Josianne Nicácio Silveira

A synthetic dinuclear copper(II) hydrolase and its potential as antitumoral: Cytotoxicity, cellular uptake, and DNA cleavage

We have studied the protonation equilibria of a dicopper(II) complex [Cu(2)(micro-OH)(C(21)H(33)ON(6))](ClO(4))(2).H(2)O, (1), in aqueous solution, its interactions with DNA, its cytotoxic activity, and its uptake in tumoral cells. C(21)H(33)ON(6) corresponds to the ligand 4-methyl-2,6-bis[(6-methyl-1,4-diazepan-6-yl)iminomethyl]phenol. From spectrophotometric data the following pKa values were calculated 3.27, 4.80 and 6.10. Complex 1 effectively promotes the hydrolytic cleavage of double-strand plasmid DNA under anaerobic and aerobic conditions. The following kinetic parameters were calculated k(cat) of 2.73 x 10(-4)s(-1), K(M) of 1.36 x 10(-4)M and catalytic efficiency of 2.01 s(-1)M(-1), a 2.73 x 10(7) fold increase in the rate of the reaction compared to the uncatalyzed hydrolysis rate of DNA. Competition assays with distamycin reveal minor groove binding. Complex 1 inhibited the growth of two tumoral cell lines, GLC4 and K562, with the IC(50) values of 14.83 microM and 34.21 microM, respectively. There is a good correlation between cell growth inhibition and intracellular copper content. When treated with 1, cells accumulate approximately twice as much copper as with CuCl(2). Copper-DNA adducts are formed inside cells when they are exposed to the complex. In addition, at concentrations that compound 1 inhibits tumoral cell growth it does not affect macrophage viability. These results show that complex 1 has a good therapeutic prospect.

Preparation and cytotoxicity of cisplatin-containing liposomes

We encapsulated cisplatin into stealth pH-sensitive liposomes and studied their stability, cytotoxicity and accumulation in a human small-cell lung carcinoma cell line (GLC4) and its resistant subline (GLC4/CDDP). Since reduced cellular drug accumulation has been shown to be the main mechanism responsible for resistance in the GLC4/CDDP subline, we evaluated the ability of this new delivery system to improve cellular uptake. The liposomes were composed of dioleoylphosphatidylethanolamine (DOPE), cholesteryl hemisuccinate (CHEMS), and distearoylphosphatidylethanolamine-polyethyleneglycol 2000 (DSPE-PEG2000) and were characterized by determining the encapsulation percentage as a function of lipid concentration. Among the different formulations, DOPE/CHEMS/DSPE-PEG liposomes (lipid concentration equal to 40 mM) encapsulated cisplatin more efficiently than other concentrations of liposomes (about 20.0%, mean diameter of 174 nm). These liposomes presented good stability in mouse plasma which was obtained using a 0.24-M EDTA solution (70% cisplatin was retained inside the liposomes after 30 min of incubation). Concerning cytotoxic effects, they are more effective (1.34-fold) than free cisplatin for growth inhibition of the human lung cancer cell line A549. The study of cytotoxicity to GLC4 and GLC4/CDDP cell lines showed similar IC50 values (approximately 1.4 microM), i.e., cisplatin-resistant cells were sensitive to this cisplatin formulation. Platinum accumulation in both sensitive and resistant cell lines followed the same pattern, i.e., approximately the same intracellular platinum concentration (4.0 x 10-17 mol/cell) yielded the same cytotoxic effect. These results indicate that long-circulating pH-sensitive liposomes, also termed as stealth pH-sensitive liposomes, may present a promising delivery system for cisplatin-based cancer treatment. This liposome system proved to be able to circumvent the cisplatin resistance, whereas it was not observed when using non-long-circulating liposomes composed of phosphatidylcholine, phosphatidylserine, and cholesterol.

Impact of the carbon chain length of novel platinum complexes derived from N-alkyl-propanediamines on their cytotoxic activity and cellular uptake.

This work describes the synthesis and characterization of four new ligands derived from 1,3-propanediamine in addition to the preparation and characterization of their respective platinum(II) complexes by reaction with K(2)PtCl(4). These ligands were obtained by the reaction of the corresponding alkyl mesylate with 1,3-propanediamine. We have prepared compounds having different carbon chains lengths in an attempt to correlate this factor, which influences the lipophilicity of the compounds, with cytotoxic activity. Octanol/water partition coefficients, the effect of the four complexes on the growth of two tumoral cell lines, and their cellular uptake were investigated. Increasing lipophilicity enhances the rate of cellular uptake and, consequently, the cytotoxic activity.

