Phosphorescence Decay Rate Research Articles

Theoretical Studies on the Photophysical Properties of the Ag(I) Complex for Thermally Activated Delayed Fluorescence Based on TD-DFT and Path Integral Dynamic Approaches.

Theoretical calculation not only is a powerful tool to deeply explore photophysical processes of the emitters but also provides a theoretical basis for material renewal and design strategy in the future. In this work, the interconversion and decay rates of the thermally activated delayed fluorescence (TADF) process of the rigid Ag(dbp)(P2-nCB) complex are quantitatively calculated by employing the optimally tuned range-separated hybrid functional (ω*B97X-D3) method combined with the path integral approach to dynamics considering the Herzberg–Teller and the Duschinsky rotation effects within a multimode harmonic oscillator model. The calculated results show that the small energy splitting ΔE(S1–T1) = 742 cm–1 (experimental value of 650 cm–1) of the lowest singlet S1 and triplet T1 state and proper vibrational spin–orbit coupling interactions facilitate the reverse intersystem crossing (RISC) processes from the T1 to S1 states. The kRISC rate is estimated to be 1.72 × 108 s–1 that is far more than the intersystem crossing rate kISC of 7.28 × 107 s–1, which will greatly accelerate the RISC process. In addition, the multiple coupling routes of zero-field splitting (ZFS) interaction can provide energetically nearby lying states, to speed up the RISC pathway, and restrict the phosphorescence decay rate. A smaller ZFS D-tensor of 0.143 cm–1, E/D ≈ 0.094 ≪ 1/3, and Δg > 0 are obtained, indicating that the excited singlet states are hardly mixed into the T1 state; thus, a lower phosphorescence decay rate (kp = 9.29 × 101 s–1) is expected to occur, and the T1 state has a long lifetime, which is helpful for the occurrence of the RISC process. These works are in excellent agreement with the experimental observation and are useful for improving and designing efficient TADF materials.

Enhancing the phosphorescence decay pathway of Cu(i) emitters – the role of copper–iodide moiety

Copper–iodide moiety is an alternative to increase the spin–orbit coupling and the phosphorescence decay rate versus the classical [Cu(NN)(PP)]+ system, moving closer to an iridium(iii) complex.

Manipulation of Triplet Excited States for Long‐Lived and Efficient Organic Afterglow

AbstractIn organic systems, it is very challenging to simultaneously achieve long afterglow lifetimes (τAG) and high afterglow efficiency (ΦAG). Here, luminescent dopants which feature a small rate of phosphorescence decay (kP) and modest rate of reverse intersystem crossing (kRISC) are designed and knr + kq values (nonradiative decay and quenching) of triplet excited states are suppressed by all means that include increasing molecular rigidity of luminescent dopants, screening organic matrices to strongly inhibit intramolecular motions of luminescent dopants, and deuteration of the luminescent dopants. Organic matrices are selected with large dipole moments to stabilize the singlet excited states of luminescent dopants via dipole–dipole interactions, reduce singlet–triplet splitting energy, and thus enhance ΦISC, leading to significant population of triplet excited states. Thermally activated delayed fluorescence mechanism is also used with modest kRISC to harvest triplet energies, significantly improve ΦAG to 64%, and maintain long τAG > 1.0 s. The obtained materials display intense afterglow brightness, excellent processability, and temperature‐sensing function.

Simultaneous measurement of two-dimensional temperature and strain fields based on thermographic phosphor and digital image correlation

A two-dimensional (2D) phosphorescence-based method is presented for simultaneous measurement of strain and temperature. 6 μm Mg4FGeO6:Mn4+ phosphor particles were sprayed on the surface of the test target for use as a sensor. A measurement system was established, which included a high-speed camera, a 385 nm LED, and a signal generator. The signal generator controls the LED to output a 100 Hz light pulse to excite the phosphor. The phosphorescence is then detected by the high-speed camera with a frequency of 10 kHz. The temperature information is obtained from the phosphorescence decay rate using the lifetime method. A digital image correlation method was then used with the random markings formed by spraying. The 100 Hz temperature and strain measurement technique was implemented based on the current experimental conditions with an accuracy of 2% in temperature measurement and 16% and 9.3% in u- and v-direction respectively in strain measurement. The measurement procedure was used for measurements of temperature and deformation of an aluminum plate with a pulsed current in a temperature range of 0 °C–600 °C and a displacement range of 0–300 μm. The results from experiments show the possibility of 2D measurements of surface temperature and strain in a harsh environment with a non-invasive method.

