Breast cancer detection using high-density flexible electrode arrays and electrical impedance tomography.

While mammography remains the gold standard for breast cancer screening, additional adjunctive tools for early detection of breast cancer are needed especially for young women, women with dense breast tissue and those at increased risk due to genetic factors. These patient populations, along with those populations for whom mammography is not readily available, require alternative technologies capable of effectively detecting breast cancer. One such adjunctive modality for breast cancer detection is Electrical Impedance Tomography (EIT). It is a non-invasive technique that measures tissue conductivity by injecting a small current through a surface electrode while measuring electrode voltage(s). The surface measurements are then used to reconstruct a conductivity mapping of the tissue. The difference in conductivities between healthy tissue and that of carcinoma enable EIT to detect cancer. Electrical Impedance Tomography does not subject the patient to ionizing radiation, and offers significant potential for detecting very small tumors in early stages of development at a low cost. While prior systems have demonstrated success using EIT for breast cancer detection, the resolution of the reconstructed image was limited by the spatial resolution of the sensing electrode array. Here, we report the use of higher density (3mm spacing) flexible micro-electrode arrays to obtain tissue impedance maps. Accurate EIT reconstruction is highly dependent on the spatial resolution and fidelity of the surface measurements. High-density, flexible arrays that conform to the breast surface can offer great potential in reconstructing higher resolution conductivity maps than have been previously achieved.

Label-free detection of single protein using a nanoplasmonic-photonic hybrid microcavity.

Recently we reported the detection and sizing of the smallest RNA virus MS2 with a mass of 6 ag from the resonance frequency shift of a whispering gallery mode-nanoshell hybrid resonator (WGM-h) upon adsorption on the nanoshell and anticipated that single protein above 0.4 ag should be detectable but with considerably smaller signals. Here, we report the detection of single thyroid cancer marker (Thyroglobulin, Tg) and bovine serum albumin (BSA) proteins with masses of only 1 ag and 0.11 ag (66 kDa), respectively. However, the wavelength shifts are enhanced beyond those anticipated in our earlier work by 240% for Tg and 1500% for BSA. This surprising sensitivity is traced to a short-range reactive field near the surface of our Au nanoshell receptor due to intrinsic random bumps of protein size, leading to an unanticipated increase in sensitivity to single protein, which grows larger as the protein diminishes in size. As a consequence of the largest signal-to-noise ratio in our BSA experiments (S/N ≈ 13), we conservatively estimated a new protein limit of detection for our WGM-h of 5 kDa.

Periodic plasmonic enhancing epitopes on a whispering gallery mode biosensor.

We propose the attachment of a periodic array of gold nanoparticles (epitopes) to the equator of a Whispering Gallery Mode Biosensor for the purpose of plasmonically enhancing nanoparticle sensing in a self-referencing manner while increasing the capture rate of analyte to antibodies attached to these plasmonic epitopes. Our approach can be applied to a variety of whispering gallery mode resonators from silicon/silica rings and disks to capillaries. The interpretation of the signals is particularly simple since the optical phase difference between the epitopes is designed to be an integer multiple of ?, allowing the wavelength shift from each binding event to add independently.