We study the effect of functionalization of Carbon Nanotubes (CNTs) with a primary monoclonal mouse immunoglobin G (IgG) specific to the cell-surface receptors of breast cancer cells, and secondary polyclonal goat ant- mouse IgG. The CNTs, in solution with a surfactant (sodium dodecyl benzene sulfonate) were labeled with dihexyloxacarbocyanine iodide (DiOC6), a fluorescent dye, in order to view them with fluorescently labeled antibodies through confocal microscopy. Co-localization for CNTs in combination with the primary antibody conjugated to the secondary was determined to be 90%, whereas CNTs in combination with the secondary antibody and polyethylene glycol (PEG), a polymer used to block CNTs from proteins binding to their surface, was found to be very minimal (0.5%). Preliminary studies on the electrical measurements of the primary mouse IgG incubated with CNTs show a decrease in conductance compared to that of bare CNT field effect transistors (CNTFETs). This observed change in conductance, can eventually be amplified and utilized in applications leading to a full-fledged breast cancer detection system in the future.