Photochemical transformation of fentanyl under the simulated solar radiation - Enhancement of the process by heterogeneous photocatalysis and in silico analysis of toxicity

Environmental life cycle of fentanyl: From the cradle to an unknown grave

The lack of available information on the presence and persistence of fentanyl in the environment is a significant gap in the technical literature. Although the origins of the opioid in the environment are well-known because they follow the same pathways of other drug-related environmental contaminants, the downstream effects of fentanyl in the water supply and its retention in soil are less understood. The characterization of fentanyl and its potential degradation products in complex environmental samples such as soil is severely understudied. Very few articles are available that work to identify fentanyl and its degradation products in complex samples or name the possible hazards that may result from environmental exposure and degradation. Therefore, the objectives were to identify available articles focused on environmental fentanyl and its pathways and highlight quantifiable research or results that included specific degradation products or downstream effects. Research articles focused on fentanyl between 2000 and 2024 were identified and reviewed and then filtered using Boolean search terms for environmental parameters. Various studies have determined that trace levels of fentanyl can be found in a variety of environments, and additional data suggest preferential partitioning into soils from water and long-term persistence. Despite this knowledge, very little data exists on the long-term downstream effects of fentanyl or its analogs. As the chronic effects from low-level fentanyl exposure are currently unknown, this lack of insight brings to the forefront the need for further research to improve our understanding of fentanyl persistence, degradation, and toxicity within the environment.

Photodegradation of typical psychotropic drugs in the aquatic environment: a critical review

Continuous consumption combined with incomplete removal during wastewater treatment means residues of psychotropic drugs (PDs), including antidepressants, antipsychotics, antiepileptics and illicit drugs, are continuously entering the aquatic environment, where they have the potential to affect non-target organisms. Photochemical transformation is an important aspect to consider when evaluating the environmental persistence of PDs, particularly for those present in sunlit surface waters. This review summarizes the latest research on the photodegradation of typical PDs under environmentally relevant conditions. According to the analysis results, four classes of PDs discussed in this paper are influenced by direct and indirect photolysis. Indirect photodegradation has been more extensively studied for antidepressants and antiepileptics compared to antipsychotics and illicit drugs. Particularly, the photosensitization process of dissolved organic materials (DOM) in natural waters has received significant research attention due to its ubiquity and specificity. The direct photolysis pathway plays a less significant role, but it is still relevant for most PDs discussed in this paper. The photodegradation rates and pathways of PDs are influenced by various water constituents and parameters such as DOM, nitrate and pH value. The contradictory results reported in some studies can be attributed to differences in experimental conditions. Based on this analysis of the existing literature, the review also identifies several key aspects that warrant further research on PD photodegradation. These results and recommendations contribute to a better understanding of the environmental role of water matrixes and provide important new insights into the photochemical fate of PDs in aquatic environments.

Detection of low-level fentanyl concentrations in mixtures of cocaine, MDMA, methamphetamine, and caffeine via surface-enhanced Raman spectroscopy

Surface-enhanced Raman spectroscopy (SERS) was utilized to measure low-level fentanyl concentrations mixed in common cutting agents, cocaine, 3,4-methylenedioxymethamphetamine (MDMA), methamphetamine, and caffeine. Mixtures were prepared with a fentanyl concentration range of 0-339 μM. Data was initially analyzed by plotting the area of a diagnostic peak (1026 cm-1) against concentration to generate a calibration model. This method was successful with fentanyl/MDMA samples (LOD 0.04 μM) but not for the other mixtures. A chemometric approach was then employed. The data was evaluated using principal component analysis (PCA), partial least squares (PLS1) regression, and linear discriminant analysis (LDA). The LDA model was used to classify samples into one of three designated concentration ranges, low = 0-0.4 mM, medium = 0.4-14 mM, or high >14 mM, with fentanyl concentrations correctly classified with greater than 85% accuracy. This model was then validated using a series of "blind" fentanyl mixtures and these unknown samples were assigned to the correct concentration range with an accuracy >95%. The PLS1 model failed to provide accurate quantitative assignments for the samples but did provide an accurate prediction for the presence or absence of fentanyl. The combination of the two models enabled accurate quantitative assignment of fentanyl in binary mixtures. This work establishes a proof of concept, indicating a larger sample size could generate a more accurate model. It demonstrates that samples, containing variable, low concentrations of fentanyl, can be accurately quantified, using SERS.

Accumulation of micropollutants, byproducts, and metabolites in vegetables cultivated with treated water

Due to a lack of water resources, people are starting to use treated wastewater to irrigate crops and vegetables. However, the risk of micropollutant exposure from vegetables cultivated with treated wastewater has been largely underestimated. To elucidate this underestimation, a hydroponic system for lettuce cultivation using a nutrient solution spiked with three pharmaceuticals with different log KOW values (acetaminophen (0.46), ketamine (2.18) and methadone (3.93)) was examined, and the total bioconcentration factors (BCFs) (including the transformation of metabolites) of the pharmaceuticals were found to be 0, 120 ± 7.76 and 176 ± 16.0 L/kg, respectively. To simulate treated wastewater, these nutrient solutions were first treated by sunlight photolysis, chlorination, and sunlight/chlorine before use in lettuce cultivation. During the treatment, ketamine and methadone were transformed into norketamine (up to 6.0 %) and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) (up to 16 %), respectively; the BCF of norketamine (162 ± 22.6 L/kg) was found to be even greater than ketamine. In addition, other degradation byproducts (including 3 trace and 13 undetected byproducts in the nutrient solutions) were taken up by the lettuce. In parallel, ketamine and methadone can also undergo metabolism in lettuce; the conversion rate to norketamine increased from 22 ± 7.0 % to 45 ± 0.062 when the ketamine concentration decreased from 1000 to 50 μg/L.

