Why Do Ionic Surfactants Significantly Alter the Chemiluminogenic Properties of Acridinium Salt?

Acridinium esters, due to their capability for chemiluminescence (CL), are employed as indicators and labels in biomedical diagnostics and other fields. In this work, the influence of ionic surfactants, hexadecyltrimethylammonium chloride and bromide (CTAC and CTAB, cationic) and sodium dodecyl sulphate (SDS, anionic) on the CL parameters and mechanism of representative emitter, 10-methyl-9-[(2-methylphenoxy)carbonyl]acridinium trifluoromethanesulphonate (2MeX) in a H2O2/NaOH environment, is studied. Our investigations revealed that the type of surfactant and its form in solution have an impact on the CL kinetic constants and integral efficiencies, while changes in those emission properties resulting from the type of ion (Cl- vs. Br-) are negligible. The major changes were recorded for systems containing surfactants at concentrations higher than the critical micelle concentration. The cationic surfactants (CTAC, CTAB) cause a substantial increase in CL emission kinetics and a moderate increase in its integral efficiency. At the same time, the opposite effect is observed in the case of SDS. Molecular dynamics simulations suggest that changes in emission parameters are likely due to differences in the binding strength of 2MeX substrate with surfactant molecules, which is higher for SDS than for CTAC. The results can help in rational designing of optimal acridinium CL systems and demonstrate their usefulness in distinguishing the pre- and post-micellar environment and the charge of surfactants.

Combined anticancer therapy with imidazoacridinone analogue C-1305 and paclitaxel in human lung and colon cancer xenografts-Modulation of tumour angiogenesis.

The acridanone derivative 5-dimethylaminopropylamino-8-hydroxytriazoloacridinone (C-1305) has been described as a potent inhibitor of cancer cell growth. Its mechanism of action in in vitro conditions was attributed, among others, to its ability to bind and stabilize the microtubule network and subsequently exhibit its tumour-suppressive effects in synergy with paclitaxel (PTX). Therefore, the objective of the present study was to analyse the effects of the combined treatment of C-1305 and PTX in vivo. In addition, considering the results of previous genomic analyses, particular attention was given to the effects of this treatment on tumour angiogenesis. Treatment with C-1305 revealed antitumor effect in A549 lung cancer cells, and combined treatment with PTX showed tendency to anticancer activity in HCT116 colon cancer xenografts. It also improved tumour blood perfusion in both tumour models. The plasma level of CCL2 was increased and that of PDGF was decreased after combined treatment with C-1305 and PTX. The experimental results showed that the levels of FGF1, TGF-ß and Ang-4 decreased, whereas the levels of ERK1/2 and Akt phosphorylation increased in HCT116 tumour tissue following combined treatment with both drugs. The results of in vitro capillary-like structure formation assay demonstrated the inhibiting effect of C-1305 on this process. Although previous in vitro and in vivo studies suggested a positive effect of C-1305 on cancer cells, combined treatment of HCT116 human colon and A549 lung cancer cells with both PTX and C-1305 in vivo showed that the antitumor activity was restricted and associated with the modulation of tumour angiogenesis.

New luminometric method for quantification of biological sulfur nucleophiles with the participation of 9-cyano-10-methylacridinium salt.

Biologically active compounds containing sulfhydryl groups (RSHs: N-acetyl-l-cysteine, d-penicillamine, glutathione and acetylthiocholine chloride) were used to develop a luminometric method for their quantification. The title substrate capable of chemiluminescence (CL) was isolated in a highly pure state as a chloride salt (99.9% using RP-HPLC) and identified using mass spectrometry (ESI Q-TOF) and 1 H NMR spectroscopy. The cation included in the salt, 9-CMA+ , underwent oxidation in an alkaline environment containing RSHs by molecular oxygen, generating CL of various intensities, with no need for the use of hydrogen peroxide. The amount of produced light was linearly proportional to the content of investigated analytes in the system over the concentration range ~0.2-2 µM, with the detection limits in the range 0.19-1.73 µM. The mechanism of chemiluminogenic oxidation of 9-CMA+ in the presence of RSHs and molecular oxygen is proposed, using computational methods at the density-functional theory level. The presence of RSHs in an alkaline medium seems to be crucial to produce hydroperoxide anions (- OOH), which initiate the 'light path' of 9-CMA+ transformations, ending with the excretion of electronically excited molecules of 10 methyl-acridan-9-one.

On the use of acridinium indicators for the chemiluminescent determination of the total antioxidant capacity of dietary supplements.

