Longer Irradiation Times Research Articles

Interplay between a Heptamethine Cyanine Dye Sensitizer (IR806) and Lanthanide Upconversion Nanoparticles

AbstractLanthanide‐doped upconversion nanoparticles (UCNPs) have attractive emission properties but suffer from weak light‐absorbing capacities and thereby relatively low brightnesses. This motivates using strongly absorbing dye molecules as antennas and sensitizers. However, despite much effort, understanding of this dye‐UCNP interplay is still limited. Major sensitization mechanisms are still under discussion, largely because there is a lack of effective means to observe key factors such as dark state transitions within the dyes. Here, a combined spectroscopic procedure is established to systematically investigate the photophysics behind the dye‐UCNP interaction, embracing fluorescence‐based transient‐state excitation‐modulation, lifetime and correlation spectroscopy, and spectrofluorometry/spectrophotometry. With this procedure the heptamethine cyanine dye IR806, a typical UCNP sensitizer is studied, its photophysical model is established, its photophysics in UCL‐sensitization‐related environments is deciphered, and the energy transfer from the IR806 singlet excited state to Yb3+ (UCNP sensitizer ion) can be identified as the dominant sensitization mechanism. These studies suggest that IR806 can form non‐emissive H‐aggregates at the nanoparticle surfaces, which can be dissociated after certain light excitation duration (typically>100 µs). Moreover, buildup of a non‐fluorescent, photo‐redox state of IR806 after longer irradiation times (10–100 ms) can deleteriously affect its UCL sensitization effect, inferring an optimal excitation duration for dye‐sensitized UCNPs, relevant for, e.g., optical imaging applications.

Biological-equivalent-dose-based integrated optimization framework for fast-energy-switching Bragg peak FLASH-RT using single-beam-per-fraction.

When comparing the delivery of all beams per fraction (ABPF) to single beam per fraction (SBPF), it is observed that SBPF not only helps meet the FLASH dose threshold but also mitigates the uncertainty with beam switching in the FLASH effect. However, SBPF might lead to a higher biological equivalent dose in 2Gy (EQD2) for normal tissues. This study aims to develop an EQD2-based integrated optimization framework (EQD2-IOF), encompassing robust dose, delivery efficiency, and beam orientation optimization (BOO) for Bragg peak FLASH plans using the SBPF treatment schedule. The EQD2-IOF aims to enhance both dose sparing and the FLASH effect. A superconducting gantry was employed for fast energy switching within 27ms, while universal range shifters were utilized to improve beam current in the implementation of FLASH plans with five Bragg peak beams. To enhance dose delivery efficiency while maintaining plan quality, a simultaneous dose and spot map optimization (SDSMO) algorithm for single field optimization was incorporated into a Bayesian optimization-based auto-planning algorithm. Subsequently, a BOO algorithm based on Tabu search was developed to select beam angle combinations (BACs) for 10 lung cases. To simultaneously consider dose sparing and FLASH effect, a quantitative model based on dose-dependent dose modification factor (DMF) was used to calculate FLASH-enhanced dose distribution. The EQD2-IOF plan was compared to the plan optimized without SDSMO using BAC selected by a medical physicist (Manual plan) in the SBPF treatment schedule. Meanwhile, the mean EQD2 in the normal tissue was evaluated for the EQD2-IOF plan in both SBPF and ABPF treatment schedules. No significant difference was found in D2% and D98% of the target between EQD2-IOF plans and Manual Plans. When using a minimum DMF of 0.67 and a dose threshold of 4Gy, EQD2-IOF plans showed a significant reduction in FLASH-enhanced EQD2mean of the ipsilateral lung and normal tissue by 10.5% and 11.5%, respectively, compared to Manual plans. For normal tissues that received a dose greater than 70% of the prescription dose, using a minimum DMF of 0.7 for FLASH sparing compensated for the increase in EQD2mean resulting from replacing ABPF with SBPF schedules. The EQD2-IOF can automatically optimize SBPF FLASH-RT plans to achieve optimal sparing of normal tissues. With an energy switching time of 27ms, the loss of fractionate repairing using SBPF schedules in high-dose regions can be compensated for by the FLASH effect. However, when an energy switching time of 500ms is utilized, the SBPF schedule needs careful consideration, as the FLASH effect diminishes with longer irradiation time.

