Real-Time Detection of Circulating Tumor Cells in Living Animals Using Functionalized Large Gold Nanorods.

Optical coherence tomography (OCT) can be utilized with significant speckle reduction techniques and highly scattering contrast agents for non-invasive, contrast-enhanced imaging of living tissues at the cellular scale. The advantages of reduced speckle noise and improved targeted contrast can be harnessed to track objects as small as 2 µm in vivo, which enables applications for cell tracking and quantification in living subjects. Here we demonstrate the use of large gold nanorods as contrast agents for detecting individual micron-sized polystyrene beads and single myeloma cells in blood circulation using speckle-modulating OCT. This report marks the first time that OCT has been used to detect individual cells within blood in vivo. This technical capability unlocks exciting opportunities for dynamic detection and quantification of tumor cells circulating in living subjects.

Behavioral Evaluation of Angelman Syndrome Mice at Older Ages.

Angelman syndrome is a neurodevelopmental disorder presenting with severe deficits in motor, speech, and cognitive abilities. The primary genetic cause of Angelman syndrome is a maternally transmitted mutation in the Ube3a gene, which has been successfully modeled in Ube3a mutant mice. Phenotypes have been extensively reported in young adult Ube3a mice. Because symptoms continue throughout life in Angelman syndrome, we tested multiple behavioral phenotypes of male Ube3a mice and WT littermate controls at older adult ages. Social behaviors on both the 3-chambered social approach and male-female social interaction tests showed impairments in Ube3a at 12 months of age. Anxiety-related scores on both the elevated plus-maze and the light ↔ dark transitions assays indicated anxiety-like phenotypes in 12 month old Ube3a mice. Open field locomotion parameters were consistently lower at 12 months. Reduced general exploratory locomotion at this age prevented the interpretation of an anxiety-like phenotype, and likely impacted social tasks. Robust phenotypes in middle-aged Ube3a mice appear to result from continued motor decline. Motor deficits may provide the best outcome measures for preclinical testing of pharmacological targets, towards reductions of symptoms in adults with Angelman syndrome.

Speckle modulation enables high-resolution wide-field human brain tumor margin detection and in vivo murine neuroimaging.

Current in vivo neuroimaging techniques provide limited field of view or spatial resolution and often require exogenous contrast. These limitations prohibit detailed structural imaging across wide fields of view and hinder intraoperative tumor margin detection. Here we present a novel neuroimaging technique, speckle-modulating optical coherence tomography (SM-OCT), which allows us to image the brains of live mice and ex vivo human samples with unprecedented resolution and wide field of view using only endogenous contrast. The increased visibility provided by speckle elimination reveals white matter fascicles and cortical layer architecture in brains of live mice. To our knowledge, the data reported herein represents the highest resolution imaging of murine white matter structure achieved in vivo across a wide field of view of several millimeters. When applied to an orthotopic murine glioblastoma xenograft model, SM-OCT readily identifies brain tumor margins with resolution of approximately 10 µm. SM-OCT of ex vivo human temporal lobe tissue reveals fine structures including cortical layers and myelinated axons. Finally, when applied to an ex vivo sample of a low-grade glioma resection margin, SM-OCT is able to resolve the brain tumor margin. Based on these findings, SM-OCT represents a novel approach for intraoperative tumor margin detection and in vivo neuroimaging.

Spatiotemporal Tracking of Brain-Tumor-Associated Myeloid Cells in Vivo through Optical Coherence Tomography with Plasmonic Labeling and Speckle Modulation.

By their nature, tumors pose a set of profound challenges to the immune system with respect to cellular recognition and response coordination. Recent research indicates that leukocyte subpopulations, especially tumor-associated macrophages (TAMs), can exert substantial influence on the efficacy of various cancer immunotherapy treatment strategies. To better study and understand the roles of TAMs in determining immunotherapeutic outcomes, significant technical challenges associated with dynamically monitoring single cells of interest in relevant live animal models of solid tumors must be overcome. However, imaging techniques with the requisite combination of spatiotemporal resolution, cell-specific contrast, and sufficient signal-to-noise at increasing depths in tissue are exceedingly limited. Here we describe a method to enable high-resolution, wide-field, longitudinal imaging of TAMs based on speckle-modulating optical coherence tomography (SM-OCT) and spectral scattering from an optimized contrast agent. The approach's improvements to OCT detection sensitivity and noise reduction enabled high-resolution OCT-based observation of individual cells of a specific host lineage in live animals. We found that large gold nanorods (LGNRs) that exhibit a narrow-band, enhanced scattering cross-section can selectively label TAMs and activate microglia in an in vivo orthotopic murine model of glioblastoma multiforme. We demonstrated near real-time tracking of the migration of cells within these myeloid subpopulations. The intrinsic spatiotemporal resolution, imaging depth, and contrast sensitivity reported herein may facilitate detailed studies of the fundamental behaviors of TAMs and other leukocytes at the single-cell level in vivo, including intratumoral distribution heterogeneity and roles in modulating cancer proliferation.

