The quantum spin properties of nitrogen-vacancy defects in diamond enable diverse applications in quantum computing and communications1. However, fluorescent nanodiamonds also have attractive properties for in vitro biosensing, including brightness2, low cost3 and selective manipulation of their emission4. Nanoparticle-based biosensors are essential for the early detection of disease, but they often lack the required sensitivity. Here we investigate fluorescent nanodiamonds as an ultrasensitive label for in vitro diagnostics, using a microwave field to modulate emission intensity5 and frequency-domain analysis6 to separate the signal from background autofluorescence7, which typically limits sensitivity. Focusing on the widely used, low-cost lateral flow format as an exemplar, we achieve a detection limit of 8.2 × 10-19 molar for a biotin-avidin model, 105 times more sensitive than that obtained using gold nanoparticles. Single-copy detection of HIV-1 RNA can be achieved with the addition of a 10-minute isothermal amplification step, and is further demonstrated using a clinical plasma sample with an extraction step. This ultrasensitive quantum diagnostics platform is applicable to numerous diagnostic test formats and diseases, and has the potential to transform early diagnosis of disease for the benefit of patients and populations.

中文翻译：

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用于超灵敏诊断的自旋增强纳米金刚石生物传感

金刚石中氮空位缺陷的量子自旋特性可在量子计算和通信中实现多种应用。然而，荧光纳米金刚石在体外生物传感方面也具有吸引人的特性，包括亮度 2、低成本 3 和选择性操纵其发射 4。基于纳米颗粒的生物传感器对于疾病的早期检测至关重要，但它们通常缺乏所需的灵敏度。在这里，我们研究了荧光纳米金刚石作为体外诊断的超灵敏标记，使用微波场调节发射强度5 和频域分析 6 以将信号与背景自发荧光 7 分离，这通常会限制灵敏度。以广泛使用的低成本侧向流格式为例，我们实现了 8 的检测限。生物素-亲和素模型的 2 × 10-19 摩尔，比使用金纳米颗粒获得的灵敏度高 105 倍。通过增加 10 分钟的等温扩增步骤可以实现 HIV-1 RNA 的单拷贝检测，并使用带有提取步骤的临床血浆样本进一步证明。这种超灵敏的量子诊断平台适用于多种诊断测试形式和疾病，并有可能改变疾病的早期诊断，造福患者和人群。