Mechanism study of TADF and phosphorescence in dinuclear copper (I) molecular crystal using QM/MM combined with an optimally tuned range-separated hybrid functional

Abstract Investigations of the detailed photophysical processes are of great significance for future material improvements and novel designing strategies. Herein, the interconversion and decay rates of the first excited singlet state (S1) and triplet state (T1) for the Cu2I2(P^N)3 complex are calculated using the thermal vibration correlation function (TVCF) theory, combined with the optimally tuned range-separated hybrid functional (OT-ωB97XD) method at different temperature. A methodology with the building different ONIOM models, was carried over into simulation of crystal environment. All calculated results perfectly match the experimentally available data, demonstrating the validity of our applied theoretical approach. It has been found that the reverse intersystem crossing (RISC) rate kRISC from T1 to S1 is 3.11 × 1010 s−1 at 300 K, about 7 order of magnitude larger than the phosphorescence rate kr(T) = 3.71 × 103 s−1, and far more than ISC rate kISC(T1-S0) of 6.38 s−1. The S1 state can be an efficient thermal population from the T1 state by the RISC pathway, leading to an occurrence of thermally activated delayed fluorescence (TADF), and the estimated delayed time of τ(TADF) = 10 μs. On the other hand, the T1 state also exhibits stronger admixtures with higher lying singlet states due to stronger SOC, having a larger ZFS of 17 cm−1, thus, a relatively fast phosphorescence decay rate of kr(T) = 8.542 × 103 s−1 estimated by Einstein emission formula is observed. Further calculation results show that the emission intensities are stemming by 91% from the S1 state as TADF and by 9% as phosphorescence from the T1 state at 300 K, which indicates the ambient temperature emission represents the combined luminescence of TADF and phosphorescence. Our work would be useful for improving and designing the luminescent material combined high-efficiency TADF with phosphorescence.

Dual Emission through Thermally Activated Delayed Fluorescence and Room-Temperature Phosphorescence, and Their Thermal Enhancement via Solid-State Structural Change in a Carbazole-Quinoline Conjugate.

The emergence of single-component organic dual light emitters holds great promise for white light-emitting diodes (WLEDs) and biological detection due to the involvement of broad emission covering visible spectrum. Here we show experimental studies on dual emission of carbazole-quinoline conjugate (CQ) that exhibits both thermally activated delayed fluorescence (TADF) via reverse intersystem crossing (r ISC) from the higher-lying triplet state ( T2) to the singlet state ( S1) and room-temperature phosphorescence (RTP) from the lowest triplet state ( T1) due to low energy gap between T2 and S1, and energetic proximity of T1 with T2. We found in thermal effect that the intensity of the dual features is enhanced with increasing temperatures up to 100 °C, which can be explained by a thermal-induced structural change (TISC) mechanism that compensates the emission losses due to nonradiative transitions at elevated temperatures. This property, in addition to its enhanced TADF and phosphorescence decay rates (∼107 s-1and 101 s-1) at 100 °C, would have great promise for high-efficiency LEDs.

Deep blue emitting Cu(i) tripod complexes. Design of high quantum yield materials showing TADF-assisted phosphorescence.

