Jodi Nicolai

Photothermal ablation of pancreatic cancer cells with hybrid iron-oxide core gold-shell nanoparticles

Purpose Photothermal ablation is a minimally invasive approach, which typically involves delivery of photothermal sensitizers to targeted tissues. The purpose of our study was to demonstrate that gold nanoparticles are phagocytosed by pancreatic cancer cells, thus permitting magnetic resonance imaging (MRI) of sensitizer delivery and photothermal ablation. Patients and methods Iron-oxide core/gold-shell nanoparticles (GoldMag®, 30 nm diameter; Xi’an GoldMag Biotechnology Co, Xi’an, People’s Republic of China) were used. In a 96-well plate, 3 × 104 PANC-1 (human pancreatic cancer cell line) cells were placed. GoldMag (0, 25, or 50 μg/mL) was added to each well and 24 hours allowed for cellular uptake. Samples were then divided into two groups: one treated with photothermal ablation (7.9 W/cm2) for 5 minutes, the other not treated. Photothermal ablation was performed using laser system (BWF5; B&W Tek, Inc, Newark, DE, USA). Intraprocedural temperature changes were measured using a fiber optic temperature probe (FTP-LN2; Photon Control Inc, Burnaby, BC, Canada). After 24 hours, the remaining number of viable cells was counted using trypan blue staining; cell proliferation percentage was calculated based on the total number of viable cells after treatment compared with control. MRI of GoldMag uptake was performed using a 7.0T ClinScan system (Bruker BioSpin, Ettlingen, Germany). Results Temperature curves demonstrated that with increased GoldMag uptake, laser irradiation produced higher temperature elevations in the corresponding samples; temperature elevations of 12.89°C, 35.16°C, and 79.51°C were achieved for 0, 25, and 50 μg/mL GoldMag. Without photothermal ablation, the cell proliferation percentage changed from 100% to 71.3% and 47.0% for cells treated with 25 and 50 μg/mL GoldMag. Photothermal ablation of PANC-1 cells demonstrated an effective treatment response, specifically a reduction to only 61%, 21.9%, and 2.3% cell proliferation for cells treated with 0, 25, and 50 μg/mL GoldMag. MRI was able to visualize GoldMag uptake within PANC-1 cells. Conclusion Our findings suggest that photothermal ablation may be effective in the treatment of pancreatic cancer. GoldMag nanoparticles could serve as photothermal sensitizers, and MRI is feasible to quantify delivery.

Temperature Sensitive Magnetic Drug Carriers for Concurrent Gemcitabine Chemohyperthermia

To improve the efficacy of gemcitabine (GEM) for the treatment of advanced pancreatic cancer via local hyperthermia potentiated via a multi-functional nanoplatform permitting both in vivo heating and drug delivery is the goal of this study. Here, a chemohyperthermia approach to synergistically achieve high intra-tumoral drug concentrations, while permitting concurrent hyperthermia for more effective tumor cell kill and growth inhibition, is proposed. Drug delivery and hyperthermia are achieved using a hydroxypropyl cellulose (HPC)-grafted porous magnetic drug carrier that is MRI visible to permit in vivo visualization of the biodistribution. These synthesized magnetic drug carriers produce strong T2 -weighted image contrast and permit efficient heating using low-magnetic-field intensities. The thermomechanical response of HPC permits triggered GEM release confirmed during in vitro drug release studies. During in vitro studies, pancreatic cancer cell growth is significantly inhibited (≈82% reduction) with chemohyperthermia compared to chemotherapy or hyperthermia alone. Using PANC-1 xenografts in nude mice, the delivery of injected GEM-loaded magnetic carriers (GEM-magnetic carriers) is visualized with both MRI and fluorescent imaging techniques. Chemohyperthermia with intra-tumoral injections of GEM-magnetic carriers (followed by heating) results in significant increases in apoptotic cell death compared to tumors treated with GEM-magnetic carriers injections alone. Chemohyperthermia with GEM-magnetic carriers offers the potential to significantly improve the therapeutic efficacy of GEM for the treatment of pancreatic cancer. In vivo delivery confirmation with non-invasive imaging techniques could permit patient-specific adjustments therapeutic regimens for improve longitudinal outcomes.

Image-guided local delivery strategies enhance therapeutic nanoparticle uptake in solid tumors.

