Cationic Probe Research Articles

Research Progress on Naphthalimide Fluorescent Probes

AbstractNaphthalimide derivatives are attracting increasing attention as fluorescent probes due to their excellent modifiability and photophysical properties. Their large, rigid coplanar structures and conjugated systems enable easy generation of fluorescence. The imide units and bromonaphthalene functionality offer facile and concise modification pathways in preparing amenable probes for different metal cations, anions, small molecules, and organelles. Therefore, naphthalimide probes have great potential for application in research fields, such as analytical chemistry, cell biology, and clinical diagnosis.

A photoluminescence strategy for detection nanoplastics in water and biological imaging in cells and plants

Nanoplastics exposure poses a significant threat to the environment and human health, and accurate measurement of nanoparticles in aqueous solutions remains challenging. In this work, we synthesized the cationic fluorescent probe 4-[1-Cyano- 2-[4-(Diethylamino)−2-hydroxyphenyl]ethenyl]−1-ethylpyridinium (PCP) through a straightforward procedure for the rapid and accurate detection and labeling of nanoplastics in aqueous solutions. PCP binds to nanoplastics through electrostatic and hydrophobic interactions with restricted intramolecular rotation and exhibits enhanced fluorescence emission. Using carboxylation-modified polystyrene nanoplastics as a model, PCP could accurately detect concentrations as low as 0.525 mg∙L−1 in aqueous solution and perform wash-free semi-quantitative direct observation. The method demonstrated good reproducibility and recovery in actual sample spiking experiments. In addition, PCP-labeled nanoplastics were successfully used to visualize the uptake and distribution of cells and Arabidopsis thaliana when exposed to different concentrations of nanoplastics. This work provides a simple and sensitive method for efficiently identify, track, and quantify nanoplastics without requiring additional pretreatment and complex instrumentation, making it an ideal tool for accurately quantifying nanoplastics in aqueous solutions and studying the biological interactions of nanoplastics.

Bipolar hemicyanine cationic probe for simultaneous sensing of ATP and GTP

Adenosine 5′-triphosphate (ATP) and guanosine 5′-triphosphate (GTP) are the most essential energy source in enormous biological processes. Various probes for ATP or GTP sensing, have been widely established, but the probe that could simultaneously monitor ATP and GTP is still rarely reported. Herein, we report a bipolar hemicyanine cationic probe for simultaneous sensing of ATP and GTP via a one-step monitoring process. This probe exhibited strong affinity to ATP and GTP through intramolecular electrostatic and π-π stacking interactions, which the binding constant on each step were determined as 6.15 × 107 M−1 and 1.57 × 106 M−1 for ATP, 3.19 × 107 M−1 and 3.81 × 106 M−1 for GTP. The sensitivity and specificity of this probe toward ATP or GTP over other twelve biological analogues (adenosine 5′-diphosphate (ADP), adenosine 5′-monophosphate (AMP), guanosine 5′-diphosphate (GDP), guanosine 5′-monophosphate (GMP), Etc.) have also been successfully demonstrated. Furthermore, due to the rapid response rate (within 10 s), we also proved that this probe could be employed as a monitor tool during the ATP or GTP-related enzymatic reaction process.

Fluorescent detection of tartrazine based on the supramolecular self-assembly of cationic perylene diimide.

A cationic perylene probe was designed and synthesized for sensitive determination of tartrazine. In the presence of tartrazine, the fluorescence of theperylene probe was quenched by efficient supramolecular self-assembly of theperylene derivate. The quenching iscaused by the synergistic effect of noncovalent interactions including static electricity, π-π stacking, and hydrophobic interaction. Benefiting from these advantages, the probe exhibited excellent sensing performance to tartrazine within 2 min. The detection and quantification limit of tartrazine are as low as 2.42 and 8.07 nmol L-1, respectively, with a wide linear operation range from 15 to 500 nmol L-1. Most importantly, due to the high binding affinity (3.22 × 107 mol L-1) between the perylene probe and tartrazine, the sensing system shows great anti-interference capacity. Subsequently, the visualization application of the approach was evaluated by portable device, and the limits of detection for visual detection for test strip, membrane, and hydrogel were 0.5, 0.5, and 5 μmol L-1, respectively. Theapproach has been applied to monitor tartrazine in various food condiments with recoveries in the range 91.29-108.83%. As far as we know, this is the first report of using perylene-based probe for tartrazine determination, offering a promising strategy for the construction of perylene-based detection system in the field of food safety.