Acridinium salts, due to their chemiluminogenic properties, have found several applications in biomedical analysis as labels and indicators, where the assessment of emission intensity is used for the end-point detection. This work presents the use of chemiluminescent indicators in the form of selected acridinium esters in order to determine the antioxidant properties of exemplary formulations, namely quercetin, vitamin C and the dietary supplement, Apiextract. The principle of measurements is based on a change in the kinetics of emission decay derived from the acridinium cations in alkaline solutions of hydrogen peroxide in the presence of an antioxidant (the analyte). The proposed system makes a beneficial alternative to related methods, which mostly rely on the assessment of emission efficiency and use the luminometric standard luminol - due to superior parameters of acridinium chemiluminescence, among others - high temporary emission efficiency. The features of the proposed method are manifested by a shorter time period of analysis and lower background signals associated with the environmental influences, as compared to typical approaches. The chromatographic (RP-HPLC) analyses of the substrates and products generated during chemiluminogenic oxidation of acridinium cations under assay conditions are also presented.

Thiamine Diphosphate Status and Dialysis-Related Losses in End-Stage Kidney Disease Patients Treated with Hemodialysis.

AIM: (1) To describe the whole blood content of thiamine diphosphate (TDP), a biologically active form of vitamin B1 in end-stage kidney disease patients treated with hemodialysis (HD); (2) to establish the impact of a single HD procedure on TDP blood concentrations; and (3) to describe potential explanatory variables influencing TDP dialysis related losses, including dialysis prescription, vitamin B1 dietary intake and supplementation. METHODS: Single-center, cross-sectional study in 50 clinically stable maintenance HD patients. The assessment of whole blood TDP with the High Performance Liquid Chromatography method, before and after a single, middle-week dialysis session and analysis of clinical and laboratory parameters potentially influencing TDP status Results: We report a significant difference in TDP levels before and after HD sessions - 42.5 (95% CI 38.7-46.2) µg/L and 23.6 (95% CI 18.9-28.2) µg/L, respectively (p = 0.000). The magnitude of intradialytic TDP changes is highly variable among individuals and is negatively associated only with the body weight of the patients (p < 0.013). Vitamin B1 dietary intake and supplementation do not influence whole blood TDP and dialysis-related loss of TDP. CONCLUSIONS: TDP, a bioactive compound of vitamin B1, is substantially lost during the HD procedure, and the magnitude of its loss is associated with the patient's body weight but it is not influenced by vitamin B1 dietary intake and standard supplementation dose.

Effective chemiluminogenic systems based on acridinium esters bearing substituents of various electronic and steric properties.

A series of 10-methyl-9-(phenoxycarbonyl)acridinium trifluoromethanesulfonates (XAEs), bearing substituents of various characteristics in the lateral benzene ring (2-halogen, 2,6-dihalogen, 2-trifluoromethyl, 2-nitro, 2-methoxy, 3-halogen and 4-halogen) were synthesized with high yields, identified and subjected to a physicochemical and theoretical investigation. The main task of the work was to assess the mechanism and optimal conditions of light emission in various liquid systems based on the above salts in order to evaluate their potential usefulness as chemiluminescence (CL) labels and indicators in ultra-sensitive analyses. Density functional theory (DFT) calculations were performed to investigate the detailed mechanism of the oxidation of 9-substituted 10-methylacridinium cations involved in XAEs by hydrogen peroxide in alkaline media. Three general pathways were drawn, which are termed the "light path" (chemiluminogenic) and there were two "dark paths" (non-chemiluminogenic): hydrolytic and "pseudobase". The CL time profiles, triggered in alkaline solutions containing hydrogen peroxide, enabled us to establish crucial physicochemical parameters, including pseudo-first order kinetic constants of CL decay and relative efficiencies of emission. In order to optimize the systems' luminogenic performance, different bases, such as sodium hydroxide, tetrabutylammonium hydroxide (TBAOH) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), as well as enhancers, such as cationic, zwitterionic and neutral surfactants (cetyltrimethylammonium chloride (CTAC), N,N-dimethyldodecylammonio-1,3-propane sulfonate (DDAPS) and Triton X-100, respectively) were tested. The results revealed the optimal CL systems, which enabled us to obtain substantially higher emissions than typical ones, based on acridinium esters or luminol. The derived parameters, characterizing the potential utility of the acridinium esters, such as stability in aqueous environments and usefulness (the product of emission efficiency and stability at a given pH), enabled us to reveal the best candidates and their practical applications. The post-reaction mixtures, analyzed by means of chromatography (RP-HPLC) and mass spectrometry (ESI-MS), allowed us to verify the occurrence and population of the products that were theoretically predicted, i.e. 10-methyl-9-acridinone (NMAON), 10-methylacridinium-9-carboxylic acid (NMACA) and substituted phenols (RPhOHs).

