National Center for Nanoscience and Technology, 11 Zhongguancun Beiyitiao, Beijing 100190, China.
Nano Lett. 2013 Jun 12;13(6):2436-41. doi: 10.1021/nl400368v. Epub 2013 May 15.
Bright two-photon fluorescent probes are highly desirable to be able to optically probe biological activities deep inside living organisms with larger imaging depth, minor autofluorescence background, and less photodamage. In this study, we report the biocompatible nitrogen-doped graphene quantum dots (N-GQDs) as efficient two-photon fluorescent probes for cellular and deep-tissue imaging. The N-GQD was prepared by a facile solvothermal method using dimethylformamide as a solvent and nitrogen source. The two-photon absorption cross-section of N-GQD reaches 48,000 Göppert-Mayer units, which far surpasses that of the organic dyes and is comparable to that of the high performance semiconductor QDs, achieving the highest value ever reported for carbon-based nanomaterials. More importantly, a study of penetration depth in tissue phantom demonstrates that the N-GQD can achieve a large imaging depth of 1800 μm, significantly extending the fundamental two-photon imaging depth limit. In addition, the N-GQD is nontoxic to living cells and exhibits super photostability under repeated laser irradiation. The high two-photon absorption cross-section, large imaging depth, good biocompatibility, and extraordinary photostability render the N-GQD an attractive alternative probe for efficient two-photon imaging in biological and biomedical applications.
明亮的双光子荧光探针是高度可取的，能够用光探测生物活性在活生物体内部具有更大的成像深度、较小的自发荧光背景和较少的光损伤。在这项研究中，我们报告了生物相容性的氮掺杂石墨烯量子点（N-GQDs）作为高效的双光子荧光探针用于细胞和深层组织成像。N-GQD 是通过一种简单的溶剂热法用二甲基甲酰胺作为溶剂和氮源制备的。N-GQD 的双光子吸收截面达到 48000 个戈珀特-迈尔单位，远远超过有机染料，与高性能半导体量子点相当，实现了碳基纳米材料的最高值。更重要的是，在组织模拟物中的穿透深度研究表明，N-GQD 可以实现 1800μm 的大成像深度，显著扩展了基本的双光子成像深度极限。此外，N-GQD 对活细胞无毒，并在重复激光照射下表现出超稳定的光稳定性。高双光子吸收截面、大成像深度、良好的生物相容性和非凡的光稳定性使 N-GQD 成为生物和生物医学应用中高效双光子成像的有吸引力的替代探针。
