The study reports an investigation of the photoproducts obtained by exposure of chlorpromazine hydrochloride in ultrapure water (concentration 2 mg/mL) to a 266-nm laser beam obtained by fourth harmonic generation from a Nd:YAG laser (6-ns full time width at half maximum, 10-Hz pulse repetition rate). The photoproducts were analyzed by steady-state UV-Vis absorption, laser-induced fluorescence, Fourier transform infrared spectroscopy, and liquid chromatography–tandem time-of-flight mass spectroscopy. Two figures showing pathways that take place during irradiation for obtaining the final products are shown. The quantum yield of singlet oxygen generation by chlorpromazine (CPZ) was determined relative to standard Zn-phthalocyanine in dimethyl sulfoxide. To outline the role of fluorescence in photoproducts formation rates, fluorescence quantum yield of CPZ during exposure to 355-nm radiation (third harmonic of the fundamental beam of Nd:YAG laser) was investigated relative to standard Coumarin 1 in ethanol. The CPZ solutions exposed 60 and 240 min to 266-nm laser beam, respectively, were tested against Staphylococcus aureus ATCC 25923 strain. For 25 μL of CPZ samples irradiated 240 min, a higher diameter of inhibition has obtained against the tested strain than for the 60-min exposed ones.
Phenothiazine exposed to white light or UV radiation undergoes a variety of reactions that result in the degradation of the parental compound and the formation of new species. Chlorpromazine exposed to the 266 nm laser beam of given energy levels yielded species derived from it, whose number increased with the exposure duration. At distinct time intervals the irradiation products were evaluated by spectrophotometry between 200-1500 nm, Thin Layer Chromatography, and for antimicrobial activity of Chlorpromazine against different test organisms such as Staphylococcus aureus.
One of the alternatives to the existing medicines and treatment procedures in fighting multi drug
resistance (MDR) is strengthening the effects of medicines by modifying their molecular structures through
exposure to laser radiation. A method associated with this, is the generation of micro-droplets which contain
medicines solutions; the droplets are utilized/produced as vectors to transport the medicines to targets.
In our studies we try to combine these two methods in order to obtain a new technique to deliver the
efficient medicines to targets that can be applied for a relative large number of chemicals. For this purpose we
have developed an experimental set-up containing a liquid droplets generator, a tunable laser source used to
irradiate droplets, a subunit to measure the laser induced fluorescence (LIF) signals and a real time recording
system for droplet image analysis.
Measurements on different probes, like ultrapure water, commercial grade medicines, newly
developed medicines and laser dyes were performed.. All these measurements were performed on waterbased
solutions.
We present in this paper the laser induced fluorescence measurements results on medicine solutions
(in bulk or in a micro-droplet form) that exhibit important modifications after the exposure at laser radiation. It
was evidenced that the exposures to laser beams/coherent optical radiation of some medicines solutions in
ultrapure water may produce molecular modifications in solutions. These slight modifications of the molecules
made them more efficient against bacteria strains.
Among other carbonaceous species, polycyclic aromatic hydrocarbons (PAHs) are of relevance for astrophysics. It is expected that they are present in the interstellar medium and they are considered as possible carriers of the diffuse interstellar bands. To prove this, absorption spectra of PAHs under conditions similar to those met in the interstellar medium should be obtained. We report here the application of cavity ring-down laser absorption spectroscopy to neutral PAHs, namely anthracene and pyrene, cooled in a supersonic jet. The absorption spectra corresponding to the S1(0) ← S0(0) transition of anthracene near 361 nm and to the S2(1,0) ← S0(0) transitions of pyrene around 321 nm and 316 nm have been studied. The results are similar to the excitation spectra previously reported in the literature.
Hydroxypyrimidine 5-fluorouracil (5-FU) belongs to the cytostatics group known as antimetabolites. The effect of UV irradiation on 5-FU was investigated by absorption and fluorescence spectroscopy. The study of the photosensitizer properties of 5-FU was made since their effects could be enhanced by exposure to UV radiation at different doses. Solutions 2.5x10-4M in natural saline water (0.8% NaCl), irradiated with optical beams emitted by N2 laser and UV Hg classic lamp, were used. The 5-FU was chosen due to its strong absorption along a large spectral range which makes possible the fluorescence excitation in UV. The absorption spectra exhibit bands between 250 - 450 nm. The emission fluorescence was measured in the 400-550 nm spectral range, with λex=320 and 350 nm for samples irradiated with Hg lamp and with λex=360 nm for samples irradiated with N2 laser. The excitation fluorescence was measured in the spectral range 200-400 nm, with λem=440 nm for samples irradiated with N2 laser. The spectra reveal a fluorescence enhancement with the exposure time, with a maximum at 3 min due to the transformation of 5-FU molecule into a fluorescent tautomeric form. The destruction more rapid than usual of the neovascularisation was observed for conjunctive of rabbit eyes, when they are impregnated with 5-FU solution and exposed to incoherent UV and visible light.
