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Self-assembled monolayers (SAMs) are ordered molecular assemblies of organic molecules that form spontaneously on the substrate surface by exposing the substrate to a solution or gas containing molecules with self-assembling properties. Their application can change the surface properties of an object by forming a barrier between the substrate material and its environment. Therefore, their application has been extensively studied, including the protection of metals. Among their many advantages, studies have shown that while SAMs of many molecules exhibit good short-term protective properties, they are easily removed from the surface when exposed to corrosive media. Accordingly, many studies have focused on improving the long-term protective properties of SAMs. Crosslinking the already well- ordered molecular layer on the surface of a metal would make the film more resistant and significantly extend its lifetime by reducing the penetration of external molecules into the coatings. Radiation crosslinking is the process of using high-energy gamma rays or electron beams to initiate rapid chemical reactions between monomers and/or polymers that follow the free radical mechanism. The radiation-induced crosslinking is homogeneous, fast and can be carried out at room temperature without the use of solvents, initiators and/or catalysts. In this work, SAMs of different fatty acids were crosslinked on copper using gamma radiation. The protective properties of the crosslinked coatings were investigated by electrochemical measurements under simulated atmospheric conditions, while the surface properties of the coated metals were studied by contact angle measurements, Fourier transform infrared spectroscopy, and atomic force microscopy. The results have shown that crosslinking of the coatings significantly improves the long-term properties. Acknowledgements: We thank the Croatian Science Foundation (HRZZ IP-2020-02-4344) for supporting this research.

Corrosion causes major financial losses worldwide every year, and due to increasing air pollution, metals such as copper tend to degrade faster. Conventional methods of protecting metals, such as coatings, often contain toxic degradation products, so there is a need to develop a new environmentally friendly method of protecting metals. Fatty acids are non-toxic compounds that have an affinity for metals and self-assembling properties, forming self-assembled monolayers (SAMs) on the metal surface. In addition, SAMs from fatty acids can be crosslinked by gamma radiation, resulting in polymer nanocoatings with improved stability, durability, and other important properties. The aim of this research was to investigate the influence of double bonds and conformations of fatty acids on the protective properties of the nanocoatings obtained upon crosslinking using gamma irradiation. The influence of double bonds was investigated using two fatty acids: stearic acid, C18H36O2, a saturated fatty acid, and elaidic acid, C18H34O2, an unsaturated trans fatty acid. Two monounsaturated fatty acids with the same number of carbon atoms, C18H34O2: oleic acid, a cis-fatty acid, and elaidic acid, a trans-fatty acid, were used to study how the conformation of the fatty acids’ double bond affects the corrosion protection properties upon crosslinking. The properties of the obtained coatings under simulated atmospheric conditions were investigated using electrochemical impedance spectroscopy and Tafel extrapolation method, while the hydrophobic properties of the coated copper surface were determined using contact angle goniometry. The results showed that the saturated fatty acid (stearic acid) exhibited better protective properties compared to elaidic acid, while oleic acid showed slightly inferior properties compared to elaidic acid. We thank the Croatian Science Foundation (HRZZ IP-2020-02-4344) for supporting the research.

Selfassembled monolayers (SAMs) are an important element of modern nanotechnology and surface functionalization. Recently, the application of SAMs for corrosion protection of various metals has been reported. Studies have shown that while SAMs exhibit significant short-term protective properties, their long-term protective properties are not significant because SAMs are removed from the metal surface when exposed to corrosive media. Crosslinking of SAMs improves both their short- term and long-term protective properties. It has been shown that SAMs from fatty acids on metals can be efficiently crosslinked by gamma irradiation in an inert air atmosphere. The doses required for crosslinking under these conditions are in excess of 100 kGy. The irradiation dose is one of the main factors determining the price of the commercial irradiation process. Therefore, the possibility of reducing the irradiation dose for a given crosslinking process is an important consideration that should be investigated. In this work, a SAM of elaidic acid, an unsaturated trans fatty acid with 18 carbon atoms, HOC–(CH₂–)₇CH=CH–(CH₂–)₈H and with the double bond in trans configuration, was applied to copper. The crosslinking of SAM was studied under different conditions, in air and in solvents. Figure 1 shows the studied SAM and the nanocoating crosslinked by gamma irradiation. The protective properties of the coatings were studied by electrochemical methods (polarisation measurements and electrochemical impedance spectroscopy) under simulated atmospheric conditions (0.2 g/L Na2SO4 + 0.2 g/L NaHCO3 + 0.2 g/L NaNO3 at pH 5). The hydrophobicity of the coatings was investigated by contact angle measurements, while the surface morphology was studied by atomic force microscopy. The results showed that it is possible to obtain similar protective properties when the SAM is crosslinked in an inert air atmosphere and in inert water media. Acknowledgements: We thank the Croatian Science Foundation (HRZZ IP-2020-02-4344) for supporting this research.

