聚合物PVP表面修饰CdS纳米棒的制备及其光谱特性

用水热合成方法制备了PVP表面修饰CdS纳米棒,用XRD,TEM,TG-DTA,IR,UV-Vis,PL等光谱技术进行了表征。与未修饰的CdS纳米棒相比,PVP修饰后的CdS纳米棒具有更均匀的尺寸分布,吸收光谱具有结构峰特征,其荧光发射谱增强。     

半胱氨酸修饰金纳米棒光学性质的研究

采用种子生长法制备了不同长径比的金纳米棒,并通过金硫键的结合在其表面包覆半胱氨酸分子。利用紫外-可见吸收光谱仪,扫描电子显微镜以及拉曼光谱仪等对样品进行分析和表征。实验结果表明金纳米棒产率较高,且一致性较好。表面修饰后的金纳米棒的纵向吸收峰发生蓝移,表明半胱氨酸分子与金纳米棒的结合有助于溶液分散性的提升。以结晶紫为探针分子,随着金纳米棒长径比的增加其拉曼增强效果变强。进一步分析发现,修饰后的金纳米棒的表面增强拉曼光谱的增强效果并未受到影响。通过金纳米棒与半胱氨酸分子牢固的结合,一方面可以提高金纳米棒溶液的分散性与稳定性;另一方面半胱氨酸分子可为金纳米棒修饰其它有机官能团提供了一个牢固的桥梁,有效地拓展了金纳米棒的应用方向。     

吲哚菁绿对大鼠脑皮层血管近红外光学特性及光学相干层析成像的影响

研究观察了吲哚菁绿(ICG)对大鼠脑皮层血管近红外光谱学特性及光学相干层析成像(OCT)的影响。实验中,将SD大鼠颞部开颅,暴露并标记大脑中动脉,给予动物尾静脉注射ICG溶液,应用可见-近红外反射光谱仪和OCT系统检测脑皮层血管反射光谱的动态变化和衰减系数的特征性变化。结果显示,ICG注射后,大脑中动脉的反射光谱在ICG的吸收峰(800nm)左右出现一个特异性的低反射峰并随时间而逐渐变化;在注射ICG 3min时,本特异性低反射峰值达到最强,反射光谱的特征性变化可以为实现最佳OCT图像效果提供时间点。此外,ICG注射后的脑动脉OCT信号衰减系数为24.692±1.471,明显高于未注射ICG时15.088±1.602(p<0.01)。实验结果说明ICG可以增加血管对近红外光的吸收,为增强血管的检测能力提供理论参考,也为无损监测血管病变、肿瘤血管新生及血液动力学变化提供一种可行性检测手段。     

基于受激辐射信号的谱域光学相干层析分子成像方法

鉴于不同生理病理状态下组织复折射率实部的变化不大,传统光学相干层析(OCT)成像技术在分子特异性识别上存在先天不足.为此,本文提出了基于受激辐射信号的OCT成像方法,可在实现传统散射成像的同时,实现基于受激辐射信号的分子成像.在超高分辨率谱域OCT系统的基础上,通过增设光谱分光与调制抽运光支路,建立了基于单宽谱光源的抽运探测谱域OCT系统,详细推导了调制抽运下受激辐射信号的获取与成像公式.利用搭建的抽运探测谱域OCT系统,实现了瞬态受激辐射信号的相干探测.基于同时获取的受激辐射OCT信号和传统OCT信号,成功重构了氮化物粉末构建样品的基于受激辐射信号的分子对比OCT图像.     