2,6-Dimethyl-phenyl acridine-9-carboxyl-ate.

In the title compound, C(22)H(17)NO(2), the acridine ring system and the benzene ring are oriented at a dihedral angle of 37.7 (1)°. The carboxyl group is twisted at an angle of 67.7 (1)° relative to the acridine skeleton. In the crystal, mol-ecules are arranged in stacks along the b axis, with all of the acridine rings involved in multiple π-π inter-actions [centroid-centroid distances in the range 3.632 (2)-4.101 (2) Å]. The acridine moieties are parallel within the stacks, but inclined at an angle of 52.7 (1)° in adjacent stacks.

Phenyl acridine-9-carboxyl-ate.

The acridine ring system and the benzene ring in the title compound, C(20)H(13)NO(2), are oriented at a dihedral angle of 6.4 (2)°. The carboxyl group is twisted at an angle of 83.6 (2)° relative to the acridine skeleton. The mol-ecules in the crystal are arranged in stacks along the b axis, with two of the acridine rings involved in multiple π-π inter-actions [centroid-centroid distances in the range 3.536 (2)-3.894 (2) Å]. Stacks arranged parallel are linked via C-H⋯π inter-actions, forming layers in the ac plane that are in contact with adjacent, inversely oriented layers via other C-H⋯π inter-actions, giving rise to double layers. The inversely oriented double layers inter-act dispersively. The acridine units are parallel within the parallel-oriented stacks, but inclined at an angle of 79.6 (2)° in the inversely oriented stacks.

9-(2-Bromo-phen-oxy-carbon-yl)-10-methyl-acridinium trifluoro-methane-sulfonate.

In the crystal structure of the title compound, C(21)H(15)BrNO(2) (+)·CF(3)SO(3) (-), adjacent cations are linked through C-Br⋯π and π-π contacts [centroid-centroid distance = 3.744 (2) Å], and neighbouring cations and anions via C-H⋯O, C-F⋯π and S-O⋯π inter-actions. The acridine and benzene ring systems are oriented at a dihedral angle of 18.7 (1)°. The carb-oxy group is twisted at an angle of 69.3 (1)° relative to the acridine skeleton. The mean planes of adjacent acridine moieties are either parallel or inclined at an angle of 27.8 (1)° in the lattice.

9-(3-Fluoro-phen-oxy-carbon-yl)-10-methyl-acridinium trifluoro-methane-sulfonate monohydrate.

In the crystal structure of the title mol-ecular salt, C(21)H(15)FNO(2) (+)·CF(3)SO(3) (-)·H(2)O, the cations form inversion dimers through π-π inter-actions between the acridine ring systems. These dimers are linked via C-H⋯O and C-F⋯π inter-actions to adjacent anions, and by C-H⋯π and C-F⋯π inter-actions to neighbouring cations. The water mol-ecule links two sites of the cation by C-H⋯O inter-actions and two adjacent anions by O-H⋯O hydrogen bonds. The mean planes of the acridine and benzene ring systems are oriented at a dihedral angle of 15.1 (1)°. The carboxyl group is twisted at an angle of 84.5 (1)° relative to the acridine skeleton. The mean planes of the acridine ring systems are parallel in the crystal.

Chemiluminogenic features of 10-methyl-9-(phenoxycarbonyl)acridinium trifluoromethanesulfonates alkyl substituted at the benzene ring in aqueous media.

10-Methyl-9-(phenoxycarbonyl)acridinium trifluoromethanesulfonates bearing alkyl substituents at the benzene ring were synthesized, purified, and identified. In the reaction with OOH(-) in basic aqueous media, the cations of the compounds investigated were converted to electronically excited 10-methyl-9-acridinone, whose relaxation was accompanied by chemiluminescence (CL). The kinetic constants of CL decay, relative efficiencies of light emission, chemiluminescence quantum yields, and resistance toward alkaline hydrolysis were determined experimentally under various conditions. The mechanism of CL generation is considered on the basis of thermodynamic and kinetic parameters of the reaction steps predicted at the DFT level of theory. The chemiluminescence efficiency is the result of competition of the electrophilic center at C(9) between nucleophilic substitution by OOH(-) or OH(-) and the ability of the intermediates thus formed to decompose to electronically excited 10-methyl-9-acridinone. Identification of stable and intermediate reaction products corroborated the suggested reaction scheme. The results obtained, particularly the dependency of the "usefulness" parameter, which takes into account the CL quantum yield and the susceptibility to hydrolysis, on the cavity volume of the entity removed during oxidation, form a convenient framework within which to rationally design chemiluminescent 10-methyl-9-(phenoxycarbonyl)acridinium cations.

