Cancer imaging approaching single-cell levels is highly desirable for studying in vivo cell migration and cancer metastasis. However, current imaging probes struggle to simultaneously achieve high sensitivity, deep-tissue penetration and tissue specificity. Here we report size- and shape-resolved fluorescent DNA framework (FDF) dots with tail emission in the second near-infrared window (1,000–1,700 nm, NIR-II), which enable near-single-cell-level, tumour-targeting deep-tissue (~1 cm) NIR-II imaging in tumour-bearing mouse models. The construction of DNA frameworks with embedded hydrophobic nanocavity results in the non-covalent encapsulation of a designed NIR-Ib (900–1,000 nm) probe (dye Sq964). The FDF dots exhibit high water solubility, brightness and photostability. We find that the stable tumour retention of FDF dots with enhanced signal intensity arises from their shape-dependent accumulation in tumour cells. FDF-dot-based cancer imaging reveals in vivo sensitivity down to ~40 tumour cells, high tumour-to-normal tissue ratios up to ~26 and long-term imaging over 11 days. We also demonstrate NIR-II-image-guided breast cancer surgery with the complete excision of metastases with a minimum size of ~53 μm (~20 cells).

接近单细胞水平的癌症成像对于研究体内细胞迁移和癌症转移非常可取。然而，目前的成像探针难以同时实现高灵敏度、深层组织渗透和组织特异性。在这里，我们报告了在第二个近红外窗口 （1,000–1,700 nm，NIR-II） 中具有尾部发射的大小和形状分辨的荧光 DNA 框架 （FDF） 点，从而在荷瘤小鼠模型中实现接近单细胞水平、靶向肿瘤的深组织 （~1 cm） NIR-II 成像。构建具有嵌入疏水纳米腔的 DNA 框架导致设计的 NIR-Ib （900–1,000 nm） 探针（染料 Sq964）的非共价封装。FDF 点表现出高水溶性、亮度和光稳定性。我们发现，信号强度增强的 FDF 点的稳定肿瘤保留源于它们在肿瘤细胞中的形状依赖性积累。基于 FDF 点的癌症成像显示体内敏感性低至 ~40 个肿瘤细胞，肿瘤与正常组织的高比率高达 ~26 以及 11 天内的长期成像。我们还展示了 NIR-II 图像引导的乳腺癌手术，完全切除了最小尺寸为 ~53 μm （~20 个细胞） 的转移灶。