Instructor, Radiology - Diagnostic Radiology
Biomedical Engineering and Nanotechnology with a focus on Raman Spectroscopy and Early Cancer Detection
Development and evaluation of novel tumor targeting nanoparticles for either diagnostic, therapeutic or combination applications
Development and evaluation of new molecular imaging devices including both preclinical and clinically translatable optical imaging endoscopes for ultrasensitive cancer detection
Evaluating biodistribution patterns of various clinically translatable nanoparticles after various routes of administration (Intravenously, Intraperitoneally, Intrarectally, or Topical Application)
Raman spectroscopy is a powerful technique for detecting and quantifying analytes in chemical mixtures. A critical part of Raman spectroscopy is the use of a computer algorithm to analyze the measured Raman spectra. The most commonly used algorithm is the classical least squares method, which is popular due to its speed and ease of implementation. However, it is sensitive to inaccuracies or variations in the reference spectra of the analytes (compounds of interest) and the background. Many algorithms, primarily multivariate calibration methods, have been proposed that increase robustness to such variations. In this study, we propose a novel method that improves robustness even further by explicitly modeling variations in both the background and analyte signals. More specifically, it extends the classical least squares model by allowing the declared reference spectra to vary in accordance with the principal components obtained from training sets of spectra measured in prior characterization experiments. The amount of variation allowed is constrained by the eigenvalues of this principal component analysis. We compare the novel algorithm to the least squares method with a low-order polynomial residual model, as well as a state-of-the-art hybrid linear analysis method. The latter is a multivariate calibration method designed specifically to improve robustness to background variability in cases where training spectra of the background, as well as the mean spectrum of the analyte, are available. We demonstrate the novel algorithm's superior performance by comparing quantitative error metrics generated by each method. The experiments consider both simulated data and experimental data acquired from in vitro solutions of Raman-enhanced gold-silica nanoparticles.
View details for DOI 10.1371/journal.pone.0038850
View details for Web of Science ID 000305583300060
View details for PubMedID 22723895
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
Raman spectroscopy is an optical technique that offers unsurpassed sensitivity and multiplexing capabilities to the field of molecular imaging. In the past, Raman spectroscopy had predominantly been used as an analytic tool for routine chemical analysis, but more recently, researchers have been able to harness its unique properties for imaging and spectral analysis of molecular interactions in cell populations and preclinical animal models. Additionally, researchers have already begun to translate this optical technique into a novel clinical diagnostic tool using various endoscopic strategies.
View details for DOI 10.2967/jnumed.111.087775
View details for Web of Science ID 000298162500016
View details for PubMedID 21868625
Gold has been used as a therapeutic agent to treat a wide variety of rheumatic diseases including psoriatic arthritis, juvenile arthritis, and discoid lupus erythematosus. Although the use of gold has been largely superseded by newer drugs, gold nanoparticles are being used effectively in laboratory based clinical diagnostic methods while concurrently showing great promise in vivo either as a diagnostic imaging agent or a therapeutic agent. For these reasons, gold nanoparticles are therefore well placed to enter mainstream clinical practice in the near future. Hence, the present review summarizes the chemistry, pharmacokinetics, biodistribution, metabolism, and toxicity of bulk gold in humans based on decades of clinical observation and experiments in which gold was used to treat patients with rheumatoid arthritis. The beneficial attributes of gold nanoparticles, such as their ease of synthesis, functionalization, and shape control are also highlighted demonstrating why gold nanoparticles are an attractive target for further development and optimization. The importance of controlling the size and shape of gold nanoparticles to minimize any potential toxic side effects is also discussed.
View details for DOI 10.1021/nl202559p
View details for Web of Science ID 000295667000001
View details for PubMedID 21846107
Raman imaging offers unsurpassed sensitivity and multiplexing capabilities. However, its limited depth of light penetration makes direct clinical translation challenging. Therefore, a more suitable way to harness its attributes in a clinical setting would be to couple Raman spectroscopy with endoscopy. The use of an accessory Raman endoscope in conjunction with topically administered tumor-targeting Raman nanoparticles during a routine colonoscopy could offer a new way to sensitively detect dysplastic lesions while circumventing Raman's limited depth of penetration and avoiding systemic toxicity. In this study, the natural biodistribution of gold surface-enhanced Raman scattering (SERS) nanoparticles is evaluated by radiolabeling them with (64) Cu and imaging their localization over time using micropositron emission tomography (PET). Mice are injected either intravenously (IV) or intrarectally (IR) with approximately 100 microcuries (?Ci) (3.7 megabecquerel (MBq)) of (64) Cu-SERS nanoparticles and imaged with microPET at various time points post injection. Quantitative biodistribution data are obtained as % injected dose per gram (%ID g(-1)) from each organ, and the results correlate well with the corresponding microPET images, revealing that IV-injected mice have significantly higher uptake (p < 0.05) in the liver (5 h = 8.96% ID g(-1); 24 h = 8.27% ID g(-1)) than IR-injected mice (5 h = 0.09% ID g(-1); 24 h = 0.08% ID g(-1)). IR-injected mice show localized uptake in the large intestine (5 h = 10.37% ID g(-1); 24 h = 0.42% ID g(-1)) with minimal uptake in other organs. Raman imaging of excised tissues correlate well with biodistribution data. These results suggest that the topical application of SERS nanoparticles in the mouse colon appears to minimize their systemic distribution, thus avoiding potential toxicity and supporting the clinical translation of Raman spectroscopy as an endoscopic imaging tool.
