Degradation Of 5-fluorouracil Research Articles

In2O3/NIO/MOS2 Composite as a Novel Photocatalytic towards Imatinib and 5-Fluorouracil Degradation

Photocatalysts with high efficiency in water and wastewater treatment have gained increasing attention in recent years. This study synthesized an In2O3/NiO/MoS2 composite using the hydrothermal method and characterized its crystal structure, particle size, morphology, elemental purity, and optical properties. This nanocomposite exhibits high photocatalytic activity under visible light radiation. It achieved efficiencies of 91.57% and 88.23% in decomposing Imatinib and 5-fluorouracil, respectively. The formation of heterogeneity between MoS2 and NiO enhances the photocatalytic activity, which facilitates the separation and transfer efficiency of photo-generated electron-hole pairs, increases the catalytic active sites, and inhibits the rate of electron-hole recombination. The photocatalytic mechanism shows that both O2− and H+ are reactive species for the degradation of the studied pollutant. The stability and reusability tests deposited that the In2O3/NiO/MoS2 composite photocatalyst has superior stability during four reuse cycles. The results of the study show that a unique photocatalyst system can provide a new perspective and create new opportunities for the design of efficient composite photocatalysts.

Removal of the chemotherapeutic drugs 5-fluorouracil and cyclophosphamide by UV/peracetic acid: Reaction kinetics and mechanism

5-Fluorouracil and cyclophosphamide, the two most commonly used chemotherapeutic drugs, are widely detected in aquatic environments and cause cytotoxic and other adverse effects in ecosystems. In this work, UV/peracetic acid (UV/PAA) treatment was investigated for the first time for 5-fluorouracil and cyclophosphamide removal. The results showed that 5-fluorouracil and cyclophosphamide can be efficiently removed via UV/PAA within 20 min, with pseudo-first-order rate constants (kobs) of 0.197 and 0.135 min−1, respectively. The influences of PAA dosage, initial compound concentration, solution pH and common water constituents (Cl−, HCO3−, NO3− and dissolved organic matter) were systematically studied. OH was the predominant species involved in the degradation of the two pharmaceuticals, while direct UV photolysis and R–C were also involved in removing 5-fluorouracil. Two and five byproducts were detected in UV/PAA degradation of 5-fluorouracil and cyclophosphamide, respectively, and the possible degradation pathways were proposed. Although total organic carbon was not completely removed during the reaction, the Microtox® toxicity trend (an increase and further decrease) implied further detoxification of the byproducts. Additionally, UV/PAA treatment applied to real water samples (river water and effluent from a wastewater treatment plant) still exhibited good efficiency for removing the two compounds, revealing its applicability in water/wastewater treatment.

Functional Characterization of 12 Dihydropyrimidinase Allelic Variants in Japanese Individuals for the Prediction of 5-Fluorouracil Treatment-Related Toxicity.

The drug 5-fluorouracil (5-FU) is the first-choice chemotherapeutic agent against advanced-stage cancers. However, 10% to 30% of treated patients experience grade 3 to 4 toxicity. The deficiency of dihydropyrimidinase (DHPase), which catalyzes the second step of the 5-FU degradation pathway, is correlated with the risk of developing toxicity. Thus, genetic polymorphisms within DPYS, the DHPase-encoding gene, could potentially serve as predictors of severe 5-FU-related toxicity. We identified 12 novel DPYS variants in 3554 Japanese individuals, but the effects of these mutations on function remain unknown. In the current study, we performed in vitro enzymatic analyses of the 12 newly identified DHPase variants. Dihydrouracil or dihydro-5-FU hydrolytic ring-opening kinetic parameters, Km and Vmax , and intrinsic clearance (CLint = Vmax /Km ) of the wild-type DHPase and eight variants were measured. Five of these variants (R118Q, H295R, T418I, Y448H, and T513A) showed significantly reduced CLint compared with that in the wild-type. The parameters for the remaining four variants (V59F, D81H, T136M, and R490H) could not be determined as dihydrouracil and dihydro-5-FU hydrolytic ring-opening activity was undetectable. We also determined DHPase variant protein stability using cycloheximide and bortezomib. The mechanism underlying the observed changes in the kinetic parameters was clarified using blue-native polyacrylamide gel electrophoresis and three-dimensional structural modeling. The results suggested that the decrease or loss of DHPase enzymatic activity was due to reduced stability and oligomerization of DHPase variant proteins. Our findings support the use of DPYS polymorphisms as novel pharmacogenomic markers for predicting severe 5-FU-related toxicity in the Japanese population. SIGNIFICANCE STATEMENT: DHPase contributes to the degradation of 5-fluorouracil, and genetic polymorphisms that cause decreased activity of DHPase can cause severe toxicity. In this study, we performed functional analysis of 12 DHPase variants in the Japanese population and identified 9 genetic polymorphisms that cause reduced DHPase function. In addition, we found that the ability to oligomerize and the conformation of the active site are important for the enzymatic activity of DHPase.