In a previous investigation, it was shown that [Cu(tpym)(PPh3)]PF61 with tpym = tris(2-pyridyl)methane represents a deep blue emitter (λmax = 466 nm) though with a low emission quantum yield ΦPL if doped in a polymer (7%) or dissolved in a fluid solvent (≪1%). In this study, we present new tripod compounds with sterically demanding ligands: [Cu(tpym)(P(o-tol)3)]PF62 and [Cu(tpym)(P(o-butyl-ph)3)]PF63 with P(o-tol)3 = tris(ortho-tolyl)phosphine and P(o-butyl-ph)3 = tris(ortho-n-butylphenyl)phosphine. These compounds show high emission quantum yields even in a fluid solution (dichloromethane) reaching a benchmark value for 3 of ΦPL = 76%. This becomes possible due to the specific design of rigidifying the complexes. Importantly, the deep blue emission color is maintained or even further blue shifted to λmax = 452 nm (compound 3 powder). Compound 2 is characterized photophysically in detail. In particular, it is shown that the lowest excited triplet state T1 experiences very efficient spin-orbit coupling (SOC). Accordingly, the phosphorescence decay rate is as large as 5 × 104 s-1 (20 μs) belonging to the fastest T1→ S0 transition values (shortest decay times) reported so far. Investigations down to T = 1.5 K reveal a large total zero-field splitting (ZFS) of 7 cm-1 (0.9 meV). Although thermally activated delayed fluorescence (TADF) grows in at T≥ 160 K, the phosphorescence of 2 still dominates (60%) over TADF (40%) at ambient temperature. Thus, the compound represents a singlet harvesting-plus-triplet harvesting material, if applied in an OLED.

Inhibition of murine cardiomyocyte respiration by amine local anesthetics

The hydrophobic amino acyl amide-linked local anesthetics (e.g., lidocaine and bupivacaine) impose potent cardiac toxicity and direct mitochondrial dysfunction. To investigate these adverse events, an in vitro system was employed to measure their effects on O2 consumption (cellular respiration) by murine myocardium. Specimens were collected from the ventricular myocardium and immediately immersed in ice-cold Krebs-Henseleit buffer saturated with 95% O2:5% CO2. O2 concentration was determined as a function of time from the phosphorescence decay rates of Pd(II)-meso-tetra-(4-sulfonatophenyl)-tetrabenzoporphyrin. Myocardial O2 consumption was linear with time (zero-order kinetics); its rate (k, in μMO2min(-1)), thus, was the negative of the slope of [O2] vs. time. Cyanide inhibited O2 consumption, confirming the oxidation occurred in the respiratory chain. Lidocaine and bupivacaine produced immediate and sustained inhibition of cellular respiration at plasma concentrations of the drugs (low micromolar range). Bupivacaine was twice as potent as lidocaine. The inhibition was dose-dependent, saturating at concentrations ≥30μM. At saturating doses, lidocaine produced ~20% inhibition and bupivacaine ~40% inhibition. Cellular ATP was also decreased in the presence of 30μM lidocaine or bupivacaine. The studied amines inhibited myocardial cellular respiration. This effect is consistent with their known adverse events on mitochondrial function. The described approach allows accurate assessments and comparisons of the toxic effects of local anesthetics on heart tissue bioenergetics.

On the trap depth of the IR-sensitive trap in Na- and K-feldspar

Feldspars are natural radiation dosimeters used in geological dating. The processes that underlie the measured natural- and laboratory induced infrared stimulated luminescence (IRSL) signals are, however, not fully understood. In this study we aim to determine the optical depth of the electron trap that is used in luminescence dating. A series of optically stimulated luminescence (OSL) experiments were performed on two feldspar minerals (single-crystal museum specimens of Na- and K-feldspar) at a low temperature (10 K). The low temperature suppresses thermal processes that may be active during excitation and facilitates the monitoring of mainly optical transitions. Additional experiments at room temperature were performed for comparison. The continuous wave OSL and the post-stimulation phosphorescence were recorded in the ultra violet (3.2–4.8 eV) for stimulation energies ranging between 1.7 and 2.8 eV.From the dependence of the OSL intensity on the excitation energy is deduced that band-tail states play a significant role during charge transport, thus complicating the precise determination of the optical trap depth. Both minerals display a small resonant transition when stimulated at ∼2.05 eV. From the OSL data, the trap depth is tentatively estimated to be ∼2.1 and ∼2.5 eV for Na- and K-feldspar, respectively.The fast phosphorescence following IRSL in both crystals is likely the result of tunnelling from band-tail states in the vicinity of the excited state of the IR-trap. The post-OSL phosphorescence decay is an order of magnitude slower, owing to the contribution from tunnelling of charge from a range of occupied band-tail states. The lack of dependence of the phosphorescence decay rate on the excitation energy (in the range of 1.7–2.8 eV), unambiguously indicates that a single mechanism causes the post-OSL phosphorescence signal.

