Adsorption of DNA on biomimetic apatites: Toward the understanding of the role of bone and tooth mineral on the preservation of ancient DNA

In order to shed some light on DNA preservation over time in skeletal remains from a physicochemicalviewpoint, adsorption and desorption of DNA on a well characterized synthetic apatite mimicking boneand dentin biominerals were studied. Batch adsorption experiments have been carried out to determinethe effect of contact time (kinetics), DNA concentration (isotherms) and environmentally relevant factorssuch as temperature, ionic strength and pH on the adsorption behavior. The analogy of the nanocrystallinecarbonated apatite used in this work with biological apatite was first demonstrated by XRD, FTIR, andchemical analyses. Then, DNA adsorption kinetics was fitted with the pseudo-first order, pseudo-secondorder, Elovich, Ritchie and double exponential models. The best results were achieved with the Elovichkinetic model. The adsorption isotherms of partially sheared calf thymus DNA conformed satisfacto-rily to Temkin’s equation which is often used to describe heterogeneous adsorption behavior involvingpolyelectrolytes. For the first time, the irreversibility of DNA adsorption toward dilution and significantphosphate-promoted DNA desorption were evidenced, suggesting that a concomitant ion exchange pro-cess between phosphate anionic groups of DNA backbone and labile non-apatitic hydrogenphosphateions potentially released from the hydrated layer of apatite crystals. This work should prove helpful fora better understanding of diagenetic processes related to DNA preservation in calcified tissues