Combination of photothermal and photodynamic inactivation of cancer cells through surface plasmon resonance of a gold nanoring.

We demonstrate effective inactivation of oral cancer cells SAS through a combination of photothermal therapy (PTT) and photodynamic therapy (PDT) effects based on localized surface plasmon resonance (LSPR) around 1064 nm in wavelength of a Au nanoring (NRI) under femtosecond (fs) laser illumination. The PTT effect is caused by the LSPR-enhanced absorption of the Au NRI. The PDT effect is generated by linking the Au NRI with the photosensitizer of sulfonated aluminum phthalocyanines (AlPcS) for producing singlet oxygen through the LSPR-enhanced two-photon absorption (TPA) excitation of AlPcS. The laser threshold intensity for cancer cell inactivation with the applied Au NRI linked with AlPcS is significantly lower when compared to that with the Au NRI not linked with AlPcS. The comparison of inactivation threshold intensity between the cases of fs and continuous laser illuminations at the same wavelength and with the same average power confirms the crucial factor of TPA under fs laser illumination for producing the PDT effect.

Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition.

To achieve green emission from the sidewall non-polar quantum wells (QWs) of a GaN nanorod (NR) light-emitting diode, regularly patterned InGaN/GaN QW NR arrays are grown under various growth conditions of indium supply rate, QW growth temperature, and QW growth time for comparing their emission wavelength variations of the top-face c-plane and sidewall m-plane QWs based on photoluminescence and cathodoluminescence (CL) measurements. Although the variation trends of QW emission wavelength by changing those growth conditions in the NR structure are similar to those in the planar structure, the emission wavelength range of the QWs on an NR is significantly shorter than that in a planar structure under the same growth conditions. Under the growth conditions for a longer NR QW emission wavelength, the difference of emission wavelength between the top-face and sidewall QWs is smaller. Also, the variation range of the emission wavelength from the sidewall QWs over different heights on the sidewall becomes larger. On the other hand, strain state analysis based on transmission electron microscopy is undertaken to calibrate the average QW widths and average indium contents in the two groups of QW of an NR. The variation trends of the calibrated QW widths and indium contents are consistent with those of the CL emission wavelengths from various portions of NR QWs.

Photothermal optical coherence tomography based on the localized surface plasmon resonance of Au nanoring.

The conventional optical coherence tomography (OCT) images based on enhanced scattering and the photothermal (PT) images based on enhanced absorption of the localized surface plasmon (LSP) resonance of Au nanorings (NRIs) in a bio-tissue sample are demonstrated with the scans of an OCT system (1310-nm system), in which the spectral range covers the LSP resonance peak wavelength, and another OCT system (1060-nm system), in which the spectral range is away from the LSP resonance peak wavelength. A PT image is formed by evaluating the modulation frequency (400 Hz) response of an excitation laser with its wavelength (1308 nm) close to the LSP resonance peak at 1305 nm of the Au NRI solution. With the scan of the 1310-nm OCT system, the Au NRI distribution in the bio-tissue sample can be observed in both conventional OCT and PT images. However, with the scan of the 1060-nm OCT system, the Au NRI distribution can be clearly observed only in the PT image. The diffusion process of Au NRIs in the bio-tissue sample can be traced with the scan of either OCT system. Based on phantom experiments, it is shown that the PT image can help in resolving the ambiguity of a conventional OCT image between the enhanced scattering of Au NRIs and the strong scattering of a tissue structure in the 1310-nm OCT scanning. Also, under the condition of weak intrinsic sample scattering, particularly in the scan of the 1060-nm system, the PT signal can be lower than a saturating level, which is determined by the excitation power. By increasing OCT system signal-to-noise ratio or M-mode scan time, the PT signal level can be enhanced.