Search Results (3,078)

Purpose: This study sought to extract and characterize fucoidan from brown seaweed Padina tetrastromatica for the synthesis of fucoidan–gold nanoparticles (F-AuNPs) and to assess their physicochemical properties, as well as their antioxidant, anti-inflammatory, and anticancer activities, alongside potential molecular interactions with specific cancer-related targets. Methods: The extracted fucoidan-rich fraction was characterized for its sulfate content. Citrate-stabilized plain gold nanoparticles (plain AuNPs) were prepared and characterized as non-fucoidan nanoparticle controls. Comprehensive physicochemical characterization, including UV–Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), zeta-potential analysis, and thermogravimetric analysis (TGA), was performed on the resultant fucoidan-functionalized AuNPs (F-AuNPs). Biological activities were assessed using different techniques: antioxidant potential (Ferric Reducing Antioxidant Power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays), anti-inflammatory effects (NO inhibition in macrophages), and anticancer efficacy against HepG2 cells (MTT and flow cytometry). Potential molecular targets relevant to these activities were further explored in silico using molecular docking against key cancer-related proteins, providing hypotheses for future experimental validation. Results: The fucoidan-rich fraction showed a sulfate content of 10.08%. Strong antioxidant activity was observed, especially in FRAP (11.20 ± 0.29 mg TE g⁻¹ DW). F-AuNPs exhibited enhanced cytotoxicity against HepG2 cells (IC₅₀ 138.1 µg mL⁻¹) compared to plain AuNPs (IC₅₀ 271.2 µg mL⁻¹) and the fucoidan-rich fraction (IC₅₀ 390.2 µg mL⁻¹), inducing G1 phase arrest. In addition, F-AuNPs reduced nitric oxide production in LPS-stimulated RAW 264.7 macrophages, reaching 21.42 ± 1.29% inhibition at 100 µg mL⁻¹. As an exploratory, hypothesis-generating step, an in silico target-prioritization screen identified HPSE and MMP-2 as the highest-scoring candidate proteins, proposed solely as targets for future experimental validation. Conclusions: F-AuNPs represent a promising multifunctional nanoplatform with antioxidant, anti-inflammatory, and antiproliferative activities. The integration of in vitro biological evaluation with in silico target prediction supports the potential biomedical relevance of F-AuNPs and generates testable hypotheses regarding their molecular targets, which require experimental validation. Full article

Background: Photodynamic therapy (PDT) is a promising minimally invasive approach for melanoma; however, many photosensitizers lose activity in aqueous media due to aggregation-induced quenching effects. Objectives: The aim of this study was to develop and characterize castor oil–based nanoemulsions containing chlorophyll (NFs-Chl) and to evaluate their in vitro photodynamic potential against melanoma cells (B16-F10), as well as their selectivity compared with human keratinocytes (HaCaT). Methods: NFs-Chl were prepared by spontaneous emulsification. Physicochemical characterization was carried out using dynamic light scattering (DLS), UV–Vis spectroscopy, FTIR, and Raman spectroscopy. In vitro assays included MTT for cell viability (IC₅₀ determination), real-time cell proliferation (RealTime-Glo™), and cell migration analysis (scratch assay). All photodynamic treatments were performed under irradiation at 660 nm. Results: NFs-Chl exhibited homogeneous nanometric sizes (≈24–31 nm) and a low polydispersity index (≈0.25–0.40), indicating a narrow size distribution. UV–Vis spectra confirmed the preservation of the characteristic absorption peaks of chlorophyll after encapsulation. In B16-F10 cells, NFs-Chl associated with PDT significantly reduced cell viability and metabolic activity over 48 h. Furthermore, NFs-Chl inhibited the migratory capacity of B16-F10 cancer cells. Cell migration assays revealed a clear inhibition of B16-F10 cell migration following treatment with NFs-Chl + PDT. Conclusions: Encapsulation of chlorophyll into castor oil nanoemulsions protected the photosensitizer, improved its cellular delivery, and enhanced its photodynamic cytotoxic effect against melanoma cells, while relatively preserving normal keratinocytes in vitro. Full article