Nanoparticles (NP) have emerged as a novel class of therapeutic agents that overcome many of the limitations of current cancer chemotherapeutics. However, a major challenge to many current NP platforms is unfavorable biodistribution, and limited tumor uptake, upon systemic delivery. Delivery, therefore, remains a critical barrier to widespread clinical adoption of NP therapeutics. To overcome these limitations, we have adapted the techniques of image-guided local drug delivery to develop nanoablation and nanoembolization. Nanoablation is a tumor ablative strategy that employs image-guided placement of electrodes into tumor tissue to electroporate tumor cells, resulting in a rapid influx of NPs that is not dependent on cellular uptake machinery or stage of the cell cycle. Nanoembolization involves the image-guided delivery of NPs and embolic agents directly into the blood supply of tumors. We describe the design and testing of our innovative local delivery strategies using doxorubicin-functionalized superparamagnetic iron oxide nanoparticles (DOX-SPIOs) in cell culture, and the N1S1 hepatoma and VX2 tumor models, imaged by high resolution 7T MRI. We demonstrate that local delivery techniques result in significantly increased intratumoral DOX-SPIO uptake, with limited off-target delivery in tumor-bearing animal models. The techniques described are versatile enough to be extended to any NP platform, targeting any solid organ malignancy that can be accessed via imaging guidance.

Magnetization transfer MRI in pancreatic cancer xenograft models

Magnetization transfer magnetic resonance imaging measurements were performed in three pancreatic ductal adenocarcinoma mouse xenograft models. For each of 28 pancreatic ductal adenocarcinoma xenografts, MT ratios (MTRs) were calculated and compared to histologic fibrosis levels from reference standard trichrome staining. MTR was found to be significantly higher in tumors grown using BxPC‐3 cell line (39.4 ± 5.1, mean ± SD) compared to the MTR for the tumors grown from Panc‐1 (32.4 ± 2.8) and Capan‐1 (27.3 ± 2.9) cell lines (P < 0.05 for each comparison). Histologic measurements showed a similar trend with BxPC‐3 tumors demonstrating significantly higher fibrosis levels (percentage of fibrotic tissue area, 6.48 ± 2.59) when compared to Panc‐1 (3.54 ± 2.18) and Capan‐1 (2.07 ± 1.60) tumors. MTR measurements were well correlated to quantitative fibrosis levels (r = 0.69, P = 0.01). Results indicated that MTR measurements offer the potential to serve as a valuable in vivo biomarker of desmoplasia in pancreatic ductal adenocarcinoma. Magn Reson Med, 2012.

Multimodality Imaging to Assess Immediate Response to Irreversible Electroporation in a Rat Liver Tumor Model

PURPOSE To compare changes on ultrasonographic (US), computed tomographic (CT), and magnetic resonance (MR) images after irreversible electroporation (IRE) ablation of liver and tumor tissues in a rodent hepatoma model. MATERIALS AND METHODS Studies received approval from the institutional animal care and use committee. Forty-eight rats were used, and N1-S1 tumors were implanted in 24. Rats were divided into groups and allocated for studies with each modality. Imaging was performed in normal liver tissues and tumors before and after IRE. MR imaging was performed in one group before and after IRE after hepatic vessel ligation. US images were graded to determine echogenicity changes, CT attenuation was measured (in Hounsfield units), and MR imaging signal-to-noise ratio (SNR) was measured before and after IRE. Student t test was used to compare attenuation and SNR measurements before and after IRE (P < .05 indicated a significant difference). RESULTS IRE ablation produced greater alterations to echogenicity in normal tissues than in tumors. Attenuation in ablated liver tissues was reduced compared with that in control tissues (P < .001), while small attenuation differences between ablated (42.11 HU ± 2.11) and control (45.14 HU ± 2.64) tumors trended toward significance (P = .052). SNR in ablated normal tissues was significantly altered after IRE (T1-weighted images: pre-IRE, 145.95 ± 24.32; post-IRE, 97.80 ± 18.03; P = .004; T2-weighted images, pre-IRE, 47.37 ± 18.31; post-IRE, 90.88 ± 37.15; P = .023). In tumors, SNR differences before and after IRE were not significant. No post-IRE signal changes were observed after hepatic vessel ligation. CONCLUSION IRE induces rapid changes on gray-scale US, unenhanced CT, and MR images. These changes are readily visible and may assist a performing physician to delineate ablation zones from the unablated surrounding parenchyma.