Modified Painless Photodynamic Therapy for Actinic Keratosis in China

SignificanceAminolevulinic acid photodynamic therapy (ALA-PDT) is an effective treatment for actinic keratosis (AK). However, the pain during illumination usually caused patient to discontinue PDT treatment and resulted lower efficacy. Previous study showed modified painless PDT (M-PDT) with short ALA incubation time and longer irradiation time can reduce pain and preserve the efficacy. If M-PDT worked in AK still need to investigate. ApproachA splie-face controlled clinical study was conducted. Eleven patients with facial AK received C-PDT (conventional PDT) on the left and M-PDT in the contralateral area. The left area was illuminated by a red LED light (a total light dose of 140 J/cm2) after applying the ALA cream for 3 hours; the other had illumination for a total light dose of 288 J/cm2 after applying the ALA cream for 0.5 hours. The primary endpoint was the lesion clearance rate at 1 month. Secondary endpoints included pain scores, the incidence of adverse events, and cosmetic outcomes. ResultsAt one month following 3 treatments, the lesion clearance rate of M-PDT was non-inferior to that of C-PDT (93.1% vs. 86.4%, respectively. The lesion clearance rate of M-PDT to reach 100% clearance earlier than C-PDT for grade I lesions and higher clearance rates for grade III lesions. Moreover, the pain score during illumination was significantly lower for M-PDT than for C-PDT (P < 0.01). Regarding photoaging, the Global Subjective Skin Aging Assessment (GS2A2) score showed that the total and atrophy scores of C-PDT and M-PDT were significantly improved, and M-PDT also reduced discoloration. There was no significant difference in adverse reactions between C-PDT and M-PDT. ConclusionsM-PDT is non-inferior to C-PDT in terms of efficacy for treating AK, resulting in much lower pain scores.

Photocatalytic degradation of tetracycline by Fe-doped mechanically activated SrTiO3 powders in aqueous solution

Mechanically activated strontium titanate (SrTiO3) powders with various iron (III)oxide (Fe2O3) doping levels (1.5, 3, and 6 wt%) were prepared by solid state method. Due to the possibility of iron ion incorporation in SrTiO3 onto Sr2+ and/or Ti4+ sites a detailed analysis of the influence of dopants on the microstructure, morphology, optical properties and photocatalytic activity was conducted. The XRD analysis showed that iron was incorporated into the lattice of SrTiO3 particles. In the case of a lower concentration of dopant (1.5 wt%), there was a significant relative contribution of the substitution of Sr2+ ions by Fe3+ ions. In contrast, substituting Ti4+ ions with Fe3+ ions dominated samples with an increased concentration. Optical measurements indicated a shift of the absorption edge to higher values of wavelengths where the lowest value of the band gap (Eg=1.85 eV) was for the longest activation time (120 min) and the highest weight percentages of dopant (6 wt%). All samples have degraded tetracycline (TC) where degradation increases with longer irradiation time and dopant concentration. The highest degradation at 43 % was for 120 min activated sample with 6 wt% of Fe2O3.

In Vitro Photoinactivation of Fusarium oxysporum Conidia with Light-Activated Ammonium Phthalocyanines.

