光電所所訊

Cancer Cell Uptake Behavior of Au Nanoring and Its Localized Surface Plasmon Resonance Induced Cell Inactivation

Professor C. C. (Chih-Chung) Yang

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

臺灣大學光電所楊志忠教授

Au nanorings (NRIs), which have the localized surface plasmon resonance (LSPR) wavelength around 1058 nm, either with or without linked antibodies, are applied to SAS oral cancer cells for cell inactivation through the LSPR-induced photothermal effect when they are illuminated by a laser of 1065 nm in wavelength. Different incubation times of cells with Au NRIs are considered for observing the variations of cell uptake efficiency of Au NRI and the threshold laser intensity for cell inactivation. In each case of incubation time, cell sample is washed for evaluating the total Au NRI number per cell adsorbed and internalized by the cells based on inductively coupled plasma mass spectrometry measurement. Also, the Au NRIs remaining on cell membrane are etched with KI/I₂ solution to evaluate the internalized Au NRI number per cell. The threshold laser intensities for cell inactivation before washout, after washout, and after KI/I₂ etching are calibrated from the circular area sizes of inactivated cells around the illuminated laser spot center with various laser power levels. By using Au NRIs with antibodies (NRI-AB), the internalized Au NRI number per cell increases monotonically with incubation time up to 24 hrs. However, the number of Au NRI remaining on cell membrane reaches a maximum at 12 hrs in incubation time. The cell uptake behavior of an Au NRI without antibodies (NRI-control) is similar to that with antibodies except that the uptake NRI number is significantly smaller and the incubation time for the maximum NRI number remaining on cell membrane is delayed to 20 hrs. By comparing the threshold laser intensities before and after KI/I₂ etching, it is found that the Au NRIs remaining on cell membrane cause more effective cancer cell inactivation, when compared with the internalized Au NRIs.


Fig. 1 Normalized extinction spectrum of the fabricated Au NRIs in PBS. The inset shows the SEM image of the Au NRIs before liftoff.
Fig. 2 (a)-(d): Microscopic images of cells after laser illumination with the laser powers of 230, 200, 200, and 180 mW, respectively, under the pre-washout condition when NRI-AB is applied to the cells and the incubation time is 16 hrs. (e)-(h) and (i)-(l): Corresponding microscopic images under the post-washout and after-etching conditions, respectively.


Fig. 3 Threshold laser intensities under the pre-washout, post-washout, and after-etching conditions for various incubation times when NRI-AB is applied to the cells.
Fig. 4 Threshold laser intensities similar to those in Fig.3 when NRI-control is applied to the cells.

Enhancements of the emission and light extraction of a radiating dipole coupled with localized surface plasmon induced on a surface metal nanoparticle in a light-emitting device

Professor Y. W. Kiang’s Laboratory

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

臺灣大學光電所江衍偉教授

The radiated power enhancement and more congregated radiation of a radiating dipole within a GaN material when it is coupled with the localized surface plasmon (LSP) resonance modes induced on a surface Ag nanoparticle (NP) are numerically demonstrated. The numerical study is based on an algorithm including the induction of LSP resonance on the Ag NP by the source dipole and the feedback effect of the LSP resonance field on the source dipole behavior. The spectral peaks of radiated power enhancement correspond to the substrate LSP resonance modes with mode fields mainly distributed around the bottom of the Ag NP such that the coupling system radiates mainly into the GaN half-space. By moving the radiating dipole laterally away from the bottom of the Ag NP, the spectral peaks of radiated power enhancement red shift and their levels diminish with increasing lateral distance. The radiation patterns in the GaN half-space show more congregated radiation around the vertical direction, indicating that the light extraction efficiency can be enhanced in an LSP-coupled light-emitting device with surface metal NPs.

Fig. 1 Demonstration of the problem geometry, in which an Ag NP is placed on the surface of a thick GaN layer with an embedded thin QW layer at the depth of d. A radiating dipole, which is represented by a thick (red) arrow, is located in the QW layer.

Fig. 2 Normalized downward radiated powers of the NP-dipole coupling system as functions of wavelength for d = 30, 50, 70, 90, and 120 nm when the dipole is located exactly below the Ag NP, i.e., at x = 0. The Ag NP is surrounded by air in the upper-half-space. For comparison, the result in the case of no Ag NP at the air/GaN interface with d = 70 nm is also plotted as the dashed curve.