View details for DOI 10.1002/smll.201002317
View details for Web of Science ID 000294361200015
View details for PubMedID 21608124
Raman spectroscopy is an optical imaging method that is based on the Raman effect, the inelastic scattering of a photon when energy is absorbed from light by a surface. Although Raman spectroscopy is widely used for chemical and molecular analysis, its clinical application has been hindered by the inherently weak nature of the Raman effect. Raman-silica-gold-nanoparticles (R-Si-Au-NPs) overcome this limitation by producing larger Raman signals through surface-enhanced Raman scattering. Because we are developing these particles for use as targeted molecular imaging agents, we examined the acute toxicity and biodistribution of core polyethylene glycol (PEG)-ylated R-Si-Au-NPs after different routes of administration in mice. After intravenous administration, PEG-R-Si-Au-NPs were removed from the circulation by macrophages in the liver and spleen (that is, the reticuloendothelial system). At 24 hours, PEG-R-Si-Au-NPs elicited a mild inflammatory response and an increase in oxidative stress in the liver, which subsided by 2 weeks after administration. No evidence of significant toxicity was observed by measuring clinical, histological, biochemical, or cardiovascular parameters for 2 weeks. Because we are designing targeted PEG-R-Si-Au-NPs (for example, PEG-R-Si-Au-NPs labeled with an affibody that binds specifically to the epidermal growth factor receptor) to detect colorectal cancer after administration into the bowel lumen, we tested the toxicity of the core nanoparticle after administration per rectum. We observed no significant bowel or systemic toxicity, and no PEG-R-Si-Au-NPs were detected systemically. Although additional studies are required to investigate the long-term effects of PEG-R-Si-Au-NPs and their toxicity when carrying the targeting moiety, the results presented here support the idea that PEG-R-Si-Au-NPs can be safely used in living subjects, especially when administered rectally.
View details for DOI 10.1126/scitranslmed.3001963
View details for Web of Science ID 000292976700004
View details for PubMedID 21508310
The affibody functionalization of fluorescent surface-enhanced Raman scattering gold-silica nanoparticles as multimodal contrast agents for molecular imaging specific to epidermal growth factor receptor (EGFR) is reported. This nanoparticle bioconjugate reports EGFR-positive A431 tumors with a signal nearly 35-fold higher than EGFR-negative MDA-435S tumors. The low-level EGFR expression in adjacent healthy tissue is 7-fold lower than in the positive tumors. Validation via competitive inhibition reduces the signal by a factor of six, and independent measurement of EGFR via flow cytometry correlates at R(2) = 0.92.