Benzothiazole-Based Fluorescent Probe as a Simple and Effective Platform for Functional Mitochondria Imaging.

Mitochondrial imaging is crucial for studying disease pathogenesis and diagnosis. However, commercially available mitochondria-specific fluorescent probes are limited due to the difficulty in modifying cationic probes for functional bioimaging of mitochondria. To address this, we prepared a hydroxythiophene-conjugated benzothiazole (BzT-OH) as a platform for the design of functional fluorescent probes. Two probes, BzT-OAc and BzT-OAcryl, were synthesized by substituting the hydroxy group in BzT-OH with acetate and acrylate groups, respectively. BzT-OAc demonstrated blue fluorescence that shifted to green emission after enzymatic cleavage of the acetate group, allowing for monitoring of endogenous esterase activity. BzT-OAcryl showed high selectivity for cysteine at pH > 8.0, owing to its pH-responsive property, and could detect pH perturbations caused by mitochondrial dysfunction. Both probes exhibited high biocompatibility, quantum yield, and large Stokes shifts in mitochondria. BzT-OH can be easily conjugated with other functional groups and substrates of various enzymes for designing fluorescent probes for functional mitochondrial imaging. The photofunctional property of the probe can be changed due to the involvement of the hydroxyl group in the excited state intermolecular proton transfer.

Homogeneous Electrochemical Aptamer Sensor Based on Two-Dimensional Nanocomposite Probe and Nanochannel Modified Electrode for Sensitive Detection of Carcinoembryonic Antigen.

A rapid and convenient homogeneous aptamer sensor with high sensitivity is highly desirable for the electrochemical detection of tumor biomarkers. In this work, a homogeneous electrochemical aptamer sensor is demonstrated based on a two-dimensional (2D) nanocomposite probe and nanochannel modified electrode, which can realize sensitive detection of carcinoembryonic antigen (CEA). Using π-π stacking and electrostatic interaction, CEA aptamer (Apt) and cationic redox probe (hexaammineruthenium(III), Ru(NH3)63+) are co-loaded on graphite oxide (GO), leading to a 2D nanocomposite probe (Ru(NH3)63+/Apt@GO). Vertically ordered mesoporous silica-nanochannel film (VMSF) is easily grown on the supporting indium tin oxide (ITO) electrode (VMSF/ITO) using the electrochemical assisted self-assembly (EASA) method within 10 s. The ultrasmall nanochannels of VMSF exhibits electrostatic enrichment towards Ru(NH3)63+ and size exclusion towards 2D material. When CEA is added in the Ru(NH3)63+/Apt@GO solution, DNA aptamer recognizes and binds to CEA and Ru(NH3)63+ releases to the solution, which can be enriched and detected by VMSF/ITO electrodes. Based on this mechanism, CEA can be an electrochemical detection ranging from 60 fg/mL to 100 ng/mL with a limit of detection (LOD) of 14 fg/mL. Detection of CEA in human serum is also realized. The constructed homogeneous detection system does not require the fixation of a recognitive aptamer on the electrode surface or magnetic separation before detection, demonstrating potential applications in rapid, convenient and sensitive electrochemical sensing of tumor biomarkers.

Styryl-NIR Mitochondrial Probes with Rapid HOCl Detection in Live-Cells.

Hypochlorous acid (HOCl) is critical for maintaining immune system balance, but it can harm mitochondria by hindering enzyme activity, leading to decreased ATP and increased cell death. In this study, we have designed a fluorophore with a pyridinium scaffold for selective staining of the mitochondria and to detect hypochlorite. The fluorophore exhibits strong solvatochromic emission due to intramolecular charge transfer and excellent sub-cellular localization in the mitochondria. Additionally, it shows a rapid response to HOCl with high selectivity among different reactive oxygen/nitrogen compounds with a detection limit of 2.31 μM. Moreover, it is also utilized for the exogenous and endogenous detection of HOCl in live cells, which may help study the role of hypochlorite in organelles at the cellular level. DFT and TDDFT calculations have been carried out to understand the relationship between the structure and properties of the cationic probes with respect to the α-cyano substitution and extension of π-conjugation. The selective detection of HOCl by C4 over other cationic probes has also been well-demonstrated, showing how the binding of HOCl affects the electronic properties of C4 through the analysis of non-bonding orbitals (NBO) population, electrostatic potential surface (ESP), and density of states (DOS) projected DOS investigations.

