Research & Scholarship
Current Research and Scholarly Interests
Molecular imaging technologies for studying cancer biology in vivo
- Biochips and Medical Imaging
EE 225, MATSCI 382, SBIO 225 (Win)
- Biotechnology in the Natural World
BIOS 251 (Win)
Independent Studies (8)
- Directed Reading in Biophysics
BIOPHYS 399 (Aut, Win, Spr)
- Directed Reading in Structural Biology
SBIO 299 (Aut, Win, Spr)
- Graduate Research
BIOPHYS 300 (Aut, Win, Spr)
- Graduate Research
SBIO 399 (Aut, Win, Spr)
- Medical Scholars Research
SBIO 370 (Aut, Win, Spr)
- Special Studies and Reports in Electrical Engineering
EE 391 (Aut, Win, Spr, Sum)
- Special Studies or Projects in Electrical Engineering
EE 390 (Aut, Win, Spr)
- Undergraduate Research
SBIO 199 (Aut, Win, Spr)
- Directed Reading in Biophysics
- Prior Year Courses
- Quantitative contrast-enhanced optical coherence tomography APPLIED PHYSICS LETTERS 2016; 108 (2)
Contrast-enhanced optical coherence tomography with picomolar sensitivity for functional in vivo imaging.
2016; 6: 23337-?
Optical Coherence Tomography (OCT) enables real-time imaging of living tissues at cell-scale resolution over millimeters in three dimensions. Despite these advantages, functional biological studies with OCT have been limited by a lack of exogenous contrast agents that can be distinguished from tissue. Here we report an approach to functional OCT imaging that implements custom algorithms to spectrally identify unique contrast agents: large gold nanorods (LGNRs). LGNRs exhibit 110-fold greater spectral signal per particle than conventional GNRs, which enables detection of individual LGNRs in water and concentrations as low as 250 pM in the circulation of living mice. This translates to ~40 particles per imaging voxel in vivo. Unlike previous implementations of OCT spectral detection, the methods described herein adaptively compensate for depth and processing artifacts on a per sample basis. Collectively, these methods enable high-quality noninvasive contrast-enhanced imaging of OCT in living subjects, including detection of tumor microvasculature at twice the depth achievable with conventional OCT. Additionally, multiplexed detection of spectrally-distinct LGNRs was demonstrated to observe discrete patterns of lymphatic drainage and identify individual lymphangions and lymphatic valve functional states. These capabilities provide a powerful platform for molecular imaging and characterization of tissue noninvasively at cellular resolution, called MOZART.
View details for DOI 10.1038/srep23337
View details for PubMedID 26987475
- Biofunctionalization of Large Gold Nanorods Realizes Ultrahigh-Sensitivity Optical Imaging Agents LANGMUIR 2015; 31 (45): 12339-12347
Optical coherence contrast imaging using gold nanorods in living mice eyes
CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY
2015; 43 (4): 358-366
Optical coherence tomography (OCT) is a powerful imaging modality to visualize tissue structures, with axial image pixel resolution as high as 1.6 μm in tissue. However, OCT is intrinsically limited to providing structural information as the OCT contrast is produced by optically scattering tissues.Gold nanorods (GNRs) were injected into the anterior chamber (AC) and cornea of mice eyes which could create a significant OCT signal and hence could be used as a contrast agent for in vivo OCT imaging.A dose of 30 nM of GNRs (13 nm in diameter and 45 nm in length) were injected to the AC of mice eyes and produced an OCT contrast nearly 50-fold higher than control mice injected with saline. Furthermore, the lowest detectable concentration of GNRs in living mice AC was experimentally estimated to be as low as 120 pM.The high sensitivity and low toxicity of GNRs brings great promise for OCT to uniquely become a high-resolution molecular imaging modality.
View details for DOI 10.1111/ceo.12299
View details for Web of Science ID 000356810200009
A correlative optical microscopy and scanning electron microscopy approach to locating nanoparticles in brain tumors
2015; 68: 70-76
The growing use of nanoparticles in biomedical applications, including cancer diagnosis and treatment, demands the capability to exactly locate them within complex biological systems. In this work a correlative optical and scanning electron microscopy technique was developed to locate and observe multi-modal gold core nanoparticle accumulation in brain tumor models. Entire brain sections from mice containing orthotopic brain tumors injected intravenously with nanoparticles were imaged using both optical microscopy to identify the brain tumor, and scanning electron microscopy to identify the individual nanoparticles. Gold-based nanoparticles were readily identified in the scanning electron microscope using backscattered electron imaging as bright spots against a darker background. This information was then correlated to determine the exact location of the nanoparticles within the brain tissue. The nanoparticles were located only in areas that contained tumor cells, and not in the surrounding healthy brain tissue. This correlative technique provides a powerful method to relate the macro- and micro-scale features visible in light microscopy with the nanoscale features resolvable in scanning electron microscopy.