Electroporation-mediated transcatheter arterial chemoembolization in the rabbit VX2 liver tumor model.

Rationale and Objectives:Electropermeabilization involves the application of electrical pulses to increase cell membrane permeability. The purpose of our study was to demonstrate the potential to use electroporation-mediated transcatheter arterial chemoembolization (E-TACE) approaches to increase liver tumor drug uptake while using magnetic resonance imaging (MRI) for intraprocedural optimization of these procedures. Methods:Fourteen VX2 tumors were grown in the left hepatic lobes of 8 rabbits. Two tumors were grown in each of 6 rabbits (1 tumor serving as E-TACE-treated tumor and the other as nonelectroporated control), and solitary larger tumors were grown in 2 rabbits (half of the tumor treated with E-TACE, remaining half serving as control). Each rabbit was selectively catheterized under digital subtraction angiography guidance. Baseline MRI was performed to generate tumor contrast enhancement curves following catheter-directed infusion of gadopentetate dimeglumine to estimate the proper time delay between subsequent bolus infusion of cisplatin and application of electrical pulses (electrodes were used to deliver 8, 100-&mgr;s, 1300-V pulses at the selected delay interval postinfusion). Three hours after E-TACE, rabbits were euthanized, and tumors were sectioned for inductively coupled plasma mass spectroscopy measurements of platinum concentration (serving as reference standard of cisplatin uptake levels). Results:Inductively coupled plasma mass spectroscopy results demonstrated significantly increased cisplatin uptake in E-TACE-treated tumor tissues, increases of 6.0 ± 3.3-fold compared with transcatheter infusion alone (P = 0.017). Conclusions:Our findings suggest that our E-TACE approach may significantly increase liver tumor drug uptake after targeted transcatheter infusion. MRI measurements permitted intraprocedural guidance during these catheter-directed E-TACE procedures.

Quantitative magnetization transfer MRI of desmoplasia in pancreatic ductal adenocarcinoma xenografts

Quantitative assessment of desmoplasia in pancreatic ductal adenocarcinoma (PDAC) may be critical for staging or prediction of response to therapy. We performed quantitative magnetization transfer (qMT) MRI measurements in 18 mouse xenograft tumors generated from three PDAC cell lines. The qMT parameter bound proton fraction (BPF) was found to be significantly higher in tumors grown using the BxPC‐3 cell line (5.31 ± 0.87, mean ± standard deviation) compared with the BPF measured for tumors grown from Panc‐1 (3.65 ± 0.60) and Capan‐1 (1.50 ± 0.58) cell lines (P < 0.05 for each comparison). Histologic measurements demonstrated a similar trend; BxPC‐3 tumors had significantly higher fibrosis levels (percentage of fibrotic tissue area, 6.21 ± 2.10) compared with Panc‐1 (2.88 ± 1.13) and Capan‐1 (1.69 ± 1.01) tumors. BPF was well correlated with quantitative fibrosis levels (r = 0.77, P < 0.01). Our results indicate that qMT measurements offer the potential to noninvasively quantify fibrosis levels in PDAC mouse xenograft models and thus serve as a valuable in vivo biomarker of desmoplasia in PDAC. Copyright

Gas challenge-blood oxygen level-dependent (GC-BOLD) MRI in the rat Novikoff hepatoma model.

PURPOSE The purpose of the study was to investigate the relationship between gas challenge-blood oxygen level-dependent (GC-BOLD) response angiogenesis and tumor size in rat Novikoff hepatoma model. MATERIALS AND METHODS Twenty adult male Sprague-Dawley rats (weighting 301-325 g) were used for our Animal Care and Use Committee-approved experiments. N1-S1 Novikoff hepatomas were grown in 14 rats with sizes ranging from 0.42 to 2.81 cm. All experiments were performed at 3.0 T using a custom-built rodent receiver coil. A multiple gradient-echo sequence was used for R2* measurements, first during room air (78% N(2)/20% O(2)) breathing and then after 10 min of carbogen (95% O(2)/5% CO(2)) breathing. After image acquisition, rats were euthanized, and the tumors were harvested for histological evaluation. RESULTS The R2* change between air and carbogen breathing for small hepatomas was positive; R2* changes changed to negative values for larger hepatomas. We found a significant positive correlation between tumor R2* change and tumor microvessel density (MVD) (r=0.798, P=.001) and a significant inverse correlation between tumor R2* change and tumor size (r=-0.840, P<.0001). CONCLUSIONS GC-BOLD magnetic resonance imaging measurements are well correlated to MVD levels and tumor size in the N1-S1 Novikoff hepatoma model; GC-BOLD measurements may serve as noninvasive biomarkers for evaluating angiogenesis and disease progression and/or therapy response.

