Oxoplatin-B, a cisplatin-based platinum(IV) complex with photoactive BODIPY for mitochondria specific "chemo-PDT" activity.

Oxoplatin-B, a platinum(IV) complex [Pt(NH3)2Cl2(L1)(OH)] (1) of 4-methylbenzoic acid (HL1) functionalized with 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) was prepared, characterized and its antitumor activity studied. [Pt(NH3)2Cl2(L2)(OH)] (2) of 4-methylbenzoic acid (HL2) was studied as a control. Complex 1 showed an absorption band at 500 nm (ɛ = 4.34 × 104 M-1 cm-1) and an emission band at 515 nm (λex = 488 nm, ΦF = 0.64) in 1% dimethyl sulfoxide/Dulbecco's Modified Eagle's Medium (pH = 7.2). Visible light-induced (400-700 nm) generation of singlet oxygen was evidenced from 1,3-diphenylisobenzofuran titration study. Complex 1 showed photo-induced cytotoxicity in visible light (400-700 nm, 10 J cm-2) against human breast cancer (MCF-7), cervical cancer (HeLa) and lung cancer (A549) cells (IC50: 1.1-3.8 µM) while being less toxic in normal cells. Confocal imaging showed mitochondrial localization with additional evidence from platinum content from isolated mitochondria and 5,5,6,6'-tetrachloro-1,1',3,3' tetraethylbenzimi-dazoylcarbocyanine iodide (JC-1) assay. Cellular apoptosis was observed from Annexin-V-FITC (fluorescein isothiocyanate)/propidium iodide assay.

Near-infrared emission tracks inter-individual variability of carboxylesterase-2 via a novel molecular substrate.

A low-molecular-weight molecule (4-(2-(3-(dicyanomethyl)-5,5-dimethylcyclohex-1-en-1-yl)vinyl)phenyl-benzoate, DDPB) has been developed. The organic framework possesses very weak fluorescence . The feasibility of the signal transduction has been performed via fluorometric titrations in solution. DDPB gives rise to responses to carboxylesterase 2 (CES2) based on "off-on" responses. The red emission at 670 nm has been derived from the enzyme-induced hydrolysis of ester linkages, thus suppressing the intramolecular charge transfer (ICT) effect and thereby generating the fluorescent segment. The optical excitation window for this probe is extended to the visible light range (λex = 516 nm), and it will induce less harmful influence on biological substances. The detection limit for the measurement of CES2 concentration is as low as 2.33 mU/mL. The conventional studies concerning the activation process are generally performed within only a single liveing cell system. In this study, it is the first time that expression of carboxylesterase 2 in five kinds of cell lines (HeLa > C1498 > active T cell > Jurkat > unactive T cell) has been clarified by flow cytometry, Western blotting, and confocal microscopy analysis. The elucidation of CES2 and its variability in a variety of cells will open new ways for drug metabolism and disease prevention. Graphical abstract We reported a new "substrate-mediated light-on" strategy based on an ester bond cleavage reaction. Most of prepared nanomaterials and organic fluorophores possessed short wavelength emissions in the blue or green region which will not be difficult for cellular imaging. In this study, a novel functional molecule (DDPB) was considered as the substrate for CES2 and the optical "off-on" response was realized. DDPB was cell permeable and possessed very low cytotoxicity. Moreover, the identification of CES2 and their subtle changes in five different cells afforded the sequence for carboxylesterase-2 as Hela > C1498 > Active T cell > Jurkat > Unactive T cell. Inhibition studies showed that the hydrolysis of DDPB was effectively suppressed by bis-p-nitrophenyl phosphate and the cellular tracking results firmly supported this point. To our knowledge, the inter-individual variability for the CES2 expressions in five different cell lines has never been reported via the substrate induced optical changes.

A sequential targeting nanoplatform for anaplastic thyroid carcinoma theranostics.