Antimicrobial photodynamic therapy (aPDT) has been explored as an innovative therapeutic approach because it can be used to inactivate a variety of microbial forms (vegetative forms and spores) without causing significant damage to host tissues, and without the development of resistance to the photosensitization process. This study assesses the photodynamic antifungal/sporicidal activity of tetra- and octasubstituted phthalocyanine (Pc) dyes with ammonium groups. Tetra- and octasubstituted zinc(II) phthalocyanines (1 and 2) were prepared and tested as photosensitizers (PSs) on Fusarium oxysporum conidia. Photoinactivation (PDI) tests were conducted with photosensitizer (PS) concentrations of 20, 40, and 60 µM under white-light exposure at an irradiance of 135 mW·cm-2, applied during 30 and 60 min (light doses of 243 and 486 J·cm-2). High PDI efficiency corresponding to the inactivation process until the detection limit was observed for both PSs. The tetrasubstituted PS was the most effective, requiring the lowest concentration and the shortest irradiation time for the complete inactivation of conidia (40 µM, 30 min, 243 J·cm-2). Complete inactivation was also achieved with PS 2, but a longer irradiation time and a higher concentration (60 µM, 60 min, 486 J·cm-2) were necessary. Because of the low concentrations and moderate energy doses required to inactivate resistant biological forms such as fungal conidia, these phthalocyanines can be considered potent antifungal photodynamic drugs.

Ambient dose simulation of the ProtherWal proton therapy centre radioactive shielding decay using BDSIM and FISPACT-II

Next-generation proton therapy centres couple treatment and research programs, leading to higher beam currents and longer irradiation times than in clinical conditions. Large fluxes of energetic secondary particles are produced and long- and short-term radioactive nuclides are generated in the concrete shielding of the cyclotron vault. While the overall long-term activation of the centre is well known from the shielding design activation studies, the short-term activation peaks are still of importance when radiation protection studies are involved. The centre shielding design was validated using the BDSIM/FISPACT-II methodology combining particle tracking and Monte Carlo particle-matter interactions simulations using Beam Delivery Simulation (BDSIM) and the computation of the activation using FISPACT-II. We establish, as the next stage of our methodology, the simulation of the decay radiation of the activated concrete shielding and the accurate scoring of the related radiation protection quantities. A single BDSIM simulation per radioactive nuclide is performed based on the nuclide concentration obtained from the prior FISPACT-II activation computations at the start of a given cooling period. The evolution of the radiation protection quantities is obtained by scaling the results with the nuclides activity obtained at later times from fast FISPACT-II computations. We show the evolution of the ambient dose equivalent in the centre vault when considering regular concrete and Low Activation Concrete (LAC) as shielding material to demonstrate the efficiency of LAC mix in mitigating the shielding activation.

A study on the influence of dose rate on total ionizing dose effect of anti-fuse field programmable gate array—The irradiation damage is attenuated at low dose rate

The TID (total ionizing dose) in-situ experiments of LC1020B, an anti-fuse FPGA (Field Programmable Gate Array) device, were designed and carried out under different dose rates, and the influence of dose rate on the TID effect of FPGA was studied. The experimental results show that: 1) the TID irradiation failure of the FPGA under different dose rates has nothing to do with the input voltage parameter exceeding the standard. 2) with the decrease of cobalt source irradiation dose rate [171, 26.83, and 2.68 mGy(Si)/s], the TID effect failure dose threshold [168, 229, and 334 Gy(Si), respectively] of the FPGA gradually increased, showing obvious attenuation of low dose rate damage. Theoretical analysis suggests that, compared with the space charge limitation effect, the oxide charge annealing effect plays a dominant role, and longer irradiation time is beneficial to the oxide charge annealing. And based on the experimental data, an FPGA TID analytical model with power consumption current as the damage characterization parameter is established, which lays a foundation for scientific evaluation of radiation effect of anti-fuse FPGAs.

