Electronic structure and vibrational spectra of cis-diammine(orotato)platinum(II), a potential cisplatin analogue: DFT and experimental study

Raman spectra-based structural classification analysis of quinoidal and derived molecular systems

This work reports a classification analysis method based on the vibrational Raman spectra of 38 quinones and related structures, spectrally ordering and classifying the compounds. The molecular systems are relevant for chemical and biological processes, with applications in pharmacology, toxicology and medicine. The classification strategy uses a combination of principal component analysis with K-means clustering methods. Both theoretical simulations and experimental data are analysed, thus establishing their spectral characteristics, as related to their chemical structures and properties. The protocol introduced here should be broadly applicable in other molecular and solid state systems.

Hypoxia Active Platinum(IV) Prodrugs of Orotic Acid Selective to Liver Cancer Cells

Platinum(IV) complexes of orotic acid selectively target liver cancer cells displaying enhanced activity and higher uptake in Hep G2. The comparatively higher expression of Organic Anion Transporter 2 (OAT2) in Hep G2 and decrease in toxicity in the presence of OAT2 inhibitor suggest its involvement in the uptake of the complexes. They are resistant to sequestration by the copper transporter ATP7B, unlike cisplatin and oxaliplatin.

Simple Trans-Platinum Complex Bearing 3-Aminoflavone Ligand Could Be a Useful Drug: Structure-Activity Relationship of Platinum Complex in Comparison with Cisplatin

Following previous studies devoted to trans–Pt(3-af)₂Cl₂, in this paper, the molecular structure and intermolecular interactions of the title complex are compared with other cisplatin analogues of which the crystal structures are presented in the Cambridge Structural Database (CSD). Molecular Hirshfeld surface analysis and computational methods were used to examine a possible relationship between the structure and anticancer activity of trans–Pt(3-af)₂Cl₂. The purpose of the article was also to investigate the effect of hyperthermia on the anticancer activity of cisplatin, cytostatics used in the treatment of patients with ovarian cancer and a new analogue of cisplatin-trans–Pt(3-af)₂Cl₂. The study was conducted on two cell lines of ovarian cancer sensitive to Caov-3 cytostatics and the OVCAR-3 resistant cisplatin line. The study used the MTT (3-(4,5-dimethylthiazol-2,5-diphenyltetrazolium bromide) cell viability assay, LDH (lactate dehydrogenase), and the quantitative evaluation method for measuring gene expression, i.e., qPCR with TagMan probes. Reduced survivability of OVCAR-3 and Caov-3 cells exposed to cytostatics at elevated temperatures (37 °C, 40 °C, 43 °C) was observed. Hyperthermia may increase the sensitivity of cells to platinum-based antineoplastic drugs and paclitaxel, which may be associated with the reduction of gene expression related to apoptotic processes.

Cisplatin bioconjugated enzymatic GNPs amplify the effect of cisplatin with acquiescence

Enzymatic gold nanoparticles (B-GNPs) have been synthesized using a natural anticancer agent bromelain (a cysteine protease) and these nanoparticles were used to bioconjugate Cisplatin (highly effective against osteosarcoma and lung cancer). Cisplatin bioconjugated bromelain encapsulated gold nanoparticles (B-C-GNPs) were found profoundly potent against same cancers at much lower concentration with minimum side effects due to the synergistic effect of bromelain. The B-C-GNPs have been observed to inhibit the proliferation of osteosarcoma cell lines Saos-2 and MG-63 with IC₅₀ estimation of 4.51 µg/ml and 3.21 µg/ml, respectively, and against small lung cancer cell line A-549 with IC₅₀ 2.5 µg/ml which is lower than IC₅₀ of cisplatin against same cell lines. The B-GNPs/B-C-GNPs were characterized by TEM, UV-Visible spectroscopy, Zeta potential and DLS to confirm the production, purity, crystalline nature, stability of nanoemulsion, size and shape distribution. The change in 2D and 3D conformation of bromelain after encapsulation was studied by Circular Dichroism and Fluorometry, respectively. It was found that after encapsulation, a 19.4% loss in secondary structure was observed, but tertiary structure was not altered significantly and this loss improved the anticancer activity. The confirmation of bioconjugation of cisplatin with B-GNPs was done by UV-Visible spectroscopy, TEM, FTIR, 2D ¹H NMR DOSY and ICP-MS. Further, it was found that almost ~4 cisplatin molecules bound with each B-GNPs nanoparticle.

Influence of DFT Functionals and Solvation Models on the Prediction of Far-Infrared Spectra of Pt-Based Anticancer Drugs: Why Do Different Complexes Require Different Levels of Theory?

