Metal-Mediated DNA Adsorption on Carboxylated, Hydroxylated and Hydrogenated Nanodiamonds

Nanodiamonds (NDs) have attracted considerable attention owing to their quantum properties and versatility in biological applications. In this study, we systematically investigated the adsorption of DNA oligonucleotides onto NDs with three types of surface groups: carboxylated (COOH-), hydroxylated (OH-), and hydrogenated (H-). Among them, only the H-NDs showed fluorescence quenching property that is useful for real-time DNA adsorption kinetic studies. The effect of common metal ions on DNA adsorption was studied. In the presence of Na+, the order of DNA adsorption efficiency was H-> OH- > COOH-, whereas all the NDs showed a similar DNA adsorption efficiency in the presence of divalent metal ions such as Ca2+ and Zn2+. Desorption studies revealed that hydrogen bonding and metal-mediated interactions were dominant for the adsorption of DNA, and the H-NDs exhibited extraordinarily tight DNA adsorption. Finally, a fluorescently labeled DNA was adsorbed on NDs for DNA detection, and the COOH-NDs had the highest target specificity, and a detection limit of 1.4 nM was achieved. This study indicates the feasibility of using metal ions to mediate the physical adsorption of DNA to NDs and compares various NDs with graphene oxide for fundamental understanding.

纳米金刚石（Nanodiamonds, NDs）凭借其量子特性与生物应用的多功能性，受到了广泛关注。本研究系统探究了三类表面改性纳米金刚石——羧基化（COOH-）、羟基化（OH-）与氢化（H-）纳米金刚石对DNA寡核苷酸的吸附行为。其中仅氢化纳米金刚石（H-NDs）具备荧光淬灭特性，可用于开展DNA吸附的实时动力学研究。本研究还考察了常见金属离子对DNA吸附行为的影响。在一价金属离子Na+存在的条件下，DNA吸附效率的排序为H-NDs > OH-NDs > COOH-NDs；而在Ca²+、Zn²+等二价金属离子存在时，三类纳米金刚石的DNA吸附效率则无显著差异。解吸实验结果表明，氢键作用与金属介导的相互作用是DNA吸附的主要驱动力，且H-NDs对DNA的吸附结合能力极强。最后，本研究将荧光标记的DNA吸附于纳米金刚石表面以实现DNA检测，其中羧基化纳米金刚石（COOH-NDs）的靶标特异性最优，检测限可达1.4 nM。本研究证实了利用金属离子介导DNA在纳米金刚石表面物理吸附的可行性，并通过将各类纳米金刚石与氧化石墨烯（graphene oxide）进行对比分析，为相关基础研究提供了更深入的认知。