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Spatial Measurements of Perfusion, Interstitial Fluid Pressure and Liposomes Accumulation in Solid Tumors

Published: August 18th, 2016



1Department of Medical Biophysics, University of Toronto, 2Leslie Dan Faculty of Pharmacy, University of Toronto, 3STTARR Innovation Centre, Princess Margaret Cancer Centre, 4Institute of Biomaterials and Biomedical Engineering, University of Toronto, 5Techna Institute, University Health Network, 6Radiation Medicine Program, Princess Margaret Cancer Centre

The heterogeneous intra-tumoral accumulation of liposomes has been linked to an abnormal tumor microenvironment. Herein methods are presented to measure tumor microcirculation by perfusion imaging and elevated interstitial fluid pressure (IFP) using an image-guided robotic system. Measurements are compared to the intra-tumoral accumulation of liposomes, determined using volumetric micro-CT imaging.

The heterogeneous intra-tumoral accumulation of liposomes is a critical determinant of their efficacy. Both the chaotic tumor microcirculation and elevated IFP are linked to the heterogeneous intra-tumoral distribution of nanotechnology-based drug delivery systems such as liposomes. In the present study, the relationship between tumor microcirculation, elevated IFP, and accumulation of nanoparticles was investigated through in vivo experimentation. This was accomplished by evaluation of the tumor microcirculation using dynamic contrast enhanced computed tomography (DCE-CT) and measurement of tumor IFP using a novel image-guided robotic needle placement system connected to the micro-CT scanner. The intra-tumoral accumulation of liposomes was determined by CT image-based assessment of a nanoparticle liposomal formulation that stably encapsulate the contrast agent iohexol (CT-liposomes). CT imaging allowed for co-localization of the spatial distribution of tumor hemodynamics, IFP and CT-liposome accumulation in an individual subcutaneous xenograft mouse model of breast cancer. Measurements led to the discovery that perfusion and plasma volume fraction are strong mediators of the intra-tumoral distribution of liposomes. Furthermore, the results suggest that IFP plays an indirect role in mediating liposome distribution through modulating blood flow.

Measuring the intra-tumoral accumulation of nanoparticle drug delivery systems may provide an important tool to determine if an adequate concentration of cytotoxic drug has been achieved within the tumor. The development of "image-able" liposomal systems allows for non-invasive and quantitative in vivo detection of the drug delivery vehicle using imaging modalities such as positron emission tomography (PET)1, optical fluorescence2, and computed tomography (CT)3,4 and magnetic resonance imaging (MRI)5. Imaging has been used to determine the pharmacokinetics and biodistribution of liposome delivery systems and....

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All in vivo experiments were performed under a protocol approved by the University Health Network Institutional Animal Care and Use Committee.

1. Animal Model

  1. Culture between 5 to 7 x 106 MDA-MB-231 breast adenocarcinoma tumor cells in DMEM together with 10% Fetal Bovine Serum (FBS) and 100x dilution of penicillin-streptomycin.
  2. Harvest cells when they are 80% confluent using a 0.05% trypsin-EDTA solution. After 3-5 min neutralize trypsin-EDTA .......

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The aforementioned protocol should yield CT-liposomes with an encapsulated concentration of iohexol, mean liposome diameter, and zeta potential of 55 mg ml-1, 91.8 ± 0.3 nm and -45.5 ± 2.5 mV, respectively. Figure 1a includes representative DCE-CT imaging results, yielding a time series of volumetric data that show the temporal changes in intra-tumoral accumulation of iohexol. Selecting a ROI within the tumor yields a TIC that can be quantified using .......

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The methods for image-based measurement presented herein enable determination of the spatial distribution of tumor microcirculation properties, IFP, and CT-liposome accumulation. Previous attempts to relate these properties have relied on performing bulk measurements across multiple tumor-bearing animals and therefore lack the sensitivity to elucidate mechanisms responsible for heterogeneity in intra-tumoral accumulation that has commonly been observed for nano-sized drug delivery systems15. DCE-CT provides a .......

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The authors would like to thank Dr. Javed Mahmood for assistance with culturing MDA-MB-231 cells and implanting the MDA-MB-231 xenografts, Linyu Fan for preparing the CT-liposomes. Shawn Stapleton is grateful for funding from the Natural Sciences and Engineering Research Postgraduate Scholarships Program and the Terry Fox Foundation Strategic Initiative for Excellence in Radiation Research for the 21st Century (EIRR21) at CIHR. This study was supported by grants from the Terry Fox New Frontiers Program (020005) and the Canadian Institutes of Health Research (102569).


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Name Company Catalog Number Comments
MDA-MB-231 metastatic breast adenocarcinoma tumor cells  ATCC HTB-26
Dulbecco's Modified Eagle Medium (DMEM)  Life Technologies 11965-092
Fetal Bovine Serum (FBS) Sigma-Aldrich F1051
HyClone Penicillin-Streptomycin 100x Solution GE Healthcare Life Sciences SV30010
Trypsin-EDTA (0.05%), phenol red ThermoFisher Scientific 25300-054
1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) Avanti Lipids Inc., USA 850355P
Cholesterol (CH) Avanti Lipids Inc., USA 700000P
1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-poly(ethylene glycol) 2000 (DSPE-PEG2000) Avanti Lipids Inc., USA 880128P
Omnipaque (Iohexol) 300 mg of iodine/mL  GE Healthcare, CA
80 nm pore size Track-Etch polycarbonate membranes Whatman Inc., USA
200 nm pore size Track-Etch polycarbonate membranes Whatman Inc., USA
10 mL Lipex Extruder  Nothern Lipids Inc, CA
Dialysis Bag Molecular Weight Cut Off (MWCO) of 8 kDa Spectrum Labs, USA 
750,000 Nomical Molecular Weight Cut Off (NMWC) Tangential flow column  MidGee ultrafiltration cartridge, GE Healthcare, CA
Peristaltic pump  Watson Marlow Inc., USA
UV spectrometer Helios γ, Spectronic Unicam,  USA
90Plus particle size analyzer  Brookhaven, Holtsville, USA
eXplore Locus Ultra micro-CT system  GE Healthcare, CA Manipulated using CT-Console Software
AxRecon GPU-based Reconstruction  Acceleware Corp. CA
27G Catheter SURFLO Winged Infusion Set Terumo Medical Products, USA SV*27EL
PE20 polyethylyne tubing Becton Dickinson, USA 427406
Pen tip 25G × 3.5′′ Whitacre spinal needle  Becton Dickinson, USA 405140 IFP needle
P23XL  pressure transducer  Harvard Apparatus, CA P23XL
PowerLab 4/35, Bridge Amp, with LabChart Pro 7.0 ADInstruments Pty Ltd., USA PL3504, FE221 IFP acquisition system and acquisition software
CT-Sabre Small Animall Intervention system (CT-IFP Robot) Parallax Innovations, CA Manipulated using CT-IFP robot Control Software
CT-IFP robot alignment software Custom Matlab software
DCE-CT Analysis Software Custom Matlab software
Matlab 2013b Mathworks, USA

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