Three New Complexes of Platinum(II) with Doxycycline, Oxytetracycline and Chlortetracycline and their Antimicrobial Activity

Este artigo descreve a sintese e a caracterizacao de tres novos complexos de platina(II) com a oxitetraciclina, doxiciclina e clortetraciclina por analise elementar, espectroscopias IV e RMN de 195Pt. As interacoes da doxiciclina com ions PtII em funcao do pH foram estudadas por RMN de 1H. Todas as tetraciclinas investigadas formam complexos 1:1 com a PtII via oxigenio do grupo hidroxila e oxigenio do grupo amida do anel A. As concentracoes minimas inibitorias (MIC) dos ligantes e de seus complexos de PtII foram determinadas em duas cepas sensiveis (E. coli HB 101 and E. coli ATCC 25922) e em uma resistente (E. coli HB101/pBR322). O complexo de platina da doxiciclina e duas vezes mais potente do que o antibiotico livre na cepa resistente. Os coeficientes de particao dos complexos em octanol e agua foram determinados. O aumento da lipofilia causa um aumento da atividade antimicrobiana na cepa resistente.

Possible Effects of Drinking and Smoking Habits on Hippuric Acid Levels in Urine of Adults with No Occupational Toluene Exposure.

Drinking and Smoking Habits and Urinary Level of Hippuric Acid in Adults not Exposed to Toluene: Edna Maria Alvarez‐leite, et al. Department of Clinical Chemistry and Toxicology, College of Pharmacy, Federal University of Minas Gerais‐UFMG, Brazil—Hippuric acid (HA) is still the biomarker most used for monitoring exposure to toluene, but it is produced by the body even in the absence of this solvent, and has the disadvantage of showing significant variation in and between individuals, depending on environmental factors and individual characteristics. A number of studies have reported the influence of individual drinking and smoking habits on toluene metabolism, but the effect on urinary excretion of HA is still controversial. This study was conducted in an attempt to examine whether these individual habits also affect HA excretion in individuals not exposed to toluene. Urine sample from 195 people (99 women and 96 men), ranging in age from 17 to 46 years old, were collected. The individuals were classified in groups according their drinking and smoking habits. The data from the current study indicate that these two social habits, either separately or combined, do not influence basal urinary HA levels in this study group.

Platinum(II) compounds of tetracyclines as potential anticancer agents: cytotoxicity, uptake and interactions with DNA

As propriedades antitumorais de complexos de PtII e as caracteristicas favoraveis das tetraciclinas levaram-nos a estudar compostos de PtII da tetraciclina (tc) e doxiciclina (dox) como candidatos a agentes antitumorais. [PtCl2(dox)], 1, e mais potente que[PtCl2(tc)], 2,em inibir o crescimento de celulas de leucemia mieloide cronica.Os compostos 1 e 2 formam um complexo ternario com o ADN com valores de K iguais a 3,85×104 e 5,43×104, respectivamente. Os complexos deslocam o brometo de etideo dos sitios no ADN, o que indica um mecanismo intercalativo. Ambos os complexos diminuem a mobilidade eletroforetica e a temperatura de fusao do ADN. Apos a incubacao das celulas com 1 e 2, o ADN foi extraido e os adutos formados foram quantificados. Na concentracao em que os compostos sao citotoxicos contra celulas cancerosas, eles nao afetam a viabilidade de macrofagos. A velocidade de entrada do complexo da doxiciclina nas celulas e tres vezes maior do que a do complexo da tetraciclina e isto parece ser determinante para a sua maior atividade.

Teores de chumbo e cádmio em chás comercializados na região metropolitana de Belo Horizonte

This research aims at evaluating the levels of lead and cadmium in industrialized and non-industrialized samples of tea traded in the metropolitan area of Belo Horizonte, due to the constant use of different kinds of tea by the Brazilians. Camomile and mate have been selected and analyzed as tea-infusion and digested-plant. The levels of Pb and Cd were determined by spectrometry of atomic absorption with graphite furnace and Zeeman background corrector. The average levels of Pb and Cd in samples of camomile and mate tea-infusion were below the values established by the Brazilian legislation for metals in soft drinks (0.2 mg/L). The concentrations of metals in plant-digested camomile samples (0.15 µg/g to Cd and 0.42 µg/g to Pb) and plant-digesgted mate samples (0.53 µg/g) were considered normal according to the literature with exception of Cd levels in plant-digested mate samples (2.59 µg/g). Difference was not found significant between the levels of quantified Cd and Pb in samples of industrialized and not industrialized tea-infusion camomile and mate teas. The concentrations of metals were higher in industrialized digested-plant camomile and mate, when compared with not industrialized. There was no significant difference among tea-infusion samples.