Effective accumulation of nanoparticles (NPs) in tumor regions is one of the major motivations in nanotechnology research and that the establishment of an efficient targeting nanoplatform for the treatment of malignant tumors is urgently needed for theranostic applications. In this study, we engineered multifunctional sequential targeting NPs for achieving synergistic antiangiogenic photothermal therapy (PTT) and multimodal imaging-guided diagnosis for anaplastic thyroid carcinoma (ATC) theranostics. Antibody bevacizumab with an affinity towards vascular endothelial growth factor (VEGF) on the tumor cell surface was conjugated onto the surface of polymer NPs for VEGF targeting and antiangiogenic therapy. Encapsulated IR825 was employed as a photothermal agent (PTA) with a mitochondrial targeting capability, which further cascades NPs into mitochondria to enhance hyperthermic efficiency in the ablation of tumor cells. Importantly, the combination of bevacizumab and IR825 in a single nanosystem achieved desirable accumulations of NPs and that sequential targeted PTT combined with antiangiogenesis significantly promoted the therapeutic efficiency in eradicating tumors by near-infrared (NIR) laser irradiation. Furthermore, these NPs are extraordinary contrast agents for photoacoustic, ultrasound and fluorescence imaging applications, providing multimodal imaging capabilities for therapeutic monitoring and a precise diagnosis. Therefore, this multifunctional nanoplatform provides a promising theranostic strategy for extremely malignant ATC. STATEMENT OF SIGNIFICANCE: Anaplastic thyroid carcinoma (ATC), with extremely aggressive behavior, lacks a satisfactory therapeutic method and a comprehensive early diagnostic strategy. Herein, we successfully synthesized a sequential targeting nanoplatform (IR825@Bev-PLGA-PFP NPs) with theranostic function, which specifically binds to VEGF on the tumor cell surface and further cascades into mitochondria to achieve effective accumulation of NPs in the tumor regions. As a result, it solves the urgent demand for ATC detection and therapy. By breaking the limitation of traditional target, such as low efficacy and frequent recurrence as the results of low accumulation, sequential targeting combined with synergistic antiangiogenic PTT completely eradicates tumors without any residual tissue and side effect. Therefore, this strategy paves a solid way for further investigation in the theranostic progressing of ATC.

Direct monitoring of light mediated hyperthermia induced within mammalian tissues using surface enhanced spatially offset Raman spectroscopy (T-SESORS).

Here we demonstrate light mediated heating of nanoparticles confined deep inside mammalian tissue, whilst directly monitoring their temperature non-invasively using a form of deep Raman spectroscopy, T-SESORS. One of the main barriers to the introduction of photo-thermal therapies (PTT) has been recognised as the inability to directly monitor the local temperature deep within the tissue at the point of therapy. Here Au nanoparticles with a Raman reporter molecule (temperature reporters) are used in combination with Au nanoshells (heat mediators) to provide simultaneously heating under NIR illumination and direct spectroscopic monitoring of local temperature deep within mammalian tissues. The surface enhanced Raman signal was read out at the tissue surface using a transmission geometry in this example and the temperature of the tissue was ascertained from the anti-Stokes to Stokes Raman reporter. This approach opens the prospect of non-invasive hyperthermia treatments with direct temperature feedback from deep inside within tissue, where nanoparticles can be used to both provide localised heating and accurately monitor the local temperature.

UV-irradiated 2-methyl-4'-(methylthio)-2-morpholinopropiophenone-containing injection solution produced frameshift mutations in the Ames mutagenicity assay.

