The fluorescence spectra, delayed luminescence (DL) spectra and DL decay dynamics of human serum were studied
by fluorescence and time resolved emission spectrum technology under different excitation conditions in this paper. The
results we obtained are shown as follows: (1) the DL spectrum is similar to the time resolved fluorescence spectrum
within 50ns after Ps laser pulse excitation. (2) The intensity and decay time of DL from the serum samples are dependent
on excitation power and irradiation time. Under fixed excitation power, the longer irradiation time is, the higher the DL
intensity; after the excitation energy reaches about 200mJ, the DL intensity is nearly unchanged. The change of DL decay
time follows the similar regulation to that of DL intensity. (3) As the excitation energy increases, the spectral distribution
of the relative intensities exhibits an observable change. The higher the excitation energy is, the stronger the relative
intensity at short wavelength region. The results show that the delayed luminescence of human serum is mainly
originated from its delayed fluorescence, phosphorescence, and induced bio-photon emission. These results may be also
useful for the development of serum diagnosis technology.
This letter demonstrates that the fluorescence intensity of CdSe-core CdS/ZnS-multishell quantum dots (QDs) in toluene is
related via a power-law of ~1.9 to the input intensity of femtosecond laser at 5~130 GW/cm2. This clearly indicates a broad
range of optical intensity of two-photon excitation (TPE). The two-photon absorption (TPA) cross sections of QDs of
core-size 2.9, 4.0 and 5.3 nm at 800 nm are 1980, 5680 and 14600 GM, respectively. Furthermore, the log-log plot of
CdSe-core diameters versus the TPA cross sections shows the increase with a slope >3, indicating a nonlinear dependent
relationship between TPA cross section and size of CdSe-core. The broad optical range of TPE and large TPA cross section
make these QDs excellent candidates for two-photon fluorescent microscopy and bioimaging. Based on these two-photon
properties of our QDs, we continue to investigate the bioimaging applications with two-photon microscopy. The results of
the fluorescence images of living cells with the QDs demonstrate that QDs could be penetrate into cell membrane, then
steadily and dispersedly distribute at the cytoplasm, which further indicates such QDs could be excellent candidate for
two-photon microscopy applications.
It has been proven that photodynamic therapy (PDT) is effective in treating various malignant and non-malignant
diseases. In the treatment of certain non-malignant vascular diseases, such as wet age-related macular degeneration
(AMD) and port wine stains (PWS), unlike in the treatment of malignant solid tumors, light irradiation usually
starts immediately after the intravenous (IV) injection of photosensitizers while the photosensitizers is mainly
circulating inside blood vessels. Under such vascular-targeting action mode, photoreactions between
photosensitizers and light can selectively destruct the vascular tissues. Light distribution is complex so that it is
important to understand the optical properties of targeted vessels and surrounding tissues. To better determine the
optical properties of vascular tissues, we developed a tissue-simulating phantom and adopted frequency-domain
measurement of phase difference. Absorption and reduced scattering coefficients in blood vessels were estimated
and light distribution was simulated by the Monte Carlo method. These determinations are essential for the
implication of better light dosimetry models in clinical photodynamic therapy and vascular-targeting PDT, in
particular.
The photo-induced delayed luminescence (DL) of human serum and its dependence on exciting conditions, including exciting wavelength, exciting energy and exciting power, were studied in this paper. It was found that the DL of serum follows the law of hyperbolic decay rather than exponential decay, exhibiting coherent character. The exciting conditions had affinities with the activation as well as the active reactions of biological molecules, which were sensitive and active under UV-light excitation. Exciting energy mainly decides the activation. More sufficient activation leads to more drastic active reactions and stronger re-emission ability of bio-molecules after illumination, resulting in the more intensive photon emission and lower DL decay speed rate. On the other hand, exciting power also plays an important role in impacting the active reactions. Exciting light with higher power makes the active reactions more drastic, causing the higher photon counts. However, there are few correlations between exciting power and the re-emission ability of bio-molecules. These results may be useful for investigation and application of human serum.