Reagentless Electrochemical Detection of Tumor Biomarker Based on Stable Confinement of Electrochemical Probe in Bipolar Silica Nanochannel Film.

The development of simple and probe-integrated aptamer sensors for the electrochemical detection of tumor biomarkers is of great significance for the diagnosis of tumors and evaluation of prognosis. In this work, a probe-integrated aptamer sensor is demonstrated based on the stable confinement of an electrochemical probe in a bipolar nanochannel film, which can realize the reagentless electrochemical detection of the tumor biomarker carcinoembryonic antigen (CEA). To realize the stable immobilization of a large amount of the cationic electrochemical probe methylene blue (MB), a two-layer silica nanochannel array (SNF) with asymmetric charge was grown on the supporting electrode from bipolar SNF (bp-SNF). The inner SNF is negatively charged (n-SNF), and the outer-layer SNF is positively charged (p-SNF). The dual electrostatic interaction including the electrostatic adsorption from n-SNF and the electrostatic repulsion from p-SNF achieve the stable confinement of MB in bp-SNF. The recognitive interface is fabricated by the covalent immobilization of the CEA aptamer on the outer surface of bp-SNF, followed by the blocking of non-specific binding sites. Owing to the stable and abundant immobilized probes and highly specific aptamer interface, the developed aptamer sensor enables the sensitive detection of CEA in the range of 1 pg/mL to 1 μg/mL with a low limit of detection (LOD, 0.22 pg/mL, S/N = 3). Owing to the high selectivity and stability of the developed biosensor, reagentless electrochemical detection of CEA in serum was realized.

Constant Conversion Rate of Endolysosomes Revealed by a pH-Sensitive Fluorescent Probe.

Endolysosome dynamics plays an important role in autophagosome biogenesis. Hence, imaging the subcellular dynamics of endolysosomes using high-resolution fluorescent imaging techniques would deepen our understanding of autophagy and benefit the development of pharmaceuticals against endosome-related diseases. Taking advantage of the intramolecular charge-transfer mechanism, herein we report a cationic quinolinium-based fluorescent probe (PyQPMe) that exhibits excellent pH-sensitive fluorescence in endolysosomes at different stages of interest. A systematic photophysical and computational study on PyQPMe was carried out to rationalize its highly pH-dependent absorption and emission spectra. The large Stokes shift and strong fluorescence intensity of PyQPMe can effectively reduce the background noise caused by excitation light and microenvironments and provide a high signal-to-noise ratio for high-resolution imaging of endolysosomes. By applying PyQPMe as a small molecular probe in live cells, we were able to reveal a constant conversion rate from early endosomes to late endosomes/lysosomes during autophagy at the submicron level.

An ultra-photostable and leakage-free fluorescent probe for long-term and high-fidelity mitochondria visualization and tracking

Mitochondria are important morphologically diverse organelles, and each characteristic has specific physiological significance. Thus, mitochondrial long-term and high-fidelity visualization and tracking are valuable. As a consequence, an ultra-photostable and leakage-free fluorescent probe is desired. Herein, we report a cationic probe DQPI-12 with a long alkyl chain, which can exclusively and firmly target mitochondria independent of mitochondria membrane potential changes. In particular, even after the cells have been fixed and left in place for 12 days, filamentous fluorescence signals from mitochondria could still be observed clearly, indicating DQPI-12 possesses excellent leakage-free performance. At the same time, compared with commercial mitochondria probes and those reported by others, DQPI-12 also displays excellent photostability. Inherent characters of DQPI-12 enable it to long-term and high-fidelity visualize mitochondria within a special microscopic field under continuous or intermittent irradiation of laser. Benefit from these advantages, DQPI-12 is successfully applied to track mitochondrial dynamic processes in living HeLa cells and neurons, and monitor the occurrence of mitophagy real-time, in-situ, and long-term.