In previous studies, we detected the photoinitiators 1-hydroxycyclohexyl phenyl ketone (1-HCHPK), methyl 2-benzoylbenzoate (MBB), and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMP) in intravenous injection solutions. In addition, we reported that 1-HCHPK, MBB, and MTMP exhibited cytotoxicity towards normal human peripheral blood mononuclear cells. A previous in vitro study reported that a free-radical photoinitiator introduced covalently bound purine residues into DNA. However, little is known about the in vitro mutagenicity of 1-HCHPK, MBB, and MTMP. In the present in vitro study, we evaluated the mutagenicity of 1-HCHPK, MBB, and MTMP using the Ames test. We found that untreated 1-HCHPK, MBB, and MTMP were not mutagenic in S. typhimurium strain TA97, TA98, TA100, TA102, or TA1535, regardless of the presence/absence of S9 activation. However, ultraviolet (UV) light-irradiated MTMP exhibited mutagenicity in S. typhimurium strain TA97 in the absence of S9 activation. In conclusion, we suggest that exposure to UV-irradiated MTMP, including in intravenous injection solutions, can result in frameshift mutations.

Photostability evaluation of five UV-filters, trans-resveratrol and beta-carotene in sunscreens.

Trans-resveratrol (RES) is used in cosmetic formulations and beta-carotene (BTC) is a classical sunscreen antioxidant, but their photostability in sunscreens, a property directly correlated to performance and safety has not been addressed in the literature. This paper reports the assessment of RES and/or BTC influence on the photostability of five UV-filters (octyl methoxycinnamate - OMC, avobenzone -AVO, octocrylene - OCT, bemotrizinole - BMZ, octyltriazone - OTZ) in three different combinations after UVA exposure followed by the identification of degradation products and the assessment of photoreactivity. The evaluation of sunscreen photostability was performed by HPLC and spectrophotometric analysis, and degradation products were identified by GC-MS analysis. Components RES, BTC, OMC and AVO were significantly degraded after UV exposure (reduction of around 16% in recovery). According to HPLC analysis, all formulations presented similar photostability profiles. Eleven degradation products were identified in GC-MS analysis, among them products of RES, BTC, OMC and AVO photodegradation. All evaluated formulations were considered photoreactive, as well as the isolated compounds RES and AVO. Considering HPLC, spectrophotometric and GC-MS results, it is suggested that formulations containing BMZ were considered the most photostable. The combination RES+BTC in a sunscreen improved the photostability of AVO. The benefits of using a combination of antioxidants in sunscreens was demonstrated by showing that using RES+BTC+studied UV-filters led to more photostable formulations, which in turn implies in better safety and efficacy.

Identification of halogenated photoproducts generated after ultraviolet-irradiation of parabens and benzoates in water containing chlorine by solid-phase microextraction and gas chromatography-mass spectrometry.

This work presents a new solid-phase microextraction (SPME)-based approach to investigate the formation of halogenated by-products generated by the UV-induced photodegradation of parabens and their congener benzoates in water containing chlorine. Degradation of parent species, and further identification of their transformation by-products were monitored by gas chromatography coupled to mass spectrometry (GC/MS). In order to improve detectability, SPME was applied as a preconcentration step after UV-irradiation of target preservatives. Experiments performed with dechlorinated water, ultrapure water, and tap water showed that under UV-light, the presence of even low levels of free chlorine, increases the photodegradation rate of target preservatives, enhancing the formation of halogenated photoproducts. Monobrominated, dibrominated and bromochlorinated hydroxybenzoates were identified, and the transformation of benzoates into halogenated parabens was also confirmed. Bromination is expected to occur when free chlorine is present, due to the presence of traces of bromide in water samples. Five halogenated phenols (mainly brominated) were detected as breakdown photoproducts from both families of target preservatives. On the basis of the appearance of the aforementioned by-products, a tentative transformation pathway, consistent with the photoformation-photodecay kinetics of the by-products, is proposed herein for the first time.

Interrogating selectivity in catalysis using molecular vibrations.