Background of the study. Gamma radiation is a very well-known and well-established non-contact physical method for microbial decontamination of food, preserving food and increasing its shelf- life. Since this process is non-thermal, gamma irradiation is often called a cold-pasteurisation method. Consequently, this method can be potentially applied in different technologies for food storage and processing. Considering the known fundamental effect of ionizing radiation in complex material like food is, an original assumption is made that gamma irradiation applied in food processing could result in cleaner fermentation and favorable chemical composition of fermented fruit mash. This assumption could be valid also for distillates. It is known that due to its toxicity, methanol is an undesirable fraction in distillation process, which must be separated very carefully, which is not always easy to achieve in conventional technologies. Therefore, there is a need in spirit technologies to find the appropriate method and conditions for a possible reduction of methanol formed during the mashing process thus reducing the possibility of the presence of traces of methanol in the distillate. The aim of this research was to confirm the assumption above and suggest gamma radiation as a potential method for improvement of quality and technology for preparation of fruit distillates. Methodology. Plums cv. Elena (Prunus domestica) were subjected to gamma irradiation at the panoramic 60Co source at the Radiation Chemistry and Dosimetry Laboratory at the Ruđer Bošković Institute. Irradiation were performed in the air at two irradiation doses (5 and 10 kGy) and the dose rate of 1.1 kGy/h. After de-stoning and mashing fermentation was conducted with Saccharomyces cerevisiae var. bayanus yeast strain. Distillates from the irradiated plums mash were produced by using a simple pot still. After preparation procedures, the samples of distillates were analyzed by gas chromatography (Shimatzu, GC2010) and organoleptically. Results. In comparison with the control sample, GC-FID analysis of distillates determined an impact of irradiation on the methanol content and reduction rate of 2 mg/mL a.a. (absolute alcohol) at the dose of 5 kGy and 3 mg/mL a.a. at the dose of 10 kGy, respectively. Moreover, distillates produced from irradiated plums showed the favorable composition of other volatile compounds. The concentrations of acetaldehyde and ethyl acetate decreased with the increasing absorbed irradiation dose, while higher alcohols (3-methyl- 1-butanol, 2-methyl-1-butanol, 1-propanol, 2- methyl-1- propanol) were not affected by irradiation significantly. Conclusion. Results obtained suggest that ionizing irradiation might be a suitable method for methanol reduction alternative other conventional technologies. Simultaneously better chemical properties in plum spirit could be achieved as compared with non-irradiated samples.

Copper has been used extensively throughout history, and still is today, in a wide range of applications. Due to increasing air pollution, metals including copper can degrade faster causing large financial losses. Thus, the surface of metals needs to be protected with coatings. However, traditional coatings’ degradation products are toxic which is why they don’t satisfy today’s environmental requirements. Fatty acids spontaneously form self-assembling monolayers (SAMs) on the surface of copper due to their affinity for metals. They have the potential to replace traditional coatings because they are non- toxic compounds. The main disadvantage of SAMs is that they are relatively easily removed from the metal surface when exposed to a corrosive environment. Using gamma irradiation, SAMs can be crosslinked into polymer nano-coatings (PNC) with improved properties and durability. In this work, fatty acids with different conformations have been used for obtaining PNCs. Two mono-unsaturated fatty acids: oleic acid (OA), a cis fatty acid, and elaidic acid (EA), a trans fatty acid, C18H34O2, have been self-assembled and crosslinked using gamma irradiation on the surface of copper.

Stilbene derivatives have been in the focus of scientific interest over the years as model compounds in the fundamental investigation of their E-Z photoisomerization reaction [1]. In this work, photochemical reactivity in the Z-E isomerization for two heterostilbenes containing 1, 2, 3-triazole unit were investigated theoretically and experimentally by irradiation experiments, fluorescence and laser flash photolysis (LFP) [2]. Fluorescence measurements for ortho-methyl derivative 1 indicated that the Z → E isomerization takes place in an adiabatic reaction on the potential energy surface of the S1 state. On the contrary, the para-nitro derivative 2 undergoes the Z → E isomerization via a triplet excited state, which was detected by LFP. All experimental observations were corroborated by computations. The mechanistic investigation presented gives insight in the fundamental and simple Z → E isomerization and provides new findings which are important in the rational design of different photoreactive diarylethene derivatives used in different fields of science.