Rapid detection of heavy metals is vital for monitoring surface water contamination and preventing environmental and health risks. Traditional detection methods for metals such as lead and copper often require sophisticated, costly instrumentation, limiting their use in routine analyses. To address this challenge, we developed a cost-effective fluorescence-based approach using semiconductor quantum dots (QDs) as nanosensors for metal ion detection. The QDs were synthesized directly in aqueous medium through a reflux-assisted process employing cadmium precursors, selenium, thioglycolic acid (TGA), and branched polyethyleneimine (PEI, Mw ~25,000) as stabilizing agents. Structural analysis revealed nanoparticles with diameters below 5 nm, spherical morphology, and a zinc blende (face-centered cubic) crystalline structure. Optical characterization by UV–Vis, photoluminescence (PL), and FTIR spectroscopy confirmed effective surface functionalization and strong quantum confinement. PEI-capped QDs exhibited enhanced colloidal stability and showed pronounced fluorescence quenching in the presence of Pb²⁺ ions, indicating high sensitivity and selectivity toward lead. Both TGA- and PEI-capped QDs also demonstrated moderate responses to Co²⁺ but negligible interaction with Sn²⁺, confirming ion-specific detection. Overall, this study demonstrates that surface-engineered QDs constitute a simple, accessible platform for selective detection of toxic metals, with promising applications in environmental monitoring and water quality assessment. Full article

To understand glycan–protein interactions at biological interfaces, designing surfaces modified with structurally controlled glycans is highly important. In particular, naturally occurring glycosaminoglycans (GAGs) possess periodic sugar arrangements that play important roles in protein recognition, highlighting the need for the development of periodic glycopolymer model systems that can serve as GAG mimics for quantitative interaction analysis. In this study, sequence-controlled periodic glycopolymers were synthesized by reversible addition–fragmentation chain-transfer (RAFT) polymerization and immobilized onto gold surfaces to construct glycan-modified interfaces. The synthesized material was a terminally functionalized periodic glycopolymer with the most basic structure, consisting of alternating maltose-containing vinyl ether (MalVE) units and ethyl maleimide (EtMI) units, with a trithiocarbonate group at the ω-terminal. This trithiocarbonate group was converted to a thiol group for immobilization through Au–S bond formation. Structural characterization by ¹H NMR spectroscopy, size exclusion chromatography (SEC), MALDI-TOF mass spectrometry, and UV–vis spectroscopy confirmed the structure as designed. Quartz crystal microbalance (QCM) measurements verified the stable immobilization of thiol-terminated periodic glycopolymers on the gold surface, and allowed for estimation of graft density and quantitative analysis of glycan-protein interactions at the modified interface. The periodic glycopolymer-modified surfaces exhibited selective binding behavior toward concanavalin A (ConA) compared to bovine serum albumin (BSA), with apparent binding constants on the order of 10⁶–10⁷ L mol⁻¹. This enhanced binding behavior indicated that specific and multivalent interactions with proteins also occurred at periodic pendant maltose residues along the main chain. These results demonstrate that the gold surface modified with end-functional periodic glycopolymers synthesized by RAFT polymerization provides a versatile platform for quantitative analysis of glycan-protein interactions and suggests potential applications for periodic glycopolymers as functional materials. Full article

To reveal the varieties and color genesis of emerald-green tourmaline crystals from Tanzania, a systematic study was conducted using conventional gemological tests, X-ray diffraction, Fourier-transform infrared spectroscopy, polarized ultraviolet–visible spectroscopy (UV–vis), X-ray photoelectron spectroscopy (XPS), low-temperature photoluminescence (PL) spectroscopy, and electron probe microanalysis (EPMA). The results indicate that the tourmaline is dravite. Its UV–vis absorption spectrum shows strong broad absorption bands at approximately 436 and 600 nm, with a pronounced transmission at 520 nm, which directly accounts for its emerald green color. Obvious polarized absorption was observed along and perpendicular to the c-axis. XPS and PL results confirm that chromium is present in the samples in the form of Cr³⁺. EPMA compositional analysis indicated a low Cr₂O₃ content of 0.804 wt.%; combined with crystal structural properties and spectral responses, these results suggest that Cr³⁺ preferentially occupies the Y site in the crystal structure and that d–d electronic transitions represent the underlying mechanism of its color formation. This study comprehensively illustrated the mineralogical and spectral properties of Cr-bearing dravite, providing fundamental data for further research on its genesis and gemological application. Full article

