scales.