Biomarkers to assess the efficiency of treatment with platinum-based drugs: what can metallomics add?

Since the approval of cisplatin as an antineoplastic drug, the medical and the scientific communities have been concerned about the side effects of platinum-based drugs, and this has been the dose-limiting factor that leads to reduced treatment efficiency. Another important issue is the intrinsic or acquired resistance of some patients to treatment. Identifying proper biomarkers is crucial in evaluating the efficiency of a treatment, assisting physicians in determining, at early stages, whether or not the patient presents resistance to the drug, minimizing severe side effects, and allowing them to redirect the established course of chemotherapy. A great effort is being made to identify biomarkers that can be used to predict the outcome of the treatment of cancer patients with platinum-based drugs. In this context, the metallomic approach has not yet been used to its full potential. Since the basis of these drugs is platinum, the monitoring of biomarkers containing this metal should be the natural approach to evaluate treatment progress. This review intends to show where the research in this field stands and points out some gaps that can be filled by metallomics.

Small cetaceans found stranded or accidentally captured in southeastern Brazil: bioindicators of essential and non-essential trace elements in the environment.

Essential (Cu, Mn, Se and Zn) and non-essential (Cd and Hg) elements were analyzed in the hepatic tissue of 22 individuals of seven different species of small cetaceans (Feresa attenuata; Orcinus orca; Pontoporia blainvillei; Sotalia guianensis; Stenella frontalis; Steno bredanensis; Tursiops truncatus) accidentally caught in fishing nets or found stranded along the northern coast of the state of Rio de Janeiro, Brazil, between 2001 and 2010. Atlantic spotted dolphin (S. frontalis) showed the highest levels of Cd (20.23µgg(-1), dry weight), while rough-toothed dolphin (S. bredanensis) showed the highest levels of Hg (825.9µgg(-1)dw) and Se (221.9µgg(-1)dw). Killer whale (O. orca) presented the highest levels of Cu (64.80µgg(-1)dw) and Zn (2220µgg(-1)dw), and Guiana dolphin (S. guianensis), the highest level of Mn (13.05µgg(-1)dw). Cu, Hg, Mn and Zn in the hepatic tissue of killer whale (O. orca), Cu, Hg, Mn, Se and Zn in the hepatic tissue of rough-toothed dolphin (S. bredanensis) and Cd and Zn in the hepatic tissue of Guiana dolphin (S. guianensis) were significantly higher when compared to other studies with these species around the world. No significant correlations were observed between element accumulation and sex, sexual maturity and body length. An analysis of the interelemental relationships in the Guiana dolphin specimens showed strong positive correlations between Cd and Se, Cu and Zn, and Hg and Se. Differences were observed in the bioaccumulation of elements between the analyzed species, probably related to each species feeding habit, and differences between different element concentrations in the different dolphin species were probably due to the preference for certain preys and their bioavailability in the environment. Thus, the bioavailability of the analyzed elements in the marine environment should also be taken in consideration. This study also presents the first data ever reported for pygmy killer whale (F. attenuata) regarding trace element concentrations in hepatic tissue.

Fish bile as a biomarker for metal exposure.

Fish accumulate several trace elements in muscle, gills and liver, however studies also indicate that metals can be excreted through bile. Since metal contamination leads to modifications in bile composition, biliary excretion offers an alternative way to evaluate the presence of trace-elements. Bile is easier to obtain than other organs and presents a simpler matrix, making it easier for chemical pre-treatment. To verify if bile can be useful as a biomonitoring tool for metal contamination, liver and bile trace element concentrations were determined and correlated. The Artificial Neural Networks statistical technique was used to verify if liver trace-element quantification could be substituted by bile analysis. Results show that significant correlations were obtained between trace elements in bile and liver and the ANN validated the hypothesis that certain trace-elements in bile could be utilized instead of liver trace-elements. Further studies in this field are of interest to further validate this biomarker.

Mercury status of the Amazon Continental Shelf: Guiana dolphins (Sotalia guianensis, Van Benédén 1864) as a bioindicator.