Computational modeling was applied to far-infrared (FIR) spectra of Pt-based anticancer drugs to study the hydrolysis of these important molecules. Here, we present a study that investigates the influence of different factors-basis sets on non-Pt atoms, relativistic effective core potentials (RECPs) on the Pt atom, density functional theory (DFT) functionals, and solvation models-on the prediction of FIR spectra of two Pt-based anticancer drugs, cisplatin and carboplatin. Geometry optimizations and frequency calculations were performed with a range of functionals (PBE, PBE0, M06-L, and M06-2X), Dunning's correlation-consisted basis sets (VDZ, VTZ, aVDZ, and aVTZ), RECPs (VDZ-pp, VTZ-pp, aVDZ-pp, and aVTZ-pp), and solvation models (IEFPCM, CPCM, and SMD). The best combination of the basis set/DFT functional/solvation model was identified for each anticancer drug by comparing with experimentally available FIR spectra. Different combinations were established for cisplatin and carboplatin, which was rationalized by means of the partial atomic charge scheme, ChelpG, that was utilized to study the charge transfer between the Pt ion and ligands in both cisplatin and carboplatin.

Anionic cyclometallated Pt(ii) square-planar complexes: new sets of highly luminescent compounds

Novel anionic Pt(ii) complexes were synthesized, displaying an outstanding enhancement of the emission efficiency in the solid state.

VP, Dasgupta S, Bose K JC, Mukherjee S, Linert W, Moi SC. Benzimidazole based Pt(ii) complexes with better normal cell viability than cisplatin: synthesis, substitution behavior, cytotoxicity, DNA binding and DFT study

Water soluble Pt(ii) complexes with higher viability towards normal cells and comparable cytotoxicity to cancer cells as compared to cisplatin.

Chemoradiotherapeutic Magnetic Nanoparticles for Targeted Treatment of Nonsmall Cell Lung Cancer

Lung cancer is the leading cause of cancer-related death in the United States and approximately 85% of all lung cancers are classified as nonsmall cell (NSCLC). We here use an innovative approach that may ultimately allow for the clinician to target tumors and aggressively reduce tumor burden in patients with NSCLC. In this study, a platinum (Pt)-based chemotherapeutic (cisplatin, carboplatin, or oxaliplatin) and holmium-165 (Ho), which can be neutron-activated to produce the holmium-166 radionuclide, have been incorporated together in a garnet magnetic nanoparticle (HoIG-Pt) for selective delivery to tumors using an external magnet. The synthesized magnetic HoIG nanoparticles were characterized using PXRD, TEM, ICP-MS, and neutron-activation. Platinum(II) drugs were incorporated onto HoIG, and these were characterized using FTIR, EDX, ICP-MS, and zeta potential measurements, and in vitro and in vivo studies were performed using a HoIG-platinum system. Results indicate that neutron-activated (166)HoIG-cisplatin is more toxic toward NSCLC A549 cells than is blank (166)HoIG and free cisplatin, and that when an external magnetic field is applied in vivo, higher tumor to liver ratios of Ho are observed than when no magnet is applied, suggesting that magnetic targeting is achieved using this system. Furthermore, an efficacy study demonstrated the inhibition of tumor growth by chemoradiotherapeutic magnetic nanoparticles, compared to no treatment controls.

Optimizing the release process and modelling of in vitro release data of cis-dichlorodiamminoplatinum (II) encapsulated into poly(2-hydroxyethyl methacrylate) nanocarriers

Drug encapsulated nanocarriers are vehicles to transport the drug molecules and release them at the immediate vicinity of the diseased sites. The aim of this study was to design poly (2-hydroxyethyl methacrylate) nanoparticles (PHEMANPs) as a swelling and diffusion controlled drug release system for achieving sustained release of (cis-dichlorodiamminoplatinum II) CDDP. The study undertakes designing and characterization of nanocarriers, optimization of drug encapsulation, and investigating release dynamics of the CDDP drug. PHEMANPs were prepared by suspension polymerization method followed by post loading of the CDDP onto the nanocarriers. The physicochemical and biopharmaceutical properties were evaluated by FTIR, TEM, FESEM, EDX, DLS, surface charge, water intake studies, in vitro cytotoxicity, protein adsorption and percent haemolysis. Chemical stability of the drug was assessed and in vitro release experiments were performed to optimize formulation by UV spectral analysis. The obtained cumulative release data were fitted to zero, first and Korsmeyer-Peppas kinetic models to gain insights into release kinetics and prevailing drug transport mechanisms. The successful encapsulation of CDDP was achieved in different PHEMANP formulations with maximum drug encapsulation efficiency of approx. 60% and the release kinetics was found to follow the Korsmeyer-Peppas model having non-Fickian mechanism. The results indicated that the CDDP can be formulated with a high payload of PHEMANPs which can serve as promising nanomedicine and help in achieving sustained delivery of drug for targeting tumour.

Platinum(II)-Based Metallo-Supramolecular Polymer with Controlled Unidirectional Dipoles for Tunable Rectification

A platinum(II)-based, luminescent, metallo-supramolecular polymer (PolyPtL1) having an inherent dipole moment was synthesized via complexation of Pt(II) ions with an asymmetric ligand L1, containing terpyridyl and pyridyl moieties. The synthesized ligand and polymer were well characterized by various NMR techniques, optical spectroscopy, and cyclic voltammetry studies. The morphological study by atomic force microscopy revealed the individual and assembled polymer chains of 1-4 nm height. The polymer was specifically attached on Au-electrodes to produce two types of film (films 1 and 2) in which the polymer chains were aligned with their dipoles in opposite directions. The Au-surface bounded films were characterized by UV-vis, Raman spectroscopy, cyclic voltammetry, and atomic force microscopy study. The quantum mechanical calculation determined the average dipole moment for each monomer unit in PolyPtL1 to be about 5.8 D. The precise surface derivatization permitted effective tuning of the direction dipole moment, as well as the direction of rectification of the resulting polymer-attached molecular diodes. Film 1 was more conductive in positive bias region with an average rectification ratio (RR = I(+4 V)/I(-4 V)) ≈ 20, whereas film 2 was more conducting in negative bias with an average rectification ratio (RR = I(-4 V)/I(+4 V)) ≈ 18.

Adsorption study of antibiotics on silver nanoparticle surfaces by surface-enhanced Raman scattering spectroscopy

In this work the adsorption of the antibiotics levofloxacin (LV), tetracycline (TC) and benzylpenicillin (BP) on the surface of silver nanoparticles (AgNP) have been investigated through both surface-enhanced Raman scattering (SERS) and UV-VIS-NIR spectroscopies. The SERS spectra were obtained using 1064 nm exciting radiation. Theoretical models for the antibiotic molecules were obtained from DFT calculations, and used in the vibrational assignment. The adsorption geometries were proposed based on the changes in the spectral patterns. The LV compound adsorbs through carboxylate group, TC compound interacts with silver atoms through carbonyl from intermediate ring, and BP compound adsorbs by carbonyl moieties from carboxylate and acyclic amide.

VP, Mitra I, Saha R, K. JCB, Reddy Dodda S, Linert W, Moi SC. In vitro model reaction of sulfur containing bio-relevant ligands with Pt(ii) complex: kinetics, mechanism, bioactivity and computational studies

In vitrodrug reservoir model reactions of thiols with novel Pt(ii) complex were investigated in aqueous medium and the complex and its substituted products show remarkable anticancer property.

Assessment of new DFT methods for predicting vibrational spectra and structure of cisplatin: which density functional should we choose for studying platinum(II) complexes?

Ten different DFT methods, including several recently developed functionals have been tested for their performances in prediction of infrared and Raman spectra and molecular structure of cisplatin. The assessed DFT methods cover the range from meta-GGA to hybrid, double hybrid and long-range corrected hybrid models (M06-L, M06, M06-2X, PBE0, mPW1PW, B3LYP, B2PLYP, CAM-B3LYP, ωB97XD and LC-ωPBE). The calculated structural parameters and theoretical spectra have been compared to the corresponding experimental data. It is shown that the LC-ωPBE scheme is superior to other DFT methods in predicting the geometry of cisplatin. Unfortunately, the M06-L, M06-2X and B3LYP functionals are deficient in the evaluation of the strength of two Pt←NH3 coordination bonds in cisplatin (the calculated bond lengths are too long and the Pt-N stretching frequencies are underestimated). Both the PBE0 and mPW1PW functionals, in conjunction with the LanL2TZ(f) basis set for Pt give very similar theoretical results and seem to be the best methods for predicting the IR and Raman spectra of cisplatin. The long-range corrected functionals (LC-ωPBE, ωB97XD and CAM-B3LYP) have shown good performances in predicting the frequencies of Pt-ligand vibrations and are promising new tools for theoretical study of novel platinum(II) compounds.