扫频光学相干层析成像应用于判断黏液型胃癌边界区域

为了在癌症外科手术中提供实时反馈,更精确地切除癌症组织,从而在术中导航领域展现应用潜力,利用光学相干层析成像(OCT)系统对39例胃癌患者肿瘤组织成像,并与对应位置的病理切片进行对比。结果表明:有效的38个病例的OCT图像能清晰地分辨癌症组织与正常组织的差别,其中有4例黏液型胃癌,黏液型胃癌的肿瘤分泌的黏液会破坏胃组织的层状结构,导致纹理紊乱,黏膜残缺;黏液对光的背向散射更弱以及与黏膜组织的背向散射对比相差更大使得黏液型胃癌的OCT图像成像更清晰,B型超声扫描(B-scan)的OCT图像能够分辨该种类型癌症的边界区域;将B-scan的OCT图像进行三维(3D)重建后显示整个成像区域的体结构,经过表面展平后提取深度方向上不同层的切面图像,提供了另一维度视角观察胃癌组织的边界区域,与B-scan图像交叉验证可以显示优异的区分效果。     

拉曼光谱研究电化学沉积聚吡咯掺杂程度对膜厚度的依赖性

本文报道电化学沉积在光滑铂电极表面上聚吡咯 (PPy)膜的拉曼光谱。研究结果表明 :聚吡咯膜的掺杂程度在其生长过程中不断增加。因此 ,PPy膜的拉曼光谱特性对膜厚具有很强的依赖性。电化学分析结果也证明了这一发现。具有已知厚度的PPy膜的掺杂程度依赖于支持电解质的性质。     

基于SERS技术的靶向修饰金纳米探针 用于Hela细胞的检测

表皮生长因子受体(EGFR)是一种肿瘤表面标记性蛋白。本文报道了基于anti-EGFR功能化金纳米棒探针AuNRs probes的表面增强拉曼散射(SERS),用于EGFR阳性肿瘤细胞的检测。通过AuNRs probes上anti-EGFR特异性结合到EGFR阳性癌细胞上,可使修饰于金纳米棒表面的拉曼活性染料4-巯基苯甲酸(4-MBA)位于1 100 cm~(-1)和1 600 cm~(-1)的特征峰强度得到信号增强。该SERS探针由于具有生物兼容性好、细胞拉曼信号稳定、特异性高等优点而具有巨大的临床应用前景。     

金纳米棒核／二氧化硅壳纳米复合结构的可控制备及细胞成像

采用模板合成以及溶胶凝胶方法制备了金纳米棒核／二氧化硅壳（GNR@SiO2）纳米复合粒子,探讨了这种新型纳米复合结构的可控制备、光谱性质、细胞毒性和细胞成像。通过紫外可见分光光度计、透射电镜、共聚焦显微镜对样品进行表征,结果表明：通过对反应时间的调控,获得的纳米复合粒子的二氧化硅壳层厚度可以控制在20～30nm。由于二氧化硅壳层的存在,大大提高了金纳米棒的稳定性,同时降低了金纳米棒的细胞毒性;此外,由于二氧化硅壳层具有良好的化学修饰作用,因此可以将荧光探针分子标记在二氧化硅壳层表面,修饰后的纳米复合粒子可以通过细胞内吞作用进入细胞,从而实现细胞内的光学成像。因此,该纳米粒子复合材料在生物传感、细胞成像以及光热治疗等方面有着良好的应用前景。     

干净、均一的表面增强拉曼基底的制备和表征

采用盐酸羟胺种子生长法制备60 nm左右的粒径均一的金纳米粒子, 通过在ITO上修饰3-氨基丙基-三甲氧基硅烷(APTMS)对金纳米粒子进行组装, 得到组装密度较高、均一的表面增强拉曼光谱(SERS)基底; 采用等离子体清洗再用醋酸溶液浸泡除去氧化层的方法, 可获得干净的SERS基底, 这种方法与其它基底除杂方法相比更为简单、操作性强且信号只衰减了20%。     

TiO_2/石墨烯/Ag复合结构SERS实验

基于氧化物半导体的光催化特性,能够降解有机物分子,使表面增强拉曼散射基底得以重复使用。提出了银纳米颗粒有效修饰覆盖有石墨烯的二氧化钛纳米棒阵列(TiO_2/石墨烯/Ag)复合结构作为表面增强拉曼散射基底,并对其进行了实验研究。利用水热法制备了二氧化钛纳米棒阵列;采用湿法转移石墨烯和光照还原方法制备了TiO_2/石墨烯/Ag复合结构。用罗丹明6G(R6G)分子作为探测分子,结果表明:随着紫外光照沉积时间增加,探针分子的拉曼信号先增强后减弱;计算得到最大增强因子值约为2.6×106。此外,还对TiO_2/石墨烯/Ag复合结构的紫外自清洁特性进行了初步实验,结果表明,紫外光照射20min后,其拉曼强度下降到42.3%,具有一定的紫外清洁效果。     

