Anal Bioanal Chem (2011) 400:1577–1582 DOI 10.1007/s00216-011-4699-7

FEATURE ARTICLE

Maria Skłodowska Curie—the precursor of radiation sterilization methods Wojciech Głuszewski & Zbigniew P. Zagórski & Quoc Khoï Tran & Laurent Cortella

Published online: 14 February 2011 # Springer-Verlag 2011

Introduction A resolution of the 63rd Assembly of the United Nations proclaimed the year 2011 as the International Year of Chemistry. The coordinators of the event are UNESCO and the International Union of Pure and Applied Chemistry (IUPAC). The patroness of this event is Marie Curie, née Skłodowska. Among women scientists, she was the first recipient of the Nobel Prize, and among all scientists, she is the only one who has received this award in different scientific fields (in 1903 in the field of physics with Pierre Curie and Henri Becquerel, in 1911 in the field of chemistry). Considering the former Polish nationality of Marie Curie, the year 2011 has been proposed by the Polish Parliament as her year, using the name Maria Skłodowska Curie, under which she is known in Poland. Celebrating the International Year of Chemistry is a good opportunity to remember the importance of the work of Maria Skłodowska Curie for the emergence and development of many fields of science. This article is an attempt to present a view of science, as taught through modern applications of the radiation chemistry of polymeric materials and radiation sterilization. Although the real Published in the special issue Radioanalytics - Dedicated to Marie Skłodowska-Curie with Guest Editors Boguslaw Buszewski and Philippe Garrigues. W. Głuszewski (*) : Z. P. Zagórski Institute of Nuclear Chemistry and Technology, ul. Dorodna 16, 03-195 Warsaw, Poland e-mail: [email protected] Q. K. Tran : L. Cortella ARC-Nucléart, Atelier Régional de Conservation, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France

development of both “cold” sterilization and polymer technology occurred in the 1950's, long after the death of Marie Curie Skłodowska, the original ideas go back to her work performed in the 1920s. Sometimes, and that is the present case, a single scientist creates a new field, in spite of the fact that at the time of discovery there are no applications. The parallel development of other branches of science and technology helps the application of the original idea.

Radiation sterilization Large parts of radiation chemistry deal with the chemical effects induced by ionizing radiation on matter. Working with aqueous solutions of radium salts, Maria Skłodowska Curie noticed that water under the action of α radiation breaks down into hydrogen and oxygen, which by analogy to electrolysis she called radiolysis. One can now discuss whether this is the most suitable term, but it has been adopted in science and is widely use. Much more important from the viewpoint of radiation chemistry of polymers is the paper “Sur l’étude des courbes de probabilité relatives à l’action des rayons X sur les bacilles” which appeared in the bulletin of the French Academy of Sciences in 1929 (Fig. 1). Maria Skłodowska Curie [1] presented the results of experimental and theoretical studies of the effects of X-rays on bacteria. Today, we can say that Maria Skłodowska Curie’s paper was the first work on radiation sterilization. At the beginning of the twentieth century, however, it was difficult to imagine the implementation of an industrial-scale idea to inactivate pathogens by radiation. Large radiation sources were not available. At that time, medical devices made of metal, glass or wood were conveniently sterilized by

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thermal methods. The study by Maria Skłodowska Curie tried to draw attention to the fact that X-ray radiation can be harmful to living organisms. For the first time it provided a quantitative relationship between the survival of bacteria and the absorbed dose of radiation. It is worth recalling that Maria and her daughter Irène were engaged in volunteer nursing of wounded soldiers at the fronts in the First World War and worked in mobile X-ray stations. During that time, radiation protection did not exist. Radiation was considered a universal remedy for many health problems. One can suppose that such scientists received radiation doses far greater than at the time of scientific research with radioisotopes. The question is whether today we would be able to estimate how big the doses involved in such treatments were. Such a study does not appear hopeless. We know now that ionizing radiation leaves almost permanent traces in Fig. 1 Front page and page with inactivation curves in the historical paper by Maria Skłodowska Curie

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irradiated solids that can be detected by electron spin resonance (ESR). Estimates of doses from older natural radioactive sources, collected from mineral artefacts and human bones of people living in 1160 BC, were done at the author’s institute in Warsaw [2]. The same was done in the case of radiation doses received by women patients during the radiation incident at a hospital in Bialystok (80 Gy) [3]. Bones are known as a natural dosimeter, which collects and stores the most essential information about the absorbed dose of radiation. To solve the riddle of whether the radiation contributed to the death of nuclear scientists, one should have appropriate research material, such as a piece of a tooth. The problem seems to be purely theoretical because the families have not given permission to study the remains of such scientists. Hopefully, as is done now with historical persons, examined for their DNA spectra, similar investigations will be possible to measure

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Fig. 1 (continued)

