Week 7

This week our team continued to work with COMSOL and conduct research related to our project. We also finalized our budget.  A summary of some of the research and what we learned from it can be found below, as well as examples of our COMSOL modeling.

• Circulating Tumor cells (CTCs) can be found in peripheral blood in billions of White blood cells and red blood cells before the first tumor can be detected by current method of diagnosing
• The number of CTCs in blood from a cancer patient may range from 0-50 mL^-1; that is 0 to 50 CTCs in 10 billion blood cells
• Due to this rarity the existing separation methods lack the ability to separate CTCs from whole blood.
• The ratio of cancer cells to blood cells (WBCs and RBCs) is 1:10,000,000.  

Commonly used method:

• Usually magnetic microbeads(microparticles) are used, but due to their low surface to volume ratio causing low binding capacity and low efficiency.
• Changing from micron to nano increases the available adsorptive areas by 100 to 1000 times
• The r(x) between microparticles and target cells is a quasi-heterogeneous reaction- hence, the microbeads generally take longer time to capture the target cells in the suspensions
• Microbeads are not stable in whole blood forming aggregation or precipitation, thereby, leading to inefficient separation
• magnetic microbeads are generally not efficient for the separation of target cells in whole blood because of high viscosity, high cell density, high protein content, and its generally complex composition preventing efficient contact the cell surface antigen 
• The magnetic separation of the CTCs is limited by aggregation when many microbeads accumulate on the cells. Once aggregated, cell detection becomes difficult especially with flow cytometry, because the size of the aggregated cells that are captured with the microbeads affect light scattering
• Complicated pretreatment of blood such as dilution with buffers, centrifugation to get the buffy coat, and lysis of the RBCs, are necessary for the successful application of these magnetic microbeads. These pretreatment processes can destroy the cells decreasing the cell density and at the same time, decreasing the number of CTCs making the detection more difficult.

Conclusions Drawn:

• We need to use the smaller size magnetic particles- for exmple- 30nm
• Know the crystallinity of our nanoparticles
• The nanopartciles must be conjugated with the Antibody specific to the protein expressed on the Cancer cells.  For example: HER2 is a cell membrane protein that is over expressed in several types of human cancer cells
• What can be used to identify binding between nanoparticles bound with antibodies and CTCs? - Prussian blue staining was used to exhibit specific attachment to the cell surface

References:

Xu, H., Aguilar, Z. P., Yang, L., Kuang, M., Duan, H., Xiong, Y., … Wang, A. (2011). Antibody Conjugated Magnetic Iron Oxide Nanoparticles for Cancer Cell Separation in Fresh Whole Blood. Biomaterials, 32(36), 9758–9765. http://doi.org/10.1016/j.biomaterials.2011.08.076

Tumor Cells Circulate in the Peripheral Blood of All Major Carcinomas but not in Healthy Subjects or Patients With Nonmalignant Diseases
W. Jeffrey Allard, Jeri Matera, M. Craig Miller, Madeline Repollet, Mark C. Connelly, Chandra Rao, Arjan G. J. Tibbe, Jonathan W. Uhr and Leon W. M. M. Terstappen
Clin Cancer Res October 15 2004 (10) (20) 6897-6904; DOI: 10.1158/1078-0432.CCR-04-037

COMSOL: