Interaction of anticancer drug cisplatin with guanine: Density functional theory and surface-enhanced Raman spectroscopy study

Investigation of Melphalan interaction as an alkylating agent with nucleotides by using surface enhanced Raman spectroscopy (SERS)

SERS (Surface Enhanced Raman Spectroscopy) is a new Raman spectroscopy which relies on Surface Plasmon Resonance (SPR) of metal nanoparticles. We have applied colloidal silver and gold nanoparticles as amplifier agents to enhance nucleotide Raman signals. It is observed that without these enhancing agents, it is impossible to investigate nucleotide spectrum due to weak Raman signals. Interaction mechanism of Melphalan, an anticancer drug with four nucleotides (Adenine, Cytosine, Guanine, Thymine) was investigated using SERS to detect and identify changes due to alkylating process in Raman spectra. After incubating Melphalan drug with nucleotides for 24 h at 37 °C, some changes occurred in SERS spectrum and interpretation of SERS spectra revealed the influence of the alkyl substitution on peaks and Raman shifts. After incubation of Melphalan with each nucleotide, intensity of relevant SERS signals assigned to Amid III group of Cytosine and Amid I of Thymine decreased significantly, confirming alkylating taking place. In this study, we also investigated the effect of nanoparticles type on nucleotide spectrum. We could not obtain useful information in the cases of guanine nucleotide. The SERS spectrum of Cytosine as an example of nucleotides in aqueous solution compared to solid state and results demonstrated that in solid state better signals were obtained than in liquid state.

Molecular Spectroscopic Markers of DNA Damage

Every cell in a living organism is constantly exposed to physical and chemical factors which damage the molecular structure of proteins, lipids, and nucleic acids. Cellular DNA lesions are the most dangerous because the genetic information, critical for the identity and function of each eukaryotic cell, is stored in the DNA. In this review, we describe spectroscopic markers of DNA damage, which can be detected by infrared, Raman, surface-enhanced Raman, and tip-enhanced Raman spectroscopies, using data acquired from DNA solutions and mammalian cells. Various physical and chemical DNA damaging factors are taken into consideration, including ionizing and non-ionizing radiation, chemicals, and chemotherapeutic compounds. All major spectral markers of DNA damage are presented in several tables, to give the reader a possibility of fast identification of the spectral signature related to a particular type of DNA damage.

Remarkably Intricate Raman Spectra of Platinum(II)-Ligand Skeletal Modes in Diamminedihalido Complexes

More than 100 calculations of vibrational frequencies for cis-[Pt(NH₃)₂X₂] (X = Cl^-, Br^-) and trans-[Pt(NH₃)₂Cl₂] have been published over the past 25 years. The high-quality Raman spectra presented here have sufficient resolution in the crucial region of metal-ligand modes to permit an assessment of frequency calculations. The peaks for symmetric and antisymmetric Pt-Cl stretching modes ν_s and ν_a are resolved in the 312-333 cm^-1 region. Frequency variations due to ³⁵Cl and ³⁷Cl isotopes are shown to be comparable in size to the differences between ν_s and ν_a. Peaks corresponding to the two Pt-Br stretching frequencies are observed at 213 and 218 cm^-1 and Pt-N stretching frequencies for all compounds between 485 and 540 cm^-1. The crystal structures of trans-[Pt(NH₃)₂Cl₂] and cis-[Pt(NH₃)₂Br₂] at 300 and 120 K are reported and complement the variable-temperature vibrational frequencies.

Cisplatin-functionalized silica nanoparticles for cancer chemotherapy

Cisplatin is used to treat a variety of tumors, but dose-limiting toxicities or intrinsic and acquired resistance limit its application in many types of cancer including breast. Cisplatin was attached to silica nanoparticles using aminopropyltriethoxy silane as a linker molecule and characterized in terms of size, shape, as well as the dissolution of cisplatin from the silica surface. The primary particle diameter of the as received silica nanoparticles ranged from 20 to 90 nm. The results show that adverse effects on cell function, as evidenced by reduced metabolic activity measured by the MTT assay and increased membrane permeability observed using the live/dead stain, can be correlated with surface area of the silica. Cisplatin-functionalized silica nanoparticles with the highest surface area incited the greatest response, which was almost equivalent to that induced by free cisplatin. Moreover, if verified by further studies, would indicate that cisplatin was attached to silica nanoparticles might prove to be useful in site-specific drug delivery.

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.