The delineation of molecular properties that underlie reactivity and selectivity is at the core of physical organic chemistry, and this knowledge can be used to inform the design of improved synthetic methods or identify new chemical transformations. For this reason, the mathematical representation of properties affecting reactivity and selectivity trends, that is, molecular parameters, is paramount. Correlations produced by equating these molecular parameters with experimental outcomes are often defined as free-energy relationships and can be used to evaluate the origin of selectivity and to generate new, experimentally testable hypotheses. The premise behind successful correlations of this type is that a systematically perturbed molecular property affects a transition-state interaction between the catalyst, substrate and any reaction components involved in the determination of selectivity. Classic physical organic molecular descriptors, such as Hammett, Taft or Charton parameters, seek to independently probe isolated electronic or steric effects. However, these parameters cannot address simultaneous, non-additive variations to more than one molecular property, which limits their utility. Here we report a parameter system based on the vibrational response of a molecule to infrared radiation that can be used to mathematically model and predict selectivity trends for reactions with interlinked steric and electronic effects at positions of interest. The disclosed parameter system is mechanistically derived and should find broad use in the study of chemical and biological systems.

Evaluation of accelerated UV and thermal testing for benzene formation in beverages containing benzoate and ascorbic acid.

Under certain conditions, benzene can form in beverages containing benzoic and ascorbic acids. The American Beverage Assn. (ABA) has published guidelines to help manufacturers mitigate benzene formation in beverages. These guidelines recommend accelerated testing conditions to test product formulations, because exposure to ultraviolet (UV) light and elevated temperature over the shelf life of the beverage may result in benzene formation in products containing benzoic and ascorbic acids. In this study, the effects of UVA exposure on benzene formation were determined. Benzene formation was examined for samples contained in UV stabilized and non-UV stabilized packaging. Additionally, the usefulness of accelerated thermal testing to simulate end of shelf-life benzene formation was evaluated for samples containing either benzoic or ascorbic acid, or both. The 24 h studies showed that under intense UVA light benzene levels increased by as much as 53% in model solutions stored in non-UV stabilized bottles, whereas the use of UV stabilized polyethylene terephthalate bottles reduced benzene formation by about 13% relative to the non-UV stabilized bottles. Similar trends were observed for the 7 d study. Retail beverages and positive and negative controls were used to study the accelerated thermal testing conditions. The amount of benzene found in the positive controls and cranberry juice suggests that testing at 40 degrees C for 14 d may more reliably simulate end of shelf-life benzene formation in beverages. Except for cranberry juice, retail beverages were not found to contain detectable amounts of benzene (<0.05 ng/g) at the end of their shelf lives.

Photovalorisation of pentafluorobenzoic acid with platinum doped TiO2.

Pt-doped TiO(2) has been prepared and characterized by various surface analytical methods such as BET surface area, scanning electron micrographs (SEM), X-ray diffraction (XRD), energy dispersive X-ray micro analysis (EDX) and diffuse reflectance spectroscopy (DRS). Photodefluoridation of pentafluorobenzoic acid (PFBA) to fluoride ions has been carried out using TiO(2) and Platinum doped TiO(2) with UV-C (200-300 nm) light. The defluoridation was monitored by the ionometer with fluoride ion selective electrode. Photodeposition of 1.5% Platinum on the surface of TiO(2) enhances its photoactivity in pentafluorobenzoic acid defluoridation. In order to optimize the working conditions, effects of pH and initial PFBA concentration were analyzed. Addition of inorganic oxidizing species KIO(4,) H(2)O(2), (NH(4))S(2)O(8) and KBrO(3) strongly influenced the photocatalytic defluoridation of PFBA. The significant enhancement in the Pt-TiO(2) photoactivity under UV irradiation can be ascribed to the platinum deposits, acting as electron traps on the Pt-TiO(2) surface. The fluoride ions formed during photodefluoridation can be used for the production of CaF(2).

Photolysis of the herbicide bispyribac sodium in aqueous medium under the influence of UV and sunlight in presence or absence of sensitizers.