Introduction of the photosensitizer properties of cytostatics drus was made, pointing out that the fact that besides the biochemical action of the cytostatics their effects could be enhanced by the exposure to light at different doses. A spectroscopical characterisation of methotrexate and fluorouracil, cytostatic drugs used frequently in cancer therpy was performed. The absorption, emission and excitation spectra were measured for methotrexate solutions in natural saline and sodium hydroxide at concentration in the range 10-5 -10-6M and pH 8.4. The absorption, emission and excitation spectra were measured for fluorouracil solutions in natural saline at concentration in the range 10-4 -10-5M. The absorption spectrum exhibits spectral bands in the range 250nm -450nm for both drugs.
The fluorescence excitatioan for methotrexate was made at 340nm and 370nm, the fluorescence emission was detected in the spectral range 400nm - 500nm with a maximum at 470nm. The fluorescence excitation was measured in teh range 200nm-500nm with the emission centred on 530nm, for Xe lamp irradiation, and 300nm for Hg lamp and laser irradiation. The fluorescence emission spectra was monitored in the spectral range 400nm - 600nm. The effects of irradiation on spectroscopic characteristics of methrotrexate and fluorouracil were investigated. The irraditaion was made using a UV classic lamp with Xe, for the first experimental part and for the second one it was used both a class Hg lamp and a nytorgen pulsed laser.
Two classes of substances which may be used in the treatment of malignant tumors in ophthalmology are studied from the point of view of their spectroscopic properties: synthetic porphyrines such as TNP, TPP, TSPP and Zn-TSPP and cytostatics such as 5-fluorouracil. The absorption, excitation and fluorescence spectra of the porphyrins are measured in water and DMSO solutions to allow their efficient use in photodynamic therapy studies at irradiation with UV-laser light. A spectroscopic study of 5-fluorouracyl, a cytostatic drug used in the treatment of ophthalmologic tumors is reported. Absorption, fluorescence excitation/emission spectra were measured for solutions of 5-fluorouracyl at 5 X 10-5 M concentration. The effects of UV-VIS irradiation of on the 5-fluorouracyl solutions were investigated. The irradiation was performed with a classical Xe lamp having a power density of 11 mW/cm2, at time intervals between 15 min and 60 min. While the absorption is not affected by light irradiation, the fluorescence of the solutions is increasing with the irradiation duration.
A spectroscopical characterization of methotrexate, cytostatic drug used frequently in cancer therapy, was performed. The absorption, emission and excitation spectra were measured for methotrexate solutions in natural saline and sodium hydroxide at concentration in the range 10-5 M -10-6 M and pH 8.4. The absorption bands are noticed in the spectral range 250 nm - 450 nm. The fluorescence excitation was made at 340 nm and 370 nm; the fluorescence emission was detected in the spectral range 400 nm - 500 nm with a maximum at 450 nm. The behavior of absorption and fluorescence spectra of methotrexate solution exposed to uv-visible light was investigated. The irradiation was made using an Xe lamp (emission between 325 nm and 420 nm and power density of 11 mW/cm2). The exposure time was between 15 min. and 3 h. Major modifications on absorption bands for irradiation times longer than 1 hour were observed. Furthermore, the methotrexate solutions become strongly fluorescent after irradiation. The observed changes are not linear with the exposure time indicating complex photochemical processes which implies, at least, one intermediate product.
The spectroscopic detection of NO2 has been investigated in the visible spectral range by laser induced fluorescence (LIF) and cavity ring down spectroscopy (CRDS). NO2 mixtures with air or argon at different pressures have been studied with LIF by excitation at 532 nm and detection in the range 550-580 nm. Collisional quenching and vibrational energy transfer appear to limit the application of LIF to sub-atmospheric pressures. Therefore, flow samples of NO2 in dry air at atmospheric pressure in the concentration range of 0.1 ppm to 15 ppm have been studied by CRDS. The absorption cross section of NO2 in the range between 437 nm and 450 nm has been determined and compared to literature. The sensitivity of the CRDS system was estimated to be 50 ppb. The effect of elevated temperatures on the absorption coefficient was examined for temperatures of 377 K and 433 K.