Seven-tesla magnetic resonance imaging accurately quantifies intratumoral uptake of therapeutic nanoparticles in the McA rat model of hepatocellular carcinoma: Preclinical study in a rodent model

ObjectivesAfter inducing McA tumors in Sprague-Dawley rats (McA-SD), the following hypotheses were tested: first, that hypervascular McA tumors grown in Sprague-Dawley rats provide a suitable platform to investigate drug delivery; and second, that high-field MRI can be used to measure intratumoral uptake of DOX-SPIOs. Materials and MethodsMcA cells were implanted into the livers of 18 Sprague-Dawley rats. In successfully inoculated animals, 220-&mgr;L DOX-SPIOs were delivered to tumors via the intravenous or intra-arterial route. Pretreatment and posttreatment T2*-weighted images were obtained using 7-T MRI, and change in R2* value (&Dgr;R2*) was obtained from mean signal intensities of tumors in these images. Tumor iron concentration ([Fe]), an indicator of DOX-SPIO uptake, was measured using mass spectroscopy. The primary outcome variable was the Pearson correlation between &Dgr;R2* and [Fe]. ResultsTumors grew successfully in 13 of the 18 animals (72%). Mean (SD) maximum tumor diameter was 0.83 (0.25) cm. The results of phantom studies revealed a strong positive correlation between &Dgr;R2* and [Fe], with r = 0.98 (P < 0.01). The results of in vivo drug uptake studies demonstrated a positive correlation between &Dgr;R2* and [Fe], with r = 0.72 (P = 0.0004). ConclusionsThe McA tumors grown in the Sprague-Dawley rats demonstrated uptake of nanoparticle-based therapeutic agents. Magnetic resonance imaging quantification of intratumoral uptake strongly correlated with iron concentrations in pathological specimens, suggesting that MRI may be used to quantify uptake of iron-oxide nanotherapeutics.

SPIO-labeled Yttrium Microspheres for MR Imaging Quantification of Transcatheter Intrahepatic Delivery in a Rodent Model.

PURPOSE To investigate the qualitative and quantitative impacts of labeling yttrium microspheres with increasing amounts of superparamagnetic iron oxide (SPIO) material for magnetic resonance (MR) imaging in phantom and rodent models. MATERIALS AND METHODS Animal model studies were approved by the institutional Animal Care and Use Committee. The r2* relaxivity for each of four microsphere SPIO compositions was determined from 32 phantoms constructed with agarose gel and in eight concentrations from each of the four compositions. Intrahepatic transcatheter infusion procedures were performed in rats by using each of the four compositions before MR imaging to visualize distributions within the liver. For quantitative studies, doses of 5, 10, 15, or 20 mg 2% SPIO-labeled yttrium microspheres were infused into 24 rats (six rats per group). MR imaging R2* measurements were used to quantify the dose delivered to each liver. Pearson correlation, analysis of variance, and intraclass correlation analyses were performed to compare MR imaging measurements in phantoms and animal models. RESULTS Increased r2* relaxivity was observed with incremental increases of SPIO microsphere content. R2* measurements of the 2% SPIO-labeled yttrium microsphere concentration were well correlated with known phantom concentrations (R(2) = 1.00, P < .001) over a broader linear range than observed for the other three compositions. Microspheres were heterogeneously distributed within each liver; increasing microsphere SPIO content produced marked signal voids. R2*-based measurements of 2% SPIO-labeled yttrium microsphere delivery were well correlated with infused dose (intraclass correlation coefficient, 0.98; P < .001). CONCLUSION MR imaging R2* measurements of yttrium microspheres labeled with 2% SPIO can quantitatively depict in vivo intrahepatic biodistribution in a rat model.