View details for DOI 10.1002/smll.201002291
View details for Web of Science ID 000288081900013
View details for PubMedID 21302357
Polyethylene glycol (PEG)ylated Raman-active gold nanoparticles (PEG-R-AuNPs) consist of an interchangeable Raman organic molecule layer held onto a gold nanocore by a silica shell. PEG-R-AuNPs have been shown preclinically to increase the sensitivity and specificity of Raman spectroscopy, with picomolar sensitivity and multiplexing capabilities. Although clinical trials are being designed to use functionalized PEG-R-AuNPs in various applications (e.g., to target dysplastic bowel lesions during colonoscopy), the effects of these nanoparticles on human cells remain unknown. The occurrence and mechanisms underlying any potential cytotoxicity induced by these nanoparticles (0-1000 PEG-R-AuNPs/cell) are investigated in immortalized human HeLa and HepG2 cell lines at several time points (0-48 h) after exposure. Using fluorometric assays, cell viability (MTT), reactive oxygen species (ROS) generation (dichlorofluorescein diacetate), protein oxidation (protein carbonyl content), and total cellular antioxidant concentrations the concentrations (metmyoblobin-induced oxidation of ABTS) are assessed. Analysis of lipid oxidation using an enzyme immunoassay (8-isoprostane concentrations), gene expression of antioxidant enzymes using quantitative reverse transcription polymerase chain reactions, and the intracellular location of PEG-R-AuNPs using transmission electron microscopy is also undertaken. PEG-R-AuNPs cause no cytotoxicity in either HeLa or HepG2 cells in the acute setting as ROS generation is balanced by antioxidant enzyme upregulation. Following prolonged exposures (48 h) at relatively high concentrations (1000 PEG-R-AuNPs/cell), nanoparticles are found within vesicles inside cells. Under these conditions, a minimal amount of cytotoxicity is seen in both cell lines owing to increases in cellular oxidative stress, most likely due to ROS overwhelming the antioxidant defenses. Evidence of oxidative stress-induced damage includes increased lipid and protein oxidation. Although further in vivo toxicity studies are necessary, these initial encouraging results show that PEG-R-AuNPs cause minimal toxicity in human cells in the acute setting, which bodes well for potential future applications of these nanoparticles in living subjects.
View details for DOI 10.1002/smll.201001466
View details for Web of Science ID 000285794100015
View details for PubMedID 21104804
Raman spectroscopy is a newly developed, noninvasive preclinical imaging technique that offers picomolar sensitivity and multiplexing capabilities to the field of molecular imaging. In this study, we demonstrate the ability of Raman spectroscopy to separate the spectral fingerprints of up to 10 different types of surface enhanced Raman scattering (SERS) nanoparticles in a living mouse after s.c. injection. Based on these spectral results, we simultaneously injected the five most intense and spectrally unique SERS nanoparticles i.v. to image their natural accumulation in the liver. All five types of SERS nanoparticles were successfully identified and spectrally separated using our optimized noninvasive Raman imaging system. In addition, we were able to linearly correlate Raman signal with SERS concentration after injecting four spectrally unique SERS nanoparticles either s.c. (R(2) = 0.998) or i.v. (R(2) = 0.992). These results show great potential for multiplexed imaging in living subjects in cases in which several targeted SERS probes could offer better detection of multiple biomarkers associated with a specific disease.
View details for DOI 10.1073/pnas.0813327106
View details for Web of Science ID 000268877300066
View details for PubMedID 19666578
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
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
This study determined the biodistribution of rhenium-186 ((186)Re) encapsulated in biotin-liposomes containing patent blue dye, injected intraperitoneally (IP) with avidin in an OVCAR-3 ovarian cancer xenograft model and evaluated tumor response of this therapy with fluorine-18-fluorodeoxyglucose ((18)F-FDG) microPET imaging. Treated rats (n = 8) received an IP injection of (186)Re-blue-biotin-liposomes (1000 MBq/kg) 30 min before an IP injection of avidin (5 mg), whereas control rats (n = 4) received a sham IP injection of saline. Scintigraphic images showed that (186)Re-blue-biotin liposomes/avidin were retained in the peritoneal cavity with 18% of the original activity remaining after 5 days. From 1 to 4 weeks post-treatment, peritoneal (18)F-FDG standard uptake values decreased 30% in treatment group, yet increased 44% in control group. Total number of cells in ascites was significantly higher in control versus treatment group. Omental fat in control rats had numerous tumor cells compared with treated rats. Results show the potential for (186)Re-blue-biotin-liposome/avidin system in treating advanced ovarian cancer involving peritoneal carcinomatosis.
View details for DOI 10.1080/10611860802230372
View details for PubMedID 18686134
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
The goal of this study was to determine the distribution of the avidin/biotin-liposome system in an ovarian cancer xenograft model. Optimal avidin/biotin-liposome injection sequence with enhanced liposome accumulation to the peritoneum was determined. Two weeks after NIH:OVCAR-3 cell inoculation, rats were divided into three groups. Group 1 (B-A) (n=4), received an intraperitoneal injection of (99m)Tc-blue-biotin-liposomes 30 min before an intraperitoneal injection of avidin. Group 2 (A-B) (n=4), received an intraperitoneal injection of avidin 30 min before an intraperitoneal injection of (99m)Tc-blue-biotin-liposomes. Group 3 (A-B 2h) (n=5), received an intraperitoneal injection of avidin 2h before an intraperitoneal injection of (99m)Tc-blue-biotin-liposomes. Three additional non-tumor nude rats served as controls in each group, and were subjected to the same injection sequences. Scintigraphic imaging commenced at various times post (99m)Tc-blue-biotin-liposome injection. After imaging, rats were euthanized at 23 h post-liposome injection for tissue biodistribution. Images showed no apparent difference in liposome distribution between control and tumor animals. Regional uptake analysis at 4h for tumor rats showed significantly higher lymphatic channel uptake in the A-B 2h group (p<0.05) and a trend of increased peritoneal uptake in A-B group. By 22 h, peritoneal and lymphatic channel uptake was similar for all groups. At necropsy, most activity was found in blue-stained omentum, diaphragm, mediastinal and abdominal nodes. Bowel activity was minimal. These results correlate with previous normal rat studies, and demonstrate potential use of this avidin/biotin-liposome system for prolonging drug delivery to the peritoneal cavity and associating lymph nodes in this ovarian cancer xenograft model.