Near-infrared dyes as contrast-enhancing agents for spectroscopic optical coherence tomography

Optical coherence tomography (OCT) images of biological tissues often have low contrast. Spectroscopic optical coherence tomography (SOCT) methods have been developed to enhance contrast but remain limited because most tissues are not spectrally active in the frequency bands of laser sources commonly used in OCT. Near-infrared (NIR) dyes with absorption spectra features within the OCT source spectrum can be used for enhancing contrast in this situation. We introduce and demonstrate the use of NIR dyes as contrast agents for SOCT. Contrast-enhanced images are compared with fluorescence microscopy, demonstrating a link between SOCT and fluorescence imaging.     

Gold nanocages as contrast agents for spectroscopic optical coherence tomography

We describe gold nanocages as a new class of potential contrast agent for spectroscopic optical coherence tomography (OCT). Monodispersed gold nanocages of an approximately 35 nm edge length exhibit strong optical resonance, with the peak wavelength tunable in the near-infrared range. We characterized the optical properties of the nanocage by using OCT experiments along with numerical calculations, revealing an absorption cross section approximately 5 orders of magnitude larger than conventional dyes. Experiments with tissue phantoms demonstrated that the nanocages provide enhanced contrast for spectroscopic as well as conventional intensity-based OCT imaging.     

Optical coherence tomography with plasmon resonant nanorods of gold

We explored plasmon resonant nanorods of gold as a contrast agent for optical coherence tomography (OCT). Nanorod suspensions were generated through wet chemical synthesis and characterized with spectrophotometry, transmission electron microscopy, and OCT. Polyacrylamide-based phantoms were generated with appropriate scattering and anisotropy coefficients (30 cm(-1) and 0.89, respectively) to image distribution of the contrast agent in an environment similar to that of tissue. The observed signal was dependent on whether the plasmon resonance peak overlapped the source bandwidth of the OCT, confirming the resonant character of enhancement. Gold nanorods with plasmon resonance wavelengths overlapping the OCT source yielded a signal-to-background ratio of 4.5 dB, relative to the tissue phantom. Strategies for OCT imaging with nanorods are discussed.     

Time-gated Fourier-domain optical coherence tomography

A novel optical coherence tomography (OCT) system is presented that combines Fourier-domain OCT with incoherent nonlinear time gating. By processing backscattered light in the optical domain, the user can select a restricted depth field of view for improved contrast and acquisition speed. This technique has the additional advantage that imaging is done in the infrared (approximately 1280 nm) but is detected in the visible(approximately 504 nm).     

Synergistic Effect of Thermo‐Radiotherapy Using Au@FeS Core–Shell Nanoparticles as Multifunctional Therapeutic Nanoagents

Imaging guided combined therapy has attracted great attention in recent years. This study develops core–shell Au@FeS nanoparticles with polyethylene glycol (PEG) coating as multifunctional nanotheranostic agent for tumor imaging and combined photothermal therapy (PTT) and radiotherapy (RT). In this Au@FeS nanostructure, the gold core can act as a radiosensitizer for enhanced RT, while FeS shell offers contrast for T2‐weighted magnetic resonance imaging and endows the nanoparticles with strong high near‐infrared (NIR) for photoacoustic imaging and PTT. As demonstrated by both in vitro and in vivo experiments, Au@FeS‐PEG can act as excellent therapeutic agent for cancer synergistic treatment. More importantly, mild PTT boosts the blood flow into tumor and increases oxygenation to overcome the tumor hypoxia microenvironment, further enhancing the efficacy of RT. Moreover, Au@FeS‐PEG induces on obvious toxicity at a high dose (20 mg kg^?1) to the treated mice as evidenced by blood biochemistry. Therefore, this study brings an excellent strategy for cancer enhanced RT through NIR‐triggered mild PTT to overcome hypoxia‐associated radioresistance.     