Investigation of Hibiscus sabdariffa as a new eco-friendly photo-larvicidal natural product for the control of mosquitoes

The Culex spp. is a vector of several disease-causing organisms including filarial parasites, encephalitis virus and the West Nile Virus; the control of these diseases is hinged on controlling the vector. Synthetic insecticides have previously been applied in the control of Culex spp. which poses a danger to the environment. In the present research, the use of light and a naturally occurring product, methanol extract of Hibiscus sabdariffa calyces (HSME), in controlling the breeding and spread of Culex tritaeniorhynochus was investigated. Third instar larvae of C. tritaeniorhynochus were fed with HSME and exposed to light for 18 hours. Results indicate over 80% mortality of the test sample with LC50 of 528.44 ppm; also increase in percentage mortality with corresponding increase in HSME concentration and longer irradiation time was established. The trend observed in light reactions was not seen in the control and dark reactions, implying that the presence of light and the photosensitizer (HSME) is required to induce mortality in Culex tritaeniorhynochus larvae population.

Self-consistent numerical evaluation of concrete shielding activation for proton therapy systems

Due to the advancement of proton therapy for cancer treatment, there has been a worldwide increase in the construction of treatment facilities. Therapy centres are often coupled with clinical, biological or material-science research programs. Research activities require proton beams at energies spanning an extensive range with higher beam currents and longer irradiation times than clinical conditions. Additionally, next-generation proton therapy systems are evolving towards more compact designs. In addition to the increased centres’ workloads, reducing the system in size produces a more significant number of secondary particles per unit volume and time. Therefore, the activation level of materials constituting those future proton therapy centres is expected to be higher, increasing the ambient dose and the amount of radioactive waste collected at the end of a centre’s lifetime. These operating conditions pose new challenges for the shielding design and the reduction of the concrete activation. To tackle them, we propose a novel approach to seamlessly simulate all the processes relevant for the evaluation of the concrete shielding activation using, as an illustration, the Ion Beam Applications Proteus^circledR One system. A realistic model of the system is developed using Beam Delivery Simulation (BDSIM), a Geant4-based particle tracking code. It allows a single model to simulate primary and secondary particle tracking in the beamline, its surroundings, and all particle-matter interactions. The code system and library database FISPACT-II allows the computation of the shielding activation by solving the rate equations using ENDF-compliant group library data for nuclear reactions, particle-induced or spontaneous fission yields, and radioactive decay. As input, FISPACT-II is provided with the secondary particle fluences scored using the BDSIM Monte Carlo simulations. This approach is applied to the proton therapy research centre of Charleroi, Belgium. Results compare the evolution of the clearance level and the long-lived nuclide concentrations throughout the facility lifetime when using regular concrete or the newly developed Low Activation Concrete (LAC). A comparison with the initial shielding dimensioning has been performed for all the shielding walls to validate the methodology and highlight the clear benefits of integrating LAC inserts in the shielding design. The effectiveness of coupling BDSIM and FISPACT-II gives a glimpse of the possibility of a complete activation study following the actual workloads of the centre, allowing a better assessment of the shielding activation level at any time of the facility lifespan.

Investigation of Hibiscus sabdariffa as a new eco-friendly photo-larvicidal natural product for the control of mosquitoes

The Culex spp. is a vector of several disease-causing organisms including filarial parasites, encephalitis virus and the West Nile Virus; the control of these diseases is hinged on controlling the vector. Synthetic insecticides have previously been applied in the control of Culex spp. which poses a danger to the environment. In the present research, the use of light and a naturally occurring product, methanol extract of Hibiscus sabdariffa calyces (HSME), in controlling the breeding and spread of Culex tritaeniorhynochus was investigated. Third instar larvae of C. tritaeniorhynochus were fed with HSME and exposed to light for 18 hours. Results indicate over 80% mortality of the test sample with LC50 of 528.44 ppm; also increase in percentage mortality with corresponding increase in HSME concentration and longer irradiation time was established. The trend observed in light reactions was not seen in the control and dark reactions, implying that the presence of light and the photosensitizer (HSME) is required to induce mortality in Culex tritaeniorhynochus larvae population.

