Two-Photon Tracer for Human Epidermal Growth Factor Receptor-2: Detection of Breast Cancer in a Live Tissue

We have developed a two-photon fluorescent tracer (Pyr-affibody) that shows high selectivity for human epidermal growth factor receptor-2 (HER-2). Pyr-affibody showed absorption and emission maxima at 439 and 574 nm, respectively, with a two-photon absorption cross-section value of 40 × 10^–50 cm⁴s/photon (GM) at 750 nm in aqueous buffer solution. The effective two-photon action cross-section value measured in HeLa cells was 600 GM at 730 nm, a value sufficient to obtain bright two-photon microscopy (TPM) images. Using Pyr-affibody, it was possible to detect HER-2 overexpressing cells and breast cancers at a depth of 90–130 μm in live mouse tissue by TPM

Two-Photon Probes for pH: Detection of Human Colon Cancer using Two-Photon Microscopy

We have developed two-photon (TP) pH-sensitive probes (BH-2 and BHEt-1) that exhibit absorption and emission maxima at 370 and 466 nm, and TP absorption cross-section values of 51 and 61 GM (1 GM = 10^–50cm⁴s/photon), respectively, at 750 nm and pH 3.0 in a universal buffer (0.1 M citric acid, 0.1 M KH₂PO₄, 0.1 M Na₂B₄O₇, 0.1 M Tris, 0.1 M KCl)/1,4-dioxane (7/3) solution. The TPM images of CCD-18co (a normal colon cell line) and HCT116 cells (a colon cancer cell line) labeled with BH-2 were too dim to be distinguished. When the same cells were labeled with BHEt-1, however, the TPM image of the HCT116 cells was much brighter than that of CCD-18co cells, and the relative proportion of the acidic vesicles (<i>P</i>_acid) of the former was 5-fold larger than that of latter. BHEt-1 could also differentiate HepG2 cells (a human liver cancer cell line) from LX-2 cells (a human hepatic stellate cell line) with a 6-fold larger <i>P</i>_acid value. Human colon cancer tissues labeled with BHEt-1 showed similar results, demonstrating much brighter TPM images and 6-fold larger <i>P</i>_acid values compared to normal tissue. These results suggest the potential utility of BHEt-1 for detecting colon cancer in human tissues using TPM