Cell samples flowing along a microfluidic tube are scanned with an optical coherence tomography (OCT) system and their correlation times in M-mode scans are calibrated. In particular, the variations of correlation time with waiting time after 5 and 10 % ethanol are applied to the cell samples are compared for understanding the evolution of cell morphology in the cell death pathways of apoptosis and necrosis, respectively. Also, Au nanorings (NRIs) are taken up by cells for increasing the scattering strength in OCT scanning and hence increasing the signal-to-noise ratio. It is found that when cells are incubated with 5 % ethanol, the correlation time keeps decreasing with waiting time and then increases at 7 hours. On the other hand, when cells are incubated with 10 % ethanol, the correlation time keeps decreasing with waiting time all the way up to 7 hours. This difference may imply that the correlation time from OCT scanning may be determined not only by the size of cell fragment, but also by the smoothness of the cell fragment in a scale of several hundred nm during the apoptosis and necrosis processes. In particular, the results imply that the surface smoothness of the apoptotic bodies formed at the final stage of an apoptosis process is higher than that of the cell fragments formed at the final stage of a necrosis process. This OCT scanning technique has the potential application to the determination of cell death condition with the function similar to cell flow cytometry.
Photosensitizer can be taken up directly by cells or through the linkage with gold nanoparticles (NPs). When gold NPs linked with a photosensitizer are taken up by cells, both photodynamic (PDT) and photothermal effects for damaging cells can be generated under the illumination of a light source of an appropriate wavelength. The gold NPs and photosensitizer can escape from cells through an exocytosis process such that the efficiency of cell damage may decay with time. In this study, we investigate the dependencies of cell damage efficiency, gold nanoring (NRI) and photosensitizer amounts stayed in cells on the delay time. In particular, we differentiate the two possible escape pathways of the photosensitizer, AlPcS, i.e., AlPcS escape alone after its linkage with Au NRI is broken and AlPcS escape together with the linked Au NRI. Also, we intend to understand the dependence of the aforementioned AlPcS escape pathway on the location of Au NRIs inside a cell after they are taken up. It is found that generally, the PDT-induced cell damage efficiency decays more slowly when AlPcS is taken up together with linked Au NRI, compared with the case that AlPcS is taken up alone by cells. This trend indicates that the photosensitizer is more stable when it is linked with an Au NP. This result is confirmed by the observations of Au NRI and photosensitizer escapes through mass spectrometry, flow cytometry, and confocal fluorescent microscopy.
A cell spheroid can be as large as 1 mm in diameter, containing more than 300,000 cells. It can be used for simulating a cancer tumor in cell treatment study. In this study, the cell uptake behaviors in cell spheroids are investigated. In particular, the penetration depths of Au nanoring, Au nanorod, and photosensitizer (AlPcS) in cell spheroids are evaluated based on a newly proposed technique of using confocal fluorescent microscopy. By using a geometric computation process, we can estimate the width of a fluorescent belt region, which corresponds to the uptake depth. Based on such evaluations, we can understand whether the quiescent viable cells in the middle layer of a cell spheroid. Also, by using a cell culture insert, we can estimate the uptake Au nanoparticle number per cell through mass spectrometry measurement. It is found that after 48-hour incubation time, the Au nanoparticles and photosensitizer all have the penetration depths in the range of 110-140 m. Such uptake penetration depths control the cell damage depths under laser illuminations. For observing the uptake depths, we use different fluorescent dyes to incubate the cell spheroids. It is found that the penetration depth of a dye also relies on its molecular weight. The smaller uptake penetration depths of Au nanoparticles into a cell spheroid can be attributed to the settlement of Au nanoparticles in the incubation solutions such that the upper portion of a cell spheroid has no access to the Au nanoparticles.
The use of a high-resolution optical coherence tomography (OCT) system with the operation wavelength around 800 nm to scan SCC4 cancer cells under different laser illumination conditions is demonstrated. The cancer cells are incubated with Au nanorings (NRIs), which are linked with photosensitizer, AlPcS, for them to be up-taken by the cells. Two Au NRI samples of different geometries for inducing localized surface plasmon (LSP) resonance around 1310 and 1064 nm are used. Four different lasers are utilized for illuminating the cells under OCT scanning, including 1310-nm continuous (cw) laser, 1064-nm cw laser, 1064-nm femtosecond (fs) laser, and 660-nm cw laser. The 1310- and 1064-nm cw lasers mainly produce the photothermal effect through the LSP resonance of Au NRIs for damaging the observed cells. Besides the photothermal effect, the 1064-nm fs laser can produce strong two-photon absorption through the assistance of the LSP resonance of Au NRI for exciting AlPcS to effectively generate singlet oxygen and damage the observed cells. The 660-nm laser can excite AlPcS through single-photon absorption for generating singlet oxygen and damaging the observed cells. With the photothermal effect, the observed cells can be killed through the process of necrosis. Through the generation of singlet oxygen, the cell membrane can be preserved and the interior substances are solidified to become a hard body of strong scattering. In this situation, the cells are killed through the apoptosis process. Illuminated by the 660-nm cw laser, a process of interior substance escape is observed through high-speed OCT scanning.