Reusable magnetic catalysed synthesis of fluorescent imidazole derivatives: Their use as chromogenic and fluorogenic probes for metal cation's detection

In this contribution, we report the design of magnetic functionalized nanocellulose by an in-Situ approach. The fabricated polymer matrix was utilized as an efficient heterogeneous catalyst for one-pot multi-component synthesis of fluorescent multi-substituted imidazoles under green optimized conditions. The eco-friendly protocol afforded, short reaction times, excellent yields and catalyst easy recycling through magnetic recovery. The geometric optimization, MEP and FMOs have also been carried out at B3LYP‐D3/6–311++G (d, p) level of Density Functional Theory simulations in ethanol to elucidate the substituent's effect on molecule's planarity, surface studies, their electronic structure as well as their intermolecular charge transfer. Furthermore, the synthesized multi-substituted Imidazole derivatives exhibited remarkable fluorescent properties explored in cation metal's chromogenic and fluorogenic detection.

An Activatable NIR Fluorescent Probe for NAD(P)H and Its Application to the Real‐Time Monitoring of p53 Abnormalities In Vivo

AbstractNAD(P)H is crucial for biosynthetic reactions and antioxidant functions. However, the current probes developed for detecting NAD(P)H in vivo require intratumoral injection, which limited their application for animal imaging. To address this issue, we have developed a liposoluble cationic probe, KC8, which exhibits excellent tumor‐targeting ability and near‐infrared (NIR) fluorescence after reaction with NAD(P)H. By using KC8, it was demonstrated for the first time that the level of NAD(P)H in the mitochondria of living colorectal cancer (CRC) cells was highly related to the abnormality of the p53. Furthermore, KC8 was successfully used to differentiate not only between tumor and normal tissue but also between tumors with p53 abnormality and normal tumors when administered intravenously. Finally, we evaluated tumor heterogeneity through two fluorescent channels after treating a tumor with 5‐Fu. This study provides a new tool for real‐time monitoring of the p53 abnormality of CRC cells.

An Activatable NIR Fluorescent Probe for NAD(P)H and Its Application to the Real-Time Monitoring of p53 Abnormalities In Vivo.

NAD(P)H is crucial for biosynthetic reactions and antioxidant functions. However, the current probes developed for detecting NAD(P)H in vivo require intratumoral injection, which limited their application for animal imaging. To address this issue, we have developed a liposoluble cationic probe, KC8, which exhibits excellent tumor-targeting ability and near-infrared (NIR) fluorescence after reaction with NAD(P)H. By using KC8, it was demonstrated for the first time that the level of NAD(P)H in the mitochondria of living colorectal cancer (CRC) cells was highly related to the abnormality of the p53. Furthermore, KC8 was successfully used to differentiate not only between tumor and normal tissue but also between tumors with p53 abnormality and normal tumors when administered intravenously. Finally, we evaluated tumor heterogeneity through two fluorescent channels after treating a tumor with 5-Fu. This study provides a new tool for real-time monitoring of the p53 abnormality of CRC cells.

Julolidine-based small molecular probes for fluorescence imaging of RNA in live cells.

Intracellular RNA imaging with organic small molecular probes has been an intense topic, although the number of such reported dyes, particularly dyes with high quantum yields and long wavelength excitation/emission, is quite limited. The present work reports the design and synthesis of three cationic julolidine-azolium conjugates (OX-JLD, BTZ-JLD and SEZ-JLD) as turn-on fluorescent probes with appreciably high quantum yields and brightness upon interaction with RNA. A structure-efficiency relationship has been established for their potential for the interaction and imaging of intracellular RNA. Given their chemical structure, the free rotation between the donor and the acceptor gets restricted when the probes bind with RNA resulting in strong fluorescence emission towards a higher wavelength upon photoexcitation. A detailed investigation revealed that the photophysical properties and the optical responses of two probes, viz. BTZ-JLD and SEZ-JLD, towards RNA are very promising and qualify them to be suitable candidates for biological studies, particularly for cellular imaging applications. The probes allow imaging of intracellular RNA with prominent staining of nucleoli in live cells under a range of physiological conditions. The results of the cellular digest test established the appreciable RNA selectivity of BTZ-JLD and SEZ-JLD inside the cellular environment. Moreover, a comparison between the relative intensity profile of SEZ-JLD before and after the RNA-digestion test inside the cellular environment indicated that the interference of cellular viscosity in fluorescence enhancement is insignificant, and hence, SEZ-JLD can be used as a cell membrane permeable cationic molecular probe for deep-red imaging of intracellular RNA with a good degree of selectivity.

ESIPT-based probes for cations, anions and neutral species: recent progress, multidisciplinary applications and future perspectives.

