Department of Chemistry and the Smalley-Curl Institute, 6100 Main Street, Houston, TX 77005, USA.
Nanoscale. 2016 May 21;8(19):10348-57. doi: 10.1039/c6nr01376g. Epub 2016 May 3.
Nanomaterials with luminescence in the short-wave infrared (SWIR) region are of special interest for biological research and medical diagnostics because of favorable tissue transparency and low autofluorescence backgrounds in that region. Single-walled carbon nanotubes (SWCNTs) show well-known sharp SWIR spectral signatures and therefore have potential for noninvasive detection and imaging of cancer tumours, when linked to selective targeting agents such as antibodies. However, such applications face the challenge of sensitively detecting and localizing the source of SWIR emission from inside tissues. A new method, called spectral triangulation, is presented for three dimensional (3D) localization using sparse optical measurements made at the specimen surface. Structurally unsorted SWCNT samples emitting over a range of wavelengths are excited inside tissue phantoms by an LED matrix. The resulting SWIR emission is sampled at points on the surface by a scanning fibre optic probe leading to an InGaAs spectrometer or a spectrally filtered InGaAs avalanche photodiode detector. Because of water absorption, attenuation of the SWCNT fluorescence in tissues is strongly wavelength-dependent. We therefore gauge the SWCNT-probe distance by analysing differential changes in the measured SWCNT emission spectra. SWCNT fluorescence can be clearly detected through at least 20 mm of tissue phantom, and the 3D locations of embedded SWCNT test samples are found with sub-millimeter accuracy at depths up to 10 mm. Our method can also distinguish and locate two embedded SWCNT sources at distinct positions.
短波长红外（SWIR）区域具有发光性能的纳米材料在生物研究和医学诊断中特别有趣，因为在该区域组织具有良好的透明度和低自发荧光背景。单壁碳纳米管（SWCNT）在 SWIR 光谱区域具有明显的光谱特征，因此当与选择性靶向剂（如抗体）结合时，具有用于癌症肿瘤的非侵入性检测和成像的潜力。然而，此类应用面临着从组织内部敏感地检测和定位 SWIR 发射源的挑战。提出了一种称为光谱三角测量的新方法，用于使用在样品表面进行的稀疏光学测量进行三维（3D）定位。在组织体模内部，通过 LED 矩阵激发发射不同波长的结构无序 SWCNT 样品。通过扫描光纤探头在表面上的点对 SWIR 发射进行采样，导致 InGaAs 光谱仪或光谱过滤的 InGaAs 雪崩光电二极管检测器。由于水吸收，组织中 SWCNT 荧光的衰减强烈依赖于波长。因此，我们通过分析测量的 SWCNT 发射光谱中的差异变化来测量 SWCNT-探头的距离。通过至少 20mm 的组织体模可以清晰地检测到 SWCNT 荧光，并且可以以亚毫米的精度找到嵌入的 SWCNT 测试样品的 3D 位置，深度可达 10mm。我们的方法还可以区分和定位位于不同位置的两个嵌入式 SWCNT 源。