Total mercury (Hg) was analyzed in muscle tissue of 27 accidentally captured Guiana dolphins (Sotalia guianensis) in order to evaluate Hg contamination levels present in the Amazon Continental Shelf, in Amapá state, North Brazil. The samples showed a mean concentration of 0.4 ± 0.16 µg/g wet weight (ww), ranging from 0.07 to 0.79 µg/g ww. As observed in several other cetacean species, Hg concentrations presented positive correlations to body length, related to the capacity to bioaccumulate this element throughout life. Hg concentrations were not significantly different between males (mean = 0.38 µg/g ww; n = 15) and females (mean = 0.42 µg/g ww; n = 12). Concentrations were low when compared to results of studies carried out with small cetaceans in the Northern Hemisphere, and with some previous studies in the south-eastern region of Brazil. In contrast with high Hg concentrations normally detected in river dolphin samples from Amazon River tributaries, our results suggest that the Amazon coast contains low levels of Hg in bioavailable form.

Fish metalloproteins as biomarkers of environmental contamination.

Fish are well-recognized bioindicators of environmental contamination. Several recent proteomic studies have demonstrated the validity and value of using fish in the search and discovery of new biomarkers. Certain analytical tools, such as comparative protein expression analyses, both in field and lab exposure studies, have been used to improve the understanding of the potential for chemical pollutants to cause harmful effects. The metallomic approach is in its early stages of development, but has already shown great potential for use in ecological and environmental monitoring contexts. Besides discovering new metalloproteins that may be used as biomarkers for environmental contamination, metallomics can be used to more comprehensively elucidate existing biomarkers, which may enhance their effectiveness. Unfortunately, metallomic profiling for fish has not been explored, because only a few fish metalloproteins have thus far been discovered and studied. Of those that have, some have shown ecological importance, and are now successfully used as biomarkers of environmental contamination. These biomarkers have been shown to respond to several types of environmental contamination, such as cyanotoxins, metals, and sewage effluents, although many do not yet possess any known function. Examples of successes include MMPs, superoxide dismutases, selenoproteins, and iron-bound proteins. Unfortunately, none of these have, as yet, been extensively studied. As data are developed for them, valuable new information on their roles in fish physiology and in inducing environmental effects should become available.

A novel report of metallothioneins in fish bile: SDS-PAGE analysis, spectrophotometry quantification and metal speciation characterization by liquid chromatography coupled to ICP-MS.

Metallothioneins (MT) are a validated biomarker for metal exposure. In fish they are usually determined in the liver, while some studies have observed MT in kidney, muscle and gills. There are, however, no reports on MT in fish bile. This study aimed to verify if these proteins are present in fish bile, if they can be used as biomarkers for metal exposure and to characterize the metal speciation present in the different species. Three independent methods to verify MT presence in fish bile were conducted: 1D/2D gel electrophoresis, spectrophotometric analyses and SEC-HPLC-ICP-MS. Results show that all methods verified the presence of these proteins in fish bile, while SEC-HPLC-ICP-MS also characterized also characterized metals responsible for the contamination of the studied sites. Quantification was successfully conducted by two methods, densitometry (1D electrophoresis) and spectrophotometry, and the data indicates that bile MTs follow the same trend as in liver. Therefore, Biliary MT show the potential to be used the same way as MT from other matrices in metal exposure studies, with the advantage of being a simpler matrix and showing the possibility of not sacrificing the animals, as chronic duct cannulation is available.

Guiana dolphins (Sotalia guianensis, Van Benédén 1864) as indicators of the bioaccumulation of total mercury along the coast of Rio de Janeiro state, Southeastern Brazil.