Laser induced phosphorescence imaging for the investigation of evaporating liquid flows

The phosphorescence properties of liquid and gaseous acetone, following excitation at 308 nm, are studied and utilized in order to overcome two main challenges of two-phase flow laser induced fluorescence imaging: the large fluorescence intensity disparity between the two phases and the ensuing effect of halation. This is achieved on account of the different phosphorescence decay rates of the liquid and vapour phases, which allow for a more favourable signal ratio to be obtained. The benefits of visualizing the phosphorescence emission, instead of the fluorescence, are demonstrated by droplet stream experiments set up in different bath gases, at 1 atm and 297 K. The liquid–vapour interface can be accurately located, while the vapour surrounding the droplets is clearly visualized without any halation interference. The vapour phase phosphorescence signal was calibrated in order to quantify the vapour concentration around an evaporating droplet stream, and the results are compared to laser induced fluorescence images collected in the present study and results found in the literature. The effect of halation in the fluorescence images is shown to extend as far as 10 droplet diameters away from the interface for 161 μm droplets, resulting in a significant overprediction of acetone vapour mole fractions in that region. The vapour profile obtained by laser induced phosphorescence (LIP) imaging agrees with data found in the literature, for which a halation correction on fluorescence images was successfully performed. The demonstrated LIP technique for simultaneous vapour and liquid phase visualisation is only applicable to oxygen-free environments, as even trace quantities of oxygen completely quench the vapour phase phosphorescence emission.

Lymphocyte respiration in children with Trisomy 21

BackgroundThis study measured lymphocyte mitochondrial O2 consumption (cellular respiration) in children with trisomy 21.MethodsPeripheral blood mononuclear cells were isolated from whole blood of trisomy 21 and control children and these cells were immediately used to measure cellular respiration rate. [O2] was determined as a function of time from the phosphorescence decay rates (1/τ) of Pd (II)-meso-tetra-(4-sulfonatophenyl)-tetrabenzoporphyrin. In sealed vials containing lymphocytes and glucose as a respiratory substrate, [O2] declined linearly with time, confirming the zero-order kinetics of O2 conversion to H2O by cytochrome oxidase. The rate of respiration (k, in μM O2 min-1), thus, was the negative of the slope of [O2] vs. time. Cyanide inhibited O2 consumption, confirming that oxidation occurred in the mitochondrial respiratory chain.ResultsFor control children (age = 8.8 ± 5.6 years, n = 26), the mean (± SD) value of kc (in μM O2 per min per 107 cells) was 1.36 ± 0.79 (coefficient of variation, Cv = 58%; median = 1.17; range = 0.60 to 3.12; -2SD = 0.61). For children with trisomy 21 (age = 7.2 ± 4.6 years, n = 26), the values of kc were 0.82 ± 0.62 (Cv = 76%; median = 0.60; range = 0.20 to 2.80), p<0.001. Similar results (p<0.000) were obtained after excluding the five trisomy 21 children with elevated serum TSH (values >6.1 mU/L). Fourteen of 26 (54%) children with trisomy 21 had kc values of 0.20 to 0.60 (i.e., <−2SD). The values of kc positively correlated with body-mass index (BMI, R >0.302), serum creatinine (R >0.507), blood urea nitrogen (BUN, R >0.535) and albumin (R >0.446).ConclusionsChildren with trisomy 21 in this study have reduced lymphocyte bioenergetics. The clinical importance of this finding requires further studies.

725 Lymphocyte Respiration in Children with Trisomy 21

AimsThis study aimed to measure lymphocyte mitochondrial O2 consumption (cellular respiration) in children with trisomy 21.MethodsPeripheral blood mononuclear cells were isolated from whole blood of trisomy 21 and control children...

