EPR study of free radicals in some drugs γ-irradiated in the solid state

Gamma irradiation effect on some asthma drugs: EPR detection of radiosterilization

Among many sterilization methods, radiosterilization is a preferred method in the pharmaceutical industry because of its advantages. However, the detection of radiosterilization of drugs is a growing concern for many government regulatory agencies around the world because of changes in the drug's structure because of exposure to radiation. Electron Paramagnetic Resonance (EPR) proved to be a very sensitive technique to discriminate between irradiated and nonirradiated drugs and detect radicals for days even to years. In this study, the focus is on the detection of radiosterilization of irradiated three asthma drugs (Airfix, Ventolin and Prednol) by using EPR spectroscopy. Regarding the commercial aspects of drugs, it was found that radicals can be detected at least 2 y after irradiation. Therefore, paramagnetic centers formed by the effect of radiation in the samples were determined and the stability of these centers was examined for 2 y by performing the fading study.

To infinity and beyond: Strategies for fabricating medicines in outer space

Recent advancements in next generation spacecrafts have reignited public excitement over life beyond Earth. However, to safeguard the health and safety of humans in the hostile environment of space, innovation in pharmaceutical manufacturing and drug delivery deserves urgent attention. In this review/commentary, the current state of medicines provision in space is explored, accompanied by a forward look on the future of pharmaceutical manufacturing in outer space. The hazards associated with spaceflight, and their corresponding medical problems, are first briefly discussed. Subsequently, the infeasibility of present-day medicines provision systems for supporting deep space exploration is examined. The existing knowledge gaps on the altered clinical effects of medicines in space are evaluated, and suggestions are provided on how clinical trials in space might be conducted. An envisioned model of on-site production and delivery of medicines in space is proposed, referencing emerging technologies (e.g. Chemputing, synthetic biology, and 3D printing) being developed on Earth that may be adapted for extra-terrestrial use. This review concludes with a critical analysis on the regulatory considerations necessary to facilitate the adoption of these technologies and proposes a framework by which these may be enforced. In doing so, this commentary aims to instigate discussions on the pharmaceutical needs of deep space exploration, and strategies on how these may be met.

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Space is a hostile environment that threatens human health and drug stability.

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Data on the behaviour of medicines in space is critical but lacking.

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Novel drug manufacturing and delivery strategies are needed to safeguard crewmembers’ safety.

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Chemputing, synthetic biology, and 3D printing are examples of such emerging technologies.

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A regulatory framework for space medicines must be implemented to assure quality.

Limitations in predicting radiation-induced pharmaceutical instability during long-duration spaceflight

As human spaceflight seeks to expand beyond low-Earth orbit, NASA and its international partners face numerous challenges related to ensuring the safety of their astronauts, including the need to provide a safe and effective pharmacy for long-duration spaceflight. Historical missions have relied upon frequent resupply of onboard pharmaceuticals; as a result, there has been little study into the effects of long-term exposure of pharmaceuticals to the space environment. Of particular concern are the long-term effects of space radiation on drug stability, especially as missions venture away from the protective proximity of the Earth. Here we highlight the risk of space radiation to pharmaceuticals during exploration spaceflight, identifying the limitations of current understanding. We further seek to identify ways in which these limitations could be addressed through dedicated research efforts aimed toward the rapid development of an effective pharmacy for future spaceflight endeavors.

An Electron Paramagnetic Resonance (EPR) spectroscopy study on the γ-irradiation sterilization of the pharmaceutical excipient l-histidine: Regeneration of the radicals in solution

The effects of γ-radiation sterilization on the parenteral excipient l-histidine were analysed by means of EPR spectroscopy. The irradiation process was found to induce the formation of a deamination radical which was persistent in the solid state. The nature and reactivity of the radicals following dissolution in water was evaluated using spin-trapping EPR experiments. The deamination radical was found to regenerate in solution in the presence of trace metals, potentially leading to radical induced degradation reactions occurring up to an hour after the dissolution process. Understanding this process is significant for the improved design of parental pharmaceutical formulations in which unwanted radical reactions after γ-radiation sterilization could lead to degradation of active ingredients.