Corrosion is the spontaneous degradation of a material (usually a metal), causing major financial losses in the world every year. Self- assembled molecular layers (SAMs) have recently been investigated as a cheap and safe protective coating, that is easy to apply. Fatty acids have self-assembling properties with an affinity for metals and their degradation products are mostly non-toxic, making such protection environment friendly compared to conventional methods. In order to prolong their longevity, and improve their stability and protective properties, we propose crosslinking of SAMs using ionizing radiation (gamma rays) which results in more resistant and stronger coatings. The protective efficiency of coatings depends on many parameters, primarily the preparation procedure. In this work, the influence of irradiation atmosphere and fatty acids’ application method to the surface of copper was investigated. Crosslinking in air was compared to crosslinking in water, and three application methods of EA from an ethanol solution onto copper were investigated: (1) immersion, (2) application by spraying and (3) application by brush.

Background of the study. Copper is a malleable and ductile metal with numerous advantages and a wide range of applications. To protect it copper surface may be coated. Many of the different coatings used are unsafe for the environment so the development of protective coatings that satisfy environmental requirements is a serious scientific challenge. Fatty acids are long chain molecules and non-toxic compounds that spontaneously form self-assembled monolayers (SAMs) on metal surface. Fatty acid SAMs are hydrophobic and block water access to the metal. However, the main flaw of SAMs coatings for corrosion protection is that they get relatively easily desorbed in corrosive conditions. That problem may be solved by crosslinking SAM film consisting of unsaturated fatty acids but most of the agents used for classical crosslinking are toxic. By radiation crosslinking toxic agents are avoided and more durable and stable SAMs films that retain numerous advantages are obtained. The protective efficiency of coatings developed this way depends on the type of fatty acid used, preparation conditions, and the environment metal is exposed to. In this work, the protective efficiency of coatings prepared with different unsaturated fatty acids is compared. Methodology. SAMs on the copper surface were obtained of several unsaturated trans-fatty acids with different positions of the single double bond. The SAMs were then irradiated with gamma radiation to selected absorbed doses. The radiation effects on the coatings were assessed by FTIR, their hydrophobicity was tested by contact angle goniometry. Protective properties of irradiated coatings were investigated by electrochemical methods in a solution simulating urban atmospheres. Polarization methods were used to determine the optimal crosslinking doses and electrochemical impedance spectroscopy was used to study the long-term behavior of the coatings. Results and conclusions. While all studied SAMs coatings offer good protective properties to copper in atmospheric conditions after irradiation the properties are significantly improved. Upon irradiation to appropriate doses, the SAMs can be efficiently crosslinked what increases their stability and protective properties. Upon irradiation, the protective efficiencies of all the coatings increase significantly offering protection. We thank the Croatian Science Foundation (HRZZ IP- 2020-02-4344) for supporting the research.

Rosuvastatin je lijek skupine statina koji se koristi za regulaciju visoke razine kolesterola u ljudskom tijelu. Isto tako, rosuvastatin i ostali statini pokazuju zaštitnu ulogu protiv oksidativnog stresa uzrokovanog slobodnim radikalima. Cilj ovog istraživanja bio je identificirati krajnje produkte koji su nastali radikalnom razgradnjom rosuvastatina. Kako bi se potaknula radikalna razgradnja, vodena otopina rosuvastatina ozračena je različitim dozama gama zračenja (50-1000 Gy) pri oksidativnim uvjetima. Rosuvastatin i srodni degradacijski produkti odvojeni su nanoC18 kolonom gradijentnom elucijom, a identifikacija je provedena pomoću vezanog sustava nanoUPLC i nanoESI-QTOF. Pomoću točno mjerenih masa, zajedno s algoritmom usporedbe izotopnih raspodjela, provedena je elementna analiza kojom je identificirano devet degradacijskih produkata. U ovom je istraživanju po prvi puta provedena gama-inducirana razgradnja rosuvastatina te detaljno opisana kemijska struktura, MS/MS fragmentacija te mehanizam nastanka pojedinog degradacijskog produkta. Priloženi rezultati doprinose razumijevanju razgradnog puta rosuvastatina i ostalih statina pri gama zračenju.

Crosslinking of a well-ordered layer of self- assembled molecules (SAMs) on the surface of copper additionally enhances SAMs protective properties by improving their functional properties as well as reducing penetration of external molecules into the coatings [1]. Thus, the obtained polymer nanocoating (PNC) has significantly higher stability and better protective properties while retaining SAMs numerous advantages. In this work elaidic acid (EA), a non-toxic unsaturated fatty acid (FA) was used as the self-assembling molecule, while crosslinking was initiated by ionizing irradiation. By using irradiation toxic agents that are used for classical crosslinking can be avoided, while on the other hand the process is homogeneous, fast and simple to perform. Since FAs are environment friendly molecules and crosslinking is performed without toxic agents the process can be considered as a Green Technology [2]. The aim of this work was to reduce the irradiation dose needed for successful crosslinking of a SAM of EA on copper by changing the irradiation media from air to water. Namely, previous research has shown that EA SAMs can be successfully crosslinked in air with 110 kGy. Reducing the applied irradiation dose would reduce the treatment price. This work has shown that when irradiated in water doses can be reduced to 40 kGy, but the polymer coatings obtained by crosslinking in air have somewhat better properties. The obtained coatings properties were investigated by contact angle measurements and FTIR Spectroscopy, while their behavior in atmospheric conditions was studied by electrochemical methods (Tafel extrapolation method and electrochemical impedance spectroscopy). ACKNOWLEDGEMENTS: We thank the Croatian Science Foundation (HRZZ IP-2020-02-4344) for supporting the research. REFERENCES [1] A. Pathania, J. Sharma, R. K. Arya, S. Ahuja. Prog. Org. Coat. 2018, 114, 78. [3] Woods, R.J. & Pikaev, A.L. Applied Radiation Chemistry: Radiation Processing (John Wiley & Sons, Inc., 1994).

