Tianyi Wang, J. Jacob Mancuso, Veronika Sapozhnikova, Jordan Dwelle, Li Ma, Brian Willsey, S. Shams Kazmi, Jinze Qiu, Xiankai Li, Reto Asmis, Keith Johnston, Marc Feldman, Thomas Milner
The objective of this study was to assess the ability of combined photothermal wave (PTW) imaging and optical coherence tomography (OCT) to detect, and further characterize the distribution of macrophages (having taken up plasmonic gold nanorose as a contrast agent) and lipid deposits in atherosclerotic plaques. Aortas with atherosclerotic plaques were harvested from nine male New Zealand white rabbits divided into nanorose- and saline-injected groups and were imaged by dual-wavelength (800 and 1210 nm) multifrequency (0.1, 1 and 4 Hz) PTW imaging in combination with OCT. Amplitude PTW images suggest that lateral and depth distribution of nanorose-loaded macrophages (confirmed by two-photon luminescence microscopy and RAM-11 macrophage stain) and lipid deposits can be identified at selected modulation frequencies. Radiometric temperature increase and modulation amplitude of superficial nanoroses in response to 4 Hz laser irradiation (800 nm) were significantly higher than native plaque (P<0.001). Amplitude PTW images (4 Hz) were merged into a coregistered OCT image, suggesting that superficial nanorose-loaded macrophages are distributed at shoulders on the upstream side of atherosclerotic plaques (P<0.001) at edges of lipid deposits. Results suggest that combined PTW-OCT imaging can simultaneously reveal plaque structure and composition, permitting characterization of nanorose-loaded macrophages and lipid deposits in atherosclerotic plaques.
Veronika Sapozhnikova, Brian Willsey, Li Leo Ma, Keith Johnston, Reto Asmis, Tianyi Wang, James Jenkins, Jacob Mancuso, Roman Kuranov, Thomas Milner, Marc Feldman
We determined the effect of aggregation and coating thickness of gold on the luminescence of nanoparticles engulfed by macrophages and in gelatin phantoms. Thin gold-coated iron oxide nanoclusters (nanoroses) have been developed to target macrophages to provide contrast enhancement for near-infrared optical imaging applications. We compare the brightness of nanoroses luminescent emissions in response to 635 nm laser excitation to other nanoparticles including nanoshells, nanorods, and Cy5 conjugated iron oxide nanoparticles. Luminescent properties of all these nanoparticles were investigated in monomeric and aggregated form in gelatin phantoms and primary macrophage cell cultures using confocal microscopy. Aggregation of the gold nanoparticles increased luminescence emission and correlated with increased surface mass of gold per nanoparticle (nanoshells 37±14.30×10−3 brightness with 1.23×10−4 wt of gold (g)/nanoparticle versus original nanorose 1.45±0.37×10−3 with 2.10×10−16 wt of gold/nanoparticle, p<0.05). Nanoshells showed greater luminescent intensity than original nanoroses or Cy5 conjugated iron oxide nanoparticles when compared as nanoparticles per macrophage (38±10 versus 11±2.8 versus 17±6.5, p<0.05, respectively, ANOVA), but showed relatively poor macrophage uptake (1025±128 versus 7549±236 versus 96,000 nanoparticles/cell, p<0.05, student t-test nanoshells versus nanoroses). Enhancement of gold fluorescent emissions by nanoparticles can be achieved by reducing the thickness of the gold coating, by clustering the gold on the surface of the nanoparticles (nanoshells), and by clustering the gold nanoparticles themselves.
Macrophages are one of the most important cell types involved in the progression of atherosclerosis which can
lead to myocardial infarction. To detect macrophages in atherosclerotic plaques, plasmonic gold nanorose is
introduced as a nontoxic contrast agent for fluorescence imaging. We report macrophage cell culture and ex
vivo tissue studies to visualize macrophages targeted by nanorose using scanning confocal microscopy.
Atherosclerotic lesions were created in the aorta of a New Zealand white rabbit model subjected to a high
cholesterol diet and double balloon injury. The rabbit was injected with nanoroses coated with dextran. A HeNe
laser at 633 nm was used as an excitation light source and a acousto-optical beam splitter was utilized to collect
fluorescence emission in 650-760 nm spectral range. Results of scanning confocal microscopy of macrophage
cell culture and ex vivo tissue showed that nanoroses produce a strong fluorescence signal. The presence of
nanorose in ex vivo tissue was further confirmed by photothermal wave imaging. These results suggest that
scanning confocal microscopy can identify the presence and location of nanorose-loaded macrophages in
atherosclerotic plaques.
Using contrast agents with desired targeting moiety and optical absorption, intravascular photoacoustic imaging may
be used to identify various biomarkers expressed during the progression of atherosclerotic lesions. In this paper, we
present intravascular photoacoustic imaging of macrophages in the atherosclerotic lesions using bio-conjugated gold
nanoparticles as the contrast agent. Atherosclerotic lesions were created in the aorta of a New Zealand white rabbit
subjected to a high cholesterol diet and balloon injury. The rabbit was injected with 20 nm spherical gold
nanoparticles conjugated with antibodies. The macrophages with internalized gold nanoparticles were imaged by
intravascular photoacoustic imaging in the near infrared range; this was possible because of plasmon resonance
coupling between closely spaced gold nanoparticles internalized by macrophages. The multi-wavelength
intravascular photoacoustic images of the diseased aorta were analyzed to identify the presence and location of
macrophages labeled with gold nanoparticles. Spectroscopic intravascular photoacoustic image showing the
distribution of gold nanoparticles was further confirmed by the gold-specific silver staining of the tissue crosssection.
