Nanoparticles as OCT Contrast Agents

描述（由申请人提供）：光学相干断层扫描（OCT）提供视网膜和视神经的实时、客观、体内、高分辨率光学横截面。OCT图像采集的最新创新，包括傅立叶/谱域检测的结合，提高了成像速度，灵敏度和分辨率。尽管如此，在眼部OCT图像中仍然存在特定的结构，例如视网膜神经节细胞（RGC），其是临床医生感兴趣的，但始终具有低对比度。这使得很难区分周围的层和结构。因此，我们的目标是设计适合于增强视网膜中感兴趣的结构之间的对比度的分子OCT造影剂，以改善与疾病相关的这些结构的检测和测量。我们将重点关注RGC，它在青光眼中以加速的速度丢失。我们提出将金纳米颗粒用于眼科造影剂，因为它们的设计可以定制为在当前眼科OCT成像方案中使用的相同波长的光下增强散射响应，并且它们的表面可以涂覆有抗体，这将有助于靶向特定结构。我们的假设是，纳米粒子可以直接使用细胞受体特异性抗体的视网膜组织，他们将通过调制OCT检测到的反向散射光的强度，提高对比度。我们将首先使用金纳米棒与特异性靶向视网膜神经节细胞的抗体共轭。通过OCT检测的纳米颗粒的最佳浓度将通过使用体模模型来定义，并且将在小鼠眼中确定颗粒循环的时间过程。将进行纳米颗粒的基线玻璃体内注射，并在每个时间点（时间零、一小时、六小时、一天、三天和一周）评估小鼠的子集，并对切除的眼睛进行荧光显微镜检查和透射电子显微镜检查以确定纳米棒运输的时间顺序。纳米颗粒的生物相容性将通过用于功能评估、炎症生物标志物和组织学的模式视网膜电图进行评价。在该实验期间的每个时间点，我们还将通过在处死小鼠进行显微镜检查之前对小鼠进行高速、高分辨率视网膜OCT成像来评估我们的抗体包被的纳米颗粒增强OCT信号强度水平的能力。我们将使用这些OCT图像来比较随时间推移的纳米颗粒对比度增强以及通过图像分割来量化RGC厚度。 公共卫生相关性：在这项研究中，我们建议设计能够附着在视网膜特定层上的颗粒，并通过光学特性的变化来增强光学相干断层扫描中该层的外观。这可能会提高在早期阶段检测病理结构变化的能力，并可能使针对特定视网膜层的治疗成为可能。

DESCRIPTION (provided by applicant): Optical coherence tomography (OCT) provides real-time, objective, in-vivo, high resolution optical cross- sections of the retina and optic nerve. Recent innovations in OCT image acquisition, including the incorporation of Fourier/spectral-domain detection, have improved imaging speed, sensitivity and resolution. Still, there remain specific structures within ocular OCT images, such as retinal ganglion cells (RGCs), which are of interest to clinicians but consistently have low contrast. This makes it difficult to differentiate between surrounding layers and structures. Our goal, therefore, is to engineer molecular OCT contrast agents suitable for enhancing contrast between structures of interest in the retina in order to improve the detection and measurement of these structures that are associated with disease. We will focus on RGCs, which are lost at an accelerated rate in glaucoma. We are proposing gold nanoparticles for ophthalmic contrast agents because their design can be tailored to augment the scattering response at the same wavelengths of light used in current ophthalmic OCT imaging schemes and their surfaces can be coated with antibodies that will facilitate targeting of specific structures. Our hypotheses are that nanoparticles can be directed to retinal tissue using antibodies specific to cellular receptors and that they will improve contrast by modulating the intensity of backscattered light detected by OCT. We will initially use gold nanorods conjugated with antibodies specifically targeting the retinal ganglion cells. The optimal concentration of nanoparticles for detection by OCT will be defined by using a phantom model and the time course of circulation of particles will be determined in mice eyes. A baseline intravitreal injection of nanoparticles will be performed and a subset of mice will be evaluated at each time point (time zero, one hour, six hours, one day, three days, and one week) and fluorescence microscopy and transmission electron microscopy will be performed on excised eyes to determine the time sequence of the nanorods transportation. The biocompatibility of the nanoparticles will be evaluated by pattern electroretinogram for functional assessment, inflammatory biomarkers and histology. At each time point during this experiment, we will also evaluate the ability of our antibody-coated nanoparticles to enhance OCT signal intensity level by performing high-speed, ultrahigh resolution retinal OCT imaging on mice prior to sacrificing them for microscopic examination. We will use these OCT images to compare nanoparticle contrast enhancement over time as well as to quantify RGC thickness by image segmentation. PUBLIC HEALTH RELEVANCE: In this study we propose to design particles that will be able to attach to specific layers in the retina and through changes in optical properties enhance the appearance of the layer in optical coherence tomography. This might improve the ability to detect pathological structural changes at an early stage and might enable targeting treatment to specific retinal layers.