Seasonal variation of particle-induced oxidative potential of airborne particulate matter in Beijing

An in vitro plasmid scission assay (PSA), the cell apoptosis assay, and ICP-MS were employed to study the oxidative potentials and trace element compositions of the airborne particulate matter (PM) in Beijing during a one year-long field campaign from June 2010 to June 2011. The cell damages induced by PM reveled by the cell apoptosis assay showed a similar variation pattern to the DNA damages obtained by PSA, verifying the feasibility of the PSA in analyzing the oxidative capacity of PM samples. The PSA experiments showed that the particle-induced DNA damage was highest in summer, followed by spring, winter and autumn in descending order. The percentages of the oxidative damages to plasmid DNA induced by the water-soluble fractions of PM under the particle doses from 10 to 250μg/ml were generally lower than 45%, with some values peaking at above 50%. The peak values were frequently present in late spring (i.e. April and May) and early summer (i.e. June) but they were scarcely observed in other seasons. These peak values were mostly associated with haze days or the days with low wind speed (less than 4m/s), indicating that the PM samples during haze had higher oxidative potential than those during non-haze periods. The oxidative potential induced by the water-soluble fraction of the PM displayed a significant positive correlation with the concentrations of the water-soluble elements Cd, Cs, Pb, Rb, Zn, Be and Bi, demonstrating that the particle-induced oxidative potentials were mainly sourced from these elements. The exposure risk represented by the mass concentration of these elements in unit volume of atmosphere was higher in summer and winter, and lower in autumn and spring. The haze day PM samples not only had higher level of oxidative potentials but also had higher concentrations of water-soluble elements.

Increased proapoptotic activity of electron beam irradiated doxorubicin and epirubicin in multidrug-resistant human leukemic cells

This study evaluated the effect of electron beam irradiation on the cytotoxic activity of anthracycline antibiotics such as doxorubicin (DOX), epirubicin (EPI), and dunorubicin (DAU) in human acute lymphoblastic leukemia cell line CCRF-CEM and its multidrug-resistant variant CCRF-VCR1000 cell line characterized by the overexpression of ABCB1 gene. Drugs were irradiated at doses of 10 and 25 kGy. Data from EPR studies proved that the highest concentration of free radicals was found in DOX and that the number of stable free radicals is always greater after irradiation. In in vitro studies, a higher cytotoxic activity of irradiated DOX and EPI in multidrug-resistant CCRF-VCR1000 cells was observed. This tendency was maintained during the storage at 4 °C for 90 days. Changes in CCRF-CEM cells' viability were not dependent on the irradiation status and its dose and were only drug-concentration dependent in all measurement time points. It was proved that increased potency of 25 kGy e-beam irradiated drugs results from their enhanced proapoptotic activity. Apoptotic cell death observed in CCRF-VCR1000 cells treated with irradiated drugs was caspase-8, -9, and -3 dependent and related to the increased Bax/Bcl-2 ratio. No significant differences in the effects of irradiated and non-irradiated drugs on p53 and NFκB transcription factor level and their translocation to the nucleus were noted. Increased activity of the irradiated drugs was not dependent on ABCB1 level.

Electron spin resonance. Part one: a diagnostic method in the biomedical sciences

A review is presented of some of the ways in which electron spin resonance (ESR) spectroscopy may be useful to investigate systems of relevance to the biomedical sciences. Specifically considered are: spin-trapping in biological media; the determination of antioxidant efficiencies; lipid-peroxidation; the use of nitroxides as probes of metabolic activity in cells and as structumral probes of cell-membranes; ESR coupled with materials for radiation-dosimetry; food- and drug-irradiation; studies of enzyme systems and ofcyclodextrins; diagnosis of cancer and rheumatoid arthritis; measurement of oxidative stress in synovial tissue in preparation for joint replacement; determination of oxidative species during kidney dialysis; measurement of biological oxygen concentrations (oximetry); trapping in living cells of the endothelium-derived relaxing factor nitric oxide (NO); measurement of hydrogen peroxide; determination of drugs of abuse (opiates); ESR measurements of whole blood and as a means to determine the age of bloodstains for forensic analysis are surveyed, and also a determination of the aqueous volume of human sperm cells is described, among other topics.

The Use of Multi-frequency EPR Techniques to Identify the Radicals Produced in Irradiated β-Blockers

The identification of radicals trapped in irradiated drugs can be very intricate. A multi-frequency electron paramagnetic resonance (EPR) study is proposed to resolve this problem. The Q-band (ca. 34 GHz) comparison with X-band (ca. 9 GHz) did not show significant differences for the four beta-blockers studied (atenolol, esmolol, nadolol and propranolol). The use of a higher frequency (285 GHz) was required. It enabled us to determine the g-tensor values of the radicals present in atenolol and esmolol, respectively, g1 = 2.0086, g2 = 2.0059 and g3 = 2.0021 and g1 = 2.0066, g2 = 2.0044 and g3 = 2.0021. The latter was assigned as a phenoxyl radical, which can not be the case for the former. Therefore, radicals produced in esmolol may result from a more complex mechanism than the abstraction followed by the diffusion of an H atom inside the solid. In addition, two molecules as similar as atenolol and esmolol hydrochloride do not contain the same radicals after irradiation. These two conclusions drawn from the EPR results on beta-blockers show clearly the importance of continuing the investigations on radiolytic mechanisms in solid-state drugs.