0D/3D CNQDs/CuFe2O4/Cu0 heterostructures as broad spectrum photocatalyst for efficient 5-fluorouracil degradation: Structural evolution and relay oxidation process

Undesirable solar energy absorption, poor charge transfer efficiency, and sluggish metallic ions redox cycle are three pressing problems, restricting the application of photocatalysis and peroxymonosulfate (PMS) techniques. Herein, an interface engineering of g-C3N4 quantum dots anchoring on the CuFe2O4/Cu0 hollow microspheres (CNQDs@CFO) was developed to construct a novel 0D/3D broad-spectrum-response photocatalyst. In the relaying PMS-photocatalysis process, 30 μM 5-fluorouracil (5-FLU, 50 mL) was degraded by 99.4 % in 60 min with 0.2 g L−1 1.0CNQDs@C1F1O and 0.3 mM PMS. The reusability test showed that 1.0CNQDs@C1F1O maintained superior performance with a 5-FLU removal of 92.6 % after the fifth run. Meanwhile, this newly-designed material can be applied in a large temperature and pH range, and even actual water bodies with strong environmental adaptability. Theoretic and experimental analysis demonstrated that the CNQDs and Cu0 sites on CNQDs@CFO promoted the earlier PMS activation, and then dual Z-scheme heterostructures (CNQDs/CuFe2O4/CuO) was established, boosting the follow-up photocatalytic activity.

Importance of Rare DPYD Genetic Polymorphisms for 5-Fluorouracil Therapy in the Japanese Population.

Dihydropyrimidine dehydrogenase (DPD), encoded by the DPYD gene, is the rate-limiting enzyme in 5-fluorouracil (5-FU) degradation. In Caucasians, four DPYD risk variants are recognized to be responsible for interindividual variations in the development of 5-FU toxicity. However, these risk variants have not been identified in Asian populations. Recently, 41 DPYD allelic variants, including 15 novel single nucleotide variants, were identified in 3,554 Japanese individuals by analyzing their whole-genome sequences; however, the effects of these variants on DPD enzymatic activity remain unknown. In the present study, an in vitro analysis was performed on 41 DPD allelic variants and three DPD risk variants to elucidate the changes in enzymatic activity. Wild-type and 44 DPD-variant proteins were heterologously expressed in 293FT cells. DPD expression levels and dimerization of DPD were determined by immunoblotting after SDS-PAGE and blue native PAGE, respectively. The enzymatic activity of DPD was evaluated by quantification of dihydro-5-FU, a metabolite of 5-FU, using high-performance liquid chromatography-tandem mass spectrometry. Moreover, we used 3D simulation modeling to analyze the effect of amino acid substitutions on the conformation of DPD. Among the 41 DPD variants, seven exhibited drastically decreased intrinsic clearance (CL int ) compared to the wild-type protein. Moreover, R353C and G926V exhibited no enzymatic activity, and the band patterns observed in the immunoblots after blue native PAGE indicated that DPD dimerization is required for its enzymatic activity. Our data suggest that these variants may contribute to the significant inter-individual variability observed in the pharmacokinetics and pharmacodynamics of 5-FU. In our study, nine DPD variants exhibited drastically decreased or no enzymatic activity due to dimerization inhibition or conformational changes in each domain. Especially, the rare DPYD variants, although at very low frequencies, may serve as important pharmacogenomic markers associated with the severe 5-FU toxicity in Japanese population.