The photolysis of a rice herbicide Bispyribac sodium (Sodium 2, 6-bis [(4, 6-dimethoxypyrimidin-2-yl) oxy] benzoate) has been studied in different aqueous medium (distilled water, pond water and Irrigation water) under the influence of UV (lambda max > or = 250 nm) and sunlight in presence or absence of sensitizers (TiO(2) and KNO(3)). The study was conducted under laboratory simulated condition which made it possible to evaluate the contribution of different factors viz. source of irradiation, solvent and sensitizers towards the photolysis of bispyribac sodium. The photodegradation proceeds via first order reaction Kinetics in all the cases. Five photo metabolites (M(1)-M(5)) were isolated in pure form by column chromatographic method from the irradiation system under UV influenced and TiO(2) as sensitizer. From the different spectral data (IR, NMR, UV-VIS, Mass) the structure of these five metabolites were assigned as M(1) (Phenol), M(2) [2, 6-Dihydroxy benzoic acid], M(3) [2, 6-bis [(4, 6 dimethoxypyrimidin-2yl) oxy] benzoic acid], M(4) [2-(3-Hydroxy-phenoxy)-pyrimidine-4, 6-diol] and M(5) as [2,4-Dihydroxy-3, 5-dimethoxy-6-(4-methoxy pyrimidine-2-yloxy)-benzoic acid]. Moreover, another six photometabolites (M(6)-M(11)) were identified from the different irradiation system on the basis of Micromass analysis. On the basis of MS/MS data analysis, the structure of these six photometabolites were assigned as M(6) [2-(4, 6-Dimethoxy-pyrimidin-2-yloxy)-6-hydroxy-benzoic acid], M(7) [2-Hydroxy-6-(4-hydroxy-6-methoxy-pyrimidin-2-yloxy)-benzoic acid], M(8) [4, 6-Dimethoxy-pyrimidin-2-ol], M(9) [6-Methoxy-pyrimidine-2, 4-diol], M(10) [2-Hydroxy-6-(pyrimidin-2-yloxy)-benzoic acid] and M(11) [2, 4, 6-Trimethoxy-pyrimidine]. The plausible Photodegradation pathways of bispyribac sodium in the present investigation were portrayed which proceeds via hydrolysis, hydrolytic cleavage, O-dealkylation, decarboxylation, dehydroxylation, O-alkylation and hydroxylation.

Determination of tris(2-ethylhexyl)trimellitate released from PVC tube by LC-MS/MS.

Tris(2-ethylhexyl)trimellitate (TOTM) is used as an alternative plasticizer of polyvinyl chloride (PVC) medical devices. A method for the determination of TOTM released from PVC medical devices into intravenous preparations was developed, which uses liquid chromatography-tandem mass spectrometry (LC-MS/MS). A PVC tube was filled with an intravenous preparation and extraction was carried out by shaking for 1h at room temperature. LC was performed with an Inertsil-C8 (50 mm x 2.1 mm, 5 microm) column. The isocratic mobile phase was acetonitrile:purified water (90:10, v/v) at a flow rate of 0.2 ml/min. MS detection was accomplished with an MS/MS detector equipped with a turbo ionspray ionization source in the positive ion mode. The limit of detection and the limit of quantification for the standard solution of TOTM was 0.5 ng/ml (S/N=3) and 1.0 ng/ml (S/N > or =10), respectively. When Prograf (tacrolimus) was used, the average recovery of TOTM was 101.1% (R.S.D.=4.72%; n=3). When our method was applied to the determination of TOTM released from unsterilized and gamma-ray-sterilized PVC tubes, we found that a higher concentration of TOTM was released from the unsterilized PVC tube than from the gamma-ray-sterilized one.

8-Bromo-7-hydroxyquinoline as a photoremovable protecting group for physiological use: mechanism and scope.

