Thermodynamics of sorption of platinum on superparamagnetic nanoparticles functionalized with mercapto groups

The adsorption of Pt(IV) by iron oxide (Fe₃O₄) superparamagnetic nanoparticles (SPION) functionalized with 3-mercaptopropionic acid (3-MPA) is investigated by means of inductively coupled plasma optical emission spectrometry and isothermal titration calorimetry. Experimental ICP data are better fitted by Langmuir rather than Freundlich isotherms. The whole thermodynamic parameters and maximum loading capacity for the adsorption process of Pt(IV) on the functionalized SPION nanoparticles (SPION@3-MPA) are obtained. The process is enthalpy-driven, while entropy is largely unfavourable suggesting that some other interaction should be present in addition to the electrostatic ones with the coverage surface. When compared to other thiol-functionalized materials, the SPION@3-MPA can be considered an interesting adsorbent for Pt(IV), especially with respect to the short contact time evidenced

Using Theory to Reinterpret the Kinetics of Monofunctional Platinum Anticancer Drugs: Stacking Matters

The monofunctional platinum drug phenanthriplatin (phenPt) blocks the replication of cancer cells even if it reacts with only one guanine base. However, there is still insufficient experimental data to improve its cytotoxicity and all previously proposed chemical modifications of the parent structure have resulted in a loss of activity. We use theoretical tools to illustrate the key steps in the biological mechanisms of phenPt; that is, its activation in water and the subsequent attack on DNA. Our simulations suggest that the measured kinetic parameters, which are based on free nucleobases in solution, need to be reinterpreted because the self-assembled stacked reactive adduct formed in the reaction is inaccessible in real DNA. The constants reported here will help guide future work in the synthesis of anticancer platinum drugs

Effect of the Counterion on Circularly Polarized Luminescence of Europium(III) and Samarium(III) Complexes

Each enantiopure europium(III) and samarium(III) nitrate and triflate complex of the ligand L, with L = N,N'-bis(2-pyridylmethylidene)-1,2-(R,R + S,S)-cyclohexanediamine ([LnL(tta)2]·NO3 and [LnL(tta)2(H2O)]·CF3SO3, where tta = 2-thenoyltrifluoroacetylacetonate) has been synthesized and characterized from a spectroscopic point of view, using a chiroptical technique such as electronic circular dichroism (ECD) and circularly polarized luminescence (CPL). In all cases, both ligands are capable of sensitizing the luminescence of both metal ions upon absorption of light around 280 and 350 nm. Despite small differences in the total luminescence (TL) and ECD spectra, the CPL activity of the complexes is strongly influenced by a concurrent effect of the solvent and counterion. This particularly applies to europium(III) complexes where the CPL spectra in acetonitrile can be described as a weighed linear combination of the CPL spectra in dichloromethane and methanol, which show nearly opposite signatures when their ligand stereochemistries are the same. This phenomenon could be related to the presence of equilibria interconverting solvated, anion-coordinated complexes and isomers differing by the relative orientation of the tta ligands. The difference between some bond lengths (M-N bonds, in particular) in the different species could be at the basis of such an unusual CPL activity

Eu(iii) and Tb(iii) complexes of 6-fold coordinating ligands showing high affinity for the hydrogen carbonate ion: A spectroscopic and thermodynamic study

In the present contribution, four classes of Ln(iii) complexes (Ln = Eu and Tb) have been synthesized and characterized in aqueous solution. They differ by charge, Ln(bpcd)+ [bpcd2- = N,N'-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane N,N'-diacetate] and Ln(bQcd)+ (bQcd2- = N,N'-bis(2-quinolinmethyl)-trans-1,2-diaminocyclohexane N,N'-diacetate) being positively charged and Ln(PyC3A) (PyC3A3- = N-picolyl-N,N',N'-trans-l,2-cyclohexylenediaminetriacetate) and Ln(QC3A) (QC3A3- = N-quinolyl-N,N',N'-trans-l,2-cyclohexylenediaminetriacetate) being neutral. Combined DFT, spectrophotometric and potentiometric studies reveal the presence, under physiological conditions (pH 7.4), of a couple of equally and highly stable isomers differing by the stereochemistry of the ligands (trans-N,N and trans-O,O for bpcd2- and bQcd2-; trans-O,O and trans-N,O for PyC3A3- and QC3A3-). Their high log\u2009\u3b2 values (9.97 < log\u2009\u3b2 < 15.68), the presence of an efficient antenna effect and the strong increase of the Ln(iii) luminescence intensity as a function of the hydrogen carbonate concentration in physiological solution, render these complexes as very promising optical probes for a selective detection of HCO3-in cellulo or in extracellular fluid. This particularly applies to the cationic Eu(bpcd)+, Tb(bpcd)+ and Eu(bQcd)+ complexes, which are capable of guesting up to two hydrogen carbonate anions in the inner coordination sphere of the metal ion, so that they show an unprecedented affinity towards HCO3- (log\u2009K for the formation of the adduct in the 4.6-5.9 range)

