NIR-Ⅱ Excitation and NIR-I Emission Based Two-photon Fluorescence Lifetime Microscopic Imaging Using Aggregation-induced Emission Dots

Near-infrared(NIR)lights are powerful tools to conduct deep-tissue imaging since NIR-Ⅰ wavelengths hold less photon absorption and NIR-Ⅱ wavelengths serve low photon scattering in the biological tissues compared with visible lights.Two-photon fluorescence lifetime microscopy(2PFLM)can utilize NIR-Ⅱ excitation and NIR-Ⅰ emission at the same time with the assistance of a well-designed fluorescent agent.Aggregation induced emission(AIE)dyes are famous for unique optical properties and could serve a large two-photon absorption(2PA)cross-section as aggregated dots.Herein,we report two-photon fluorescence lifetime microscopic imaging with NIR-Ⅱ excitation and NIR-Ⅰ emission using a novel deep-red AIE dye.The AIE-gens held a 2PA cross-section as large as 1.61×10⁴GM at 1040 nm.Prepared AIE dots had a two-photon fluorescence peak at 790 nm and a stable lifetime of 2.2 ns under the excitation of 1040 nm femtosecond laser.The brain vessels of a living mouse were vividly reconstructed with the two-photon fluorescence lifetime information obtained by our home-made 2PFLM system.Abundant vessels as small as 3.17μm were still observed with a nice signal-background ratio at the depth of 750μm.Our work will inspire more insight into the improvement of the working wavelength of fluorescent agents and traditional 2PFLM.     

Stable Cross‐linked Fluorescent Polymeric Nanoparticles for Cell Imaging

Aggregation‐induced emission (AIE) dye‐based cross‐linked fluorescent polymeric nanoparticles (FPNs) are facilely prepared via a two‐step polymerization process including emulsion polymerization and subsequent anhydride cross‐linking. Then, a variety of characterization methods are carried out to determine the performance of the FPNs, which show high dispersibility and strong fluorescence in an aqueous solution due to the hydrophilic carboxyl groups on the surfaces and the AIE components as the cores. Biocompatibility evaluation and cell imaging results suggest that these FPNs are biocompatible for cell imaging. More importantly, this cross‐linking strategy is proven to overcome the issue of critical micelle concentration and opens the opportunity to develop more robust fluorescent bioprobes.

     

Donor-Acceptor Typed AIE Luminogens with Near-infrared Emission for Super-resolution Imaging

Aggregation-induced emission(AIE)luminogens(AIEgens)with high brightness in aggregates exhibit great potentials in biological imaging,but these AIEgens are seldom applied in super-resolution biological imaging,especially in the imaging by using the structural illumination microscope(SIM).Based on this consideration,we synthesized the donor-acceptor typed AIEgen of DTPA-BTN,which not only owns high brightness in the near-infrared(NIR)emission region from 600 nm to 1000 nm(photoluminescence quantum yield,PLQYs=11.35%),but also displays excellent photo-stability.In addition,AIE nanoparticles based on 4,7-ditriphenylamine-[1,2,5]-thiadiazolo[3,4-c]pyridine(DTPA-BTN)were also prepared with highly emissive features and excellent biocompatibility.Finally,the developed DTPA-BTN-based AIE nanoparticles were applied in the super-resolution cellular imaging via SIM,where much smaller full width at half-maximum values and high signal to noise ratios were obtained,indicating the superior imaging resolution.The results here imply that highly emissive AIEgens or AIE nanoparticles can be promising imaging agents for super-resolution imaging via SIM.     

荧光猝灭法测定超氧阴离子自由基的研究

合成了一种新的荧光探针试剂香草醛缩苯胺,利用元素分析、红外光谱等手段对探针试剂进行结构表征;结合邻苯三酚的自氧化作用,建立了一种荧光法测定超氧阴离子自由基(O_2~(-·))的新方法.该方法具有操作简单、灵敏度高和选择性好等特点.邻苯三酚线性范围为4.0×10~(-6)～1.0×10~(-5) mol·~(-1).检出限为2.0×10~(-7) mol·~(-1).方法用于大蒜等样品中超氧化物歧化酶(SOD)活性检测,结果满意.     

Intracellular Self-assembly of TPE-biotin Nanoparticles Enables Aggregation-Induced Emission Fluorescence for Cancer-Targeted Imaging

Fluorogens with aggregation-induced emission (AIE) characteristics have recently been widely applied for studying biological events, and fluorogens with "smart" properties are especially desirable. Herein, we rationally designed and synthesized a biotinylated and reduction-activatable probe (Cys(StBu)-Lys(biotin)-Lys(TPE)-CBT (begin{document}$textbf{1}$end{document})) with AIE properties for cancer-targeted imaging. The biotinylated probe begin{document}$textbf{1}$end{document} can be actively uptaken by the biotin receptor-overexpressing cancer cells, and then "smartly" self-assemble into nanoparticles inside cells and turn the fluorescence "On". Employing this "smart" strategy, we successfully applied probe begin{document}$textbf{1}$end{document} for cancer-targeted imaging. We envision that this biotinylated intelligent probe begin{document}$textbf{1}$end{document} might be further developed for cancer-targeted imaging in routine clinical studies in the near future.     