Two-photon excitation (2PE) of "caged" biomolecules represents a powerful method to investigate the temporal and spatial relevance of physiological function in real time and on living tissue, because the excitation volume can be restricted to 1 fL. Additionally, low-energy IR light is used, which minimizes tissue destruction and enables deeper penetration into tissue preparations. Exploitation of this technology for studying cell physiology requires the further development of photoremovable protecting groups with sufficient sensitivity to 2PE for use in "caged" compounds. 8-Bromo-7-hydroxyquinoline (BHQ) is efficiently photolyzed by classic 1PE (365 nm) and 2PE (740 nm) under simulated physiological conditions (aqueous buffer of high ionic strength, pH 7.2) to release carboxylates, phosphates, and diols-functional groups commonly found on bioactive molecules such as neurotransmitters, nucleic acids, and drugs. It is stable in the dark, soluble in water, and exhibits low levels of fluorescence, which will enable use in conjunction with fluorescent indicators of biological function. BHQ-protected effectors are synthetically accessible. Stern-Volmer quenching, time-resolved infrared (TRIR), and (18)O-labeling experiments suggest that the photolysis occurs through a solvent-assisted photoheterolysis (S(N)1) reaction mechanism on the sub-microsecond time scale. BHQ has the requisite photochemical and photophysical properties as a photoremovable protecting group to regulate the action of biological effectors in cell and tissue culture with light, especially 2PE.

Electric-field-induced reorientation of liquid crystalline p-cyanophenyl-p-n-alkylbenzoates: a time-resolved study by fourier transform infrared transmission and attenuated total reflection spectroscopy.

Time-resolved polarization Fourier transform infrared (FT-IR) transmission and attenuated total reflection (ATR) spectroscopy were applied to investigate the reorientation phenomena of the three members of the homologous series of nematic liquid crystalline p-cyanophenyl-p-n-alkylbenzoates 6CPB, 7CPB, and 10CPB under the external perturbation of an electric field. In conjunction with a newly constructed measurement cell, this method allowed us to differentiate the response of the LC system in the surface layer and in the bulk of the cell at different temperatures and voltages. The relaxation time of the LC molecules close to the wall of the cell was found to be shorter than in the bulk. However, at a field strength of 7 V, the initial orientation in the bulk preceeds the analogous process in the surface region.

Influence of hydroxypropyl-beta-cyclodextrin on photo-induced free radical production by the sunscreen agent, butyl-methoxydibenzoylmethane.

The aim of the study was to investigate the effect of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on the photo-induced production of free radicals by the sunscreen agent, butyl-methoxydibenzoylmethane (BMDBM). Spin-trapping/electron paramagnetic resonance spectroscopy was used to evaluate the formation of radicals and the extent of BMDBM photodegradation was measured by high-performance liquid chromatography. The stable 2,2,6,6-tetramethylpiperidine-1-oxyl, nitroxide radical (TEMPO) was used as spin-trap. Any free radicals generated during irradiation of the sunscreen agent will couple with the TEMPO radicals giving diamagnetic species and thus a decrease of the signal intensity in the electron paramagnetic resonance spectrum. Following 2-h illumination with simulated sunlight, the solution containing free BMDBM exhibited a 93.9% decrease of the intensity of the TEMPO signal. Under the same irradiation conditions, only a 12.2% reduction of the TEMPO concentration was measured in the sample containing BMDBM complexed with HP-beta-CD. Moreover, the decrease of the spin-trap level observed for the HP-beta-CD/BMDBM complex was not significantly different from that produced when solutions containing TEMPO only or TEMPO in the presence of HP-beta-CD alone were subjected to irradiation. In addition, the photodegradation of the sunscreen agent was reduced by complexation with HP-beta-CD (the extent of degradation was 27.6% for the complex compared with 63.1% for free BMDBM). The results obtained indicate that the free radicals generated by BMDBM when exposed to simulated sunlight are effectively scavenged by inclusion complexation of the sunscreen agent with HP-beta-CD.

Photostabilization of butyl methoxydibenzoylmethane (Avobenzone) and ethylhexyl methoxycinnamate by bis-ethylhexyloxyphenol methoxyphenyl triazine (Tinosorb S), a new UV broadband filter.