Perspectives in the use of spectroscopy to characterise pharmaceutical solids

Knowledge of the solid-state properties is one of the key issues in understanding the performance of drugs. Recent developments in spectroscopic techniques have made them popular tools for solid phase analysis; they are fast, accurate and suitable for real-time measurements during processing, and further, they can be used to obtain structural understanding of solid forms, for example, by the use of multivariate analysis and computational chemistry. In this article emerging topics related to spectroscopic analysis of pharmaceutical solids are reviewed. The following areas are highlighted: (1) the importance of multivariate methods in the analysis of solid forms when using spectroscopic techniques, (2) spectroscopic analysis of processing-induced solid phase transformations in the manufacturing setting, (3) novel spectroscopic techniques and pharmaceutical examples of their use, and (4) the advantages and the use of computational simulation of vibrational spectra. The topics listed are thought to be of the foremost importance in improving the understanding of pharmaceutical materials, processes and formulations.

Cisplatin-loaded Au–Au2S nanoparticles for potential cancer therapy: Cytotoxicity,in vitro carcinogenicity, and cellular uptake

Cisplatin is one of the most effective cytotoxic agents against cancers. Its usage, however, is limited because of severe resistance and systemic toxicity. A formulation of cisplatin-loaded Au-Au(2)S nanoparticles (NPs) with near-IR (NIR) sensitivity is reported to partly overcome this limitation in this paper. NIR sensitive Au-Au(2)S NPs were successfully synthesized by the reduction of tetrachloroauric acid (HAuCl(4)) using sodium sulfide (Na(2)S), and cisplatin was loaded onto Au-Au(2)S NPs via a MUA (11-mercaptoundecanoic acid) layer. To further investigate the biological safety of cisplatin-loaded Au-Au(2)S NPs, three different cell lines were used to investigate the acute cytotoxicity and the long-term potential carcinogenicity in vitro. Cisplatin-loaded Au-Au(2)S NPs were also tested for limited hemocompatibility in vitro. Our in vitro short and long-term data provided preliminary evidence suggesting that cisplatin-loaded Au-Au(2)S NPs with NIR sensitivity are nontoxic below the maximum recommended dosage.

Mass spectrometric study of dirhenium biscarboxylate:purine dinucleotide complexes

Dirhenium adducts of purine dinucleotides were identified by mass spectrometry. In consecutive studies, Re(2)(O(2)C(2)H(3))(2)Cl(4) . 2H(2)O was reacted with 2'-deoxyguanylyl(3'-->5')-2'-deoxyguanosine (dGpG) and 2'-deoxyadenylyl(3'-->5')-2'-deoxyguanosine (dApG) in H(2)O or D(2)O. These reactions were monitored to identify novel dinuclear rhenium:dinucleotide complexes as confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), electrospray ionization mass spectrometry (ESI-MS) and collision-induced dissociation tandem mass spectrometry (CID MS/MS) experiments. However, the most abundant adducts detected by ES-MS were dirhenium:nucleotide species. Of these, guanine-containing ions were observed with highest ion counts suggesting a preference for guanine coordination. Dimetal adducts showed coordination of the purine bases and common metalated fragments were observed for both dGpG and dApG reactions.

Cisplatin delivery from poly(acrylic acid-co-methyl methacrylate) microparticles

To develop a platform for tumor chemotherapy, poly(acrylic acid-co-methyl methacrylate) microparticles have been synthesized. Carboxylate containing monomers were included to complex therapeutic agents, specifically cisplatin. Microparticles were prepared by free radical emulsion polymerization in aqueous media. Particle diameter, zeta-potential, in vitro cytotoxicity, and in vivo acute toxicity were characterized for both cisplatin-loaded microparticles and unloaded microparticles. In vitro cytotoxicity and FT-IR were used to characterize cisplatin released from cisplatin-loaded microparticles. Acrylic acid feed mole fraction determined several key microparticle properties, including particle size, zeta-potential, and yield. A burst release of cisplatin (40%) in the first day was followed by a zero-order release phase. The interaction between cisplatin and microparticles allowed approximately 20% additional cisplatin release in the next five days. Cisplatin-loaded and unloaded microparticles are non-toxic (LC50>15 mM) to the cell line used in in vitro tests. Cisplatin released from cisplatin-loaded microparticles retained activity, but that activity was slightly lower than freshly prepared cisplatin. Other than a slight reduction in cisplatin activity, microparticles exhibited low in vivo acute toxicity (LD50>170 mg/kg), which suggests that this hydrogel particulate system and the hydrogel complexation mechanism should further be studied for drug delivery.

Quantum chemical modeling of the reduction of cis-diammineplatinum(IV) tetrachloride [Pt(NH3)2Cl4] by methyl thiolate anion

We present here both an ab initio and quantum mechanical/molecular mechanical (QM/MM) study of the cis-[Pt(NH3)2Cl4] complex reduction by methyl thiolate anion, SCH(-3), which is used as a model of glutathione. Geometry and electronic structure of cis-[Pt(NH3)2Cl4] are determined without and in aqueous medium. The mechanism of the reaction of reduction is characterized. The calculated activation energy of the reaction compares remarkably well with the experimental value.