Photocatalytic mechanisms and photocatalyst deactivation during the degradation of 5-fluorouracil in water

Photocatalytic oxidation and micropollutants have both attracted extensive attention in the field of wastewater treatment. However, invalidation mechanism of photocatalytic system and target transformation are still a challenge. Here, we used TiO2 supported on nickel foam (TiO2/NF) and 5-fluorouracil (5-FU) as model photocatalyst and pharmaceutical micropollutant to investigate photocatalytic transformation pathways of 5-FU and inhibition mechanisms of its degradation efficiency reduction. Incredibly, removal efficiency of 5-FU dramatically decreased from 80% to 20% after 120 h continuous operation, owning to the competition for hydroxyl radical (•OH) between trans-intermediates and 5-FU, accumulated in the solution. Using HR-MS, the produced intermediates during photocatalytic degradation of 5-FU were revealed to be that mono/polyhydroxylated compounds, short-chain oxides and carboxylation ones were main trans-intermediates. Combining ATR-FTIR, SEM-EDS and validation experiments for factors, it was found that the inhibition of 5-FU degradation should be contributed to the competition for •OH in the bulk or preferential consumption of •OH in TiO2 diffusion layer, by the aforementioned intermediates. The present study provides insights into photocatalytic oxidation of 5-FU and basic information about mechanisms of inhibition on target contaminant removal.

Development of novel (BiO)2OHCl/BiOBr enriched with boron doped-carbon nanowalls for photocatalytic cytostatic drug degradation: Assessing photocatalytic process utilization in environmental condition

In this work, a series of novel (BiO)2OHCl/BiOBr-x%B:DGNW (x = 0%, 1%, 1.5%, 2%) composites with different content of boron-doped diamond/graphene nanowalls (B:DGNW) were fabricated by simple solvothermal synthesis. A boron-doped diamond/graphene nanowalls (B:DGNW) were prepared by CVD method. A series of analyses: XRD, XPS, SEM, and TEM showed that the photocatalyst (BiO)2OHCl/BiOBr-x%B:DGNW with a “flower-like” morphology was successfully synthesized. The photocatalytic activity of the obtained composites in the degradation of 5-fluorouracil (5-FU) in various water matrices (deionized water, sea, and surface water) under the influence of artificial solar radiation was assessed. The results showed that all the prepared (BiO)2OHCl/BiOBr-x%B:DGNW composites were characterized by excellent photocatalytic activity. The calculated pseudo-first rate constant for 5-FU degradation increased with the elevation of amount of B:DGNW up to 1.5% in (BiO)2OHCl/BiOBr, and it dropped down to value obtained for non-riched material by B:DGNW, when of 2% B:DGNW was introduced to composite. The results showed that B:DGNW play a key role in the separation of charge carriers h+/e- enhancing degradation rate of 5-FU. The photoactivity of (BiO)2OHCl/BiOBr-1.5%B:DGNW composite to 5-FU removal was also satisfied in natural water, although its structure has changed in seawater.

One-Pot Thermal Synthesis of g-C3N4/ZnO Composites for the Degradation of 5-Fluoruracil Cytostatic Drug under UV-LED Irradiation.

Graphitic carbon nitride (g-C3N4) was used to enhance the photocatalytic activity of ZnO nanoparticles for the degradation of 5-fluorouracil (5-FU) cytostatic drug under UV-LED irradiation. CN/ZnO composites were synthetized by an easy one-pot thermal method, varying the g-C3N4 loading, i.e., from 10 to 67 wt% and a post-thermal exfoliation in air. The physicochemical and optical properties of the materials were analyzed by several techniques. CN/ZnO composites showed a coral-like structure of spherical ZnO wurtzite particles on the g-C3N4 structure. In general, the synergism and heterojunction interface between both phases allowed the enhancement of the mesoporosity, light absorption ability, and the aromaticity of the corresponding composites. Moreover, the photocatalytic activity of the CN/ZnO composites was increased with the addition of g-C3N4 in comparison with pristine ZnO. The highest activity was found for the composite containing 25 wt% of g-C3N4 (i.e., CN25/ZnO), reaching the total degradation of 5-FU and a mineralization of 48% at 180 min, as well as a good photostability during four reuse cycles. Experiments with different pH solutions and scavengers allowed for the assessment of the reactive oxygen species (ROS) involved in the 5-FU degradation pathway, with radicals and non-radical species as the main responsible active species. Furthermore, a tentative photocatalytic mechanism was proposed for CN/ZnO composites.

