Affinity binding phenomena of DNA onto apatite crystals

The effect of DNA on the crystal growth of hydroxyapatite (HAp) and its mor phology was examined. X-ray diffraction patterns of DNA-containing apatites showed typical apatitic features. However, crystal growth was greatly inhi bited in the presence of DNA during synthesis; particularly, the crystallin ity in the a-axis direction decreased dramatically at low concentrations of DNA. The a- and c-axis dimensions of each precipitate were almost the same , which implies that DNA molecules affect only the crystal surface. CHN ana lysis clearly showed the presence of these elements, which increased with a n increase in DNA concentration in the solution. Scanning electron microgra phs of the precipitates formed in the presence of DNA showed typical needle -like crystals, with a decreased crystal size, especially width. Infrared a bsorption spectroscopy of the DNA-containing apatites showed that the 1630- 1700 cm(-1) absorption band due to C=C and C=N stretching increased with an increase in DNA concentration during precipitation. The ESCA spectrum of H Ap(DNA1.0) shows N 1s and C 1s peaks that are absent and weak, respectively in HAp. P-31 NMR spectroscopy revealed a weak peak at the base of the P-31 peak from the PO43- ions in the HAp crystals. This weak P-31 peak had a sm all positive shift from the position found in native DNA which may be due t o the phosphate backbone of adsorbed DNA. The apparent solubility of the HA ps increased with an increase in DNA concentration. These results suggest t hat there is an affinity binding between apatite crystal and DNA molecules. (C) 2001 Elsevier Science Ltd. All rights reserved.