Nanoparticles as OCT Contrast Agents

描述(申请人提供)：光学相干断层扫描(OCT)提供实时、客观、活体、高分辨率的视网膜和视神经光学横断面。最近在OCT图像采集方面的创新，包括结合傅立叶/谱域检测，提高了成像速度、灵敏度和分辨率。尽管如此，眼部OCT图像中仍有特定的结构，如视网膜神经节细胞(RGCs)，临床医生对此很感兴趣，但对比度始终较低。这使得区分周围的层和结构变得困难。因此，我们的目标是设计适合于增强视网膜感兴趣结构之间的对比度的分子OCT造影剂，以改进对与疾病相关的这些结构的检测和测量。我们将重点关注视网膜节细胞，它在青光眼中以加速的速度丢失。我们建议将金纳米颗粒用作眼科造影剂，因为它们的设计可以定制成增强在当前眼科OCT成像方案中使用的相同波长的光的散射响应，并且它们的表面可以涂覆抗体，这将有助于靶向特定结构。我们的假设是，纳米颗粒可以使用针对细胞受体的抗体定向到视网膜组织，并且它们将通过调节OCT检测到的反向散射光的强度来改善对比度。我们最初将使用金纳米棒与专门针对视网膜神经节细胞的抗体结合。OCT检测的最佳纳米颗粒浓度将通过模体模型确定，并将在小鼠眼睛中确定颗粒循环的时间过程。将进行基线玻璃体内注射纳米颗粒，并在每个时间点(时间0、1小时、6小时、1天、3天和1周)评估一组小鼠，并对切除的眼睛进行荧光显微镜和透射电子显微镜检查，以确定纳米棒运输的时间序列。纳米粒的生物相容性将通过图形视网膜电信号功能评估、炎症生物标志物和组织学进行评估。在本实验的每个时间点，我们还将评估我们的抗体包裹纳米颗粒在牺牲小鼠进行显微镜检查之前，通过对小鼠进行高速、超高分辨率的视网膜OCT成像来增强OCT信号强度水平的能力。我们将使用这些OCT图像来比较纳米颗粒随时间的对比度增强，并通过图像分割来量化RGC厚度。 与公共健康相关：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，并通过改变光学属性来增强光学相干断层扫描中的层外观。这可能会提高在早期阶段发现病理结构变化的能力，并可能针对特定的视网膜层进行靶向治疗。

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.