Comparative degradation of 5-fluorouracil in aqueous solution by using H2O2-modified subcritical water, photocatalytic oxidation and electro-Fenton processes

This study investigated the degradation of the antineoplastic agent 5-fluorouracil (5-FU) widely applied to treat different cancers using different advanced oxidation processes such as electro-Fenton (EF), photocatalysis with TiO2, and H2O2-modified subcritical water oxidation. The treatment with the EF process was the most efficient compared to others. Interestingly, in the EF process, the oxidative degradation of 5-FU behaved differently depending on the anode used. At low currents (20 and 40 mA), Pt and DSA anodes performed better than BDD and Ti4O7 anodes. In contrast, at the higher current of 120 mA, the production of heterogeneous hydroxyl radicals (M(•OH)) became important and contributed significantly to the oxidation of 5-FU in addition to homogeneous •OH generated in the bulk solution. These latter have high O2-evolution overpotential leading to the high amount of physisorbed M(•OH) compared to Pt and DSA. The oxidative degradation of 5-FU was then performed by titanium dioxide-based photocatalytic oxidation and subcritical water oxidation processes, both of which showed a lower degradation efficiency and failed to achieve complete mineralization. Finally, a comparison was performed in laboratory-scale, taking into account the following performance indicators: the degradation efficiency, the mineralization power, the cost of equipment and reagents, and the energy required for the treatment of 5-FU.

Individualized Dosing of Fluoropyrimidine-Based Chemotherapy to Prevent Severe Fluoropyrimidine-Related Toxicity: What Are the Options?

Fluoropyrimidines are widely used in the treatment of several types of solid tumors. Although most often well tolerated, severe toxicity is encountered in ~ 20–30% of the patients. Individualized dosing for these patients can reduce the incidence of severe fluoropyrimidine‐related toxicity. However, no consensus has been achieved on which dosing strategy is preferred. The most established strategy for individualized dosing of fluoropyrimidines is upfront genotyping of the DPYD gene. Prospective research has shown that DPYD‐guided dose‐individualization significantly reduces the incidence of severe toxicity and can be easily applied in routine daily practice. Furthermore, the measurement of the dihydropyrimidine dehydrogenase (DPD) enzyme activity has shown to accurately detect patients with a DPD deficiency. Yet, because this assay is time‐consuming and expensive, it is not widely implemented in routine clinical care. Other methods include the measurement of pretreatment endogenous serum uracil concentrations, the uracil/dihydrouracil‐ratio, and the 5‐fluorouracil (5‐FU) degradation rate. These methods have shown mixed results. Next to these methods to detect DPD deficiency, pharmacokinetically guided follow‐up of 5‐FU could potentially be used as an addition to dosing strategies to further improve the safety of fluoropyrimidines. Furthermore, baseline characteristics, such as sex, age, body composition, and renal function have shown to have a relationship with the development of severe toxicity. Therefore, these baseline characteristics should be considered as a dose‐individualization strategy. We present an overview of the current dose‐individualization strategies and provide perspectives for a future multiparametric approach.

An in vitro approach to simulate the process of 5-fluorouracil degradation with dihydropyrimidine dehydrogenase: the process in accordance to the first-order kinetic reaction

Partial or complete deficiency in the dihydropyrimidine dehydrogenase (DPD) has been observed in 3%–5% and 0.1% of the general population, respectively. It causes severe toxicity in the context of 5-fluorouracil (5-FU) therapy. However, the current tests for determination of DPD deficiency have limitations in routine clinical usage. Therefore, an in vitro approach for simulating 5-FU degradation was established by mixing 5-FU with blank whole blood matrix in this study. The effects of initial 5-FU concentrations and temperatures on DPD activities were investigated as well. The degradation process followed the first-order kinetic reaction (r2 > 0.98). The degradation rates were determined by temperature and individually different. The DPD inhibitor, gimeracil, could block this degradation, which indicated that DPD was the main factor. The degradation process of 5-FU in patients’ whole blood in vitro was consistent with it after mixing 5-FU with blank whole blood matrix. In conclusion, mixing 5-FU with blank matrix can simulate the process of 5-FU degradation with DPD.