View details for DOI 10.1016/j.ijpharm.2007.01.010
View details for Web of Science ID 000247355800037
View details for PubMedID 17276633
MicroPET is a noninvasive imaging modality that can potentially track tumor development in nude rats using the radiotracer fluorine 18-fluorodeoxyglucose ((18)F-FDG). Our goal was to determine whether microPET, as opposed to more invasive techniques, could be used to noninvasively monitor the development of ovarian cancer in the peritoneal cavity of nude rats for monitoring treatment response in future studies. Female nude rats were inoculated intraperitoneally with 36 million NIH:OVCAR-3 cells. Imaging was carried out at 2, 4, 6, or 8 weeks postinoculation. Each rat was fasted overnight and intravenously injected with 11.1 MBq (300 microCi) of (18)F-FDG in 0.2 mL of saline. Thirty minutes following injection, the rats were placed in the microPET and scanned for 30 min. After imaging, rats were euthanized for ascites and tissue collection for biodistribution and histopathologic correlation. Standard uptake values (SUVs) of (18)F-FDG within the peritoneal cavity were also calculated from regions of interest analysis of the microPET images. MicroPET images showed diffuse increased uptake of (18)F-FDG throughout the peritoneal cavity of tumor rats (mean SUV=4.64) compared with control rats (mean SUV=1.03). Ascites gathered from tumor-bearing rats had increased (18)F-FDG uptake as opposed to the peritoneal fluid collected from control rats. Biodistribution data revealed that the percent injected dose per gram (% ID/g) was significantly higher in tumor-bearing rats (6.29%) than in control rats (0.59%) in the peritoneal lymph nodes. Pathology verified that these lymph nodes were more reactive in tumor-bearing rats. By 6 weeks, some rats developed solid masses within the peritoneum, which could be detected on microPET images and confirmed as tumor by histopathology. (18)F-FDG uptake in these tumors at necropsy was 2.83% ID/g. These results correlate with previous invasive laparoscopic studies of the same tumor model and demonstrate that microPET using (18)F-FDG is a promising noninvasive tool to localize and follow tumor growth in an intraperitoneal ovarian cancer model.
View details for DOI 10.1111/j.1525-1438.2007.00814.x
View details for Web of Science ID 000244885300014
View details for PubMedID 17362319
Liposomes have recognized advantages as nano-particle drug carriers for tumor therapy. In this study, the pharmacokinetics and distribution of intratumorally administered liposomes were investigated as drug carriers for treating solid tumors via direct intratumoral administration. 99mTc-liposomes were administered intratumorally to nude rats bearing human head and neck squamous cell carcinoma xenografts. Planar gamma camera images were analyzed to evaluate the local retention of the intratumorally administered liposomes. Co-registered pinhole micro-single photon emission computed tomography (SPECT)/computed tomography (CT) images were acquired of the whole animal as well as the dissected tumors to determine intratumoral distribution of the 99mTc-liposomes. For 99mTc-liposomes, there was an initial retention of 47.4 +/- 11.0% (n = 4) in tumors and surrounding tissues. At 20 h, 39.2 +/- 10.6% (n = 4) of 99mTc-activity still remained in the tumor. In contrast, only 18.7 +/- 3.3% (n = 3) of the intratumoral 99mTc-activity remained for unencapsulated 99mTc-complex at 20 h. Pinhole micro-SPECT images demonstrated that 99mTc-liposomes also have a superior intratumoral 99mTc-activity diffusion compared with unencapsulated 99mTc-complex. Higher intratumoral retention of 99mTc-liposomes accompanied by an improved intratumoral diffusion suggests that intratumorally administered liposomal drugs are potentially promising agents for solid tumor local therapy.
View details for DOI 10.1016/j.ijpharm.2006.02.039
View details for Web of Science ID 000238551100023
View details for PubMedID 16580161