ICP-MS determination of Pt in biological fluids of patients treated with antitumor agents: evaluation of analytical uncertainty

Fast and reliable ICP-MS quantification of palladium and platinum-based drugs in animal pharmacokinetic and biodistribution studies

Palladium-(Pd)-based drugs are emerging as alternatives to platinum (Pt) anticancer chemotherapeutics, which increases the need for efficient and suitable procedures of Pd analysis in reduced amounts of pre-clinical animal samples. Herein, an ICP-MS (inductively coupled plasma-mass spectrometry) method was developed and validated for simple and fast analysis of Pd/Pt-based drugs in 11 distinct biological matrices (adipose tissue, muscle, liver, kidney, spleen, testis, heart, lungs, brain, blood and serum). The critical variables affecting sample preparation and Pd/Pt extraction were optimized using two-level (2^k) factorial and central composite designs. Biological samples (50 mg) were digested in closed tubes with a screw cap, using a 3 : 1 (v/v) mixture of nitric acid (900 μL) and hydrochloric acid (300 μL) for 60 min in a 90 °C water bath. Full method validation using in-house materials showed a LOD of 0.001 μg L^-1, linear dynamic range from 0.025-10 μg L^-1 (R² = 0.9999 for Pd; R² = 0.9998 for Pt), good repeatability (CV: 0.02-1.9%) and intermediate precision (CV: 0.52-1.53%) for both the studied metals. The accuracy ranged from 83.5-105.1% considering microwave-assisted digestion as the reference method. The developed and validated method allows the processing of hundreds of biological samples simultaneously, with low reagent and sample consumption. Therefore, the method is highly suitable for analysis of novel Pd/Pt-based drugs in pharmaco-toxicokinetic and biodistribution animal studies that involve a large number of multi-organ samples.

On the facile and accurate determination of the Pt content in standard carbon supported Pt fuel cell catalysts

We introduce a new and straight-forward methodology to accurately determine the Pt content in polymer membrane electrolyte fuel cell (PEMFC) catalysts consisting of carbon supported Pt nanoparticles (Pt/C). The method is based on an indirect Pt proof (IPP) consisting of the oxidative removal of the carbon support, the digestion of the Pt in aqua regia followed by a replacement reaction to form Cu ions (CuCl₂). The Pt content is then determined via the Cu-ions with the help a complexometric indicator using a simple titration. The procedure is fast and does not require any expensive equipment. Thus, it can be implemented in any standard chemistry laboratory. The advantages and disadvantages of the IPP method are evaluated in a comparison to alternative methods for the determination of the Pt content in supported catalysts, i.e. inductively coupled plasma mass spectrometry (ICP-MS) and UV/Vis spectroscopy (UV/Vis). It is demonstrated that the IPP method delivers reliable and accurate results and is less influenced than for example ICP-MS by side effects such as excess in nitric acid or organic impurities. Furthermore, during the procedure up to 60% of the Pt material is recovered during the IPP procedure.

Optimized intrapleural cisplatin chemotherapy with a fibrin carrier after extrapleural pneumonectomy: a preclinical study

OBJECTIVE

Our objective was to evaluate whether platinum concentrations in chest wall tissue and in serum are optimized by intracavitary application of cisplatin loaded to a fibrin carrier compared with cisplatin solution in a randomized setting of a pig model.

METHODS

After left-sided pneumonectomy including parietal pleurectomy, pigs were randomly assigned to receive either 90 mg/m(2) cisplatin intracavitary solution (n = 6) or to receive 5 mg cisplatin-fibrin (n = 5) applied on a predefined area of the chest wall. Platinum concentration in serum as well as in chest wall tissue was determined at several early time points until day 5 after treatment. Platinum levels were measured by inductively coupled plasma sector field mass spectrometric detection with a matrix-matched calibration procedure.

RESULTS

The dose- and surface-corrected (geometric) mean concentration of cisplatin in chest wall tissue 2 hours but also at day 5 after the application was doubled in animals treated with cisplatin-fibrin compared with the animals treated with cisplatin-solution. In serum, the dose- and surface-corrected exposure toward cisplatin (area under the curve(0-5d)) was significantly lower with cisplatin-fibrin than with cisplatin-solution (P < .0005). This is also reflected by significantly reduced serum creatinine and urea values in the cisplatin-fibrin group (P < .0001). Animals treated with cisplatin-fibrin additionally had a significantly better postoperative course as assessed by a well-being score (P < .001).