Sonochemical synthesis of amphoteric Cu0-Nanoparticles using Hibiscus rosa-sinensis extract and their applications for degradation of 5-fluorouracil and lovastatin drugs

Recent studies reported the detection of numerous emerging and active pharmaceutical constituents in the ground and surface water. To address these issues, the present study reported the ultrasound-assisted synthesis of zero-valent copper (Cu0) nanoparticles using Hibiscus rosa-sinensis extract as reducing and stabilizing agent. The catalyst was characterized using XRD, SEM, EDX, PSA, BET, etc., and the results revealed that sonochemical synthesis technique influenced the crystallinity with controlled growth of Cu0. While the hard ligand hydroxyl group (−OH) reduces the Cu2+ to Cu0 and soft ligand carbonyl group (CO) present in the oxidized polyphenols helps in capping and stabilizing the Cu0-nanoparticles. During the ultrasound application, continuous release of Cu+ from Cu0 promoted the degradation by producing OH and O2•− radicals. Approx. 91.3 % and 93.2 % degradation efficiencies were achieved for 5-fluorouracil and lovastatin. The results showed that Cu0 nanoparticles were amphoteric in nature and the synergy calculation revealed that ultrasound has a direct influence on degradation of drugs which are difficult to degrade/mineralize using conventional techniques. Based on the results, a possible degradation mechanism of drug molecules in the presence of oxidants, zero-valent copper and ultrasound has been proposed.

Electro-Fenton treatment of a complex pharmaceutical mixture: Mineralization efficiency and biodegradability enhancement

Combination of the electro-Fenton process with a post-biological treatment could represent a cost-effective solution for application of electrochemical advanced oxidation processes. The objective of this study was to assess this treatment strategy in the case of a complex pharmaceutical mixture. First, main operating parameters ([Fe2+] and current) of the electro-Fenton process were optimized. An optimal concentration of 0.2 mM of Fe2+ was obtained for mineralization of the pharmaceutical mixture. An optimal current of 400 mA was also obtained for degradation of caffeine and 5-fluorouracil in the mixture. However, mineralization of the effluent was continuously improved when increasing the current owing to the promotion of mineralization of organic compounds at the BDD anode. Besides, energy efficiency was decreased at prolonged treatment time because of mass transport limitation. Interestingly, it was observed a strong biodegradability enhancement of the solution after short treatment times (<3 h) at 500 and 1000 mA, which can be related to the degradation of parent compounds into more biodegradable by-products. The need for an acclimation time of the biomass to the pre-treated effluent was also emphasized, most probably because of the formation of some toxic by-products as observed during acute toxicity tests. Therefore, a biological post-treatment could represent a cost-effective solution for the removal of biodegradable residual organic compounds as well as for the removal of nitrogen released from mineralization of organic compounds under the form of NO3− and NH4+ during electro-Fenton pre-treatment.

5-Fluorouracil degradation rate as a predictive biomarker of toxicity in breast cancer patients treated with capecitabine

Capecitabine is an oral prodrug of 5-fluorouracil with a relevant role in the treatment of breast cancer. Severe and unexpected toxicities related to capecitabine are not rare, and the identification of biomarkers is challenging. We evaluate the relationship between dihydropyrimidine dehydrogenase, thymidylate synthase enhancer region and methylenetetrahydrofolate reductase polymorphisms, 5-fluorouracil degradation rate and the onset of G3-4 toxicities in breast cancer patients. Genetic polymorphisms and the 5-fluorouracil degradation rate of breast cancer patients treated with capecitabine were retrospectively studied. Genetic markers and the 5-fluorouracil degradation rate were correlated with the reported toxicities. Thirty-seven patients with a median age of 58 years old treated with capecitabine for stages II-IV breast cancer were included in this study. Overall, 34 (91.9%) patients suffered from at least an episode of any grade toxicity while nine patients had G3-4 toxicity. Homozygous methylenetetrahydrofolate reductase 677TT was found to be significantly related to haematological toxicity (OR = 6.5 [95% IC 1.1-37.5], P = 0.04). Three patients had a degradation rate less than 0.86 ng/mL/106 cells/min and three patients greater than 2.1 ng/mL/106 cells/min. At a univariate logistic regression analysis, an altered value of 5-fluorouracil degradation rate (values < 0.86 or >2.10 ng/mL/106 cells/min) increased the risk of G3-4 adverse events (OR = 10.40 [95% IC: 1.48-7.99], P = 0.02). A multivariate logistic regression analysis, adjusted for age, comorbidity and CAPE-regimen, confirmed the role of 5-fluorouracil degradation rate as a predictor of G3-4 toxicity occurrence (OR = 10.9 [95% IC 1.2-96.2], P = 0.03). The pre-treatment evaluation of 5-fluorouracil degradation rate allows to identify breast cancer patients at high risk for severe 5-FU toxicity.

