Gold nanoparticle mediated detection of prostate cancer cells using photoacoustic flowmetry with optical reflectance

The presence of circulating tumor cells in the bloodstream has been correlated with disease state in cancer patients. While we have successfully exploited melanin, the natural light absorber in melanoma cells, to induce photoacoustic waves for tumor cell detection, non-pigmented tumor cells do not have sufficient optical contrast for such a method. For example, breast, prostate and lung cancers lack intrinsic pigmentation and thus do not generate photoacoustic waves. In order to induce optical contrast in non-pigmented cancer cells, we have attached gold nanoparticles to a prostate cancer cell line. This optical absorption will enable us to detect such cells in a photoacoustic flowmeter designed to find circulating tumor cells in blood samples. We tested a prostate cancer cell line, PC-3, by tagging them with gold nanoparticles. We determined the photoacoustic response over the wavelengths 470-570 nm to identify the absorption peak. We then determined the response from serial dilutions of PC-3 cells suspended in saline. Finally, we showed photoacoustic response from PC-3 cells suspended among white blood cells in the flow meter to demonstrate our ability to detect single cells under flow.