In combining the photothermal and photodynamic effects for killing cancer cells through the localized surface plasmon resonance (LSP) of photosensitizer-linked Au nanorings (NRIs), which are up-taken by the cells, the cells can be killed via different processes, including necrosis and apoptosis. In particular, the dominating effect, either photothermal or photodynamic effect, for cancer cell killing leading to either necrosis or apoptosis process is an important issue to be understood for improving the therapy efficiency. In this paper, we demonstrate the study results in differentiating the necrosis and apoptosis processes of cell death under different laser illumination conditions. With the LSP resonance wavelength of the Au NRIs around 1064 nm, the illumination of a 1064-nm cw laser can mainly produce the photothermal effect. The illumination of a 1064-nm fs laser can lead to LSP resonance-assisted two-photon absorption of the photosensitizer (AlPcS) for generating singlet oxygen and hence the photodynamic effect, besides the photothermal effect. Also, the illumination of a 660-nm cw laser can result in single-photon absorption of the photosensitizer for generating singlet oxygen and the photodynamic effect. By comparing the necrosis and apoptosis distributions in dead cells between the cases of different laser illumination conditions, we can differentiate the cancer cell killing processes between the photothermal effect, photodynamic effect, and the mixed effect.
Cancer cell killing efficiencies based on the photothermal effect caused by the surface plasmon resonance of metal nanoparticles (NPs) and the photodynamic effect caused by the singlet oxygen generation of a photosensitizer rely on the cell uptake efficiency of metal NP and photosensitizer. Perforation and heating can increase cell membrane permeability and hence can increase the cell uptake efficiency of NPs and drugs. In this paper, we demonstrate the variations of the cell damage efficiency under the illuminations of different lasers, which can produce mainly photothermal effect, mainly photodynamic effect, and mixed effect, when a pre-perforation and a pre-heating processes are applied. Au nanorings (NRIs) with their localized surface plasmon resonance wavelength around 1064 nm are used. The perforation process is undertaken by illuminating the cell samples by a femtosecond laser at 1064 nm with the power density lower than the cell damage threshold intensity. The heating process is implemented by illuminating cells with a low power continuous laser at 1064 nm. It is found that with the pre-perforation and pre-heating processes, the photodynamic effect is enhanced because the internalized Au NRI number and hence the internalized photosensitizer (AlPcS) molecule number are increased. However, the photothermal effect can be reduced because the adsorbed Au NRIs on cell membrane are effectively internalized during the pre-perforation and pre-heating processes. The photothermal effect is more effective when Au NRIs are adsorbed on cell membrane.
Although TiO2 can be used to effectively generate reactive oxygen species (ROS) for photodynamic application, its absorption in the ultraviolet range makes the excitation harmful to tissue. Based on the concept of a sensitized solar cell, TiO2 nanoparticles (NPs) are sensitized by linking with the photosensitizer, HMME, to form HMME-TiO2 nanocomposites (NCs) for demonstrating the photodynamic effects under the illumination of white light. The HMME-TiO2 NCs of different composition ratios are prepared for maximizing the generation of ROS and optimizing the inactivation effect of KB cells. The material characteristics and the ROS generation capability of the HMME-TiO2 NCs with the optimized combination ratio show their merits in a photodynamic process under white light irradiation. The application of such NCs to KB cell experiments results in a higher inactivation efficiency when compared to pure HMME of the same concentration.
In this paper, HMME-TiO2 nanocomposites was synthesized and characterized through TEM, Uv-vis spectra, Zeta potential, FTIR spectra. The characterization results show that HMME was successfully conjugated onto the surface of TiO2. It can be seen from the TEM images the average size of HMME-TiO2 conjugation is nearly spherical and the particle size range from 20 to 28 nm. Compared with HMME, the B bands of HMME-TiO2 were much broader and lower while in the region of Q bands the absorption peaks of HMME-TiO2 are higher than that of HMME. Encapsulation efficiency of HMME-loaded TiO2 was assessed and calculated as 45.46%. FTIR spectra show the bonding between TiO2 and HMME was through the hydrogen-bonding between COOH and OH bonds. Fluorescence microscope results demonstrated HMME-TiO2 mainly distributed in the membrane and cytoplasm of SCC cells and its best incubation time is six hours. After treated with HMME-TiO2 plus light irradiation (1.8J/cm2 , 632nm), the viability of SCC cells turned to 32.96% is much lower than that treated with HMME plus light irradiation. It can be concluded that the combination of HMME and TiO2 will enhance the PDT efficiency of HMME. In the process of HMME-TiO2 mediated PDT, as a kind of photosensitizer HMME can induce the death of SCC cells, meanwhile it can transform electron to the conductive band of TiO2 stimulating the photocatalytic activity of TiO2 under visible light. The photocatalytic of TiO2 can also induce the death of SCC cells. The combination of these two effects lead to more SCC cells died.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.