The protective effect of layered double hydroxide against damage to DNA induced by heavy metals

The present study is part of an investigation of the protective effect of clay on DNA in adverse environmental conditions. In this paper, layered double hydroxide (LDH) was synthesized and examined as a possible gene protective material. Herring sperm DNA was intercalated into LDH by ion-exchange reaction after which the interlayer distance of LDH increased from 0.76 to 2.3 nm. The DNA intercalated between the hydroxide layers and retained much of its structural integrity. After exposure of the LDH–DNA to a solution of Cd2 +/Pb2 + solution, the structure of protected DNA released from LDH–DNA was virtually unchanged, in contrast to the unprotected DNA which sustained a structural damage as indicated by UV–vis spectroscopy, Cyclic voltammetry, Circular Dichroism (CD) spectroscopy and Electrophoresis. Following LDH–DNA exposure to the heavy metal solution, the concentration of Cd2 + and Pb2 + in the solution decreased from 200 μg/mL to 17 μg/mL and 12 μg/mL, respectively, which indicates that they were also adsorbed by the clay. These data demonstrate that the LDH plays an important role in protecting the DNA against Cd2 + and Pb2 + by immobilizing metal ions. These findings give additional information on the potential implications for the clay used as gene reservoir.