View details for DOI 10.1016/j.micron.2014.09.004
View details for Web of Science ID 000348016500011
View details for PubMedID 25464144
- Imaging the Glycosylation State of Cell Surface Glycoproteins by Two-Photon Fluorescence Lifetime Imaging Microscopy ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 2013; 52 (52): 14045-14049
Single step nanoplasmonic immunoassay for the measurement of protein biomarkers.
2013; 3 (1): 77-88
A nanoplasmonic biosensor for highly-sensitive, single-step detection of protein biomarkers is presented. The principle is based on the utilization of the optical scattering properties of gold nanorods (GNRs) conjugated to bio-recognition molecules. The nanoplasmonic properties of the GNRs were utilized to detect proteins using near-infrared light interferometry. We show that the antibody-conjugated GNRs can specifically bind to our model analyte, Glucose Transporter-1 (Glut-1). The signal intensity of back-scattered light from the GNRs bound after incubation, correlated well to the Glut-1 concentration as per the calibration curve. The detection range using this nanoplasmonic immunoassay ranges from 10 ng/mL to 1 ug/mL for Glut-1. The minimal detectable concentration based on the lowest discernable concentration from zero is 10 ng/mL. This nanoplasmonic immunoassay can act as a simple, selective, sensitive strategy for effective disease diagnosis. It offers advantages such as wide detection range, increased speed of analysis (due to fewer incubation/washing steps), and no label development as compared to traditional immunoassay techniques. Our future goal is to incorporate this detection strategy onto a microfluidic platform to be used as a point-of-care diagnostic tool.
View details for DOI 10.3390/bios3010077
View details for PubMedID 25587399
Continuous sensing of tumor-targeted molecular probes with a vertical cavity surface emitting laser-based biosensor
JOURNAL OF BIOMEDICAL OPTICS
2012; 17 (11)
Molecular optical imaging is a widespread technique for interrogating molecular events in living subjects. However, current approaches preclude long-term, continuous measurements in awake, mobile subjects, a strategy crucial in several medical conditions. Consequently, we designed a novel, lightweight miniature biosensor for in vivo continuous optical sensing. The biosensor contains an enclosed vertical-cavity surface-emitting semiconductor laser and an adjacent pair of near-infrared optically filtered detectors. We employed two sensors (dual sensing) to simultaneously interrogate normal and diseased tumor sites. Having established the sensors are precise with phantom and in vivo studies, we performed dual, continuous sensing in tumor (human glioblastoma cells) bearing mice using the targeted molecular probe cRGD-Cy5.5, which targets ?V?3 cell surface integrins in both tumor neovasculature and tumor. The sensors capture the dynamic time-activity curve of the targeted molecular probe. The average tumor to background ratio after signal calibration for cRGD-Cy5.5 injection is approximately 2.43±0.95 at 1 h and 3.64±1.38 at 2 h (N=5 mice), consistent with data obtained with a cooled charge coupled device camera. We conclude that our novel, portable, precise biosensor can be used to evaluate both kinetics and steady state levels of molecular probes in various disease applications.
View details for DOI 10.1117/1.JBO.17.11.117004
View details for Web of Science ID 000314502700046
View details for PubMedID 23123976
Family of Enhanced Photoacoustic Imaging Agents for High-Sensitivity and Multiplexing Studies in Living Mice
2012; 6 (6): 4694-4701
Photoacoustic imaging is a unique modality that overcomes to a great extent the resolution and depth limitations of optical imaging while maintaining relatively high contrast. However, since many diseases will not manifest an endogenous photoacoustic contrast, it is essential to develop exogenous photoacoustic contrast agents that can target diseased tissue(s). Here we present a family of novel photoacoustic contrast agents that are based on the binding of small optical dyes to single-walled carbon nanotubes (SWNT-dye). We synthesized five different SWNT-dye contrast agents using different optical dyes, creating five "flavors" of SWNT-dye nanoparticles. In particular, SWNTs that were coated with either QSY(21) (SWNT-QSY) or indocyanine green (SWNT-ICG) exhibited over 100-times higher photoacoustic contrast in living animals compared to plain SWNTs, leading to subnanomolar sensitivities. We then conjugated the SWNT-dye conjugates with cyclic Arg-Gly-Asp peptides to molecularly target the ?(v)?(3) integrin, which is associated with tumor angiogenesis. Intravenous administration of these tumor-targeted imaging agents to tumor-bearing mice showed significantly higher photoacoustic signal in the tumor than in mice injected with the untargeted contrast agent. Finally, we were able to spectrally separate the photoacoustic signals of SWNT-QSY and SWNT-ICG in living animals injected subcutaneously with both particles in the same location, opening the possibility for multiplexing in vivo studies.