Total mercury (Hg) was determined in muscle tissue of 20 Guiana dolphins stranded along the coast of Rio de Janeiro state, Brazil, with a mean of 1.07 µg/g wet weight. Mercury concentrations were positively related to body length, possibly related to the capacity of the dolphins to bioaccumulate this element throughout life. The Hg concentrations were not significantly different between males and females, although females (1.08 µg/g) showed slightly higher levels than males (1.04 µg/g). Concentrations were low when compared to results of studies carried out with small cetaceans in the Northern Hemisphere, and with previous studies in the Southeastern Brazil.

Determination of platinum originated from antitumoral drugs in human urine by atomic absorption spectrometric methods.

Cisplatin and carboplatin are the most common platinum-based drugs used in cancer treatment. Pharmacokinetic investigations, the evaluation of the body burden during the treatment, as well as baseline levels of platinum in humans have attracted great interest. Thus, accurate analytical methods for fast and easy Pt monitoring in clinical samples become necessary. In the present study atomic absorption spectrometric methods for the determination of platinum in the forms of cisplatin and carboplatin in human urine were investigated. Platinum, in these different forms, could be determined in urine, after simple sample dilution. Regarding electrothermal atomic absorption spectrometry, the optimum parameters were defined by a central composite design optimization. Multiplicative matrix effects were overcome by using a mixture of HCl and NaCl as modifier. The limit of detection (LOD) was 0.004 mgL(-1) of platinum in the original sample. For the analysis of more concentrated samples, high resolution continuous source flame atomic absorption spectrometry was also investigated. Flame conditions were optimized by a multivariate D-optimal design, using as response the sum of the analyte addition calibration slopes and their standard deviations. Matrix matched external calibration with PtCl(2) calibration solutions, was possible, and the LOD was 0.06 mgL(-1) in the original sample. The results obtained by the proposed procedures were also in good agreement with those obtained by an independent comparative procedure.

Negligible expression of arsenic in some commercially available brands of Portland cement and mineral trioxide aggregate.

INTRODUCTION: This study was designed aiming to determine and compare the amount of arsenic in some brands of mineral trioxide aggregate (MTA) and Portland cement. METHODS: In the present study, arsenic species (As[III], As[V], and dimethylarsinic acid) were separated by high-performance liquid chromatography (HPLC) using a strong anion exchange column and converted into arsines by online HG. The instrumental coupling, HPLC-HG-AFS, was applied to 0.2 g of each cement that was prior digested in a solution of HCl, HNO(3), and HBF(4). Data were expressed as a part per million, and the preliminary analysis of the raw pooled data revealed a bell-shaped distribution. Statistical analysis was performed using one-way analysis of variance for multiple comparisons. RESULTS: In all chromatograms obtained, only type III arsenic could be detected. The minimum amount of arsenic was detected in samples of white MTA ProRoot (3.3 x 10-4) and the maximum in the samples MTA Bio Angelus (Angelus, Londrina, PR, Brazil) (8.6 x 10-4). In the Gray MTA (Angelus), gray ProRoot MTA (Tulsa/Dentsply, Tulsa, OK) and CP Juntalider (Brasilatex Ltda, Diadema, SP, Brazil) did not detect any trace of arsenic. The values of arsenic found in CP Irajazinho (Votorantim Cimentos, Rio Branco, SP, Brazil) and white MTA Angelus were intermediaries to minimum and maximum values. The nonparametric test Kruskal-Wallis showed statistically similar results among all cements tested (p > 0.5). CONCLUSIONS: Overall, the present study showed that all cements showed insignificant amounts of type III arsenic as well as no trace of arsenic DMA and type V could be detected.

Direct determination of nickel in petroleum by solid sampling-graphite furnace atomic absorption spectrometry.

A procedure for the direct GFAAS determination of Ni in petroleum samples using a solid sampling strategy is proposed. Palladium was used as conventional modifier. Central composite design multivariate optimization defined the optimum temperature program and the Pd mass, allowing calibration using aqueous analytical solution. The limit of detection (LOD) at the optimized conditions was 0.23 ng of Ni, for typical sample masses between of 0.10 and 0.60 mg. Linearity at least up to 11 ng of Ni and a characteristic mass of 45 pg were observed, defining a dynamic range between 0.52 and 110 microg g(-1). Typical coefficients of variation (n = 10) in the analysis of oil reference materials were 7%. Method validation was performed both by the analysis of oil certified reference materials and by comparison with an independent method (ASTM 5863-B). No statistically significant difference was observed between obtained and expected values. The total determination cycle lasted 5 min, equivalent to a sample throughput of 6 h(-1) for duplicate determinations.