The effect of UV irradiation of methotrexate was investigated by steady state absorption and fluorescence spectroscopy. Major modifications on absorption bands were detected upon irradiation fluence greater than 59J/cm2. In addition the irradiated solutions become strongly fluorescent. The detected changes are not linear with the exposure time suggesting that the photo-induced chemical processes are complex.
The spectroscopic characterization of synthetic porphyrins such as TPP, TSPP, ZnTSPP, etc. is reported, namely: absorption and laser induced fluorescence spectra in different solvents. Results about the photo toxicity of such photosensitizers in 5 percent DMSO in ns NaCl 0.9 percent on rats are shown proving the good acceptance of the solutions by the rats organisms with immediate perspectives for application on human patients. The second main line of experiments was devoted to the measurements of the irreversible modifications induced in the cell structure of the brain malignant tumors - impregnated with photosensitizers solutions - by the nitrogen pulsed laser radiation. 'In vitro' samples of brain tumor tissue were prelevated and impregnated with photosensitizer solutions during 1 hour to 48 hours. The samples were treated and kept so that before and after exposures to the laser beams the modifications due to other factors than the laser irradiation be avoided or minimized. The exposures to laser radiation were made along time intervals form 3 minutes to more than 1 hour. Irreversible modifications at cellular level following the interaction of impregnated cells with laser radiation were evidenced by optical microscopy. Concluding remarks are made about further 'in vivo' application on human patients.
Studies on beam power behavior in time and laser beam mode structures of laser diodes/LEDs used in low level laser therapy (LLLT) were performed. Two laser diodes with cw emission in red at 635nm, a cw laser diode emitting in IR at 904nm and 2 LEDs which emit radiation at 904nm, respectively 650nm were analyzed from the point of view of the beam power, 3D, 2D distributions and the variation of radiation intensity in time. A laser beam analyzers, model LBA-100 was used for laser beam profile studies. The time behaviors of the lasers/LEDs beams intensity were achieved with a LASERSTAR energy meter, OPHIR OPTRONICS. These studies are very useful for establishing the appropriate irradiation doses and procedure for LLLT.
Pulsed laser photoacoustic detection of NO2 and SO2 is reported. The laser source is a pulsed molecular nitrogen laser emitting at 337.1 nm. The average energy per pulse is about 350 (mu) J and the pulse duration 10 nsec. For detection we used a piezoelectric transducer (TUSIM-N.I.M.P., resonance frequency 4 MHz) and an electret condenser microphone (Trevi EM 27). The photoacoustic cell was a nonresonant one, with a cylindrical shape. The laser beam was centered along the cylinder axis. Linear dependence of the photoacoustic signal on pollutant pressure was obtained. This linearity is in a good agreement with theoretical considerations. The photoacoustic signal was measured for pollutants pressure between 1 torr and 100 torr for NO2 and between 35 torr and 100 torr for SO2.
Differential absorption measurements made in laboratory on air samples containing NO2 and SO2 atmospheric pollutants are reported. This type of measurement is necessary to calibrate remote sensing equipment conceived to monitor NO2 and SO2 in open atmosphere using LIDAR techniques and to perform preliminary laboratory studies on differential absorption specific to NO2 and SO2 molecules. To monitor the mentioned pollutants, a nitrogen laser pumped tunable dye laser was used, the laser pulse having the following characteristics: energy per pulse 40 (mu) J, repetition rate 5 pps, pulse time width 10 ns. The dye wavelengths used to detect NO2 were (lambda) on equals 435.1 nm, (lambda) off equals 432.6 nm obtained from POPOP in DMSO and the spectral bandwidth was 0.7 nm; for SO2, (lambda) on equals 298 nm, (lambda) off equals 299.5 nm and the spectral bandwidth was 0.2 nm, the laser beam being obtained from R6G and further SHG by an ADP crystal. The concentration interval for NO2 detection was 18.4 ppm to 26.4 ppm, whereas the measurements for SO2 pollutant were performed at 6.4 ppm. The studied gases were home made and the samples pollutant concentration was measured by mass spectrometry.
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