Fluorescent nanodiamonds (FNDs) are carbon nanoparticles containing a dense ensemble of nitrogen-vacancy defects as color centers. These centers have exceptional photostability and unique quantum properties, making them useful for ultrasensitive biosensing applications. This work employed FNDs conjugated with antibodies as magneto-optical immunosensors for tuberculosis (TB) diagnostics using competitive spin-enhanced lateral flow immunoassay (SELFIA). ESAT6 (6-kDa early secretory antigenic target) of Mycobacterium tuberculosis is a clinical marker of TB. We evaluated the assay's performance using the recombinant ESAT6 antigen and its antibodies noncovalently coated on FNDs. A detection limit of ∼0.02 ng mL⁻¹ was achieved with the lateral flow membrane strip pre-structured with a narrow channel of 1 mm width. Adopting a cut-off value of 24.0 ng mm⁻¹ for 100-nm FNDs on the strips, the method detected 49 out of 50 clinical samples with Mycobacterium tuberculosis complexes. In contrast, none of the assays for 10 clinical samples with non-tuberculous mycobacteria (NTM) isolates exhibited the presence of ESAT6. These results suggest that the SELFIA platform is applicable for TB detection and can differentiate TB from NTM infections, which also affect the human respiratory system. The FND-enabled immunosensing techniques are versatile and promising for early detection of TB and other diseases, opening a new avenue for biomedical applications of carbon-based nanomaterials.

中文翻译：

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用于结核病临床诊断的荧光纳米金刚石免疫传感器

荧光纳米金刚石（FND）是碳纳米颗粒，含有密集的氮空位缺陷作为色心。这些中心具有出色的光稳定性和独特的量子特性，使其可用于超灵敏的生物传感应用。这项工作采用与抗体缀合的 FND 作为磁光免疫传感器，使用竞争性自旋增强侧流免疫分析 (SELFIA) 进行结核病 (TB) 诊断。结核分枝杆菌的 ESAT6（6-kDa 早期分泌抗原靶标）是结核病的临床标志物。我们使用重组 ESAT6 抗原及其非共价包被在 FND 上的抗体评估了测定的性能。使用预先构造有宽度为 1 mm 的窄通道的侧流膜条实现了~0.02 ng mL ^-1的检测限。该方法采用试纸条上 100 nm FND 的截止值 24.0 ng mm ^-1 ，在 50 个临床样本中检测到 49 个样本中含有结核分枝杆菌复合体。相比之下，对 10 个非结核分枝杆菌 (NTM) 分离株的临床样本进行的检测均未显示出 ESAT6 的存在。这些结果表明，SELFIA 平台适用于结核病检测，并且可以区分结核病和 NTM 感染，后者也影响人类呼吸系统。 FND 免疫传感技术用途广泛，有望用于结核病和其他疾病的早期检测，为碳基纳米材料的生物医学应用开辟了新途径。