Sensitive and Rapid Cancer Diagnosis with Immunoplasmonic Assay Based on Plasmonic Nanoparticles: Toward Fine-Needle Aspiration Cytology

Fine-needle aspiration cytology is a minimally invasive diagnostic strategy. However, collected specimens have to undergo a series of complex preparation steps, thus limiting the use of fine-needle aspiration cytology as a diagnostic approach for cytopathologists. In this study, we propose a cytology approach, easily adaptable to the conventional one, by employing plasmonic biomarkers (gold(red_scattering), silver/gold(blue_scattering), and silver/gold(green_scattering) nanoparticles), each having a well-defined optical feature. Plasmonic nanoparticles, incubated with the suspension cells, are fully visible and differentiable on the cell membranes under the darkfield lateral RGB (red–green–blue) side-illumination microscopy. The postfabrication of plasmonic nanoparticles by the conjugation of a specific antibody (antihuman epidermal growth factor receptor 2, HER2) directly allows to visualize the selectively recognized antigens of the suspension cells (MDA-MB-453++HER2 and Jurkat–HER2) in cocultures and individual cultures by using the side-illumination compared to the conventional dark-field visualization protocol. We also incubate two cancer cell lines (trypsinized MDA-MB-231++CD44 and MDA-MB-453++HER2) with anti-CD44 and anti-HER2 functionalized plasmonic nanoparticles, and nanoimmunoplasmonic and immunofluorescence assays show a good agreement with each other for the recognition of expressed antigens (CD44 and HER2). Our results demonstrate a remarkable potential of plasmonic nanoparticles for a simple and rapid examination of small population of cells from collected specimens by using nanoimmunoplasmonic approach and the side-illumination microscopy.