9-(2,5-Dimethyl-phen-oxy-carbon-yl)-10-methyl-acridinium trifluoro-methane-sulfonate.

In the title compound, C(23)H(20)NO(2) (+)·CF(3)SO(3) (-), the acridine ring system is oriented at a dihedral angle of 23.1 (1)° with respect to the benzene ring and the carboxyl group is twisted at an angle of 74.1 (1)° relative to the acridine skeleton. In the crystal, adjacent cations are linked through C-H⋯π inter-actions and neighboring cations and anions via weak C-H⋯O hydrogen bonds. The mean planes of adjacent acridine units are either parallel or inclined at angles of 15.0 (1), 26.9 (1) and 48.1 (1)° in the crystal structure.

Comparative studies on vitamin B1 deficiency inwholeblood of chronically haemodialysed patients: chromatographic, fluorimetricandPCAstudy.

The levels of thiamine diphosphate (ThDP), the most active biologically form of vitamin B1, were assessed in whole blood oflong-term haemodialysed patients (n = 50), by applying chromatographic methods based on RP-HPLC technique with isocratic elution and fluorescence detection. The target analyte, thiochrome diphosphate (ThODP), was obtained by pre-column derivatization of vitamin B1 contained in blood samples, applying deproteination with trichloroacetic acid, following by oxidation with alkaline solution of potassium ferricyanide(III) and stabilization with DTT before assays. A simple and sensitive assay was developed, and the results were referenced to the commercially available test. Steady-state and time-resolved studies on emissive properties of ThODP enabled optimization of the proposed assay. The F-Snedecor test shown no statistically significant differences between both approaches. Assessed parameters of the proposed assay, such as linearity, precision, sensitivity, and recovery, were satisfactory if compared to the reference one. The LOQ value for ThDP in whole blood of studied group of patients was of 0.5 ng/mL and the recovery of88%. The results disclosed high individual variabilities in the interdialytic deficiencies of ThDP among the patients - ranged from afew percent to values close to 100%. A comprehensive clinical data, characterizing patients under study, were processed together, and analysed by employing achemometric discriminative tool, the Principal Components Analysis,to find interdependences among clinical data characterizing patients. The three Principal Components were disclosed, that in sum explained almost 50% of the observed variability of the clinical data set. Among the clinical parameters involved in PCs were dialyzer membrane and type, duration as well as levels of creatinine, haemoglobin, and red blood cells in patients' whole blood.

Chemiluminogenic properties of 10-methyl-9-(phenoxycarbonyl)acridinium cations in organic environments.

The chemiluminogenic (CL) properties of aryl esters of 9-carboxy-10-methylacridinium acid and 9-carboxy-2-methoxy-10-methylacridinium acid (AE), variously substituted in the benzene ring (2-H, 2-CH(3), 2-Cl) were investigated in aliphatic alcohols, acetonitrile, and dimethyl sulfoxide in the presence of hydrogen peroxide and different bases-potassium hydroxide, tetra-n-butylammonium hydroxide, and 1,8-diazabicyclo[5.4.0]undec-7-ene. The dependence of their CL properties (decay rate constants (k(CL)) and relative efficiencies (RE)) on solvent parameters, the nature and concentration of base, as well as H(2)O(2) concentration were investigated. Comparison of the various AE revealed that substituents at the benzene ring strongly influence the reaction kinetics, while 2-OCH(3) substitution of the acridine nucleus is manifested, in general, by a red shift in the emission spectrum and slight increase in CL efficiency. The values of k(CL) depend linearly on polarity and acid-base properties of solvents as well as on concentration of bases (over certain concentration ranges) and demonstrate a nonlinear dependence on H(2)O(2) concentration. RE values depend on solvent polarity and nucleophilicity but are rather weakly dependent on base and oxidant concentrations. The CL properties of the above systems are discussed in the context of their physicochemical features gained from fluorescence spectroscopy, spectrophotometric titration, MS, and HPLC. Electronically excited 10-methyl-9-acridinones are the light-emitting entities in both organic and aqueous environments. It was also found that the tendency for an unwanted side-process, the production of a pseudobase form of AE, to take place was similar in alcoholic and aqueous media, although 2-methoxy ring-substituted derivatives seemed to be less susceptible to this dark-type conversion. On the basis of these results new CL systems are postulated that are more efficient than their aqueous counterparts.

