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: 7491331
• 负责人: Jennifer A. Hollingsworth
• 金额: $ 33.08万
• 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/7491331
• 关键词: Address; Architecture; Biocompatible; Biological; Blinking; Cell Survival; Cells; Characteristics; Charge; Chemicals; Chemistry; Class; Complex; Coupled; Coupling; Cultured Cells; 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; Numbers; Optics; Output; Particle Size; Photobleaching; Photons; Physiological; Pliability; Polymers; Preparation; Process; Property; Quantum Dots; 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; fluorescence imaging; fluorophore; improved; indium arsenide; interest; lead selenide; light scattering; luminescence; molecular imaging; nanocrystal; novel; novel strategies; optical imaging; particle; quantum; radius bone structure; single molecule; size; 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)：该项目的首要目标是开发新的生物兼容的荧光探针，能够方便地检测活细胞中的单分子事件。为了实现这一目标，我们将合成未被开发的基于半导体纳米晶体量子点(NQD)的新型探针，对其光物理、结构和化学性质进行表征，并对其进行筛选以确定生物相容性。NQD具有高信号输出、窄带宽、改善的光漂白稳定性、易于激发的宽带吸收、合理的小尺寸以及表面化学的灵活性，从而潜在地实现递送能力和生理中性。这里将开发的两个基于NQD的系统是(1)近红外发射NQD和(2)掺镧(Ln)NQD，其中NQD作为Ln发射的敏化剂。我们的目标是提供600-1400纳米辐射的系统。这一低于1000 nm的光谱区域具有通过生物组织的高透射率的特点，值得进一步扩展到红外线到1400 nm进行细胞研究，因为只有在该波长以上，干扰水的吸收才会显著增加。尽管基于NQD的材料在光学成像应用中具有所有固有的优势，但仍然存在一些障碍。首先，NQD的荧光间歇性(眨眼)阻碍了细胞中对单个NQD的长期跟踪。其次，NQD的生物相容性是对含有重金属的NQD或表面钝化不当的NQD的关注。关于第一个缺陷，虽然已经假设闪烁的起源与NQD表面的电荷转移过程有关，但实验证据有限，对闪烁与NQD电荷之间的联系缺乏定量的了解。如果没有经过实验验证的对这一基本过程的理解，设计和合成不闪烁的NQD的努力本身就会受到阻碍。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光化学稳定结构的设计提供指导，这种结构预计依赖于无机异质结构(例如，复杂的核/壳结构)。我们将首次调查红外线发射的核量子点的闪烁，对于这种闪烁，甚至缺乏基本的研究，目的是了解其潜在机制并制定消除其的综合策略。我们还将研究新型的Ln-NQD耦合系统，在该系统中，发光起源于Ln掺杂，因此不会出现闪烁。这里的目的是优化从吸收体NQD到发射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的探针的毒性和在各种人类细胞系中的定位，来解决基于NQD的荧光团的第二个已知缺陷-生物相容性不足。与闪烁研究类似，生物兼容性研究将在设计具有适当组成、表面钝化和表面功能的探针方面提供有价值的反馈。当生物分子发生在活细胞内时，实时成像生物分子的位置、活性和反应性的能力是进一步推进生物医学科学，包括药物发现的基础，但目前可用的荧光分子探针不能提供对分子和分子事件的常规研究。我们计划通过基础物理、化学和生物研究相结合的方式开发基于量子点的先进分子探测器，这将使实现所需光学分子成像能力所需的进展成为可能。