In cold arid regions, the relationships between dissolved organic matter (DOM) characteristics and heavy metal distributions across ice, water, and sediment interfaces remain insufficiently resolved. This study characterized DOM spectral features and examined their associations with measured metal distributions in a typical frozen eutrophic lake using excitation–emission matrices coupled with parallel factor analysis (EEMs-PARAFAC), ultraviolet-visible absorption spectroscopy (UV-Vis), and Fourier-transform infrared spectroscopy (FTIR). Protein-like substances dominated ice DOM, whereas water and sediment-derived DOM contained more humified fluorescent components. Fluorescence indices confirmed a primarily biological origin across all media, with ice showing the highest autochthonous microbial contribution (BIX = 1.23) but the lowest humification (HIX = 0.26), suggesting a greater contribution of recently produced protein-like fluorescent DOM in the ice samples. Water DOM showed the highest average HIX (1.88), followed by sediment-derived DOM (0.61) and ice DOM (0.26). The measured hydrochemical conditions, including weak alkalinity, elevated total dissolved solids (TDS), and locally low dissolved oxygen, provide environmental context for differences in metal distributions. Exploratory Spearman analysis at 17 matched water stations identified the strongest DOM–metal associations for HIX-As (rho = 0.474, p = 0.054) and FI-Zn (rho = 0.471, p = 0.056), indicating that DOM optical properties provide testable indicators of metal-distribution patterns but should be combined with direct binding and speciation measurements for mechanistic confirmation. Because ice was collected in January 2021, whereas water and sediment were collected in October 2020, cross-medium differences are interpreted as between-campaign associations rather than synchronous partitioning. These findings provide a basis for targeted winter monitoring and future binding, speciation, and freeze-concentration experiments in shallow eutrophic lakes. Full article

Tetracycline-class antibiotics are persistent contaminants in aquatic environments and are difficult to remove by conventional treatment processes. In this study, a recoverable granular MIL-101(Fe)/γ-Al₂O₃ catalyst was prepared through ligand anchoring followed by secondary Fe-MOF growth on spherical γ-Al₂O₃ and applied to catalytic ozonation of tetracycline (TC) under ordinary-bubble and microbubble-assisted operation. Structural characterization supported the formation of Fe-containing MOF domains on the alumina support, accompanied by an increase in BET surface area from 164.28 to 210.05 m² g⁻¹ and enhanced Lewis-acid-related pyridine-IR signals. Under conventional bubbling ozonation, the optimized catalyst achieved 67.93% apparent UV–Vis-based TC removal during an overall 50 min run consisting of 30 min dark adsorption followed by 20 min ozonation. In a 12 L microbubble reactor, the catalyst-assisted system reached 93.74% apparent UV–Vis-based TC removal at pH 6 with 100 g catalyst and 6 mg min⁻¹ fed ozone, showing higher apparent removal than ordinary ozonation, microbubble ozonation, and ordinary-bubble catalytic ozonation under the tested configuration. Phosphate-blocking and radical-quenching experiments were consistent with the involvement of Lewis-acid-related sites, hydroxyl radicals, and superoxide-related pathways, but these tests are interpreted as indirect mechanistic evidence. LC-MS analysis suggested possible hydroxylation, demethylation, deamidation, ring opening, and low-molecular-weight product formation. The system also transformed chlortetracycline, oxytetracycline, and doxycycline and reduced COD and TOC in a simulated mixed-antibiotic matrix. Because parent-compound HPLC/LC-MS time-series quantification, ozone utilization/off-gas ozone measurement, bubble-size/kLa analysis, and ICP-based Fe loading/leaching data were not available, the present work is positioned as an apparent catalyst–reactor coupling study rather than a complete catalytic, hydrodynamic, or process-level demonstration. Full article

