Lim Yong Taik, Kim Sungjee, Nakayama Akira, Stott Nathan E, Bawendi Moungi G, Frangioni John V
Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA.
Mol Imaging. 2003 Jan;2(1):50-64. doi: 10.1162/15353500200302163.
Fluorescent semiconductor nanocrystals (quantum dots [QDs]) are hypothesized to be excellent contrast agents for biomedical assays and imaging. A unique property of QDs is that their absorbance increases with increasing separation between excitation and emission wavelengths. Much of the enthusiasm for using QDs in vivo stems from this property, since photon yield should be proportional to the integral of the broadband absorption. In this study, we demonstrate that tissue scatter and absorbance can sometimes offset increasing QD absorption at bluer wavelengths, and counteract this potential advantage. By using a previously validated mathematical model, we explored the effects of tissue absorbance, tissue scatter, wavelength dependence of the scatter, water-to-hemoglobin ratio, and tissue thickness on QD performance. We conclude that when embedded in biological fluids and tissues, QD excitation wavelengths will often be quite constrained, and that excitation and emission wavelengths should be selected carefully based on the particular application. Based on our results, we produced near-infrared QDs optimized for imaging surface vasculature with white light excitation and a silicon CCD camera, and used them to image the coronary vasculature in vivo. Taken together, our data should prove useful in designing fluorescent QD contrast agents optimized for specific biomedical applications.
荧光半导体纳米晶体（量子点[QDs]）被认为是生物医学检测和成像的优秀造影剂。量子点的一个独特性质是，其吸光度随着激发波长和发射波长之间间隔的增加而增大。在体内使用量子点的诸多热情都源于这一性质，因为光子产率应与宽带吸收的积分成正比。在本研究中，我们证明组织散射和吸光度有时会抵消在更短波长处量子点吸收的增加，并抵消这一潜在优势。通过使用先前验证的数学模型，我们探究了组织吸光度、组织散射、散射的波长依赖性、水与血红蛋白的比例以及组织厚度对量子点性能的影响。我们得出结论，当嵌入生物流体和组织中时，量子点激发波长通常会受到很大限制，并且应根据具体应用仔细选择激发波长和发射波长。基于我们的结果，我们制备了用于白光激发和硅电荷耦合器件相机成像表面脉管系统的近红外量子点，并将其用于体内冠状动脉脉管系统成像。总之，我们的数据应有助于设计针对特定生物医学应用优化的荧光量子点造影剂。