Fluorescent and colourimetric probes for small analytes (cations, anions and neutral molecules) have drawn significant attention in recent years. These probes interact with analytes and induce spectral change due to the variations in the photo-physical properties of the fluorophore/chromophore used. Among several photo-physical mechanisms, ESIPT (excited state intramolecular proton transfer) based probes are more advantageous due to their photo-physical properties viz. solvent polarity effect, large spectral shift with multi-channel fluorescence, high quantum yield etc. In recent years, ESIPT-based probes have shown several promising applications, especially monitoring small analytes in biological samples, smartphone app-assisted heavy metal detection in environmental samples, inkless writing, anti-counterfeiting applications etc. Therefore, this review is dedicated to recently reported ESIPT-based probes for small analytes. We have highlighted the organic units responsible for the ESIPT mechanism, their photo-physical parameters, selectivity and sensitivity properties and recent advances in their applications.

A near-infrared cationic fluorescent probe based on thieno[3,2-b]thiophene for RNA imaging and long-term cellular tracing

Gene expression and regulation in which RNA is an essential participant can be visualized by imaging RNA with fluorescent probes. However, most of the reported fluorescent probes for RNA have defects such as short emission wavelength, small Stokes shift, poor selectivity, low sensitivity, and poor membrane permeability. Herein, a NIR (710 nm) cationic fluorescent probe PCTP with D-π-A structure and large Stokes shift (285 nm) using 9-phenylcarbazole as an electron donor and pyridinium salt as an electron acceptor was designed and synthesized. Titration experiments and enzyme treatment experiments demonstrate that PCTP can differentiate RNA from DNA in solution and cells, the fluorescence intensity of PCTP increases by a maximum of 52.2 times after binding to RNA and the detection limit is 2.17 μg/mL, showing high selectivity and sensitivity to RNA. Furthermore, with low cytotoxicity, good biocompatibility and high photostability, PCTP is able to trace 4T1 cell proliferation in vitro to 9 generations and trace 4T1 cell in mice for 22 days. The probe provides a potential tool for RNA imaging and long-term cellular tracing.

Organelle-Selective Membrane Labeling through Phospholipase D-Mediated Transphosphatidylation.

The specialized functions of eukaryotic organelles have motivated chemical approaches for their selective tagging and visualization. Here, we develop chemoenzymatic tools using metabolic labeling of abundant membrane lipids for selective visualization of organelle compartments. Synthetic choline analogues with three N-methyl substituents replaced with 2-azidoethyl and additional alkyl groups enabled the generation of corresponding derivatives of phosphatidylcholine (PC), a ubiquitous and abundant membrane phospholipid. Subsequent bioorthogonal tagging via the strain-promoted azide-alkyne cycloaddition (SPAAC) with a single cyclooctyne-fluorophore reagent enabled differential labeling of the endoplasmic reticulum, the Golgi complex, mitochondria, and lysosomes depending upon the substitution pattern at the choline ammonium center. Key to the success of this strategy was the harnessing of both the organic cation transporter OCT1 to enable cytosolic delivery of these cationic metabolic probes and endogenous phospholipase D enzymes for rapid, one-step metabolic conversion of the choline analogues to the desired lipid products. Detailed analysis of the trafficking kinetics of both the SPAAC-tagged fluorescent PC analogues and their non-fluorescent, azide-containing precursors revealed that the latter exhibit time-dependent differences in organelle selectivity, suggesting their use as probes for visualizing intracellular lipid transport pathways. By contrast, the stable localizations of the fluorescent PC analogues will allow applications not only for organelle-selective imaging but also for local modulation of physiological events with organelle-level precision by tethering of bioactive small molecules, via click chemistry, within defined subcellular membrane environments.

Ionic thermoresponsive fluorescent polymers for detecting countercharged surfactants without phase separation

Thermoresponsive polymers containing ionic and fluorescent groups were designed and synthesized for use as fluorescent probes to sense ionic surfactants without phase separation. The synthesized ionic thermoresponsive fluorescent polymers interact with countercharged surfactants, resulting in increases in their fluorescence intensities, even at temperatures lower than their phase-transition temperatures. The observed increases in the fluorescence intensities are attributable to the incorporation of fluorophores within the soluble aggregates formed by the polymers and ionic surfactants at temperatures lower than the phase-transition temperatures. The synergistic effects of the hydrophobic and ionic interactions between the two moieties lead to the formation of soluble aggregates, which enhance the fluorescence of the fluorophores bound to the polymers. The fluorescence intensities of cationic and anionic fluorescent polymer probes were found to be linearly dependent on the concentrations of sodium dodecyl sulfate (SDS) and zephilamine, respectively, at the 10−5 mol/L level. Moreover, the concentration of SDS, an anionic surfactant used commonly in detergents, as determined using the cationic fluorescent probe was in keeping with that determined by the conventional methylene blue method. Thus, it was confirmed that the synthesized thermoresponsive fluorescent polymers with ionic groups can function as probes for countercharged ionic surfactants in homogeneous aqueous media without any phase-separation processes, which require hazardous organic solvents.