The effect of ionizing radiation of 1,4-dihydropyridine derivatives in the solid state

Electron paramagnetic resonance (EPR) spectroscopy was used to investigate the gamma-radiation damage in the crystalline powder form of nine calcium channel blockers from the 1,4-dihydropyridine derivatives, which are in clinical use for treatment of arteria hypertension and ischemic heart disease. EPR studies have been carried out, showing the influence of irradiation and storage parameters on the nature and concentration of the free radicals trapped. EPR spectra of isardipine and felodipine showed single EPR line. EPR spectra of nifedipine, nisoldipine, nitrendipine, nimodipine, nicardipine and nilvadipine reveal a broad anisotropic signal of hyperfine interaction. No EPR signal was observed from amlodipine.

Electron Paramagnetic Resonance Spectroscopy Studies of Oxidative Degradation of an Active Pharmaceutical Ingredient and Quantitative Analysis of the Organic Radical Intermediates Using Partial Least-Squares Regression

Electron paramagnetic resonance (EPR) spectroscopy was used to study the radical species formed during the oxidation of an active pharmaceutical ingredient in the solid state. It was found that the extent of radical generation correlated to the formation of an oxidative degradation product. Multifrequency EPR and electron nuclear double resonance spectroscopy gave additional information on the identity of the organic radical species involved in the oxidation process, and a mechanism was proposed for the degradation, involving the formation of both carbon-centered and peroxy radicals. The multivariate analysis technique of partial least-squares (PLS) regression was then used to determine the extent of oxidation of the active pharmaceutical ingredient from the EPR spectra. The suitability of this approach was demonstrated from its application to a series of standards. The conventional approach for the quantitative analysis of EPR spectra is to measure the peak height or to perform double integration of the spectral region containing the signal of interest. Both of these methods have intrinsic errors associated with them, particularly for weak EPR signals with a poor signal-to-noise ratio or a sloping background response. The results obtained showed that greatly improved quantitation was obtained using the PLS regression approach.

Attempts at Correlation of the Radiolytic Species of Irradiated Solid-State Captopril Studied by Multi-frequency EPR and HPLC

The purpose of this study was to provide insight into the processes that occur after the irradiation of solid-state drugs. Electron paramagnetic resonance (EPR) experiments were performed at two different frequencies, X-band (about 9.5 GHz) and Q-band (about 34 GHz), to identify the radicals present in irradiated captopril. The results confirmed that an irradiated drug can trap several main radicals. Moreover, the radical composition varied as a function of the treatment. In addition, non-volatile final products were studied by liquid chromatography coupled to UV and to mass spectrometry (LC-MS). The variation of the radical composition did not influence the profile of the final products; this appears to indicate that, in the case of captopril, the trapped radicals observed by EPR are not the main precursors of the final products. Finally, high-performance liquid chromatography data appear to indicate that radiosterilization of captopril is feasible.

Electron paramagnetic resonance of some gamma-irradiated drugs

Some drugs, used mainly in treatment of some neurological diseases and hypertension were exposed to gamma-irradiation, and the samples were investigated by electron paramagnetic resonance (EPR). The observed spectra were interpreted in terms of some type of alkyl and amine radical fragments. The spectra were computer simulated and the g values of the radicals and the hyperfine structure constants of the free electron with nearby protons were determined. The species were found to be stable at room temperature for more than a year. The samples were found to display no EPR signal without irradiation.

Electron paramagnetic resonance of radicals induced in drugs and excipients by radiation or mechanical treatments

Radiation as well as mechanical treatments induced in drugs and excipients radicals, which can be studied by electron paramagnetic resonance. A special attention is pointed about the use of electron paramagnetic resonance (EPR) to bring the proof whether or not a drug has been irradiated or not. We also discuss of other methods (thermoluminescence (TL), gas phase chromatography (GPC)) which can be used to bring the same proof in case of irradiated drugs, excipients and cosmetic products.