Resolution of uranium isotopes with kinetic phosphorescence analysis

This study was conducted to test the ability of the Chemchek™ Kinetic Phosphorescence Analyzer Model KPA-11 with an auto-sampler to resolve the difference in phosphorescent decay rates of several different uranium isotopes, and therefore identify the uranium isotope ratios present in a sample. Kinetic phosphorescence analysis (KPA) is a technique that provides rapid, accurate, and precise determination of uranium concentration in aqueous solutions. Utilizing a pulsed-laser source to excite an aqueous solution of uranium, this technique measures the phosphorescent emission intensity over time to determine the phosphorescence decay profile. The phosphorescence intensity at the onset of decay is proportional to the uranium concentration in the sample. Calibration with uranium standards results in the accurate determination of actual concentration of the sample. Different isotopes of uranium, however, have unique properties which should result in different phosphorescence decay rates seen via KPA. Results show that a KPA is capable of resolving uranium isotopes.

Abstract A43: The Pi3K inhibitor GSK2126458 is highly toxic in breast ductal carcinoma

Abstract Introduction: Breast carcinoma has been shown to harbor mutations that up-regulate phosphatidylinositol 3 kinase (PI3K) signaling pathway. Thus, targeting this pathway is expected to impair tumor survival. The aim of this work was to investigate the cytotoxicity of GSK2126458 (a highly potent and selective inhibitor of PI3K) in breast ductal carcinoma from a patient. Methods: A breast ductal carcinoma was collected immediately following resection. Tumor sections (0.5×0.5×0.1 cm) were immersed in ice-cold RPMI medium gassed with 95% O2:5% CO2. The samples were incubated at 37oC in RPMI (continuously gassed as above) with and without 50 nM GSK2126458 (Selleck Chemicals, cat. #S2658) for 90 min (final volume = 2.0 mL). At the end of the incubation period, 37 μM Ac-DEVD-AMC (a caspase-3 substrate) was added with and without the pan-caspase inhibitor zVAD-fmk (32.1 μM, added 10 min before the substrate). The reactions were allowed to continue at 37oC for 20 min before tissue processing for histology, immunohistochemistry for cleaved caspase -3 (Cell Signaling Technology, kit #8120), cellular respiration and caspase activation. Mitochondrial O2 consumption was determined as function of time from the phosphorescence decay rate (1/T) of Pd(II) meso-tetra-(4-sulfonatophenyl)-tetrabenzoporphyrin. For caspase activity, the Ac-DEVD-AMC cleavage reaction was quenched with tissue disruption and passages through a 27-G needle. The supernatants were collected by centrifugation (∼16,300g for 90 min) through Microcentrifuge Filter (nominal molecular weight limit = 10,000 Dalton, Sigma©), separated on HPLC, and analyzed for the free fluorogenic AMC moiety. Results: This 73-year-old female had invasive ductal carcinoma (grade 3), measuring 4.5 cm. The tumor expressed estrogen and Her2-neu receptors. Ki-67 score was 70%. Compared to untreated tumor, the treated tumor revealed cellular disintegration with loss of cohesion, cytoplasmic vacuolization and numerous apoptotic bodies. Positive cleaved caspase-3 staining was noted in 10% of untreated tumor and 20% in treated tumor. The initial rate of mitochondrial O2 consumption (kc, in μM O2 min−1 mg−1) was 0.17. At 2 h, the value of kc for untreated tumor was 0.019 and for treated tumor 0.033. The AMC peak area (arbitrary units, reflecting intracellular caspase activation) in untreated tumor was 460,886, in tumor treated with GSK2126458 was 7,234,911 (15.7 fold increment), and in tumor treated with GSK2126458 plus zVAD-fmk was 1,523,682 (79% inhibition), confirming the cleavage of Ac-DEVD-AMC was mainly mediated by caspases. Conclusions: GSK2126458 induced remarkable necrosis in invasive ductal carcinoma. This preliminarily observation supports the role of PI3K activation in breast carcinogenesis and possible therapeutic utility of PI3K inhibitors in the treatment of invasive ductal carcinoma. The described in vitro methodology provides a rapid assessment of the cytotoxicity of PI3K/PTEN/Akt/mTOR inhibitors.