Effect of TP53 deficiency and KRAS signaling on the bioenergetics of colon cancer cells in response to different substrates: A single cell study.

Metabolic reprogramming is a hallmark of cancer. Somatic mutations in genes involved in oncogenic signaling pathways, including KRAS and TP53, rewire the metabolic machinery in cancer cells. We here set out to determine, at the single cell level, metabolic signatures in human colon cancer cells engineered to express combinations of activating KRAS gene mutations and TP53 gene deletions. Specifically, we explored how somatic mutations in these genes and substrate availability (lactate, glucose, substrate deprivation) from the extracellular microenvironment affect bioenergetic parameters, including cellular ATP, NADH and mitochondrial membrane potential dynamics. Employing cytosolic and mitochondrial FRET-based ATP probes, fluorescent NADH sensors, and the membrane-permeant cationic fluorescent probe TMRM in HCT-116 cells as a model system, we observed that TP53 deletion and KRAS mutations drive a shift in metabolic signatures enabling lactate to become an efficient metabolite to replenish both ATP and NADH following nutrient deprivation. Intriguingly, cytosolic, mitochondrial and overall cellular ATP measurements revealed that, in WT KRAS cells, TP53 deficiency leads to an enhanced ATP production in the presence of extracellular lactate and glucose, and to the greatest increase in ATP following a starvation period. On the other hand, oncogenic KRAS in TP53-deficient cells reversed the alterations in cellular ATP levels. Moreover, cell population measurements of mitochondrial and glycolytic metabolism using a Seahorse analyzer demonstrated that WT KRAS TP53-silenced cells display an increase of the basal respiration and tightly-coupled mitochondria, in the presence of glucose as substrate, compared to TP53 competent cells. Furthermore, cells possessing oncogenic KRAS, independently of TP53 status, showed less pronounced mitochondrial membrane potential changes in response to metabolic nutrients. Furthermore, analysis of cytosolic and mitochondrial NADH levels revealed that the simultaneous presence of TP53 deletion and oncogenic KRAS showed the most pronounced alteration in cytosolic and mitochondrial NADH during metabolic stress. In conclusion, our findings demonstrate how activating KRAS mutation and loss of TP53 remodel cancer metabolism and lead to alterations in bioenergetics under metabolic stress conditions by modulating cellular ATP production, NADH oxidation, mitochondrial respiration and function.

Ternary Metal-Alginate-Chitosan Composites for Controlled Uptake of Methyl Orange

Three ternary metal composites (TMCs) with iron nitrate, aluminum nitrate, and copper nitrate (Fe-TMC-N, Al-TMC-N, Cu-TMC-N) were synthesized and their physicochemical properties were investigated. Characterization of the TMCs was achieved by elemental analysis (XPS), infrared (IR) spectroscopy and thermogravimetric analysis (TGA). The surface charge of the TMCs was estimated from the point-of-zero-charge (PZC), which depended on the type of metal nitrate precursor. The adsorption properties of the TMCs showed the vital role of the metal center, where methylene blue (MB) is a cationic dye probe that confirmed the effects of surface charge for effective methyl orange (MO) anion dye uptake. MB uptake was negligible for Al-TMC-N and Cu-TMC-N, whereas moderate MB uptake occurs for Fe-TMC-N (26 mg/g) at equilibrium. The adsorption capacity of MO adopted the Langmuir isotherm model, as follows: Al-TMC-N (422 mg/g), Cu-TMC-N (467 mg/g) and Fe-TMC-N (42 mg/g). The kinetic adsorption profiles followed the pseudo-second order model. Generally, iron incorporation within the TMC structure is less suitable for MO anion removal, whereas Cu- or Al-based materials show greater (10-fold) MO uptake over Fe-based TMCs. The dye uptake results herein provide new insight on adsorbent design for controlled adsorption of oxyanion species from water.