Titanium dioxide nanoparticles as a promising tool for efficient separation of trace DNA via phosphate-mediated desorption.

We systematically evaluated the DNA adsorption and desorption efficiencies of several nanoparticles. Among them, titanium dioxide (TiO₂) nanoparticles (NPs), aluminum oxide (Al₂O₃) NPs, and zinc oxide (ZnO) NPs exhibited strong DNA-binding capacities under mild conditions. However, phosphate-mediated DNA displacement efficiencies varied considerably, with only TiO₂ NPs showing consistently superior performance. Further investigation into the DNA adsorption and desorption mechanisms of TiO₂ NPs led to the following key results: (1) TiO₂ NPs achieved over 98% DNA adsorption at room temperature, but efficient desorption required elevated temperatures; (2) phosphate-induced DNA displacement depended on the full exposure of phosphate groups, and short DNA fragments were insufficient to effectively compete with adsorbed DNA; (3) the adsorption mechanism of TiO₂ NPs involved multiple interactions, such as coordination and hydrogen bonding. The combination of strong coordination and weak ionic forces likely contributed to the high efficiency of phosphate-mediated desorption. Under optimized conditions, TiO₂ NPs demonstrated excellent separation efficiency for structurally complex DNA, with recovery rates of 56.92% for genomic DNA and 66.31% for plasmid DNA, notably higher than those of amino-modified silica-coated magnetic nanoparticles (ASMNPs; 38.66% and 33.59%). These results highlight the potential of TiO₂ NPs as a powerful tool for trace DNA isolation under mild, biocompatible conditions, with promising applications in nucleic acid separation and molecular diagnostics.