It is now well documented that chronic UVA exposure induces damage to human skin. Therefore, modern sunscreens should not only provide protection from both UVB and UVA radiation but also maintain this protection during the entire period of exposure to the sun. UVA filters, however, are rare and not sufficiently photostable. We investigated the effect of the introduction of a new UV filter, bis-ethylhexyloxyphenol methoxyphenyl triazine (Tinosorb S), in oil in water sunscreen formulations on the photostability of butyl methoxydibenzoylmethane (Avobenzone [AVB]) after irradiation with an optically filtered Xenon arc source (UV irradiance adjusted at 1 mean effective dose [MED]/min). With spectrophotometrical methods to assess the sun protection factor (SPF) and UVA ratio and chromatographical methods to determine the amount of UV filters recovered after irradiation we showed that Tinosorb S prevented the photodegradation of AVB in a concentration-dependent way, leading to a sustained SPF and UVA ratio even after irradiation with doses of up to 30 MED. Since AVB was shown to destabilize ethylhexyl methoxycinnamate (EHM) we tested the effect of Tinosorb S in sunscreens containing this UV filter combination. Here too Tinosorb S showed photoprotective properties toward both UV filters. Thus, Tinosorb S can be used successfully to improve the photostability and efficiency of sunscreens containing AVB and EHM.

Application of coupled liquid chromatography-mass spectrometry in photolysis studies of the herbicide triflusulfuron-methyl.

The photochemical fate of the herbicide triflusulfuron-methyl in aqueous solution under UV light (lambda > 290 nm) was investigated. Nine photoproducts were detected and tentatively identified by LC/MS and LC/MS/MS analysis. The main routes of degradation involve the cleavage and/or contraction of the sulfonylurea bridge with the elimination of sulfur dioxide, which increases the acidity of the reaction medium. On the basis of the results obtained a photodegradation pathway is proposed.

The pH and anion effects on the heterogeneous photocatalytic degradation of o-methylbenzoic acid in TiO2 aqueous suspension.

This investigation used UV light of 365 nm and titanium dioxide in aqueous suspension to study the photocatalytic reaction of o-methylbenzoic acid under the influence of pH values, anion additives and the varieties of titanium dioxide. From experimental results, under the condition of 5 g/l TiO2, pH 3 and light intensity of 2.45 mW/cm2, 0.1 mM of o-methylbenzoic acid could be completely decomposed in 2 h. The reaction was faster with lowering pH, and was found to be apparent first-order following Langmuir-Hinshelwood model. In the presence of anion additives, the inhibitive effect of chloride ions was larger than that of sulfate ions under acidic condition for Degussa brand titanium dioxide, but without influence using Janssen brand. Both brands, however, promoted the mineralization of o-methylbenzoic acid (o-MBA).

Determination of hydroxyl radical production in aqueous solutions irradiated to clinically significant doses.

Decarboxylation of 14C-carboxylbenzoic acid in aqueous solutions after low-dose irradiation has been used to determine the relative magnitude of oxidation reactions and estimate the hydroxyl radicals produced. The G CO2 values determined from these measurements of 0.4 to 1.0 mM solutions of benzoic acid after x-ray doses of 1000 rads ranged from 0.72 to 0.77, in excellent agreement with values reported by authors using much higher doses of radiation. Superoxide dismutase and catalase, known scavengers of superoxide and hydrogen peroxide, respectively, did not show impairment of the oxidation of benzoic acid. On the other hand, biologically significant concentrations of phenol and mannitol appear to impair the radiation-induced oxidation of benzoic acid, indicating that the process is secondary to a reaction with OH . . We found that serum and glucose, common cell media contents, are potent OH . scavengers. These observations indicate that the oxidation of benzoic acid can be as a reliable method to estimate OH . with radiation doses of clinically significant magnitudes. In addition, these results suggest that the radiation induced by OH . in cell systems can be significantly modified by the type of buffer used.