Heterostructured Quantum Dots as Molecular Probes: Chemistry and Photophysics

作为分子探针的异质结构量子点：化学和光物理学

• 批准号: 7683885
• 负责人: Jennifer A. Hollingsworth
• 金额: $ 33.37万
• 依托单位: LOS ALAMOS NAT SECTY-LOS ALAMOS NAT LAB
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7683885
• 关键词: Address; Architecture; Biocompatible; Biological; Blinking; Cell Culture Techniques; Cell Survival; Cells; Characteristics; Charge; Chemicals; Chemistry; Complex; Confocal Microscopy; Coupled; Coupling; Data; Detection; Development; Dyes; Electrons; Energy Transfer; Environment; Ethylene Glycols; Event; Exhibits; Feedback; Flow Cytometry; Fluorescence; Fluorescence Microscopy; Fluorescent Probes; Gel; Gene Expression; Genetic Recombination; Goals; Green Fluorescent Proteins; Heavy Metals; Human Cell Line; Image; Ions; Lanthanoid Series Elements; Life; Ligands; Location; Measurement; Measures; Metabolism; Metals; Methods; Microscopy; Molecular; Molecular Probes; Optics; Output; Particle Size; Photobleaching; Photons; Physiological; Polymers; Preparation; Process; Property; Quantum Dots; Radial; Reaction; Relative (related person); Research; Science; Semiconductors; Sepharose; Shapes; Signal Transduction; Silicon Dioxide; Spectrum Analysis; Structure; Surface; System; Techniques; Technology; Thick; Time; Tissues; Toxic effect; Transmission Electron Microscopy; Variant; Water; X ray diffraction analysis; X-Ray Diffraction; absorption; base; biomaterial compatibility; chemical property; cytotoxic; design; drug discovery; ethylene glycol; flexibility; fluorescence imaging; fluorophore; improved; indium arsenide; interest; lead selenide; light scattering; luminescence; molecular imaging; nanocrystal; novel; novel strategies; optical imaging; particle; quantum; single molecule; uptake

DESCRIPTION (provided by applicant): The overriding objective that will be pursued in this project is to develop new biocompatible fluorescent probes capable of providing facile detection of single-molecule events in living cells. In pursuit of this goal, under-explored and novel semiconductor nanocrystal quantum dot (NQD)-based probes will be synthesized, characterized with respect to their photophysical, structural and chemical properties, and screened to ascertain biocompatibility. NQDs offer high signal output, narrow bandwidth, improved stability with respect to photobleaching, broadband absorption for facile excitation, reasonably small size, and flexibility in surface chemistry for potentially achieving deliverability and physiological neutrality. The two NQD-based systems that will be developed here are (1) Near-infrared-emitting NQDs and (2) Lanthanide (Ln) doped NQDs, where the NQD serves as a sensitizer for Ln emission. We will target systems that provide emission from 600 - 1400 nm. This spectral region below 1000 nm is distinguished by a high transmittance through biological tissue and is worth extending farther into the infrared to 1400 nm for cellular studies, as interfering water absorption increases significantly only above this wavelength. Despite all the inherent advantages of NQD-based materials for optical imaging applications, several obstacles remain. Firstly, long-term single-NQD tracking in cells is hindered by fluorescence intermittency (blinking) that is characteristic of NQDs. Secondly, NQD biocompatibility is a concern for heavy-metal-containing NQDs or for NQDs that are improperly surface passivated. With respect to the first deficiency, though it has been postulated that the origin of blinking is related to charge transfer processes at the NQD surface, the experimental evidence is limited and the quantitative understanding of the connection between blinking and NQD charging is lacking. Without an experimentally validated understanding of this fundamental process, efforts to design and synthesize non-blinking NQDs are inherently impeded. We will perform steady-state and ultrafast spectroscopic studies to elucidate the mechanism of charging and correlate these results with single-NQD blinking studies. Results of spectroscopic studies will provide guidance for the design of photochemically stable structures that is anticipated to rely on inorganic heterostructuring (e.g., complex core/shell architectures). We will for the first time investigate blinking in infrared-emitting NQDs for which even rudimentary studies are lacking with the objective to understand the underlying mechanism and to develop synthetic strategies for its elimination. We will also investigate novel Ln-NQD coupled systems, in which the luminescence originates in the Ln dopant and is therefore not expected to exhibit blinking. The aim here will be to optimize the energy transfer process from the absorber NQD to the emitting Ln and, thereby, the signal output of the combined system. In parallel with these studies, we will address the second perceived deficiency of NQD-based fluorophores - insufficient biocompatibility - by investigating the toxicity and localization of our NQD-based probes in a variety of human cell lines. Similar to the blinking studies, the biocompatibility studies will provide valuable feedback in the design of probes possessing appropriate composition, surface passivation, and surface functionality. The ability to image real-time the location, activity and reactivity of biomolecules as they occur within living cells is fundamental to furthering biomedical science, including drug discovery, but currently available fluorescent molecular probes are not capable of providing for the routine study of molecules and molecular events. The advanced quantum dot based molecular probes that we propose to develop through a combination of fundamental physical, chemical and biological studies will enable the advances necessary for achieving the required optical molecular imaging capability.