Phosphorescence parameters for platinum (II) organometallic chromophores: A study at the non-collinear four-component Kohn–Sham level of theory

A theoretical characterization of the phosphorescence decay traces of a prototypical platinum (II) organic chromophore has been conducted. The phosphorescence wavelength and radiative lifetime are predicted to equal 544nm and 160μs, respectively. The third triplet state is assigned as participator in the intersystem crossing and is predicted to have a phosphorescence decay rate 12 times larger than that of the lowest triplet state. This result offers an explanation for the experimentally observed double exponential decay. The self-consistent field (SCF) optimization of the electron density was accomplished only after introducing algorithmic improvements, now incorporated in the Dirac program.

Metal Nanoparticles Sensitize the Formation of Singlet Oxygen

Singlet oxygen (O2) is known to play an indispensible role in the photodynamic therapy (PDT) treatment of cancer, and is an important oxidant for hydroperoxidation of olefins in organic synthesis. Singlet O2 is conventionally formed by sensitization by organic photosensitizers, such as Rose Bengal, silicon phthalocyanine, etc. These organic or organometallic dyes are, however, prone to photoinduced degradation and enzymatic degradation, which becomes problematic in PDT treatments, and reduces the efficiency of the generation of singlet O2. [5,8] It is, therefore, important to search for photosensitizers with highly efficient singlet O2 generation and large absorption coefficients that are photochemically more stable and less prone to enzymatic degradation. Previously, it was reported that the yield of singlet oxygen production by a photosensitizer, namely, Rose Bengal, was enhanced by a silver island film through the metal-enhanced absorption of photosensitizer. It was also reported that a gold nanodisk could enhance the phosphorescence decay rate of singlet oxygen, leading to a larger characteristic phosphorescence emission band of singlet oxygen at 1270 nm. In another two studies, it was observed that the quantum yield of singlet O2 formation generated by phthalocyanine photosensitizers can be enhanced by the presence of gold nanoparticles. Herein we report an unprecedented observation that singlet oxygen can be formed through direct sensitization by metal nanoparticles (M NPs, M=Ag, Pt, and Au) without the presence of any organic photosensitizers. Unambiguous experimental evidence includes direct observation of singlet oxygen emission at roughly 1268 nm, hydroperoxidation of cyclohexene, green fluorescence from a selective singlet oxygen fluorescent sensor, namely, Singlet Oxygen Sensor Green (SOSG, Molecular Probe), and quenching of singlet oxygen phosphorescence by sodium azide. As shown in Figure 1, photoexcitation of M NPs at the surface plasmon resonance absorption bands of Ag (d= 55, 42 nm), Pt (10 nm), and Au (22 nm) in D2O results in characteristic singlet oxygen emission at 1264 and 1268 nm, respectively. Control experiments show that in the absence of metal nanoparticles, photoexcitation of poly(vinyl pyrrolidone (PVP) in D2O using either 254 or 508 nm light did not result in any detectable singlet O2 emission signal (see the

Measurement of oxygen consumption by murine tissues in vitro

Introduction A novel in vitro system was developed to measure O 2 consumption by murine tissues over several hours. Methods Tissue specimens (7–35 mg) excised from male Balb/c mice were immediately immersed in ice-cold Krebs–Henseleit buffer, saturated with 95% O 2:5% CO 2. The specimens were incubated at 37 °C in the buffer, continuously gassed with O 2:CO 2 (95:5). [O 2] was determined as a function of time from the phosphorescence decay rates (1 / τ) of Pd(II) meso-tetra-(4-sulfonatophenyl)-tetrabenzoporphyrin. The values of 1 / τ were linear with [O 2]: 1 / τ = 1/τo + kq [O 2]; 1 / τo = the decay rate for zero O 2, kq = the rate constant in s −1 μM −1. Results NaCN inhibited O 2 consumption, confirming oxidation occurred in the mitochondrial respiratory chain. The rate of respiration in lung specimens incubated in vitro for 3.9 ≤ t ≤ 12.4 h was 0.24 ± 0.03 μM O 2 min −1 mg −1 (mean ± SD, n = 28). The corresponding rate for the liver was 0.27 ± 0.13 ( n = 11, t ≤ 4.7 h), spleen 0.28 ± 0.07 ( n = 10, t ≤ 5 h), kidney 0.34 ± 0.12 ( n = 7, t ≤ 5 h) and pancreas 0.35 ± 0.09 ( n = 10, t ≤ 4 h). Normal tissue histology at hour 5 was confirmed by light and electron microscopy. There was negligible number of apoptotic cells by caspase 3 staining. Discussion This approach allows accurate assessment of tissue bioenergetics in vitro.