Toxicity Syndromes, Patient-Related Clinical Indicator of Toxicity Burden Induced by Intensive Triplet Chemotherapy-Based Regimens in Gastrointestinal Cancers With Metastatic Disease.

Background: Cancer treatments induce symptoms/signs superimposing on individual patient's clinical status, determining heterogenous toxicity syndromes (TS). We reviewed intensive first line triplet chemotherapy-based regimens in metastatic gastro-intestinal cancers (mGI), based on FIr/FOx schedule, fluorouracil and weekly alternating irinotecan/oxaliplatin, to point out limiting TS (LTS) relevance.Methods: Metastatic colo-rectal (mCRC), pancreatic ductal adenocarcinoma (mPDAC), gastric carcinoma (mGC) patients were enrolled by careful decision-making including age, performance status (PS), and comorbidity status in real life phase II studies: FIr-B/FOx adding bevacizumab (B) overall, FIr-C/FOx-C adding cetuximab (C) in KRAS/NRAS wild-type mCRC; FIr/FOx in mPDAC; FD/FOx adding docetaxel (D) in mGC. Toxicity, individual LTS, LT alone (LTS-single site, LTS-ss) or associated to other limiting/G2 toxicities (LTS-multiple sites, LTS-ms) were evaluated, compared by chi-square test. In FIr-C/FOx-C, 5-fluorouracil/irinotecan pharmacogenomic biomarkers, 5-fluorouracil degradation rate (5-FUDR), SNPs ABCB1, CYP3A4, DYPD, UGT1A1 were evaluated, related with LTS.Results: FIr-B/FOx, FIr-C/FOx-C in mCRC, FIr/FOx in mPDAC, FD/FOx in mGC, showed activity, efficacy, toxicities similar to reported triplet regimens. LTS: mCRC FIr-B/FOx 44%, LTS-ms 24%, LTS-ss 20%, in young-elderly 46%, LTS-ms significantly increased vs. LTS-ss; FIr-C/FOx-C 65.5%, significantly increased LTS-ms vs. LTS-ss, in young-elderly 83%; mPDAC FIr/FOx 27.5%, mostly LTS-ms, in young-elderly 38.4% all LTS-ms; mGC FD/FOx 30%, all LTS-ms, in young-elderly 25%. Reduced FUDR, SNPs CYP3A4, UGT1A1, >1 positive pharmacogenomic biomarkers were prevalent in patients with gastrointestinal LTS.Conclusions: LTS is an innovative clinical parameter of toxicity burden, differential treatment-related TS in individual patient. LTS can evaluate pharmacogenomic biomarkers predictive relevance to select mGI patients fit for intensive treatments, at risk of limiting gastrointestinal toxicity.Trial Registrations: The trials were registered at Osservatorio Nazionale sulla Sperimentazione Clinica dei Medicinali (OsSC) Agenzia Italiana del Farmaco (AIFA) Numero EudraCT 2007-004946-34, and Osservatorio Nazionale sulla Sperimentazione Clinica dei Medicinali (OsSC) Agenzia Italiana del Farmaco (AIFA) Numero EudraCT 2009- 016793-32.

Photocatalytic degradation of 5-fluorouracil in an aqueous environment via Bi–B co-doped TiO2 under artificial sunlight

The morphology of a series of Bi–B co-doped titanium oxide photocatalysts and its optical properties were characterized. The results suggested that boron and bismuth as co-dopants were incorporated into the framework of titanium matrix. For the B and Bi-doped TiO2 samples, surface area decreased while the Bi content increased. Based on the photoluminescence spectra, a decrease in recombination rate of photogenerated carriers was observed with the increasing amount from 0.5 to 3 mol% of Bi in Bi–B–TiO2 composites. The most active photocatalyst in 5-fluorouracil (5-FU) photodegradation was 3 mol% of Bi in Bi–B–TiO2. The effects of operating parameters: pH, drug concentration and natural organic matter presence (NOM) in the effluent from wastewater treatment plant, were investigated. The highest efficiency of 5-FU photodegradation was observed at neutral pH for the drug concentration equal to 1 mg/L and photocatalyst of 0.05 g/L. While in distilled water solutions, the catalyst showed good removal efficiency of the drug, the process was totally inhibited by NOM in the complex matrix which was the treated sewage, what could be connected with the internal filter and scavenging effect. Based on the identification of organic and inorganic by-products of the photooxidation, the pathway of 5-FU degradation was proposed. The mineralization was poor (5–7%) in the case of both 3Bi–B–TiO2 and pure TiO2 for the drug of 50 mg/L, but photocatalytic oxidation of drug led to non-toxic products toward Lemma minor.