36 - Low Power Laser Debonding: Ceramic Thickness and Irradiation Time

To evaluate the effect of irradiation time, for debonding purposes, on the shear bond strength of yttria-stabilized zirconia (YSZ) irradiated by an erbium-based laser at low power output under body temperature conditions. YSZ square-shaped slices of 0.5 mm, 2 mm, and 3 mm thicknesses were tribochemical silica-coated and cemented to resin composite cylinders with a resin-based cement. Five groups of specimens were tested, one served as the control group (non-irradiated) and the other four were submitted to laser irradiation for 30 s, 60 s, 90 s, and 120 s. After water storage for 24 h, the control and the irradiated group were subjected to shear bond strength (SBS) test. Both, the testing and the irradiation were performed at body temperature. For irradiation, an erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser was used with the following parameters: 1 W, 20 Hz, and 1% of air spray. Optical microscope and scanning electron microscope were used for failure analysis. SBS data were analyzed using two-way ANOVA and Tukey post hoc test to determine significant differences. Data for irradiated groups are shown in the table. The control group (9.22.4) showed only significant differences with the 0.5 mm group at 30 (p<0.001), 60 (p<0.001), 90 (p<0.001), and 120 s (p<0.001). No statistical differences were found between the 2 and 3 mm groups at any irradiation time. The 0.5 mm group presented significantly low bond strength in comparison with the other groups. For the 0.5 mm group, the SBS values were significantly different after 30 and 120 s of irradiation (p=0.018), while all the other irradiation times had similar values. All the failures were classified as mixed. Zirconia SBS in the thickest groups (2 and 3 mm) was not affected by any of the irradiation times tested. Longer irradiation times might reduce the SBS of thicker zirconia for debonding purposes. For the thin group, any irradiation time decreased the bond strength to the resin cement.

Photochemical Properties of a Mononuclear Mn(I) Triscarbonyl Complex in Water: An Insight into Different Oxidation States

AbstractThis study reports the photochemical behavior of fac‐[Mn(phen)CO3(4MeImH)]+ in neutral aqueous solution. The complex presents two 4MeImH linkage isomers, adjacent (A) and remote (R), which coexist in solution although with marked stability differences. In water, the steric effect converts A into an aqua‐complex while R remains stable. Photolysis of the mixture followed by UV‐vis, infrared (IR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and cyclic voltammetry showed changes in the coordination sphere and oxidation state of each Mn center. Upon light irradiation, the mixture behaves as an antenna system to absorb light, producing the {Mn(II)(phen.−)}+ moieties and releasing CO, which provides open sites for water coordination. Upon successive irradiation, the EPR spectra showed an increasing signal at g=2.0 corresponding to Mn(II) centers, a phenanthroline anion (2.0046) that vanishes at longer irradiation time, and an increasing component (gx∼9.85 and gy∼3.9) corresponding to Mn(IV). This makes the spectroscopic properties, excited state character, and dynamics of fac‐[Mn(phen)(CO)3(4MeImH)]+ significantly different from those of all manganese complexes studied so far.

Design of Novel Photocatalytic Films for the Protection of Architectural Surfaces via the Incorporation of Green Photocatalysts

In conservation science the demand of multifunctional green materials displaying water repellency, consolidation, resistance to organic pollutants and pigments is constantly increasing. This research developed a green nanocomposite exhibiting photocatalytic, hydrophobic, consolidation and self-cleaning properties. This was achieved by synthesizing a TiO2 photocatalyst enriched with carbon dots (C-dots) and successfully incorporated into a tetraethoxysilane nanocomposite modified with nano-calcium oxalate and polydimethylsiloxane. The TiO2/C-dots that were prepared with a simple, low temperature, cost-effective and large-scale procedure were assessed via analytical and spectroscopic techniques and were resulted in anatase structure ranging in size from 10 to 40 nm. Photooxidation measurements displayed that TiO2/C-dots nanoparticles could photodegrade completely Methyl Orange (MO) under UV and visible irradiation after 120 min. The photocatalytic performance of the nanocomposite with TiO2/C-dots resulted promising under UV after longer irradiation time. The degradation of MO was faster on bulk xerogels containing the TiO2/C-dots than the corresponding ones with TiO2. The treatment of concrete, limestone and lime mortars with the nanocomposite proved to be compatible with the substrates in terms of aesthetical aspects. This study demonstrates encouraging potential for large-scale production of a multifunctional protective composite that offers hydrophobicity, self-cleaning properties and consolidation to architectural surfaces.

