We report progress on performing a cell-based assay for the detection of EGFR on cell surfaces by using upconverting chelates. An upconversion microscope has been developed for performing assays and testing optical response. A431 cells are labeled with europium DOTA and imaged using this upconverting microscope.
We have studied the dynamic changes in tissue vasculature following the inhalation of hyperoxic gasses in rodents as a model for optical breast cancer detection. We have used a CW apparatus to measure the near infrared (NIR) optical properties of animal models immersed in a liquid tissue phantom. By looking at the transmission of different wavelengths in the NIR, we were able to qualitatively observe changes in blood oxygenation following the inhalation of different mixtures of CO<sub>2</sub> and O<sub>2</sub>. These changes enhanced the image contrast between cancerous tissue and normal tissues of the rodents. The oxygenation dynamics of the tumors, following inhalation of the hyperoxic gases, exhibited differences from surrounding tissues in both the magnitude of the observed signal change and the dynamic response.
We demonstrate a novel method for the control of small droplets using laser-based heating. Temperature dependent interfacial surface tensions were the primary force used to move droplets. With this approach, ~1.7 μL to 14 pL droplets were moved on a bare, unmodified polystyrene surface, at speeds of up to 3 mm/s. Upon contact, droplets spontaneously fused and rapidly mixed within 33 ms. We performed an optical absorption-based protein assay using horseradish peroxidase and a chromogenic substrate (ABTS), and readily detected as little as ~125 attomoles of reacting enzyme.
We are using rodent animal models to study and compare contrast mechanisms for detection of breast cancer. These measurements are performed with the animals immersed in a matching scattering medium. The matching scattering medium or liquid tissue phantom comprises a mixture of Ropaque (hollow acrylic/styrene microspheres) and ink. We have previously applied matched imaging to imaging in humans. Surrounding the imaged region with a matched tissue phantom compensates for variations in tissue thickness and geometry, provides more uniform illumination, and allows better use of the dynamic range of the imaging system. If the match is good, the boundaries of the imaged region should almost vanish, enhancing the contrast from internal structure as compared to contrast from the boundaries and surface topography. For our measurements in animals, the immersion plays two additional roles. First, we can readily study tumors through tissue thickness similar to that of a human breast. Although the heterogeneity of the breast is lost, this is a practical method to study the detection of small tumors and monitor changes as they grow. Second, the immersion enhances our ability to quantify the contrast mechanisms for peripheral tumors on the animal because the boundary effects on photon migration are eliminated. We are currently developing two systems for these measurements. One is a continuous-wave (CW) system based on near-infrared LED illumination and a CCD (charge-coupled device) camera. The second system, a frequency domain system, can help quantify the changes observed with the CW system.