Preparation and characterization of DNA/allophane composite hydrogels.

The preparation and characterization of the composite hydrogels based on double-stranded deoxyribonucleic acid (DNA) and natural allophane (AK70) were reported. To understand the propensity of the natural allophane to adsorb the DNA molecules, using zeta potential measurement, Fourier transform infrared spectroscopy (FTIR) and electrophoresis analyses assessed the adsorption characteristics. The freeze-dried DNA/AK70 hydrogels were demonstrated that the DNA bundle structure with a width of ∼2µm and a length of ∼15-20µm was wrapped around the clustered allophane particles as revealed by FE-SEM/EDX analysis. The incorporation of AK70 in hydrogels induced the increase in the enthalpy of the helix-coil transition of DNA duplex due to the restricted molecular motions of the DNA duplex facilitated by the interaction between the phosphate groups of DNA and the protonated (+)(OH2)Al(OH2) groups on the wall perforations of the allophane.

DNA adsorption characteristics of hollow spherule allophane nano-particles.

To understand the propensity of natural allophane to adsorb the DNA molecules, the adsorption characteristics were assessed against natural allophane (AK70), using single-stranded DNA (ss-DNA) and adenosine 5'-monophosphate (5'-AMP) as a reference molecule. The adsorption capacity of ss-DNA on AK70 exhibited one order of magnitude lower value as compared with that of 5'-AMP. The adsorption capacity of ss-DNA decreased with increasing pH due to the interaction generated between phosphate groups of ss-DNA and functional Al-OH groups on the wall perforations through deprotonating, associated with higher energy barrier for the adsorption of ss-DNA. The adsorption morphologies consisting of the individual ss-DNA with mono-layer coverage of the clustered allophane particle were observed successfully through transmission electron microscopy analysis.