New Inorganic Boron Assessment in environmental Samples by Neutron Activation Analysis using CR-39 Solid State Nuclear Track Detectors.

A new trend in applying nuclear solid-state track detector CR-39 for neutron activation assessment of inorganic boron compounds in environmental samples was established. The nuclear reaction 10B(n, α)7Li was selected for this purpose by using gelatin film for a sample application. It possesses many advantages such as time saving, sensitivity, and reproduciblity, and many related variables were studied. Linearity was found at the range of 1.0 - 12.5 ppm and at 10.0 -250 ppm with different slopes. There were no interfering nuclei among the naturally abundant elements and their isotopes, viz. Al, O, Na, Cl, P, Ca, Si, K, and Cu. It was applied to determine boron in simulated environments and industrial soil and water samples, with recovery within the range of 96-100 %, good precision and accuracy + 1.5 - 3.0 %. The method sensitivity can be enhanced by using longer irradiation time, and few micrograms of boron can be analysed, and hence it is more suitable to be used in the activation analysis system of nuclear reactors.

Effect of pH of bleaching agent on tooth bleaching action in vitro.

This study investigated the effect of pH of bleaching agent, photo-irradiation time or application times on bleaching action using hematoporphyrin-stained papers (HSPs) and artificially stained bovine-teeth (BT). 23% H2O2 with pH 5.5, 6.0, 7.0, 8.0 and 9.0 were applied on the specimens. HSP was photo-irradiated for 1, 3 and 5 min. BT were photo-irradiated for 10 min and the bleaching was repeated ten times (n=10). CIE L*a*b* of the specimens were measured before and after the procedure. Data were analyzed by repeated-measures ANOVA followed by multiple comparisons with Bonferroni correction. For the HSP, longer irradiation time and higher pH yielded significantly higher color difference (ΔE). As for BT, increasing application times and higher pH resulted in higher ΔE. It was concluded that the pH of the bleaching agent significantly improved the bleaching effect with increased photo-irradiation time for HSP and with an increase of repeated application times for BT.

Dosimetric study between a single isocenter dynamic conformal arc therapy technique and Gamma Knife radiosurgery for multiple brain metastases treatment: impact of target volume geometrical characteristics

PurposeTo compare linac-based mono-isocentric radiosurgery with Brainlab Elements Multiple Brain Mets (MBM) SRS and the Gamma Knife using a specific statistical method and to analyze the dosimetric impact of the target volume geometric characteristics. A dose fall-off analysis allowed to evaluate the Gradient Index relevancy for the dose spillage characterization.Material and methodsTreatments were planned on twenty patients with three to nine brain metastases with MBM 2.0 and GammaPlan 11.0. Ninety-five metastases ranging from 0.02 to 9.61 cc were included. Paddick Index (PI), Gradient Index (GI), dose fall-off, volume of healthy brain receiving more than 12 Gy (V12Gy) and DVH were used for the plan comparison according to target volume, major axis diameter and Sphericity Index (SI). The multivariate regression approach allowed to analyze the impact of each geometric characteristic keeping all the others unchanged. A parallel study was led to evaluate the impact of the isodose line (IDL) prescription on the MBM plan quality.ResultsFor mono-isocentric linac-based radiosurgery, the IDL around 70–75% was the best compromise found. For both techniques, the GI and the dose fall-off decreased with the target volume. In comparison, PI was slightly improved with MBM for targets < 1 cc or SI > 0.78. GI was improved with GP for targets < 2.5 cc. The V12Gy was higher with MBM for lesions > 0.4 cc or SI < 0.84 and exceeded 10 cc for targets > 5 cc against 6.5 cc with GP. The presence of OAR close to the PTV had no impact on the dose fall off values. The dose fall-off was higher for volumes < 3.8 cc with GP which had the sharpest dose fall-off in the infero-superior direction up to 30%/mm. The mean beam-on time was 94 min with GP against 13 min with MBM.ConclusionsThe dose fall-off and the V12Gy were more relevant indicators than the GI for the low dose spillage assessment. Both evaluated techniques have comparable plan qualities with a slightly improved selectivity with MBM for smaller lesions but with a healthy tissues sparing slightly favorable to GP at the expense of a considerably longer irradiation time. However, a higher healthy tissue exposure must be considered for large volumes in MBM plans.