Gold Nanoprisms as Optical Coherence Tomography Contrast Agents in the Second Near-Infrared Window for Enhanced Angiography in Live Animals.

Optical coherence tomography angiography (OCTA) is an important tool for investigating vascular networks and microcirculation in living tissue. Traditional OCTA detects blood vessels via intravascular dynamic scattering signals derived from the movements of red blood cells (RBCs). However, the low hematocrit and long latency between RBCs in capillaries make these OCTA signals discontinuous, leading to incomplete mapping of the vascular networks. OCTA imaging of microvascular circulation is particularly challenging in tumors due to the abnormally slow blood flow in angiogenic tumor vessels and strong attenuation of light by tumor tissue. Here, we demonstrate in vivo that gold nanoprisms (GNPRs) can be used as OCT contrast agents working in the second near-infrared window, significantly enhancing the dynamic scattering signals in microvessels and improving the sensitivity of OCTA in skin tissue and melanoma tumors in live mice. With GNPRs as contrast agents, the postinjection OCT angiograms showed 41 and 59% more microvasculature than preinjection angiograms in healthy mouse skin and melanoma tumors, respectively. By enabling better characterization of microvascular circulation in vivo, GNPR-enhanced OCTA could lead to better understanding of vascular functions during pathological conditions, more accurate measurements of therapeutic response, and improved patient prognoses.

In Vivo Molecular Optical Coherence Tomography of Lymphatic Vessel Endothelial Hyaluronan Receptors.

Optical Coherence Tomography (OCT) imaging of living subjects offers increased depth of penetration while maintaining high spatial resolution when compared to other optical microscopy techniques. However, since most protein biomarkers do not exhibit inherent contrast detectable by OCT, exogenous contrast agents must be employed for imaging specific cellular biomarkers of interest. While a number of OCT contrast agents have been previously studied, demonstrations of molecular targeting with such agents in live animals have been historically challenging and notably limited in success. Here we demonstrate for the first time that microbeads (µBs) can be used as contrast agents to target cellular biomarkers in lymphatic vessels and can be detected by OCT using a phase variance algorithm. This molecular OCT method enables in vivo imaging of the expression profiles of lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), a biomarker that plays crucial roles in inflammation and tumor metastasis. In vivo OCT imaging of LVYE-1 showed that the biomarker was significantly down-regulated during inflammation induced by acute contact hypersensitivity (CHS). Our work demonstrated a powerful molecular imaging tool that can be used for high resolution studies of lymphatic function and dynamics in models of inflammation, tumor development, and other lymphatic diseases.

Speckle-modulating optical coherence tomography in living mice and humans.

Optical coherence tomography (OCT) is a powerful biomedical imaging technology that relies on the coherent detection of backscattered light to image tissue morphology in vivo. As a consequence, OCT is susceptible to coherent noise (speckle noise), which imposes significant limitations on its diagnostic capabilities. Here we show speckle-modulating OCT (SM-OCT), a method based purely on light manipulation that virtually eliminates speckle noise originating from a sample. SM-OCT accomplishes this by creating and averaging an unlimited number of scans with uncorrelated speckle patterns without compromising spatial resolution. Using SM-OCT, we reveal small structures in the tissues of living animals, such as the inner stromal structure of a live mouse cornea, the fine structures inside the mouse pinna, and sweat ducts and Meissner's corpuscle in the human fingertip skin-features that are otherwise obscured by speckle noise when using conventional OCT or OCT with current state of the art speckle reduction methods.

Erratum: Speckle-modulating optical coherence tomography in living mice and humans.

This corrects the article DOI: 10.1038/ncomms15845.