9-(4-Methyl-phenoxy-carbon-yl)-10-methyl-acridinium trifluoro-methane-sulfonate.

In the crystal structure of the title compound, C(22)H(18)NO(2) (+)·CF(3)SO(3) (-), adjacent cations are linked through C-H⋯π and π-π inter-actions, and the cations and anions are connected by C-H⋯O and C-F⋯π inter-actions. The acridine and benzene ring systems are oriented at a dihedral angle of 3.0 (1)°. The carboxyl group is twisted at an angle of 83.1 (1)° relative to the acridine skeleton. The mean planes of adjacent acridine units are parallel or inclined at an angle of 75.2 (1)° in the crystal structure.

9-(4-Bromo-phenoxy-carbon-yl)-10-methyl-acridinium trifluoro-methane-sulfonate.

In the crystal structure of the title compound, C(21)H(15)BrNO(2) (+)·CF(3)SO(3) (-), the cations form inversion dimers through π-π inter-actions between the acridine ring systems. These dimers are further linked by C-H⋯π and C-Br⋯π inter-actions. The cations and anions are connected by multidirectional C-H⋯O and C-F⋯π inter-actions. The acridine and benzene ring systems are oriented at 10.8 (1)°. The carboxyl group is twisted at an angle of 85.2 (1)° relative to the acridine skeleton. The mean planes of adjacent acridine units are parallel or almost parallel [inclined at an angle of 1.4 (1)°] in the crystal structure.

10-Methyl-9-phenoxy-carbonyl-acridinium trifluoro-methane-sulfonate monohydrate.

In the crystal structure of the title compound, C(21)H(16)NO(2) (+)·CF(3)SO(3) (-)·H(2)O, the anions and the water mol-ecules are linked by O-H⋯O inter-actions, while the cations form inversion dimers through π-π inter-actions between acridine ring systems. These dimers are linked by C-H⋯O and C-F⋯π inter-actions to adjacent anions, and by C-H⋯π inter-actions to neighboring cations. The water mol-ecule links two H atoms of the cation by C-H⋯O inter-actions and two adjacent anions by O-H⋯O inter-actions. The acridine and benzene ring systems are oriented at 15.6 (1)°. The carboxyl group is twisted at an angle of 77.0 (1)° relative to the acridine skeleton. The mean planes of the adjacent acridine units are either parallel or inclined at an angle of 18.4 (1)°.

9-(4-Fluoro-phen-oxy-carbon-yl)-10-methyl-acridinium trifluoro-methane-sulfonate.

In the crystal structure of the title compound, C(21)H(15)FNO(2) (+)·CF(3)SO(3) (-), the cations form inversion dimers through C-H⋯O, C-F⋯π and π-π inter-actions. These dimers are further linked by π-π inter-actions. The cations and anions are connected through C-H⋯O, C-F⋯π and S-O⋯π inter-actions. The acridine and benzene ring systems are oriented at a dihedral angle of 74.1 (1)°. The carboxyl-ate group is twisted at an angle of 4.4 (1)° relative to the acridine skeleton. The mean planes of the adjacent acridine moieties are parallel or inclined at an angle of 55.4 (1)° in the crystal structure.

9-(4-Chloro-phen-oxy-carbon-yl)-10-methyl-acridinium trifluoro-methane-sulfonate.

In the crystal of the title compound, C(21)H(15)ClNO(2) (+)·CF(3)SO(3) (-), adjacent cations are linked through C-H⋯π and π-π inter-actions [centroid-centroid distance = 3.987 (2) Å], and neighboring cations and anions via C-H⋯O and C-F⋯π inter-actions. The acridine ring system and benzene ring are oriented at a dihedral angle of 1.0 (1)° while the carboxyl group is twisted at an angle of 85.0 (1)° relative to the acridine skeleton. The mean planes of adjacent acridine units are either parallel or inclined at an angle of 78.2 (1)° in the crystal structure.

10-Methyl-9-[2-(propan-2-yl)phenoxy-carbonyl]-acridinium trifluoro-methane-sulfonate.

In the crystal of the title compound, C(24)H(22)NO(2) (+)·CF(3)SO(3) (-), adjacent cations and anions are connected through C-H⋯O, C-H⋯F and S-O⋯π inter-actions, while neighboring cations via π-π inter-actions [centroid-centroid distance = 3.962 (2) Å]. The acridine and benzene ring systems are oriented at a dihedral angle of 14.6 (1)°. The carboxyl group is twisted at an angle of 87.6 (1)° relative to the acridine skeleton. The mean planes of adjacent acridine units are parallel or inclined at an angle of 13.4 (1)° in the crystal structure.