描述（由申请人提供）：本项目追求的首要目标是开发新的生物相容性荧光探针，能够提供活细胞中单分子事件的简便检测。为了实现这一目标，将合成未开发的新型半导体量子点（NQD）探针，对其物理，结构和化学性质进行表征，并筛选以确定生物相容性。NQD提供高信号输出、窄带宽、相对于光漂白的改进的稳定性、用于容易激发的宽带吸收、合理小的尺寸和表面化学的灵活性，以潜在地实现递送能力和生理中性。这里将开发的两种基于NQD的系统是（1）近红外发射NQD和（2）镧系元素（Ln）掺杂的NQD，其中NQD用作Ln发射的敏化剂。我们将瞄准提供600 - 1400 nm发射的系统。低于1000 nm的光谱区域的特征在于通过生物组织的高透射率，并且值得进一步延伸到红外线至1400 nm用于细胞研究，因为干扰水吸收仅在该波长以上显著增加。尽管NQD基材料在光学成像应用中具有所有固有的优点，但仍存在一些障碍。首先，细胞中的长期单NQD跟踪受到NQD特有的荧光闪烁（闪烁）的阻碍。其次，NQD生物相容性是含重金属的NQD或表面钝化不当的NQD的问题。关于第一个缺陷，虽然它已被假定，闪烁的起源是有关的电荷转移过程中的NQD表面，实验证据是有限的，闪烁和NQD充电之间的连接缺乏定量的了解。如果没有实验验证的理解这一基本过程，设计和合成不闪烁的NQD的努力是固有的阻碍。我们将进行稳态和超快光谱研究，以阐明充电机制，并将这些结果与单NQD闪烁研究相关联。光谱研究的结果将为预期依赖于无机异质结构化的光化学稳定结构的设计提供指导（例如，复杂的核/壳体系结构）。我们将首次研究红外发射NQD中的闪烁，即使是基本的研究也缺乏，目的是了解其潜在的机制，并制定消除其的合成策略。我们还将研究新的Ln-NQD耦合系统，其中发光起源于Ln掺杂剂，因此预计不会表现出闪烁。这里的目的是优化从吸收体NQD到发射体Ln的能量传递过程，从而优化组合系统的信号输出。在这些研究的同时，我们将通过研究我们的基于NQD的探针在各种人类细胞系中的毒性和定位来解决基于NQD的荧光团的第二个缺陷-生物相容性不足。与闪烁研究相似，生物相容性研究将为具有适当成分、表面钝化和表面功能的穿刺针设计提供有价值的反馈。当生物分子在活细胞内出现时，对生物分子的位置、活性和反应性进行实时成像的能力对于进一步的生物医学科学（包括药物发现）是基本的，但是目前可用的荧光分子探针不能提供分子和分子事件的常规研究。我们建议通过基础物理，化学和生物学研究的组合开发的先进的基于量子点的分子探针将实现实现所需的光学分子成像能力所必需的进步。