ESR fingerprints, revealing their exposure to ionizing radiation in the past. Returning to the theme, we can tell that the 1930s was the beginning of interest in radiological protection. It was supported by radiobiology, dosimetry and physics of absorption of ionizing radiation. A quantitative approach to sterilization had to be expressed in mathematical terms. The basic equation, derived by Maria Skłodowska Curie, is N ¼ No ekD ; where N is the number of bacteria that survive the irradiation experiment. It depends on the initial number of organisms, NO, the absorbed radiation dose, D, and the resistance of the bacteria, k. As one can see, the radiation dose required for

sterilization depends on the initial contamination of the irradiated product and the “size” of bacteria cells. This explains why among other things it is hard to get rid of the virus and why very higher doses of radiation are required, “not to mention the indirect actions of irradiated matrix on microorganisms”. The idea of inactivation of pathogens using ionizing radiation reappeared with the invention of disposable medical devices. This was possible with the discovery of new catalysts to produce new polymer materials. Most commercial, cheap polymers are sensitive to high temperatures, and cannot be sterilized by heat and require special methods called cold sterilization. Gamma rays and electron beams have been excellent for these purposes. Due to the competition of well working radiation sterilization, sterilization with ethylene

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oxide (EtO) has been refined to give satisfactory low level of remaining EtO in the medical device, and catalytically burning of the EtO used in the chamber before. Therefore the environment is protected. Both methods are used, sometimes by the same manufacturer. Organization in the factory is easy because the devices are put into similar package with nanoporous one wall. Radiation is a unique method for effective sterilization of the device in the entire volume at any temperature, even at subzero Celsius temperature. The search for new polymeric materials for the production of medical utensils initially stimulated the development of radiation chemistry of polymers. A lot of objects have been manufactured that undergo commercial sterilization using both gamma rays and electron beams. Currently, an estimated 50% of disposable medical devices are sterilized by irradiation. No one could have suspected the realization of Maria Skłodowska Curie’s concept at the time of publication of her paper.

Radiation chemistry of polymers Further research in the field of radiation chemistry led to a number of polymers processed by ionizing radiation in different areas, i.e. in the process of radiation cross-linking of polymers, which is commercially used in the manufacture of heat-shrinkable materials, pipes for transporting hot water in the production of car tyres and automotive accessories [4]. One can create cross-links at any temperature and additionally in the case of radiation processes, the phenomenon is easily controlled. Among various topics which currently deal with radiation chemistry and the radiation chemistry of polymers, two issues have most recently been investigated by the authors. The first is the fact that multi-ionization spurs are very often neglected. Spurs (80% are singles) are defined in the field of radiation chemistry as zones of primary events of chemical phenomena. From the standpoint of energy deposition of ionizing radiation in matter, gamma rays and electron beams are equivalent [5]. In both cases, almost the entire energy is transferred by secondary electrons. First generations of high-energy electrons produce single spurs at relatively large distances from one another. Only electrons which finish their travel in the material, and have low energy, deposit a comparatively large amount of energy in a small volume of the polymer, causing degradation of the polymer chain and formation of low molecular weight products. Many scientific papers have neglected this 20% of energy associated with multi-ionization spurs. In

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Fig. 2 Mammoth Khroma is placed in the chamber for radiation sterilization

practice, observation of multispurs is extremely difficult because in reality we have to deal with the whole range of slots set aside for energy. Work carried out by the authors indicates, however, it is possible [6]. The second phenomenon, which was not known during the time of Maria Skłodowska Curie, is interesting both to radiobiologists and to radiation chemists: the protective effect [7]. Extremely resistant to ionizing radiation, aromatic structures are able to dissipate the part of the energy absorbed by the molecules of other compounds present in their neighbourhoods. Discussions are continuing on the effect of movement of the so-called positive hole, the primary product of ionizing radiation and also secondary energy excited state. Our studies with the help of diffuse reflection spectrophotometry and gas chromatography indicate that in the case of simple polymers such as polyethylene, polypropylene and styrene, a positive hole

Fig. 3 French and Russian specialists preparing an exhibit for irradiation

Maria Skłodowska Curie—the precursor of radiation sterilization methods

transfer may take place at a distance of several monomer units [8]. How far are we from the original sterilization ideas of Maria Skłodowska Curie? Let us now mention the recent case of an unexpected application of the biocide effect of ionizing radiation with the sterilization of the mammoth Khroma. The operation was described in the media, e.g. as diffused by diverse press agencies [9–11] or in the French journal of popular science Sciences et Avenir [12] (Fig. 2). The aim of the treatment was to improve the preservation of the baby frozen mammoth specimen, which was older than 50,000 years, before further scientific investigations are undertaken and before it will be displayed to the public in a museum. It was feared, for instance, that it could carry traces of spores of Bacillus anthracis. The task was complicated owing to the size of the object and the low temperature. Only the sterilization method using gamma radiation satisfied the demand. The treatment was realized during July 2010 in Grenoble by ARC-Nucleart (Fig. 3), a conservation workshop specializing in gamma disinfestations of cultural heritage artefacts, known also for the disinfection of the mummy of Ramses II in 1977 [13]. The frozen specimen was exposed to 60Co gamma rays for 50 h at a mean dose rate of 400 Gy/h. The resulting dose of 20 kGy allowed reduction of potential traces of Bacillus anthracis by a factor of at least 104, which was sufficient in regard of the potential initial level of contamination and of the further behaviour of the specimen (which differs slightly from surgery devices). But the sanitary improvement was not the only consequence of the treatment. As a middle way between food sciences and cultural heritage sciences, the treatment offered scientists and conservators unanticipated help to maintain the very well preserved flesh of the specimen in such a good state during the following periods of thawing, as necessitated for the study and surely for the future taxidermy of the baby mammoth.