Light-triggered hydrogel systems offer precise spatiotemporal control over drug release, yet most existing approaches require direct chemical conjugation of a photocleavable linker to the payload, which risks compromising bioactivity and limits applicability to structurally diverse molecules. Here, we report a gelatin–poly(ethylene glycol) (PEG) hybrid hydrogel crosslinked via strain-promoted azide–alkyne cycloaddition (SPAAC) click chemistry, in which an o-nitrobenzyl photocleavable (PC) linker is incorporated into the PEG crosslinker arm rather than conjugated to the drug. Acetylated gelatin–azide (AGA) was synthesized by sequential azide functionalization and amine capping of gelatin, and four-arm PEG-PC-DBCO (4armPEG-PC-DBCO) was prepared by coupling a PC DBCO-PEG4-NHS ester to four-arm PEG amine. Successful incorporation of the azide, DBCO, and o-nitrobenzyl moieties was confirmed by FT-IR spectroscopy, ¹H NMR spectroscopy, and UV-Vis spectrophotometry. Hydrogel formation under physiological conditions (PBS, 37 °C) without catalysts or initiators was verified by rheological frequency sweep analysis, which confirmed elastic-dominant behavior (G′ > G″). Upon irradiation at 365 nm, the crosslinker was cleaved, and rapid network dissolution was observed both macroscopically and by in situ time sweep rheology. This platform enables on-demand, UV-selective hydrogel degradation independently of payload identity, providing a versatile foundation for future controlled drug release applications and dynamic, on-demand degradable scaffolds for tissue engineering. Full article

Invasive candidiasis caused by drug-resistant Candida species represents a critical global health challenge, with few novel therapeutic scaffolds under development. Here, silver nanoparticles were synthesized using a 21-day fermented Chun Mee kombucha tea extract (K-AgNPs) and characterized by UV-Vis spectroscopy, transmission electron microscopy, nanoparticle tracking analysis, and Fourier-transform infrared spectroscopy. LC-MS/MS profiling of the kombucha substrate documented a phytochemical landscape dominated by epigallocatechin (up to 122,631 µg/mL) and epigallocatechin gallate (up to 415 µg/mL), with a progressive ~80% decline in epicatechin and concomitant increases in gallic acid and chlorogenic acid across the 21-day fermentation. K-AgNPs obtained were spherical, 19.4 nm (±7.9 nm SD) in diameter, with a surface plasmon resonance peak at 415 nm. FTIR confirmed phenolic, carboxylate, and glycosidic surface capping. Antifungal susceptibility testing against eight Candida species, including the WHO critical–priority pathogen Candidozyma auris, showed concordant minimum inhibitory and minimum fungicidal concentrations of 0.80–1.60 µg/mL, confirming fungicidal activity. In vivo evaluation in Galleria mellonella larvae across six infection models demonstrated that K-AgNP treatment at the species-specific MIC significantly improved larval survival versus untreated infected controls (p < 0.01–0.001), while nanoparticle-only groups maintained ≥98% survival, indicating negligible toxicity. Co-treatment amplified total hemocyte mobilization, and K-AgNP-only larvae maintained hemocyte viability above 96% at all time points, indistinguishable from negative controls. Together, these findings demonstrate antifungal activity of K-AgNPs across the genus Candida in standardized in vitro and in vivo settings and provide justification for further investigation, including head-to-head comparison against licensed antifungals and physicochemical validation of nanoparticle stability under assay conditions. Full article

Breath aerosol analysis requires low-cost sensing substrates capable of capturing aerosolized biomolecular components while preserving chemically interpretable readouts. Here, methylcellulose–phenol red (MCPR) films are evaluated as multimodal sensing substrates using model bioaerosols consisting of sodium sulfate, bovine serum albumin (BSA), and polystyrene latex particles under acidic, neutral, and alkaline pH conditions. ATR-FTIR spectroscopy revealed inverse pH-dependent trends in sulfate (1000–1100 cm⁻¹) and protein amide (1500–1700 cm⁻¹) spectral regions. A sulfate-to-protein AUC ratio increased from 0.86 ± 0.01 at pH 4 to 3.56 ± 0.32 at pH 10, demonstrating ratiometric compositional discrimination of ionic and proteinaceous aerosol fractions. UV–Vis spectroscopy showed pH-dependent λmax shifts from 432 to 556 nm, confirming the preservation of phenol red optical responsiveness after aerosol exposure. FTIR-derived ratio metrics correlated linearly with optical responses, indicating coupled vibrational and optical sensing behavior. SEM-EDS analysis of methylcellulose capture films confirmed deposition of sulfate, proteinaceous, and particulate aerosol components, supporting the platform’s suitability for multimodal spectroscopic sensing. These findings establish MCPR films as integrated capture-and-sensing substrates capable of coupling optical pH responsiveness with label-free vibrational analysis, supporting future development of low-cost breath-relevant aerosol sensing platforms. Full article