Oxygen measurements via phosphorescence

Accurate measurements of dissolved O 2 as a function of time have numerous chemical and biological applications. The Pd (II) complex of meso-tetra-(4-sulfonatophenyl)-tetrabenzoporphyrin (Pd phosphor) was used for this purpose. Detection is based on the principle that the phosphorescence of this oxygen probe is inversely related to dissolved O 2 (O 2 quenches the phosphorescence). Biologic samples containing the Pd phosphor were flashed (10/s) with a peak output of 625 nm; emitted light was detected at 800 nm. Amplified pulses of phosphorescence were digitized at 1–2 MHz using an analog/digital converter (PCI-DAS 4020/12 I/O Board) with outputs ranging from 1 to 20 MHz. Assessment revealed a customized program was necessary. Pulses were captured using a developed software at 0.1–4 MHz, depending on the speed of the computer. O 2 concentration was calculated by fitting to an exponential the decay of the phosphorescence. Twelve tasks were identified, which allowed full control and customization of the data acquisition, storage and analysis. The program used Microsoft Visual Basic 6 (VB6), Microsoft Access Database 2007, and a Universal Library component that allowed direct reading from the PCI-DAS 4020/12 I/O Board. It involved a relational database design to store experiments, pulses and pulse metadata, including phosphorescence decay rates. The method permitted reliable measurements of cellular O 2 consumption over several hours.

Cigarette smoking impairs sperm bioenergetics

The growing consensus on the negative impact of cigarette smoking on fertility prompted us to compare the rate of sperm respiration in smokers and non-smokers. Semen samples from 20 smokers and 58 non-smokers consulting at the andrology laboratory for fertility evaluation were used. Smoking was defined as consumption of at least a half a pack per day. A phosphorescence analyzer that measures O(2) concentration in sperm suspensions as function of time was used to determine the rate of respiration. In a sealed vial, the rate of sperm respiration (k) was defined as -d[O(2)]/dt; where [O(2)] was obtained from the phosphorescence decay rate of a palladium phosphor. [O(2)] in solutions containing sperm and glucose declined linearly with time, showing the kinetics of O(2) consumption was zero-order. Inhibition of O(2) consumption by cyanide confirmed the oxidations that occurred in the sperm mitochondrial respiratory chain. There were no differences (p > 0.28) between smokers and non-smokers for ejaculate volume, motility, concentration, normal morphology, viability and hypo-osmotic swelling test. The rate (mean + or - SD, in microM O(2)/min/10(8) sperm) of sperm mitochondrial O(2) consumption in the smokers was 0.96 + or - 0.58 and in the non-smokers 1.39 + or - 0.67 (p = 0.004). The rate of sperm respiration was significantly lower in smokers. This negative impact of cigarette smoking on sperm aerobic metabolism may, in part, explain the lower rate of fertility in smokers.

Quantitative measure of cytotoxicity of anticancer drugs and other agents

Many anticancer drugs act on cancer cells to promote apoptosis, which includes impairment of cellular respiration (mitochondrial O 2 consumption). Other agents also inhibit cellular respiration, sometimes irreversibly. To investigate the sensitivity of cancer cells to cytotoxins, including anticancer drugs, we compare the profiles of cellular O 2 consumption in the absence and presence of these agents. Oxygen measurements are made at 37 °C, using glucose as a substrate, with [O 2] obtained from the phosphorescence decay rate of a palladium phosphor. The rate of respiration k is defined as − d[O 2]/ dt in a sealed container. Different toxins produce different profiles of impaired respiration, implying different mechanisms for the drug-induced mitochondrial dysfunction. The decrease in the average value of k over a fixed time period, I, is proposed as a characteristic value to assess mitochondrial injury. The value of I depends on the nature of the toxin, its concentration, and the exposure time as well as on the cell type. Results for several cell types and 10 cytotoxins are presented here.