Monodisperse Polypyrrole Nanoparticles Prepared via γ‐Ray Radiolysis of Water: An Efficient Near‐Infrared Photothermal Agent for Cancer Therapy

Biosafe nanoparticles with strong near‐infrared (NIR) light photothermal conversion effect can bring effective hyperthermia as one of the promising approaches in cancer therapy. In this work, a new facile and green preparation method of polypyrrole (PPy) nanoparticles based on ⁶⁰Co γ‐ray radiation on a simple air‐saturated strong acidic aqueous solution of pyrrole (pH ≤ 1) is studied. According to the MCAP‐FACSIMILE simulation on the concentrations of the radiolysis products of water at the presence of H⁺ and O₂, the main strong oxidative radiolysis products · OH and H₂O₂ rapidly induce the polymerization of pyrrole. The size of the prepared PPy nanoparticles is about several tens of nanometers and can be controlled by the pH, the concentration of the stabilizer poly(vinyl alcohol), and the absorbed dose rate (the amount of energy absorbed per unit mass of the irradiated material within per unit of time). The PPy nanoparticles show rapid and remarkable NIR (808 nm) photothermal conversion efficiency up to 40.1% in water. Furthermore, the in vitro and in vivo experiments confirm that the prepared PPy nanoparticles exhibit enough strong NIR photothermal effect in tumor cells (4T1 and HeLa) and show a promising prospect as the NIR photothermal agent for the future cancer therapy.     

Spectral domain second-harmonic optical coherence tomography

Optical coherence tomography (OCT) provides micrometer-scale structural imaging by coherent detection of backscattered light. Molecular contrast in OCT has been demonstrated using transient absorption, coherent anti-Stokes Raman scattering, and second-harmonic (SH) generation. The sensitivity of molecular contrast signals can be enhanced by use of Fourier domain techniques. We have constructed a spectrometer-based Fourier domain SH-OCT system for simultaneous acquisition of the fundamental and SH signals. We report a >30 dB increase in SH sensitivity over a similar time domain SH-OCT system and demonstrate contrast between cartilage and bone using collagen as the contrast agent.     

Optimum spectral window for imaging of art with optical coherence tomography

Optical coherence tomography (OCT) has been shown to have potential for important applications in the field of art conservation and archaeology due to its ability to image subsurface microstructures non-invasively. However, its depth of penetration in painted objects is limited due to the strong scattering properties of artists’ paints. VIS–NIR (400–2,400 nm) reflectance spectra of a wide variety of paints made with historic artists’ pigments have been measured. The best spectral window with which to use OCT for the imaging of subsurface structure of paintings was found to be around 2.2 μm. The same spectral window would also be most suitable for direct infrared imaging of preparatory sketches under the paint layers. The reflectance spectra from a large sample of chemically verified pigments provide information on the spectral transparency of historic artists’ pigments/paints as well as a reference set of spectra for pigment identification. The results of the paper suggest that broadband sources at ~2 μm are highly desirable for OCT applications in art and potentially material science in general.     

Dual-modality photothermal optical coherence tomography and magnetic-resonance imaging of carbon nanotubes

We demonstrate polyethylene-glycol-coated single-walled carbon nanotubes (CNTs) as contrast agents for both photothermal optical coherence tomography (OCT) and magnetic-resonance imaging (MRI). Photothermal OCT was accomplished with a spectral domain OCT system with an amplitude-modulated 750 nm pump beam using 10 mW of power, and T(2) MRI was achieved with a 4.7 T animal system. Photothermal OCT and T(2) MRI achieved sensitivities of nanomolar concentrations to CNTs dispersed in amine-terminated polyethylene glycol, thus establishing the potential for dual-modality molecular imaging with CNTs.