Platinum and Palladium Polyamine Complexes as Anticancer Agents: The Structural Factor

Since the introduction of cisplatin to oncology in 1978, Pt(II) and Pd(II) compounds have been intensively studied with a view to develop the improved anticancer agents. Polynuclear polyamine complexes, in particular, have attracted special attention, since they were found to yield DNA adducts not available to conventional drugs (through long-distance intra- and interstrand cross-links) and to often circumvent acquired cisplatin resistance. Moreover, the cytotoxic potency of these polyamine-bridged chelates is strictly regulated by their structural characteristics, which renders this series of compounds worth investigating and their synthesis being carefully tailored in order to develop third-generation drugs coupling an increased spectrum of activity to a lower toxicity. The present paper addresses the latest developments in the design of novel antitumor agents based on platinum and palladium, particularly polynuclear chelates with variable length aliphatic polyamines as bridging ligands, highlighting the close relationship between their structural preferences and cytotoxic ability. In particular, studies by vibrational spectroscopy techniques are emphasised, allowing to elucidate the structure-activity relationships (SARs) ruling anticancer activity.

Application of comparative vibrational spectroscopic and mechanistic studies in analysis of fisetin structure

This paper addresses experimental and theoretical research in fisetin (2-(3,4-dihydroxyphenyl)-3,7-dihydroxychromen-4-one) structure by means of experimental IR and Raman spectroscopies and mechanistic calculations. Density Functional Theory calculations, with M05-2X functional and the 6-311+G (2df, p) basis set implemented in the Gaussian 09 package, are performed with the aim to support molecular structure, vibrational bands' positions and their intensities. Potential energy distribution (PED) values and the description of the largest vibrational contributions to the normal modes are calculated. The most intense bands appear in the 1650-1500 cm(-1) wavenumber region. This region involves a combination of the CO, C2C3 and C-C stretching vibrational modes. Most of the bands in the 1500-1000 cm(-1) range involve C-C stretching, O-C stretching and in-plane C-C-H, C-O-H, C-C-O and C-C-C bending vibrations of the rings. The region below 1000 cm(-1) is characteristic to the combination of in plane C-C-C-H, H-C-C-H, C-C-C-C, C-C-O-C and out of plane O-C-C-C, C-C-O-C, C-C-C-C torsional modes. The Raman spectra of baicalein and quercetin were used for qualitative comparison with fisetin spectrum and verification of band assignments. The applied detailed vibrational spectral analysis and the assignments of the bands, proposed on the basis of fundamentals, reproduced the experimental results with high degree of accuracy.

Structural conformations and vibrational spectral study of chloroflavone with density functional theoretical simulations

NIR-FT Raman and FT-IR spectra of 6-chloroflavone were recorded and analyzed. The vibrational wavenumber of the compound have been computed using B3LYP/6-31++G(d,p) level to derive the equilibrium geometry, conformational stability, molecular orbital energies and vibrational wavenumbers. The carbonyl stretching vibrations have been lowered due to conjugation and hydrogen bonding in the molecules. The assignment of fundamental vibrations agrees well with the calculated wavenumbers.

Cisplatin interaction with amino acids cysteine and methionine from gas phase to solutions with constant pH

This work is focused on the computational studies of reactions of hydrated forms of cisplatin with sulphur-containing amino acids cysteine and methionine. First, the appropriate model for solvation of the examined complexes was searched for. The suggested procedure employs the B3LYP density functional, 6-311++G(2df,2pd) basis set with Stuttgart-Dresden pseudopotentials on heavy atoms, the D-PCM solvation model and the UAKS cavity which uses more realistic NPA partial charges instead of formal partial charges for platinum ligands. In the second part this model is applied to the evaluation of the Legendre transformed reaction Gibbs free energy of cisplatin with cysteine and methionine in solution at constant pH.

Comparison of the electronic properties, and thermodynamic and kinetic parameters of the aquation of selected platinum(II) derivatives with their anticancer IC50 indexes

Three potential anticancer agents {trans-[PtCl(2)(NH(3))(thiazole)], cis-[PtCl(2)(NH(3))(piperidine)], and PtCl(2)(NH(3))(cyclohexylamine) (JM118)} were explored and compared with cisplatin and the inactive [PtCl(dien)](+) complex. Basic electronic properties, bonding and stabilization energies were determined, and thermodynamic and kinetic parameters for the aquation reaction were estimated at the B3LYP/6-311++G(2df,2pd) level of theory. Since the aquation process represents activation of these agents, the obtained rate constants were compared with the experimental IC(50) values for several tumor cells. Despite the fact that the processes in which these drugs are involved and the way in which they affect cells are very complex, some correlations can be deduced.