高效近红外聚集诱导发光纳米粒子用于生物成像的研究

基于荧光共振能量转移机理（FRET）,利用两亲性聚合物Pluronic F-127共包覆两种聚集诱导发光（Aggregation-induced Emission,AIE）材料TPABDFN和TPE-Me,制备了高效近红外发射TPABDFN/TPE-Me@F127纳米粒子.实验表明,这种聚合物纳米粒子具有很大的斯托克斯位移和较高的荧光量子效率,很好的单分散性、稳定性,以及较好的生物相容性和低的细胞毒性,对HepG2细胞进行荧光生物成像,得到很好的细胞成像效果.     

Multifunctional Nanoprobe for MRI/Optical Dual‐Modality Imaging and Radical Scavenging

The development of novel nanomaterials for the diagnosis and/or treatment of human diseases has become an important issue. In this work, a multifunctional theranostic agent was designed by covalently binding hydroxyl‐ and amino‐bearing C₆₀ derivatives (C₆₀O_～10(OH)_～16(NH₂)_～6(NO₂)_～6 ? 24 H₂O) with gadolinium diethylenetriaminepentaacetic acid (Gd‐DTPA) to yield C₆₀O_～10(OH)_～16(NH₂)_～6(NO₂)_～6 ? 24 H₂O/(Gd‐DTPA)₃ ( DF₁Gd₃ ). The obtained DF₁Gd₃ shows more than fourfold contrast improvement over commercial Gd‐DTPA along with multiwavelength fluorescent emission for dual‐modality diagnosis. An inner‐ear magnetic resonance imaging (MRI) study was designed as a model of biological barriers, including the blood/brain barrier (BBB) for DF₁Gd₃ to investigate its in vivo behavior. This revealed that the fabricated contrast agent dramatically increases the local contrast but can not cross the middle ear/inner ear barrier and endolymph/perilymph barrier in the inner ear, and thus it is also BBB‐prohibited in normal individuals. In vivo biodistribution studies suggested that 1) DF₁Gd₃ could circulate in vessels for a relatively long time and is mainly eliminated through liver and kidney, 2) DF₁Gd₃ may potentially function as a liver‐specific MRI contrast agent. Interestingly, DF₁Gd₃ also shows an excellent quenching effect on hydroxyl radicals, as revealed by the DMPO spin trap/ESR method. The combination of enhanced MRI/FL imaging and local treatment of lesions is unique to DF₁Gd₃ and potentiates the medical paradigm of “detect and treat/prevent” in combating human diseases related to reactive oxygen.     

Tetraphenylethene End-capped Polyethylenimine Fluorescent Nanoparticles for Cell Imaging

Water soluble tetraphenylethene-based（TPE） aggregation-induced emission fluorescent organic nanoparticles（FONs） were facilely prepared via Schiff base condensation with polyethylenimine（PEI） and subsequent reduction. The obtained TPE-PEI FONs were characterized by a series of techniques including 1H-NMR, 13C-NMR, gel permeation chromatography, UV absorption spectra, fluorescence spectra, Fourier transform infrared spectroscopy, size distribution and zeta potential measurement, and transmission electron microscopy. Biocompatibility evaluation and cell imaging of TPE-PEI FONs were further explored. We demonstrated that such FONs showed intense fluorescence, spherical morphology and excellent biocompatibility, making them very suitable for cell imaging application.     

荧光成像在生物分析中的应用

荧光显微镜与荧光光谱仪耦合系统可获取显微荧光成像及微区荧光光谱、荧光寿命的测定信息,广泛应用于细胞、组织中蛋白质的结构功能分析,核酸的识别检测,金属离子、自由基的定量测定,以及纳米生物探针的研制等生物分析研究的热点领域。本文引用文献46篇,综述了荧光成像在生物分析中的应用新进展。     

Rare-earth Doped Nanoparticles with Narrow NIR-II Emission for Optical Imaging with Reduced Autofluorescence