Cytotoxicity and Cellular Accumulation of Palladium(II) Complexes of Tetracyclines

We studied the cytotoxic effect and the uptake of PdII complexes of doxycycline (Dox), [Pd(Dox)Cl2] (1), and tetracycline (Tc), [Pd(Tc)Cl2] (2), in chronic myelogenous leukemia cells. The effect of the compounds on macrophage viability was also investigated. Compound 1 is more effective than compound 2 in inhibiting the growth of K562 cells with the IC50 values of 14.44 and 34.54 μM, respectively. There is a good correlation between cell‐growth inhibition and intracellular metal concentrations, determined by inductively coupled plasma atomic emission spectroscopy (ICP‐AES). Incubation of the cells with equitoxic concentrations of both compounds yields approximately the same intracellular Pd concentration. At the IC50 doses, intracellular concentration is ca. 33×10−16 mol/cell for both compounds 1 and 2. This suggests that more [Pd(Tc)Cl2] is needed to produce a cytotoxic effect, because it enters cells more slowly. Both compounds up to 16 μM did not affect the viability of mouse peritoneal macrophages after a 48‐h incubation. After 72 h of incubation, the IC50 values are 22 for [Pd(Dox)Cl2] and 40 μM for [Pd(Tc)Cl2]. Therefore, the cytotoxic effect in cancer cells exhibited by both compounds is higher than their effect in macrophages.

ET AAS evaluation of the stability and pH-sensitivity of, pH-sensitive stealth liposomes containing cisplatin in mouse plasma

In this work, stability and the pH-sensitivity of pH-sensitive stealth liposomes containing cisplatin exposed to plasma medium and their subsequent responses to pH modifications were evaluated. A method to determine platin in mouse plasma by electrothermal atomic absorption spectroscopy (ET AAS) was developed and validated. At first, a comparative study of sample preparation treatments with basic, acidic, and acidic added with Triton X-100 as a modifier was done. The best treatment was obtained with HCl 3% (v/v). The ET AAS method with acid treatment presented linearity at a range of 10-160 ng Pt/mL. The limits of detection (LOD) was 3.1 ng/mL Pt for acid treatment, while the limit quantification (LOQ) was 10 ng/mL Pt. The acid treatment presented good repeatability (VC<15.0%) and recovery close to 100%. This treatment was chosen for subsequent studies due to its best value of repeatability, recovery, LOD and lowest cost. pH-sensitive stealth liposomes, containing cisplatin, demonstrated low stability and poor response to pH variation after plasma incubation. These findings suggest that further studies are needed to improve liposome formulation i.e., to reduce its size.

A Simple and Fast Method for Manganese Determination in Antihypertensive Drugs by Slurry Sampling Graphite Furnace Atomic Absorption Spectrometry

Abstract A simple and rapid procedure for the determination of manganese in anti‐hypertensive drugs is proposed. The samples were treated with dilute nitric acid (1.2% v/v) with stirring using a vortex stirrer to yield a slurry. To determine the best conditions for analysis by graphite furnace atomic absorption spectrometry (GF AAS), a planning factorial was initially employed that demonstrated that the non‐use of chemical modifiers and the use of lower pyrolysis temperatures were more appropriate. Next, the pyrolysis and atomization temperature curves were obtained. The best pyrolysis and atomization temperatures encountered were 500 and 2200°C, respectively. Calibration was performed by matrix matching. The characteristic mass was 0.70±0.14 pg (the recommended mass was 0.60 pg); the limits of detection and quantification were 0.23 and 0.77 µg l−1, respectively. The precision obtained in the intra‐ and inter‐assay studies of the drug spiked with 0.5, 1.0 and 1.5 µg l−1 of Mn did not exceed 11% (n=7). Recovery studies of the drug spiked with three levels (n=7) of Mn yielded results between 101.0±4.5 and 116.3±9.7%. The results of an analysis of a certified urine sample (two levels of Mn) agreed at a 95% level of confidence. Forty‐eight antihypertensive drug samples were analyzed, and the results varied from 2.9 ng to 1.9 µg of Mn per capsule−1.