PHOTO-DEGRADATION OF 5 – FLUOROURACIL. COMPARATIVE STUDY ON THE EFFICIENCIES OF UV/H2O2, UV/TIO2, UV/H2O2/TIO2 PROCESSES

Degradation experiments on 5-Fluorouracil synthetic solutions were performed using three types of advanced oxidation systems: UV/H2O2, UV/TiO2 and UV/H2O2/TiO2. Optimum parameters for all three systems were established and 5-Fluorouracil degradation efficiencies were calculated, for all systems being more than 97%. The results showed that the combined UV/H2O2/TiO2 system is offering shortest irradiation time, the possibility to recover and reuse the photo catalyst as well as the possibility to use solar radiation. Obtained results proved also that advanced oxidation processes represent a viable option for degradation of hazardous pollutants that cannot be removed properly via conventional wastewater treatment processes.

Removal of 5-fluorouracil by solar-driven photoelectrocatalytic oxidation using Ti/TiO2(NT) photoelectrodes

The efficient and safe degradation of drugs present in wastewater requires the design of a new material possessing high activity for that process. In addition to other methods, photoelectrocatalysis (PEC) merges the strengths of both photocatalytic and electrochemical methods, and the efficiency could be enhanced by the type of photoelectrode material. To address this challenge, three Ti/TiO2 nanotube-based photoelectrodes, differing in their tube morphology, were prepared by anodic oxidation and employed for the degradation of the 5-fluorouracil (5-FU) drug by the PEC process. The highest efficiency for 5-fluorouracil (5-FU) degradation by PEC was observed for the photoelectrode with a 1.7 μm length, 65 nm diameter and 8 nm wall thickness of TiO2 nanotubes, which were prepared by Ti foil anodization at 30 V. The effects of applied potential, irradiation intensity, initial pH and 5-FU concentration on PEC were investigated. Furthermore, our findings showed that the mechanism of photoelectrocatalysis in the presence of TiO2 nanotubes is based on ∙OH and h+ activity. To determine the 5-FU degradation pathway, the organic byproducts were identified by LC-MS analysis. Furthermore, the ecotoxicity evaluated during PEC dropped with decreasing 5-FU concentration.

Mechanistic investigation in degradation mechanism of 5-Fluorouracil using graphitic carbon nitride

The present study reports the synthesis of metal-free polymeric catalyst, graphitic carbon nitride (g-C3N4), through sonochemical method followed by thermal treatment. The synthesized g-C3N4 was characterized using XRD, DRS, FESEM, TGA, EDX, etc. and the characterization results revealed that it possesses medium band-gap energy, high thermal and chemical stability. The photo-activity of the catalyst was also evaluated using degradation of 5-Fluorouracil under different experimental conditions. The results revealed that the addition of H2O2 during sonolysis process did not show any significant synergy. This is attributed to the low vapor pressure of H2O2 that does not allow it to diffuse into the cavitation bubble to produce OH radicals through sonolysis process. Using sono-hybrid process, more than 90% degradation was seen within 5 min of treatment with a rate constant of 3.95 × 10−2 s−1. In alkaline medium, 5-Fluorouracil degradation occurred through defluorination and subsequently substitution of –OH group to the aromatic ring leading to formation of intermediates such as 2-fluoro-3-oxopropanoic acid and urea. While sono-hybrid advanced oxidation processes (AOPs) helped towards complete mineralization through formation of smaller molecular compounds such as maleic acids, lactic acids, propanol, etc. On the other hand, the maximum synergy effect of ∼2.4 was seen for sonocatalysis process followed by hybrid-AOPs of (US + g-C3N4 + H2O2 + UVC) with a synergy factor of ∼2.2. Also, the synthesized catalyst exhibited the same catalytic activity even after 5 runs of sono-photocatalysis process for degradation of 5-Fluorouracil.

Human liver degradation of 5-fluorouracil: endogenous uracil may result in phenoconversion of dihydropyrimidine dehydrogenase activity

Human liver degradation of 5-fluorouracil: endogenous uracil may result in phenoconversion of dihydropyrimidine dehydrogenase activity