Multimodal optical microscopy in combination with gold nanorods for cancer cell imaging

Abstract

Abstract. The multimodal optical imaging technique, which utilizes nonlinear and linear optical processes, plays an important role in biological and biomedical research. As second-order nonlinear phenomenon, the two-photon luminescence (TPL) results from the nonlinear excitation of fluorescent molecules, while the second harmonic generation (SHG) depends on the second order nonlinear polarization, orientation, and noncentrosymmetric properties of molecules. In contrast, the linear resonance light scattering (RLS) occurs when the molecules are excited by a light beam with a wavelength close to their absorption bands. Since SHG, TPL, and RLS involve different kinds of optical processes, they might be used in parallel to provide complementary information about the structure and function of cells and tissues. Herein, we develop for the first time a multimodal optical microscopy with the capability of simultaneous SHG, TPL, and RLS imaging. We analyze theoretically and demonstrate experimentally the near-infrared irradiation-induced SHG, TPL, and RLS from the gold nanorods with nanometer spatial resolution. With the gold nanorods as the contrast agents, we further demonstrate the simultaneous SHG, TPL, and RLS imaging of A431 human epithelial skin cancer cells. This multimodal optical microscopy might provide a reliable and complementary approach for biological and biomedical research.

Tannic Acid Coated Gold Nanorods Demonstrate a Distinctive Form of Endosomal Uptake and Unique Distribution within Cells

“…Recently, engineered nanomaterials (NMs) have attracted significant attention due to their innate potential to progress the development of new technologies and increase effectiveness of current biological-based applications, including drug delivery, − bioimaging techniques, − and the development of therapeutic agents. − Due to its perceived inertness, reproducible synthesis procedures, and ease of functionalization, nanogold has demonstrated itself to be an optimal material for these applications. , In particular, gold nanorods (GNRs) possess a number of shape-specific advantages over nanospheres and other morphologies, including an enhanced surface area and tunable optical properties. , It is well established that the spectral signature of GNRs extends into the near-infrared (NIR) region, making them an ideal candidate for nanobased applications as biological tissue possesses minimal absorbance in the NIR range. , Through targeted modification of the GNR size, their dependent optical properties can be precisely tuned, thus creating a mechanism that allows for design of a particle with specific optical properties for a specific function . Additionally, owing to the distinctive composition, shape, and size of GNRs, they display an augmented plasmonic effect, producing a high degree of light scattering that adds to their attractiveness for bioimaging and sensor development techniques …”