Core-shell semiconductor quantum dot (QD) has been attracting more and more extensive attentions and interests in
biomedicine photonics due to its good stability and high fluorescence quantum efficiency. In this paper, we reported that
the photoluminescence of core-multishell CdSe QDs performed a two-photon action under a femtosecond laser
excitation in wide incident power range. The two-photon absorption cross sections of such QDs were measured by the
intensity-dependent transmittance method and the results demonstrated a very strong two-photon absorption capacity of
QDs. The fluorescent spectra of QDs with an amphiphilic polymer showed that the fluorescent peak wavelength
appeared blue shift obviously and the full width at half maximum (FWHM) broadened to 40 nm. Furthermore, the
intracellular distribution of the QDs probes in cancer cells had been observed under two-photon excitation. The
experimental results indicated that the QDs mainly distribute at cell membrane and selectively gathered on cytoplasm of
cancer cells. The QDs which permeated into cancer cells quickly were very steady binding with cancer cells. Under long
time laser irradiation, the QDs hardly took place photobleaching, which demonstrated a very steady photochemical
performance of these QDs..
Absorption spectrum of CPD3 is determined. There are two absorption bands all in absorption spectrum, the
maximal absorption of band B is at 395nm in 0.9% NaCl solution and TE buffer solution, the band Q is locating at
677nm and 651nm respectively in solvents above. The order of magnitude of extinction coefficient is 104 in both
solvents. the absorption peak of CPD3-DNA mix solution have 6nm and 23nm red shift for band B and band Q
respectively compared with pure CPD3 in 0.9% NaCl solution, this indicates that interaction between
photosensitizer and DNA occurring. Time series data of absorption for CPD3-DNA mix solution supports the
interaction viewpoint further, and the full action time is about 90mins. The type of interaction needs a further
investigating. Stronger absorption in red region and the interaction with DNA suggests that CPD3 will have a bright
future in photodynamic therapy.
Photodynamic therapy (PDT) is a promising new treatment modality for several diseases, most notably cancer. In PDT,
light, O2, and photosensitizer are combined to produce a selective therapeutic effect. Chlorophyll derivative
photosensitizer(CPD) is the class of new photosensitizers for photodynamic therapy ( PDT) . And to date, little is known
about the interaction between the photosensitizer and the inner parts of tumor cell in PDT. A fluorescent microscopy and
imaging study on CPD was performed. To observe the dynamic process of how the photosensitizer (CPD) enters the
tumor cell and intracellular distribution of CPD in tumor cells, we used confocal laser scan microscopy(CLSM) under
one-photon excitation induced by a 488nm Ar+ laser. We also obtained the fluorescence photobleaching of CPD in cells
with varied intensity of excitation laser(488nm). By means of CLSM, we found most of the photosensitize CPD
distribute in on nuclear membrane but few in nuclear.
Two-photon-induced fluorescence spectrum and lifetime of Chlorin-e6-C15 Monomethyl Ester in tetrahydrofura (THF) are experimentally examined with femtosecond laser pulses at 800 nm from a Ti:sapphire laser. The two-photon excited fluorescence spectra of the molecule are basically similar to those obtained by one-photon excitation. The lifetimes of two-photon and one-photon excitation fluorescence of this molecule in the solution are of the order of 5.2 ns and 4.8 ns respectively. Our experimental results indicate that the two-photon-induced photodynamic processes of Chlorin-e6-C15 Monomethyl Ester are similar to one-photon-induced photodynamic processes. The two-photon absorption cross section of the molecule is measured at 800 nm as about σ2' ≈ 29.1 x 10-50 cm4 • s/photon. As an example for two-photon photodynamic therapy, we also further examine the cell-damaging effects of the Ester. Our preliminary results of cell viability test indicate that Chlorin-e6-C15 Monomethyl Ester can effectively damage the liver cancer cells BEL-7402 under two-photon irradiation. Our results suggest Chlorin-e6-C15 Monomethyl Ester may become a potential two-photon phototherapeutic agent.
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