CONCLUSIONS

After cisplatin-fibrin treatment, cisplatin tissue concentration was increased whereas systemic cisplatin concentrations were significantly reduced in comparison with cisplatin-solution treatment. This finding offers a clear advantage inasmuch as rate and severity of systemic adverse events can be reduced while local cytotoxic concentrations are at least maintained.

Determination of platinum in human subcellular microsamples by inductively coupled plasma mass spectrometry

A fast and robust method for the determination of platinum in human subcellular microsamples by inductively coupled plasma mass spectrometry was developed, characterized, and validated. Samples of isolated DNA and exosome fractions from human ovarian (2008) and melanoma (T289) cancer cell lines were used. To keep the sample consumption to approximately 10 microl and obtain a high robustness of the system, a flow injection sample introduction system with a 4.6-microl sample loop was used in combination with a conventional pneumatic nebulizer and a spray chamber. The system was optimized with respect to signal/noise ratio using a multivariate experimental design. The system proved to be well suited for routine analysis of large sample series, and several hundreds of samples could be analyzed without maintenance or downtime. The detection limit of the method was 0.12 pg (26 pg/g) platinum. To avoid systematic errors from nonspectral interferences, it was necessary to use reagent matched calibration standards or isotope dilution analysis. An uncertainty budget was constructed to estimate the total expanded uncertainty of the method, giving a quantification limit of 2.3 pg (0.5 ng/g) platinum in DNA samples. The uncertainty was sufficiently low to study quantitative differences in the formation of Pt-DNA adducts after treatment with cisplatin using different exposure times and concentrations.

Intrapleural topical application of cisplatin with the surgical carrier Vivostat increases the local drug concentration in an immune-competent rat model with malignant pleuromesothelioma

OBJECTIVE

We sought to investigate whether intrapleural topical application of cisplatin with a surgical carrier has a prolonged local tissue level in comparison with cisplatin solution while reducing systemic toxicity.

METHODS

Forty immune-competent Fischer rats were inoculated with 10(6) mesothelioma cells. Ten days later, left pneumonectomy with tumor debulking was performed. Twenty animals underwent local application of cisplatin solution (100 mg/m2), whereas the same quantity of cisplatin was topically applied as a gel with the Vivostat (Vivolution) system in 20 other animals. In each group 5 subgroups of 4 animals were defined according to the harvesting time of blood and tissue samples (2, 4, 24, and 72 hours and 1 week) after local therapy. Platinum concentrations in serum and tissue and systemic toxicity were analyzed.

RESULTS

Platinum concentrations in tissue were significantly higher in the gel group (group 1) than in the solution group (group 2) at 1, 3, and 7 days after therapy (1510, 1224, and 1069 pg/mg for group 1 vs 598, 382, and 287 pg/mg for group 2; P = .007, P = .005, and P = .0002, respectively). Laboratory findings showed renal insufficiency in the animals of the solution group at 1 week, with values of 98 mmol/L versus 7.7 mmol/L for urea and 410 mumol/L versus 43 mumol/L for creatinine (P = .02 and P = .01, respectively), which was confirmed by means of pathologic analysis.

CONCLUSIONS

Intrapleural administration of cisplatin with the carrier Vivostat significantly provides sustained higher platinum concentrations up to 1 week in tissue in comparison with application of cisplatin solution without conferring systemic toxicity in this model.

Determination of platinum derived from cisplatin in human tissues using electrospray ionization mass spectrometry

Determination of platinum (Pt) derived from cisplatin in tissues was performed by electrospray ionization mass spectrometry (ESI-MS) using silver (Ag) as the internal standard. Pt and Ag reacted with diethyldithiocarbamate (DDC), and were extracted using isoamylalcohol and acidified with oxalic acid. The compounds were termed Pt(DDC)(3)(+) and Ag(DDC)(2)(+), based on their m/z values exhibiting the highest peaks at m/z 639 and m/z 405, respectively. The limit of detection was 30 pg and the quantitation range was from 100 to 10,000 pg using 5 mg tissue. The present method allowed the determination of Pt in wet-ashed tissue in 10 min.