View details for DOI 10.1021/nn204352r
View details for Web of Science ID 000305661300017
View details for PubMedID 22607191
A brain tumor molecular imaging strategy using a new triple-modality MRI-photoacoustic-Raman nanoparticle
2012; 18 (5): 829-U235
The difficulty in delineating brain tumor margins is a major obstacle in the path toward better outcomes for patients with brain tumors. Current imaging methods are often limited by inadequate sensitivity, specificity and spatial resolution. Here we show that a unique triple-modality magnetic resonance imaging-photoacoustic imaging-Raman imaging nanoparticle (termed here MPR nanoparticle) can accurately help delineate the margins of brain tumors in living mice both preoperatively and intraoperatively. The MPRs were detected by all three modalities with at least a picomolar sensitivity both in vitro and in living mice. Intravenous injection of MPRs into glioblastoma-bearing mice led to MPR accumulation and retention by the tumors, with no MPR accumulation in the surrounding healthy tissue, allowing for a noninvasive tumor delineation using all three modalities through the intact skull. Raman imaging allowed for guidance of intraoperative tumor resection, and a histological correlation validated that Raman imaging was accurately delineating the brain tumor margins. This new triple-modality-nanoparticle approach has promise for enabling more accurate brain tumor imaging and resection.
View details for DOI 10.1038/nm.2721
View details for Web of Science ID 000303763500053
View details for PubMedID 22504484
Advanced contrast nanoagents for photoacoustic molecular imaging, cytometry, blood test and photothermal theranostics
CONTRAST MEDIA & MOLECULAR IMAGING
2011; 6 (5): 346-369
Various nanoparticles have raised significant interest over the past decades for their unique physical and optical properties and biological utilities. Here we summarize the vast applications of advanced nanoparticles with a focus on carbon nanotube (CNT)-based or CNT-catalyzed contrast agents for photoacoustic (PA) imaging, cytometry and theranostics applications based on the photothermal (PT) effect. We briefly review the safety and potential toxicity of the PA/PT contrast nanoagents, while showing how the physical properties as well as multiple biological coatings change their toxicity profiles and contrasts. We provide general guidelines needed for the validation of a new molecular imaging agent in living subjects, and exemplify these guidelines with single-walled CNTs targeted to ?(v) ?(3) , an integrin associated with tumor angiogenesis, and golden carbon nanotubes targeted to LYVE-1, endothelial lymphatic receptors. An extensive review of the potential applications of advanced contrast agents is provided, including imaging of static targets such as tumor angiogenesis receptors, in vivo cytometry of dynamic targets such as circulating tumor cells and nanoparticles in blood, lymph, bones and plants, methods to enhance the PA and PT effects with transient and stationary bubble conjugates, PT/PA Raman imaging and multispectral histology. Finally, theranostic applications are reviewed, including the nanophotothermolysis of individual tumor cells and bacteria with clustered nanoparticles, nanothrombolysis of blood clots, detection and purging metastasis in sentinel lymph nodes, spectral hole burning and multiplex therapy with ultrasharp rainbow nanoparticles.
View details for DOI 10.1002/cmmi.455
View details for Web of Science ID 000300110400003
View details for PubMedID 22025336
A Comparison Between Time Domain and Spectral Imaging Systems for Imaging Quantum Dots in Small Living Animals
MOLECULAR IMAGING AND BIOLOGY
2010; 12 (5): 500-508
We quantified the performance of time-domain imaging (TDI) and spectral imaging (SI) for fluorescence imaging of quantum dots (QDs) in three distinct imaging instruments: eXplore Optix (TDI, Advanced Research Technologies Inc.), Maestro (SI, CRi Inc.), and IVIS-Spectrum (SI, Caliper Life Sciences Inc.).The instruments were compared for their sensitivity in phantoms and living mice, multiplexing capabilities (ability to resolve the signal of one QD type in the presence of another), and the dependence of contrast and spatial resolution as a function of depth.In phantoms, eXplore Optix had an order of magnitude better sensitivity compared to the SI systems, detecting QD concentrations of ~40 pM in vitro. Maestro was the best instrument for multiplexing QDs. Reduction of contrast and resolution as a function of depth was smallest with eXplore Optix for depth of 2-6 mm, while other depths gave comparable results in all systems. Sensitivity experiments in living mice showed that the eXplore Optix and Maestro systems outperformed the IVIS-Spectrum.TDI was found to be an order of magnitude more sensitive than SI at the expense of speed and very limited multiplexing capabilities. For deep tissue QD imaging, TDI is most applicable for depths between 2 and 6 mm, as its contrast and resolution degrade the least at these depths.