Laboratory study of the formation of fullerene (from smaller to larger, C44 to C70)/anthracene cluster cations in the gas phase

The formation and evolution mechanism of fullerenes in the planetary nebula or in the interstellar medium are still not understood. Here, we present the study on the cluster formation and the relative reactivity of fullerene cations (from smaller to larger, C44 to C70) with anthracene molecule (C14H10). The experiment is performed in an apparatus that combines a quadrupole ion trap with a time-of-flight mass spectrometer. By using a 355 nm laser beam to irradiate the trapped fullerenes cations (C60 + or C70 +), smaller fullerene cations C(60 – 2n) +, n = 1 – 8 or C(70 – 2m) +, m = 1 – 11 are generated, respectively. Then reacting with anthracene molecules, series of fullerene/anthracene cluster cations are newly formed (e.g., (C14H10)C(60 – 2n) +, n = 1 – 8 and (C14H10)C(70 – 2m) +, m = 1 – 11), and slight difference of the reactivity within the smaller fullerene cations are observed. Nevertheless, smaller fullerenes show obviously higher reactivity when comparing to fullerene C60 + and C70 +. A successive loss of C2 fragments mechanism is suggested to account for the formation of smaller fullerene cations, which then undergo addition reaction with anthracene molecules to form the fullerene-anthracene cluster cations. It is found that the higher laser energy and longer irradiation time are key factors that affect the formation of smaller fullerene cations. This may indicate that in the strong radiation field environment (such as photon-dominated regions) in space, fullerenes are expected to follow the top-down evolution route, and then form small grain dust (e.g., clusters) through collision reaction with co-existing molecules, here, smaller PAHs.

Microwave assisted dilute organic acid pre-treatment of oil palm empty fruit bunch to improve enzyme accessibility

The depletion of fossil fuel is intriguing for researchers to find sustainable energy. Oil palm empty fruit bunch (OPEFB) is abundant biomass in Indonesia which is potential to be converted into bioethanol because of its high cellulose content. Suitable pre-treatment could increase the effectiveness of cellulose conversion into sugars. The aim of this study is to evaluate the effectiveness of Microwave-assisted Oxalic Acid pre-treatment (MOxA) and Enzymatic Hydrolysis (EH) to improve enzyme accessibility through variation of heating temperature, irradiation time, and EH incubation time. The higher the microwave heating temperature, longer irradiation time, and longer EH incubation time, the higher the glucose yield per pulp (GY) and reducing sugar yield (RSY) were observed. After MOxA at 200°C-15 min, as much as 43.22 % GY per initial biomass was obtained by EH for 10 days. SEM images showed more ruptures on the surface area of OPEFB fibre after MOxA that supported in increasing of enzyme digestibility. The XRD spectra demonstrated that the crystallinity index (CI) increased after MOxA because pre-treatment reduced amorphous components in the biomass. In addition, the FTIR spectra showed that peak intensity at 1714 cm−1 corresponded to hemicellulose was gradually reduced after MOxA while peaks corresponded to lignin was more discernible.