Solar photocatalysis application in UWWTP outlets - simulations based on predictive models in flat-plate reactors and pollutant degradation studies with in silico toxicity assessment

The application of the solar photocatalysis for the degradation of residual pollutants found in surface water was demonstrated. Semi-pilot scale flat-plate cascade reactor (FPCR) was used to study the degradation of model organic pollutants: enrofloxacin (ENRO), 17β-estradiol (E2) and 1H-benzotriazole (1H-BT) over TiO2 thin-film supported on glass fibers. A modular panel with full-spectra solar lamps with appropriate UVB and UVA irradiation levels was used as a simulation of sunlight. Pollutant degradation in FPCR was estimated using predictive models; intrinsic reaction rate constants (ki) for ENRO, E2 and 1H-BT independent of the reactor size, flow rate and irradiation conditions were determined: 9.60, 3.35 and 0.37 109 s-1 W-0.5 m1.5, respectively. Main degradation products (DPs), formed upon hydroxylation, ring opening and oxidation, were identified using LC-QTOF-MS. The ecotoxicological impact was assessed via T.E.S.T. and ECOSAR open-source tools showing the formation of less harmful DPs after sufficient reaction time. Pollutant degradation was simulated at four locations of interest, i.e. exhausts from urban wastewater treatment plants (UWWTPs) in Zagreb, Croatia (45°N), Krakow, Poland (50°N), Sevilla, Spain (37°N) and Ioannina, Greece (39.6°N). Results have proved that a simple flat-plate system with supported photocatalysts can be easily scaled up and incorporated at the outlet of UWWTP for the reduction of pollutant load and related toxicity. The exhaust canal in Zagreb with the estimated length of a photocatalytic layer of 122 m for the > 90% degradation of all target pollutants was discussed as the best installation site among studied locations. ENVIRONMENTAL IMPLICATION: A multi-disciplinary approach to the tentative application of TiO2 solar photocatalysis outdoors to reduce pollutant loads and toxicity in surface waters was demonstrated. Possible application at four selected locations in Europe, as an additional step in water treatment after urban wastewater treatment plants (UWWTPs) was discussed. Target pollutants were studied under environmentally relevant conditions (sunlight levels, water matrix, simulation of process on a real scale at selected geographical location), at both higher and low concentrations.

Energetics of high temperature degradation of fentanyl into primary and secondary products

Fentanyl is a synthetic opioid used for managing chronic pain. Due to its higher potency (50-100×) than morphine, fentanyl is also an abused drug. A sensor that could detect illicit fentanyl by identifying its thermally degraded fragments would be helpful to law enforcement. While experimental studies have probed the thermal degradation of fentanyl, little theoretical work has been done to understand the mechanism. Here, we studied the thermal degradation pathways of fentanyl using extensive ab initio molecular dynamics simulations combined with enhanced sampling via multiple-walker metadynamics. We calculated the free energy profile for each bond suggested earlier as a potential degradation point to map the thermodynamic driving forces. We also estimated the forward attempt rate of each bond degradation reaction to gain information about degradation kinetics.

Efficient removal of anti-HIV drug - maraviroc from natural water by peroxymonosulfate and TiO2 photocatalytic oxidation: Kinetic studies and identification of transformation products

In this study photochemical transformation of the antiretroviral pharmaceutical maraviroc under the simulated UV-Vis radiation was presented. The drug was shown to be extremely photo-resistant, with a half-life over 250 h, which is particularly significant, considering its presence in the aquatic environments. Addition of the natural river water matrix substantially increased the degradation rate, albeit the process led to formation of numerous phototransformation products. Due to high photostability and presumable environmental persistence of maraviroc, a photocatalytic method of its elimination was proposed. Although titanium dioxide alone presented acceptable results, its combination with peroxymonosulfate enormously accelerated the degradation process, increasing it over 67 000 times in comparison with the direct photolysis. Substitution of ultrapure water with river water resulted in inhibition of the PMS-driven processes, however the decomposition efficiency was still very high. Noteworthy, majority of the identified photoproducts were still present after termination of irradiation in all the experiments, which may indicate necessity of ecotoxicological assessment of those compounds.

Bifunctional nickel foam composite cathode co-modified with CoFe@NC and CNTs for electrocatalytic degradation of atrazine over wide pH range

Bifunctional cathodes have attracted widespread interest in the heterogeneous electro-Fenton (hetero-EF) process. In this study, the bifunctional composite cathode co-modified with N-doped carbon CoFe alloy (CoFe@NC) and carbon nanotubes (CNTs), designated as CoFe@NC-CNTs/CNTs/NF, integrating hydrogen peroxide (H₂O₂) synthesis and catalysis, was prepared for efficient degradation of atrazine (ATZ) under the near-neutral condition (pH_i = 5.9). The morphology properties, crystal structure, microstructures, and elemental composition were determined. The influences of current density, initial pH value, different anions, and water matrix on the removal of ATZ were systematically studied. In the hetero-EF process, high removal efficiencies of ATZ can be achieved over the broad pH range (3-9) under the current density of 4.5 mA cm^-2. The removal efficiency of ATZ remained at 90.2 ± 0.3% after 8 cycles under the near-neutral condition (pH_i = 5.9). Radical quenching tests and EPR spectra have verified that both free radical pathways such as superoxide anion (O₂·^-) and hydroxyl radical (·OH) and non-radical pathway such as singlet oxygen (¹O₂) contributed to ATZ removal. The degradation pathways and catalytic mechanism were proposed. Toxicity evaluation and Escherichia coli growth test showed that the toxicity gradually decreased during the degradation process. This work provided a new thought for developing an efficient and stable bifunctional cathode to construct an in-situ hetero-EF system for pollutants removal over the wide pH range.