View details for DOI 10.1007/s11307-009-0290-4
View details for Web of Science ID 000282273200006
View details for PubMedID 20012220
Ultrahigh Sensitivity Carbon Nanotube Agents for Photoacoustic Molecular Imaging in Living Mice
2010; 10 (6): 2168-2172
Photoacoustic imaging is an emerging modality that overcomes to a great extent the resolution and depth limitations of optical imaging while maintaining relatively high-contrast. However, since many diseases will not manifest an endogenous photoacoustic contrast, it is essential to develop exogenous photoacoustic contrast agents that can target diseased tissue(s). Here we present a novel photoacoustic contrast agent, Indocyanine Green dye-enhanced single walled carbon nanotube (SWNT-ICG). We conjugated this contrast agent with cyclic Arg-Gly-Asp (RGD) peptides to molecularly target the alpha(v)beta(3) integrins, which are associated with tumor angiogenesis. Intravenous administration of this tumor-targeted contrast agent to tumor-bearing mice showed significantly higher photoacoustic signal in the tumor than in mice injected with the untargeted contrast agent. The new contrast agent gave a markedly 300 times higher photoacoustic contrast in living tissues than previously reported SWNTs, leading to subnanomolar sensitivities. Finally, we show that the new contrast agent can detect approximately 20 times fewer cancer cells than previously reported SWNTs.
View details for DOI 10.1021/nl100890d
View details for Web of Science ID 000278449200033
View details for PubMedID 20499887
Photoacoustic ocular imaging
2010; 35 (3): 270-272
We developed a photoacoustic ocular imaging device and demonstrated its utility in imaging the deeper layers of the eye including the retina, choroid, and optic nerve. Using safe laser intensity, the photoacoustic system was able to visualize the blood distribution of an enucleated pig's eye and an eye of a living rabbit. Ultrasound images, which were simultaneously acquired, were overlaid on the photoacoustic images to visualize the eye's anatomy. Such a system may be used in the future for early detection and improved management of neovascular ocular diseases, including wet age-related macular degeneration and proliferative diabetic retinopathy.
View details for Web of Science ID 000274196100001
View details for PubMedID 20125691
Three-Dimensional Photoacoustic Imaging Using a Two-Dimensional CMUT Array
IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL
2009; 56 (11): 2411-2419
In this paper, we describe using a 2-D array of capacitive micromachined ultrasonic transducers (CMUTs) to perform 3-D photoacoustic and acoustic imaging. A tunable optical parametric oscillator laser system that generates nanosecond laser pulses was used to induce the photoacoustic signals. To demonstrate the feasibility of the system, 2 different phantoms were imaged. The first phantom consisted of alternating black and transparent fishing lines of 180 mum and 150 mum diameter, respectively. The second phantom comprised polyethylene tubes, embedded in chicken breast tissue, filled with liquids such as the dye indocyanine green, pig blood, and a mixture of the 2. The tubes were embedded at a depth of 0.8 cm inside the tissue and were at an overall distance of 1.8 cm from the CMUT array. Two-dimensional cross-sectional slices and 3-D volume rendered images of pulse-echo data as well as photoacoustic data are presented. The profile and beamwidths of the fishing line are analyzed and compared with a numerical simulation carried out using the Field II ultrasound simulation software. We investigated using a large aperture (64 x 64 element array) to perform photoacoustic and acoustic imaging by mechanically scanning a smaller CMUT array (16 x 16 elements). Two-dimensional transducer arrays overcome many of the limitations of a mechanically scanned system and enable volumetric imaging. Advantages of CMUT technology for photoacoustic imaging include the ease of integration with electronics, ability to fabricate large, fully populated 2-D arrays with arbitrary geometries, wide-bandwidth arrays and high-frequency arrays. A CMUT based photoacoustic system is proposed as a viable alternative to a piezoelectric transducer based photoacoustic systems.