Eradicating Infecting Bacteria while Maintaining Tissue Integration on Photothermal Nanoparticle-Coated Titanium Surfaces.

Photothermal nanoparticles locally release heat when irradiated by near-infrared (NIR). Clinical applications initially involved tumor treatment, but currently extend toward bacterial infection control. Applications toward much smaller, micrometer-sized bacterial infections, however, bear the risk of collateral damage by dissipating heat into tissues surrounding an infection site. This can become a complication when photothermal nanoparticle coatings are clinically applied on biomaterial surfaces requiring tissue integration, such as titanium-made, bone-anchored dental implants. Dental implants can fail due to infection in the pocket formed between the implant screw and the surrounding soft tissue (“peri-implantitis”). We address the hitherto neglected potential complication of collateral tissue damage by evaluating photothermal, polydopamine nanoparticle (PDA-NP) coatings on titanium surfaces in different coculture models. NIR irradiation of PDA-NP-coated (200 μg/cm2) titanium surfaces with adhering Staphylococcus aureus killed staphylococci within an irradiation time window of around 3 min. Alternatively, when covered with human gingival fibroblasts, this irradiation time window maintained surface coverage by fibroblasts. Contaminating staphylococci on PDA-NP-coated titanium surfaces, as can be per-operatively introduced, reduced surface coverage by fibroblasts, and this could be prevented by NIR irradiation for 5 min or longer prior to allowing fibroblasts to adhere and grow. Negative impacts of early postoperative staphylococcal challenges to an existing fibroblast layer covering a coated surface were maximally prevented by 3 min NIR irradiation. Longer irradiation times caused collateral fibroblast damage. Late postoperative staphylococcal challenges to a protective keratinocyte layer covering a fibroblast layer required 10 min NIR irradiation for adverting a staphylococcal challenge. This is longer than foreseen from monoculture studies because of additional heat uptake by the keratinocyte layer. Summarizing, photothermal treatment of biomaterial-associated infection requires precise timing of NIR irradiation to prevent collateral damage to tissues surrounding the infection site.

Deep proteome profiling of SW837 cells treated by photodynamic therapy (PDT) reveals the underlying mechanisms of metronomic and acute PDTs.

Metronomic photodynamic therapy (mPDT) with a longer irradiation time and lower energy compared with acute (or classic) photodynamic therapy (aPDT) is a more effective treatment than aPDT for tumor cells, especially colorectal cancer. However, the underlying mechanisms of the superior effects of mPDT are unknown. we used SWATH-MS (sequential window acquisition of all theoretical mass spectra) to identify differentially expressed proteins (DEPs) specific to aPDT (conventional fluence rate, 20 mW/cm2, 4 min 10 s), mPDT (metronomic fluence rate, 0.4 mW/cm2, 3.5 h), and control groups of SW837 cells. The photosensitizer used in both PDT methods was aminolevulinic acid which were incubated with the cells before irradiation. A total of 6805 proteins were identified in the three groups of SW837 cells. aPDT induced 333 DEPs and mPDT induced 1716 DEPs compared with the control. We identified 185 common DEPs in the two PDT groups, 148 different DEPs in the aPDT group, and 1531 different DEPs in the mPDT group. Most of the 185 common DEPs were involved in the extracellular component, participated in the processes of vesicle transport and secretion, binding, and hydrolase/catalytic activity. They were also involved in PI3K-Akt, cGMP-PKG, RAS, and aAMP signaling pathways. In addition, the 1531 different DEPs in the mPDT group participated in similar processes and molecular functions, but in a more complex manner than those in the aPDT group. our proteome data suggest that mPDT has a complex tumor destruction mechanism with more involved proteins compared with aPDT, which may explain the better tumor killing effect of mPDT.