pH-dependent surface interactions and structural changes for DNA adsorbed on TiO2 particle surfaces have implications for environmental DNA

<h2>Summary</h2> Environmental DNA (eDNA) can interact with various geochemical surfaces, including mineral surfaces. These interactions may alter the structure, stability, and reactivity of eDNA, impacting the cycling of genetic information and the accuracy of species identification. Here, we report on pH-dependent surface interactions between herring testes DNA adsorbed on titanium dioxide (TiO₂) particle surfaces. Utilizing vibrational spectroscopic probes of surface-adsorbed DNA, DNA retains its native B-form at pH values from 6.5 to 8, whereas at pH 3–5, the structure of adsorbed DNA changes to the Z-form, which can undergo dehybridization. These changes are consistent with electrostatic and hydrogen-bonding interactions at the surface that drive these large structural changes within DNA. Overall, this study provides evidence for mineral-specific DNA-surface interactions that depend on pH and shows the role that interactions with geochemical surfaces may play in eDNA structure and stability.