The copolymerization of biologically active N-(carboxyphenyl)maleimides with styrene was systematically investigated to elucidate the effect of positional isomerism (ortho-, meta-, and para-) on monomer reactivity and copolymer properties. Reactivity ratios (r₁, r₂) were determined using the Fineman–Ross method, and Q–e parameters were evaluated within the Alfrey–Price framework, revealing distinct electronic effects governing copolymerization behavior. Increasing the maleimide fraction in the feed resulted in decreased copolymer yield, intrinsic viscosity, molecular weight, and glass transition temperature, while all copolymers remained styrene-rich, indicating preferential styrene propagation. Comprehensive structural characterization (NMR, FTIR, and UV–Vis) confirmed successful incorporation of both monomer units. Rheological analysis demonstrated a clear viscosity trend (ortho > meta > para), highlighting the influence of substituent position on chain interactions and macromolecular architecture. Thermal analysis (TGA/DTA) showed good thermal stability up to 250–300 °C. Notably, the copolymers exhibited significant antibacterial and antifungal activity, with maximum inhibition observed against Candida albicans. This study establishes a direct correlation between substituent position and structure–property relationships, providing new insights for the rational design of functional styrenic copolymers with potential applications in antimicrobial and biomedical materials. Full article

Curcuminoids from Curcuma longa L. (curcumin, demethoxycurcumin, bisdemethoxycurcumin) are attractive bioactives yet constrained by low water solubility and chemical instability. Herein, we introduce a Supramolecular Deep Eutectic Solvent (SupraDES) as a “Janus” green platform, combining extraction and stabilization with a subsequent solvent-to-material strategy. Eight NaDES/SupraDES formulations based on choline chloride (ChCl) or betaine with glycerol (Gly) or citric acid (CitA), with/without β-cyclodextrin (βCD), were assessed. The extinction coefficients of the most promising solvents were extrapolated at 425 nm for the UV–vis quantification of curcuminoids, to determine extraction performance. The SupraDES ChCl:Gly:βCD gave the best performance during the first solvent screening, improving at the same time the bioactive stability (after 30-day, 47.5% loss vs. 62.8% of ChCl:Gly alone). Subsequent microwave-assisted extraction (MAE) optimization identified 80 °C as the optimal process temperature, with near-equilibrium reached within 15 min (3139.4 µgCurc/gEXT). Peleg modelling (R² = 0.997) indicated a fast extraction rate and limited benefit from longer residence times. Finally, the curcuminoid-loaded SupraDES was incorporated into polyvinyl alcohol (PVA) networks crosslinked with CitA and 2,5-bis(hydroxymethyl)furan (BHMF); thermal analysis confirmed the formation of a stable crosslinked structure. To the best of our knowledge, this is the first report of a βCD-based SupraDES acting as a Janus platform that couples supramolecular extraction of lipophilic bioactives with their direct incorporation into bio-based polymeric materials, exemplifying an integrated green chemistry approach aligned with circular bioeconomy principles. Full article

Organic–inorganic hybrid metal halides (OIMHs), especially zero-dimensional (0D) ones, have been recognized as an excellent class of luminescent materials due to their structural diversity and tunable emission properties. In this work, using the environmentally friendly Zn(II) ion as the central metal and 1,4,7,10-tetraazacyclododecane (Cyclen) as the organic component, we successfully synthesized a novel OIMH, (H₃Cyclen)(ZnBr₄)·Br·H₂O. Single-crystal X-ray diffraction analysis reveals that (H₃Cyclen)(ZnBr₄)·Br·H₂O possesses a 0D structure, in which the [ZnBr₄]²⁻ tetrahedra are uniformly separated by the organic amine cations. This structural feature is expected to enhance the material’s stability and optimize its optoelectronic properties. Under UV lamp irradiation, (H₃Cyclen)(ZnBr₄)·Br·H₂O emits bright blue-green light. Therefore, we systematically investigated its luminescence properties. The emission mechanism was further elucidated using UV–vis absorption spectroscopy and DFT calculations. Finally, (H₃Cyclen)(ZnBr₄)·Br·H₂O was employed as a luminescent material to fabricate a white light-emitting diode (WLED), demonstrating its potential as an excellent phosphor material. Full article