View details for DOI 10.1109/TUFFC.2009.1329
View details for Web of Science ID 000271478600010
View details for PubMedID 19942528
- Implantable optical biosensor for in vivo molecular imaging OPTICAL FIBERS AND SENSORS FOR MEDICAL DIAGNOSTICS AND TREATMENT APPLICATIONS IX 2009; 7173
Noninvasive Raman spectroscopy in living mice for evaluation of tumor targeting with carbon nanotubes
2008; 8 (9): 2800-2805
An optimized noninvasive Raman microscope was used to evaluate tumor targeting and localization of single walled carbon nanotubes (SWNTs) in mice. Raman images were acquired in two groups of tumor-bearing mice. The control group received plain-SWNTs, whereas the experimental group received tumor targeting RGD-SWNTs intravenously. Raman imaging commenced over the next 72 h and revealed increased accumulation of RGD-SWNTs in tumor ( p < 0.05) as opposed to plain-SWNTs. These results support the development of a new preclinical Raman imager.
View details for DOI 10.1021/nl801362a
View details for Web of Science ID 000259140200034
View details for PubMedID 18683988
Carbon nanotubes as photoacoustic molecular imaging agents in living mice
2008; 3 (9): 557-562
Photoacoustic imaging of living subjects offers higher spatial resolution and allows deeper tissues to be imaged compared with most optical imaging techniques. As many diseases do not exhibit a natural photoacoustic contrast, especially in their early stages, it is necessary to administer a photoacoustic contrast agent. A number of contrast agents for photoacoustic imaging have been suggested previously, but most were not shown to target a diseased site in living subjects. Here we show that single-walled carbon nanotubes conjugated with cyclic Arg-Gly-Asp (RGD) peptides can be used as a contrast agent for photoacoustic imaging of tumours. Intravenous administration of these targeted nanotubes to mice bearing tumours showed eight times greater photoacoustic signal in the tumour than mice injected with non-targeted nanotubes. These results were verified ex vivo using Raman microscopy. Photoacoustic imaging of targeted single-walled carbon nanotubes may contribute to non-invasive cancer imaging and monitoring of nanotherapeutics in living subjects.
View details for DOI 10.1038/nnano.2008.231
View details for Web of Science ID 000259013100014
View details for PubMedID 18772918
Noninvasive molecular imaging of small living subjects using Raman spectroscopy
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2008; 105 (15): 5844-5849
Molecular imaging of living subjects continues to rapidly evolve with bioluminescence and fluorescence strategies, in particular being frequently used for small-animal models. This article presents noninvasive deep-tissue molecular images in a living subject with the use of Raman spectroscopy. We describe a strategy for small-animal optical imaging based on Raman spectroscopy and Raman nanoparticles. Surface-enhanced Raman scattering nanoparticles and single-wall carbon nanotubes were used to demonstrate whole-body Raman imaging, nanoparticle pharmacokinetics, multiplexing, and in vivo tumor targeting, using an imaging system adapted for small-animal Raman imaging. The imaging modality reported here holds significant potential as a strategy for biomedical imaging of living subjects.
View details for DOI 10.1073/pnas.0710575105
View details for Web of Science ID 000255237200036
View details for PubMedID 18378895
- Drug delivery - Keeping tabs on nanocarriers NATURE NANOTECHNOLOGY 2007; 2 (12): 745-746
Formulating adaptive radiation therapy (ART) treatment planning into a closed-loop control framework
PHYSICS IN MEDICINE AND BIOLOGY
2007; 52 (14): 4137-4153
While ART has been studied for years, the specific quantitative implementation details have not. In order for this new scheme of radiation therapy (RT) to reach its potential, an effective ART treatment planning strategy capable of taking into account the dose delivery history and the patient's on-treatment geometric model must be in place. This paper performs a theoretical study of dynamic closed-loop control algorithms for ART and compares their utility with data from phantom and clinical cases. We developed two classes of algorithms: those Adapting to Changing Geometry and those Adapting to Geometry and Delivered Dose. The former class takes into account organ deformations found just before treatment. The latter class optimizes the dose distribution accumulated over the entire course of treatment by adapting at each fraction, not only to the information just before treatment about organ deformations but also to the dose delivery history. We showcase two algorithms in the class of those Adapting to Geometry and Delivered Dose. A comparison of the approaches indicates that certain closed-loop ART algorithms may significantly improve the current practice. We anticipate that improvements in imaging, dose verification and reporting will further increase the importance of adaptive algorithms.
View details for DOI 10.1088/0031-9155/52/14/008
View details for Web of Science ID 000247400000008
View details for PubMedID 17664599