The results of our study suggest that molecular intravascular photoacoustic imaging can be used to image
macrophages in atherosclerosis.
We proposed to use optical coherence tomography (OCT) for continuous noninvasive blood glucose monitoring, and recently we significantly improved the sensitivity of this technique. The accuracy of OCT glucose monitoring is limited by several factors, including variation of tissue pressure exerted by the OCT probe. We studied the influence of high (>10 kPa) and low (<1 kPa) pressure levels on OCT blood glucose monitoring. We showed that controlling external pressure to <1 kPa substantially improved the accuracy and reproducibility of OCT-based glucose monitoring.
Optical Coherence Tomography (OCT) was recently proposed by our group for noninvasive, continuous monitoring of blood glucose concentration in diabetics as well as in critically ill patients (both diabetic and nondiabetic). In our previous studies we tested OCT-based glucose sensing using one-dimensional (1-D) lateral scanning of the OCT probing beam over the tissue surface. The measured OCT signal was prone to motion artifacts and had high level of speckle noise. In this study we used two-dimensional (2-D) lateral scanning of the OCT probing beam and achieved 3.6-fold reduction of the speckle noise level. We also applied a post-processing Fourier filtration technique that resulted in an additional 2-2.5-fold suppression of noise. Our data indicate that the combination of acquisition time of 30-40s and the Fourier filtration technique may provide OCT monitoring of blood glucose concentration with a sensitivity of 1mM (18 mg/dL).
First experimental results on OCT imaging of internal structure of plant tissues and in situ OCT monitoring of plant tissue regeneration at different water supply are reported. Experiments for evaluating OCT capabilities were performed on Tradescantia. The investigation of seeds swelling was performed on wheat seeds (Triticum L.), barley seeds (Hordeum L.), long-fibred flax seeds (Linum usitatissimum L.) and cucumber seeds (Cucumis sativus L.). These OCT images correlate with standard microscopy data from the same tissue regions. Seeds were exposed to a low-intensity physical factor-the pulsed gradient magnetic field (GMF) with pulse duration 0.1 s and maximum amplitude 5 mT (4 successive pulses during 0.4 s). OCT and OCM enable effective monitoring of fast reactions in plants and seeds at different water supply.
A PM fiber based PS OCT setup with simultaneous acquisition of signals in orthogonal polarization channels with an isolation ratio > 28 dB was created. The principles of measuring the tissue birefringence based on detecting only an envelope of OCT signal in the orthogonal polarization were described. The birefringence and depolarization degree of in vivo and ex vivo biotissues of different types were investigated.
ELAN is a new method for treating atherosclerotic vessels. Its purpose is to restore wall flexibility by removing arterial wall tissue from the outer arterial layer. This leads to expansion of the narrowed vessel resulting in increased blood flow. We present results of treatment of arteries in vitro. Tissue removal was done by excimer-laser ablation using ns-pulses of 193nm wavelength. We also discuss therapy control. OCT images and light diffusion measurements are presented.
Diagnostic value of standard OCT for recognizing cervical neoplasia has been evaluated: sensitivity is 82%, specificity is 78%, and diagnostics accuracy is 81%. To increase it several approaches have been suggested: application of hyperosmotic agents, cross-polarization tomography, complementary use of fluorescence spectroscopy and OCT, additional computer processing of the OCT-images and optical coherence microscipy.
First experimental results on optical coherence tomography (OCT) imaging of internal structure of plant tissues and in situ OCT monitoring of plant tissue regeneration at different water supply are reported. The OCT images are a map of backscattering coefficient 200 x 200 pixels, 1.5 mm along plant surface and up to 2 mm in depth (by analogy with ultrasound B-scan). Experiments for evaluating OCT capabilities were performed on Tradescantia blossfeldiana Mild. Using OCT device, in vivo images of plant tissues were acquired with a spatial resolution of 15 μm. These OCT images correlate with standard microscopy data from the same tissue regions. Since incident light power at a wavelength of 1.3 μm is as low as 0.5 mW, two-dimensional OCT images can be obtained directly on an intact plant not damaging it. Acquisition time for a 2D image is 1-3 s. OCT enables effective monitoring of fast reactions in plants at different water supply.
A new approach to improving the diagnostic value of optical methods is suggested, which is based on a complementary investigation of different optical parameters of biotissues. The aim of this paper is comparative study of the feasibility of two optical methods - fluorescence spectroscopy and optical coherence tomography - for visualization of borders of neoplastic processes in the uterine cervix and vulva.
Fluorescence spectroscopy is based on the detection of biochemical and optical coherence tomography on backscattering properties in norm and pathological changes of tissues. By means of these optical methods changes in biochemical and morphological properties of tissues were investigated. A parallel analysis of these two optical methods and histology from the center of tumors and their optical borders was made. Thirteen female patients with neoplastic changes in uterine cervix and vulva were enrolled in this study.
The borders of the tumor determined by optical methods (fluorescence spectroscopy and optical coherence tomography) are coinciding with the biopsy proved ones. In addition, OCT and fluorescence borders of tumor in the uterine cervix and vulva exceeds colposcopically detectable borders, the averaging difference 2 mm.
In future optical methods would considerably enhance diagnostic accuracy of conventional methods used in oncogynecology.
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