Non-Invasive, Reliable, and Fast Quantification of DNA Loading on Gold Nanoparticles by a One-Step Optical Measurement

An exquisite, versatile, and reproducible quantification of DNA loading on gold nanoparticles (Au NPs) has long been pursued because this loading influences the analytical, therapeutic, and self-assembly behaviors of DNA-Au NPs. Nevertheless, the existing methods used thus far rely solely on the invasive detachment and subsequent spectroscopic quantification of DNA, which are error-prone and highly dependent on trained personnel. Here, we present a non-invasive optical framework that can determine the number of DNA strands on Au NPs by versatile one-step measurement of the visible absorption spectra of DNA-Au NP solutions without any invasive modifications or downstream processes. Using effective medium theory in conjunction with electromagnetic numerical calculation, the change in DNA loading density, resulting from varying the ion concentration, Au NP size, DNA strand length, and surrounding temperature, can be tracked in situ merely by the one-step measurement of visible absorption spectra, which is otherwise impossible to achieve. Moreover, the simplicity and robustness of this method promote reproducible DNA loading quantification regardless of experimental adeptness, which is in stark contrast with existing invasive and multistep methods. Overall, the optical framework outlined in this work can contribute to democratizing research on DNA-Au NPs and facilitating their rapid adoption in transformative applications.长期以来，学界一直致力于实现金纳米颗粒（gold nanoparticles, Au NPs）表面DNA负载量的精准、通用且可重复的定量分析——这是因为该负载量会显著影响DNA-金纳米颗粒（DNA-Au NPs）复合物的分析性能、治疗效果及自组装行为。然而，目前已有的检测方法仅能通过侵入性剥离步骤及后续的光谱法定量分析DNA，这类方法不仅误差率高，且高度依赖受过专业训练的实验人员。本研究提出一种非侵入式光学检测框架，无需任何侵入性修饰或后续处理步骤，仅通过通用一步法检测DNA-金纳米颗粒（DNA-Au NPs）溶液的可见吸收光谱，即可定量测定金纳米颗粒表面结合的DNA链数目。本方法结合有效介质理论（effective medium theory）与电磁数值计算（electromagnetic numerical calculation），仅通过一步可见吸收光谱检测，即可原位追踪离子浓度、金纳米颗粒尺寸、DNA链长度及环境温度变化所引发的DNA负载密度变化——这是传统方法无法实现的。此外，该方法操作简便且稳定性优异，无论实验人员的熟练程度如何，均可实现可重复的DNA负载量定量分析，这与现有侵入式多步骤检测方法形成鲜明对比。综上，本研究提出的光学检测框架，有助于推动DNA-金纳米颗粒研究的普及化，并促进其在各类变革性应用中的快速推广应用。