A comprehensive multiregional characterization of the spectral response of cassava leaves across different ontogenetic stages was performed. For this, ultraviolet (UV), visible (VIS) and shortwave near-infrared (UV-VIS-NIR; 200–900 nm) regions were used to identify spectral signatures and indices for their potential use as biomarkers of leaf development and physiological status of plants under induced senescence conditions. Manihot esculenta Crantz (HMC-1 variety) was used as a model. Spectral signatures were obtained from leaves at two phenological stages (4 and 6 months after planting) using UV-VIS-NIR spectroscopy by the diffuse reflectance technique. Classical and experimental spectral indices were evaluated, and their discriminatory power through different ontogenies was assessed using ANOVA/Kruskal–Wallis and post hoc tests. Senescence effects were further examined by postharvest monitoring (1–20 days), with temporal, ontogenetic, and interaction effects validated using linear mixed models (LMMs), while multivariate structure and spectral convergence were explored via principal component analysis and hierarchical clustering (PCA-HCA). Functionally Enhanced Derivative Spectroscopy (FEDS), comparative analysis, and spectral correlation mapping allowed signal’s selective enhancement and the identification of phenolic compounds, photosynthetic pigments, and structural molecular components. Results showed high ontogenetic stability of UV-associated phenolic signals (~210–220 nm), whereas the VIS region (420–600 nm) clearly differentiated young leaves. The NIR region was stable across ontogeny but highly sensitive to temporal degradation, reflecting changes in water status and internal structure. UV-VIS-NIR indices effectively differentiated young leaves and changes by stress. It is concluded that multiregional characterization of the spectral response supported by FEDS allows the extraction of robust indices with strong potential as biomarkers of leaf maturation and senescence in cassava. Full article

Green synthesis of KGM-capped CeO₂ nanoparticles was successfully achieved through a simple coprecipitation method using Konjac Glucomannan (KGM) as a biopolymeric capping and stabilizing agent. The reaction conditions were optimized by varying pH (9–11) and temperature (30–70 °C) to evaluate their influence on nanoparticle formation and photocatalytic performance. The synthesized KGM–CeO₂ nanoparticles were comprehensively characterized using FTIR, UV–Vis spectroscopy, XRD, SEM–EDS, TEM, DLS, and ZP analysis to investigate their structural, optical, morphological, and surface properties. The characterization results confirmed the successful formation of porous sponge-like branched CeO₂ nanostructures with irregular morphology. XRD analysis revealed the crystalline nature of the nanoparticles with an average crystallite size of approximately 7.7 nm, while DLS analysis showed an average hydrodynamic particle size of 29.7 nm with a biomodal particle size distribution. The positive zeta potential value (+16.75 mV) confirmed good colloidal stability and reduced agglomeration due to effective capping by KGM. The synthesized nanoparticles also exhibited favorable optical properties with band gap values suitable for photocatalytic applications. The adsorption and photocatalytic degradation performance of the KGM–CeO₂ nanoparticles was investigated against synthetic textile dyes, including Naphthol Blue Black (NBB), Methyl Orange (MO), and a mixed NBB–MO dye system under acidic conditions. Using an adsorbent dosage of 50 mg and dye concentrations of 100 mg/L, the material achieved degradation efficiencies of approximately 99% for NBB, 91% for MO, and 52% for the mixed dye system under UV irradiation for 120 min. Adsorption kinetic studies indicated that the pseudo-second-order model provided the best fit, suggesting that chemisorption is the dominant adsorption mechanism involving multifunctional surface interactions. These findings are particularly relevant for industrial wastewater treatment, since actual textile effluents typically contain complex mixtures of dyes and organic contaminants rather than single dye pollutants. The mixed dye experiments, therefore, provide a more realistic simulation of industrial wastewater conditions. Overall, the synthesized KGM–CeO₂ nanoparticles demonstrate excellent potential as an eco-friendly, cost-effective, and sustainable multifunctional material for adsorption-assisted photocatalytic treatment of dye-contaminated wastewater. Further optimization of operational conditions and catalyst surface properties may enhance its efficiency in multicomponent wastewater systems. Full article