Fluorescence imaging in the second near-infrared region(900-1700 nm, NIR-II) with a high resolution and penetration depth due to the significantly reduced tissue scattering and autofluorescence has emerged as a useful tool in biomedical fields. Recently, many efforts have been devoted to the development of fluorophores with an emission band covering the long-wavelength end of NIR-II region(1500-1700 nm) to eliminate the autofluorescence. Alternatively, we believe imaging with a narrow bandwidth could also reduce the autofluorescence. As a proof of concept, NaYF₄:Yb,Nd@NaYF₄ downconversion nanoparticles(DCNPs) with sharp NIR-II emission were synthesized. The luminescence of DCNPs showed a half-peak width of 49 nm centered at 998 nm, which was perfectly matched with a (1000±25) nm bandpass filter. With this filter, we were able to retain most of the emissions from the nanoparticles, while the autofluorescence was largely reduced. After PEGylation, the DCNPs exhibited great performance for blood vessel and tumor imaging in living mice with significantly reduced autofluorescence and interference signals. This work provided an alternative way for the low-autofluorescence imaging and emphasized the importance of narrow emitting rare-earth doped nanoparticles for NIR-II imaging.     

荧光/化学发光探针成像检测超氧阴离子自由基的研究进展

超氧阴离子自由基(O·-2)是细胞内氧气单电子还原后最先产生的一类含氧的高活性物种(活性氧,ROS),与生命过程息息相关.正常稳态浓度的O·-2起重要的信号调控作用,包括细胞的增殖、分化、自噬等.但O·-2浓度的异常,又与癌症、神经退行性疾病、糖尿病等多种疾病的发生发展密切相关.因此,监测O·-2浓度的变化对揭示相关疾病的机理具有至关重要作用.由于荧光成像检测方法具有诸多优势,发展高灵敏、高选择性检测O·-2的荧光探针成为揭示相关疾病发生发展分子机制的关键切入点.近年来,随着荧光显微技术的发展,研究者开发了多种荧光/化学发光探针,实现了对细胞及活体内O·-2水平的可视化监测.本文综述了近五年用于检测O·-2的分子探针、纳米探针、蛋白探针以及化学发光探针的研究进展,并对其发展前景进行了展望.     

Synthesis of furan-substituted aza-BODIPYs having near-infrared emission

Development of near-infrared-emissive aza-boron dipyrromethene (aza-BODIPY) derivatives having furanyl groups is reported. From the optical measurements, it was clearly indicated that the emission bands were presented in the longer wavelength region than those of the conventional aza-BODIPYs. The emission bands with the peaks at 730 nm and 758 nm were observed from the bis- and tetra-substituted furanyl aza-BODIPYs with similar extents of emission efficiencies, respectively. According to the computer calculations, it was proposed that molecular planarity could be enhanced in the case of the furan groups. As a result, band-gap energy could be lowered comparing to those of the conventional benzene and thiophene-substituted aza-BODIPYs.     

Radical chain reactions using THP as a solvent

THP (tetrahydropyran) has been found to show an excellent stability towards autooxidation, compared with THF. Tributyltin hydride mediated radical cyclization, when conducted in THF as a solvent, suffers from competition of hydrogen abstraction from the solvent, whereas the use of THP resulted in the course to negligible degree. Tributyltin hydride, TTMSS, and hexanethiol mediated radical reactions were carried out successfully using THP as a solvent.     

Fluorinated Copolymer Nanoparticles for Multimodal Imaging Applications

Nanomaterials have emerged as valuable tools in biomedical imaging techniques. Here, the synthesis and characterization of a novel fluorinated nanoparticle with potential applications as an MRI contrast agent is reported. Particles were synthesized using a free radical polymerization technique. Secondary ion mass spectrometry analysis showed that the particles' surface contained fluorinated groups and nitrogen‐containing groups. Solid‐state NMR spectroscopy suggested the presence of two distinct fluorine resonances, which conforms to the structure of the fluorinated monomer. Ongoing studies aim to evaluate the performance of the nanoparticles as MRI contrast agents both in vitro and in vivo.

     

细胞内源性分子辅助荧光信号放大策略及细胞成像

细胞内原位信号放大策略是检测低丰度内源性目标物的有效手段, 但多数信号放大策略依赖于外源性辅助物, 不可避免地改变细胞内微环境, 进而对机体造成一定干扰. 针对此问题, 可利用细胞内源性物质(如金属离子、 核酸、 蛋白酶等)实现原位荧光信号放大, 对不同生物标志物进行荧光成像, 此方法对低丰度靶分子检测及成像具有重要意义. 本文对内源性物质辅助信号放大及细胞内荧光成像相关研究进行了归纳整理, 介绍了内源性核酸、 酶、 蛋白质、 三磷酸腺苷(ATP)和金属离子辅助信号放大策略, 并探讨了其信号放大机理; 总结了内源性物质辅助信号放大探针在低丰度物质检测及成像方面的研究进展; 最后展望了该策略在细胞成像方面的优势及应用前景.     