References 1. Skłodowska Curie M (1929) Compte Rendu 198:202 2. Sadło J, Michalik J, Stachowicz W, Strzelczak G, DziedzicGocławska A, Ostrowski K (2006) Radiat Phys Chem 51(Suppl 1):421–423 3. Trompier F, Sadlo J, Michalik J, Stachowicz W, Mazal A, Clairand I, Rostkowska J, Bulski W, Kulakowski A, Sluszniak J, Gozdz S, Wojcik A (2007) Radiat Meas 42:1025–1028

1581 4. Bik J, Głuszewski W, Rzymski WM, Zagórski ZP (2003) Radiat Phys Chem 67:421–423 5. Tallentire A, Miller A, Helt-Hansen J (2010) Radiat Phys Chem 79:701–704 6. Głuszewski W, Zagórski ZP (2005) In: INCT annual report 2005. Institute of Nuclear Chemistry and Technology, Warsaw, p 42 7. Do TT, Tang VJ, Aguilera JA, Milligan JR (2010) Radiat Phys Chem 79:1144–1148 8. Głuszewski W, Zagórski ZP (2008) Nukleonika 53(1):21–24 9. Mesquita R (2010) Ice Age baby mammoth on display at French museum. Associated Press, 16 Jul 2010 10. Agence France Presse (2010) Le plus vieux bébé mammouth du monde sera exposé jeudi soir au Puy-en-Velay, 13 Jul 2010 11. RIA NOVOSTI (2010) Un bébé mammouth sibérien présenté jeudi en France, 14 Jul 2010 12. Mulot R (2010) Sci Avenir 763:68 13. Balout L, Roubet C (1985) La momie de Ramsès II – contribution scientifique à l’égyptologie. Recherche sur les Civilisations, Paris, chap 9

Wo j c i e c h G ł u s z e w s k i i s Secretary-General of the Polish Nuclear Society. He works as an assistant professor at the Centre of Radiation Research and Technology, Institute of Nuclear Chemistry and Technology, in Warsaw and is a specialist in the field of radiation chemistry and technology. He is currently dealing with issues of radiation modification of polymer materials. He recently studied the protective effects in the radiation chemistry of polypropylene. Wojciech Głuszewski works in the IAEA expert group dealing with issues of the application of nuclear techniques for the characterization and preservation of cultural heritage artefacts. He is a member of the Polish Radiation Research Society memorial to Maria Skłodowska-Curie and the editor of the Polish quarterly Advances in Nuclear Technology.

Zbigniew P. Zagórski a professor, works experimentally in the field of radiation chemistry, both basic (pulse radiolysis) and applied (radiation processing). Recently, his interests have reached fields far from those mentioned, as one can see in his chapter “Role of radiation chemistry in the origin of life, early evolution and in transportation through cosmic space”, in an astrobiological monograph (2010), supported by original papers, in the Springer journal Origins of Life and Evolution of Biospheres.

1582 Quoc Khoï Tran has been a senior conservation scientist at the ARC-Nucléart conservation laboratory since 1981. ARCNucléart, located in the CEA research centre in Grenoble, France, has implemented gamma irradiation technology for 40 years for the disinfection and the consolidation of wooden cultural heritage artefacts. His main research activities are the development of radiation-curing resins for the consolidation of artefacts initially in both the dry and the waterlogged states. He is also a senior expert in the field of the application of gamma irradiation for cultural heritage and industrial issues. He is Technical Expert for the IAEA, and participates in the IAEA European Technical Project RER 8/015 entitled “Using nuclear techniques for the characterisation and preservation of cultural heritage in the European region” (managed by the Europe division of the IAEA department of

W. Głuszewski et al. technical cooperation for the period 2008-2011). He is also in charge of the transfer of consolidation technology to other countries, especially to tropical ones with high humidity and high risk of insect attack. Laurent Cortella is a head of facility and research engineer at ARC-Nucléart, Grenoble, France, a conservation laboratory and workshop linked to the CEA, the French Ministry of the Culture, the Rhône-Alpes region and Grenoble city, and is mainly interested in conservation of organic materials. He mainly assumes the technical management of the irradiator, and irradiation services for conservation of cultural heritage artefacts and other artefacts. He is also interested in research into the effects of radiation on cultural heritage material.