Complexation of NpO2+ with Amine-Functionalized Diacetamide Ligands in Aqueous Solution: Thermodynamic, Structural, and Computational Studies

Complexation of Np(V) with three structurally related amine-functionalized diacetamide ligands, including 2,2'-azanediylbis( N, N'-dimethylacetamide) (ABDMA), 2,2'-(methylazanediyl)bis( N, N'-dimethylacetamide) (MABDMA), and 2,2'-(benzylazanediyl)bis( N, N'-dimethylacetamide) (BnABDMA), in aqueous solutions was investigated. The stability constants of two successive complexes, namely, NpO2L+ and NpO2L2+, where L stands for the ligands, were determined by absorption spectrophotometry. The results suggest that the stability constants of corresponding Np(V) complexes follow the trend: MABDMA > ABDMA ≈ BnABDMA. The data are discussed in terms of the basicity of the ligands and compared with those for the complexation of Np(V) with an ether oxygen-linked diacetamide ligand. Extended X-ray absorption fine structure data indicate that, similar to the complexation with Nd3+ and UO22+, the ligands coordinate to NpO2+ in a tridentate mode through the amine nitrogen and two oxygen atoms of the amide groups. Computational results, in conjunction with spectrophotometric data, verify that the 1:2 complexes (NpO2(L)2+) in aqueous solutions are highly symmetric with Np at the inversion center, so that the f-f transition of Np(V) is forbidden and NpO2(L)2+ does not display significant absorption in the near-IR region

Comparative study on removal of platinum cytostatic drugs at trace level by cysteine, diethylenetriamino functionalized Si-gels and polyethyleneimine functionalized sponge : Adsorption performance and mechanisms

Altres ajuts: acords transformatius de la UABTo efficiently remove trace Pt-based cytostatic drugs (Pt-CDs) from aqueous environments, a comparative investigation was conducted on the adsorption behavior of three commercial adsorbents including cysteine-functionalized silica gel (Si-Cys), 3-(diethylenetriamino) propyl-functionalized silica gel (Si-DETA) and open-celled cellulose MetalZorb® sponge (Sponge). The research on the adsorption of cisplatin and carboplatin encompasses investigations of pH dependence, adsorption kinetics, adsorption isotherms, and adsorption thermodynamics. The obtained results were compared with those of PtCl42− to better understand the adsorption mechanisms. The adsorption of cisplatin and carboplatin by Si-Cys was significantly better than Si-DETA and Sponge, which suggested that in chelation-dominated chemisorption, thiol groups provided high-affinity sites for Pt(II) complexation. Adsorption of the anion PtCl42− was more pH dependent and generally superior to that of cisplatin and carboplatin, benefiting from the contribution of ion association with protonated surfaces. The removal process of aqueous Pt(II) compounds occurred by the hydrolysis of complexes in solution and subsequent adsorption, and the specific adsorption process was explained by the synergistic action of ion association and chelation mechanisms. The rapid adsorption processes involving diffusion and chemisorption were well described by pseudo-second-order kinetic model. The isotherm studies suggested monolayer adsorption, consistent with the Langmuir model. Indicated from the adsorption enthalpy results, the chelation of cisplatin and carboplatin with thiol groups was an endothermic reaction, while the adsorption of PtCl42− was exothermic. At 343 K, Si-Cys achieved 98.5 ± 0.1 % (cisplatin) and 94.1 ± 0.1 % (carboplatin) removal. To validate the obtained findings, the described process was applied to urine samples doped with Pt-CDs as analog of hospital wastewaters and the removal was very efficient, ranging from 72 ± 1 % to 95 ± 1 %, when using Si-Cys as adsorbent, although limited matrix effects were observed