A Preliminary Study of PSMA Fluorescent Probe for Targeted Fluorescence Imaging of Prostate Cancer

Purpose: With the increasing detection rate of early prostate cancer (PCa), the proportion of surgical treatment is increasing. Surgery is the most effective treatment for PCa. Precise targeting of tumors during surgery can reduce the incidence of positive surgical margins (PSMs) and preserve the neurovascular bundles (NVBs) as much as possible. The objective of this study was to synthesize a PSMA fluorescent probe (PSMA-Cy5) and verify the targeting specificity of the probe for prostate cancer, thereby providing a theoretical basis for the development of PSMA fluorescent probes for clinical application in the future. Methods: In this study, a novel water-soluble 3H-indocyanine-type bioluminescent dye-Cy5-labeled prostate-specific membrane antigen (PSMA) ligand (PSMA-Cy5) was synthesized by liquid phase synthesis. The PSMA ligand was developed based on the glutamine-urea-lysine (Glu-urea-Lys) structure. The new fluorescent probe was evaluated in vitro and in vivo, and its safety was evaluated. Confocal microscopy was used to observe the binding uptake of PSMA-Cy5 with PSMA (+) LNCaP cells, PSMA (-) PC3 cells and blocked LNCaP cells. In in vivo optical imaging studies, the targeting specificity of PSMA (+) 22Rv1 tumors to probe binding was validated by tail vein injection of PSMA-Cy5. The safety of the PSMA-Cy5 probe was evaluated by histopathological analysis of mouse organs by a single high-dose tail vein injection of PSMA-Cy5. Results: In vitro fluorescence cell uptake experiments showed that the binding of PSMA-Cy5 to LNCaP cells has targeting specificity. PC3 cells and blocked LNCaP cells showed almost no uptake. The results of in vivo optical imaging studies showed that the tumor-to-background ratio in the 22Rv1 group was 3.39 ± 0.47; in the 22Rv1 blocking group it was 0.78 ± 0.15, and in the PC3 group it was 0.94 ± 0.09, consistent with the in vitro results. After a high-dose injection of PSMA-Cy5, there were no abnormalities in the tissues or organs of the mice. The probe showed good safety. Conclusions: PSMA-Cy5 is a probe with good targeting specificity and low toxicity that can accurately visualize tumors in vivo. This study has an important reference value for the development of PSMA fluorescent probes. In the future, it can be applied to precise tumor imaging during radical prostatectomy to reduce the incidence of postoperative PSM.     

基于双色荧光传感器的癌细胞成像及microRNA定量检测

癌细胞中microRNA(miRNA)的灵敏成像对于疾病的诊断治疗具有重要意义,其中miRNA-21通常在多种癌细胞中异常表达.本文将DNA功能化的金纳米颗粒与发射波长分离的荧光染料FAM和Cy5. 5修饰的DNA通过含有光控基团PC-linker的DNA4作为桥梁进行自组装,构建了纳米传感器GDC.将302 nm紫外光作为启动开关,用其照射该体系时,Cy5. 5修饰的DNA3被释放,其荧光强度可作为内参比信号,用于标定进入细胞的组装体含量;细胞中miRNA-21作为催化分子,与外加燃料Fuel DNA共同作用下可实现催化放大,FAM修饰的DNA2被释放且被猝灭的荧光信号得以恢复,并作为检测信号.通过2种荧光信号强度(FL)的检测及FL_FAM/FL_{Cy5. 5}比值的计算,达到定量分析细胞中miRNA含量的目的.该体系可扣除因细胞内组装体含量不同造成的背景信号误差,不仅能显著提高检测准确度,还因存在催化循环而大大降低了检出限,比传统方法至少降低了3个数量级.该传感器的检出限为23. 1 pmol/L,通过定量计算得出He La细胞中miRNA的...     

A Room-Temperature Stable Distonic Radical Cation

Distonic radical cations (DRCs) with spatially separated charge and radical sites have, so far, largely been observed by gas-phase mass spectrometry and/or matrix isolation spectroscopy work. Herein, we disclose the isolation of a crystalline dicarbondiphosphide-based β-distonic radical cation salt 3^.+ (BARF) (BARF=[B(3,5-(CF₃)₂C₆H₃)₄)]⁻) stable at room temperature and formed by a one-electron-oxidation-induced intramolecular skeletal rearrangement reaction. Such a species has been validated by electron paramagnetic resonance (EPR) spectroscopy, single-crystal X-ray diffraction, UV/Vis spectroscopy and density functional theory (DFT) calculations. Compound 3^.+ (BARF) exhibits a large majority of spin density at a two-coordinate phosphorus atom (0.74 a.u.) and a cationic charge located predominantly at the four-coordinate phosphorus atom (1.53 a.u.), which are separated by one carbon atom. This species represents an isolable entity of a phosphorus radical cation that is the closest to a genuine phosphorus DRC to date.