Determination of arsenic in diesel, gasoline and naphtha by graphite furnace atomic absorption spectrometry using microemulsion medium for sample stabilization.

A procedure for the determination of As in diesel, gasoline and naphtha at microg L(-1) levels by GFAAS is proposed. Sample stabilization was achieved by the formation of three component solutions prepared by mixing appropriate volumes of the samples propan-1-ol and nitric acid aqueous solution. This mixture resulted in a one-phase medium, which was indefinitely stable. No changes in the analyte signals were observed over several days in spiked samples, proving long-term stabilization ability. The use of conventional (Pd) and permanent (Ir) modification was investigated and the former was preferred. Central composite design multivariate optimization defined the optimum microemulsion composition as well as the temperature program. In this way, calibration using aqueous analytical solutions was possible, since the same sensitivity was observed in the investigated microemulsion media and in 0.2% v/v HNO(3). Coefficients of correlation larger than 0.999 and an As characteristic mass of 22 pg were observed. Recoveries (n=4) obtained from spiked samples were 98+/-4, 99+/-3 and 103+/-5%, and the limits of detection in the original samples were 1.8, 1.2 and 1.5 microg L(-1) for diesel, gasoline and naphtha, respectively. Validation was performed by the analysis of a set of commercial samples by independent comparative procedures. No significant difference (Student's t-test, p<0.05) was observed between comparative and proposed procedure results. The total determination cycle lasted 4 min for diesel and 3 min for gasoline and naphtha, equivalent to a sample throughput of 7 h(-1) for diesel and 10 h(-1) for gasoline and naphtha.

The determination of total Se in urine and serum by graphite furnace atomic absorption spectrometry using Ir as permanent modifier and in situ oxidation for complete trimethylselenonium recovery.

The present work evaluated the use of iridium (Ir) as permanent modifier for the determination of total selenium in urine and serum by graphite furnace atomic absorption spectrometry. Concerning urine, the presence of trimethylselenonium (TMSe(+)) was especially considered. Pyrolysis and atomization temperatures of 1,000 and 2,100 degrees C, respectively, were used. For nondigested urine and serum samples, 0.2% v/v HNO(3) and Triton X-100 were used as diluents, respectively, and the same initial platform Ir treatment was effective for up to 1,100 atomization cycles. Good precision [less than 5% relative standard deviation (RSD)] can be achieved with the proposed method. Low TMSe(+) recovery was observed for nondigested urine samples. Thus, if this species is to be considered in urine analysis, a previous external mineralization step was found to be necessary. Alternatively, an in situ oxidation treatment was developed. Detection limits of 8, 10, and 7 mug l(-1) were obtained after dilution, microwave-assisted digestion, and in situ oxidation procedures, respectively. The accuracy of the method was validated by the analysis of certified reference or commercial quality control materials and spiked samples.

The use of 2-2-thiazolylazo-p-cresol to minimize the interference of Ni and Cu for the bismuth determination in alloys by hydride generation atomic absorption spectrometry.

Thiazolylazo p-cresol (TAC) was studied as a masking agent for the determination of Bi in rich Ni and Cu alloys by hydride generation atomic absorption spectrometry (HGAAS). In the presence of TAC, Bi/Ni and Bi/Cu ratios up to 1:160 000 and 1:16 000, respectively, were found to be tolerable. No buffering was necessary once the masking agent was effective even in very acid medium. Limits of detection at the low mug g(-1) range were reached and the accuracy of the procedure was confirmed by the good concordance between found and certified values in the analysis of certified reference materials (CRM).