(Invited) Developing Short-Wave Infrared Fluorescent Immunoprobes Based on Single-Walled Carbon Nanotubes

Progress will be reported on a project to develop a new type of fluorescent immunoprobe containing antibodies conjugated to structurally sorted single-walled carbon nanotubes (SWCNTs). The (n,m)-sorted SWCNTs display sharp and distinct fluorescence at wavelengths in the short-wave infrared (SWIR) region, allowing effective spectral multiplexing and minimal interference from autofluorescence backgrounds. To avoid fluorescence quenching from covalent functionalization of nanotube sidewalls, the antibodies are linked to PEG side chains of a phospholipid surfactant that noncovalently coats individualized SWCNTs. We are preparing SWCNT-based immunoprobes containing the OC125 antibody, which binds specifically to the CA125 ovarian cancer biomarker. SWIR fluorescence microscopy is being used to assess specificity of binding to cultured ovarian cancer cells. We will also describe new developments that aid in the testing of SWCNT-based probes. One is a custom optical apparatus that scans specimens in two dimensions to sensitively measure SWIR fluorescence spectra as a function of position. The device is used to read dot blots of selected antigens spotted onto a cellulose membrane and probed by SWCNT-conjugated antibodies. Using this approach, one can quickly and quantitatively assess efficiencies of SWCNT conjugation and antigen binding.