Photodynamic therapy (PDT) is a cancer treatment that has been increasingly investigated. Photosensitizer (PS), light and oxygen are main components of PDT, and in their combination reactive oxygen species (ROS) are produced, which can lead to cytotoxic effect within the cell and consequent destruction of cancerous tissue [1]. The desired characteristics of the PS include stability of the molecule, high production of singlet oxygen and other ROS, good absorption in red or infrared region, negligible toxicity without irradiation and relative fast excretion from the body [2]. Porphyrins are often used as PSs because their structure can be relatively easily modified to achieve adequate lipophilicity of the molecule, or chelated by different cations, such as Zn(II) in our work. Amphiphilic molecules can facilitate cellular uptake while maintaining good water solubility [3], and Zn(II) is expected to increase the lifetime of the excited triplet state (3PS*), and thus the production of singlet oxygen [4]. In addition to the PS, light also plays an important role in PDT, so the optimal dose of light and the appropriate irradiation wavelenght should be selected [5]. Here we will present two groups of tripyridylporphyrins, Zn(II) and free-based, both conjugated with chains of different length. Spectroscopic properties of the ground state, as well as the excited state, of the obtained compounds were studied by using laser flash photolysis (LFP) and time-resolved single photon counting (TC-SPC). Lipophilicity and singlet oxygen production, which was investigated by using modified relative methods, will also be presented. In vitro studies of the PSs’ biological properties included evaluation of cytotoxicity on melanoma cell line (MeWo) and human foreskin fibroblasts (HFF), with two light sources used for photoactivation, with irradiation wavelength at 605 nm (orange light) and 645 nm (red light).

This study was undertaken to determine the possible harmful effects of gamma radiation on the materials commonly used as binders in artwork paint layers. Six types of binders were taken for investigation divided into two groups according to their chemical structure ; (i) polysaccharide binder, that is, Arabic gum and (ii) protein binders which include egg white, egg yolk, whole egg, casein and animal glue. The binders were exposed to radiation doses of 2, 7, 10, 25 and 100 kGy. Two different dose rates were used, a larger dose rate Ḋmax = 7, 695 Gy/s, and a lower dose rate Ḋmin = 69.98 Gy/s. After irradiation, colour changes of the binders were measured by UV-VIS spectrophotometer. Possible changes in the molecular structure were measured with the ATR FTIR spectrometer. Subsequently, all six binders were mixed with lead white pigment, and prepared samples were subjected to the same irradiation treatment as the binders themselves to investigate the influence of the most common pigment used in historic canvas paintings. Some noticeable changes in colour and structure were observed, but only at dose rates significantly greater than doses applied for radiation treatment of cultural heritage. References: 1. Adrović Feriz, Gamma Radiation, InTech, London, 2012, IX. 2. AL-Assaf Saphwan, Coqueret Xavier, Khairul Zaman Haji Mohd Dahlan, Ulanskirmurat sen Piotr, The Radiation Chemistry of Polysaccharides, International Atomic Energy Agency, Vienna, 2016, 79. 3. AL-Bachir Mahfouz, Zeinou Ruba, Effect of gamma irradiation on some characteristics of shell eggs and mayonnaise prepared from irradiated eggs, Journal of Food Safety, Vol. 26., No. 4., 2006, 348. – 360. 4. Alijani Samira, Balaghi Sima, Mohammadifar M. Amin, Effect of gamma irradiation on rheological properties od polysaccharides exuded by A. fluccosus and A. gossypinus, International Journal of Biological Macromolecules, Vol. 49., No. 1., 2001, 471. – 479. 5. Anglemie A. F., Montgomery M. W., Amino Acids, Peptides, and Proteins, Food Science, Vol. 4., 1976, 205.-284. 6. Arihara K., Ishikawa, Itoh M., I.-S., Tamaki S., Egg Yolk Protein and Egg Yolk Phosvitin Inhibit Calcium, Magnesium, and Iron Absorptions in Rats, Journal of Food Science, 72, 6, 2007, 412. – 419. 7. Atgie Marina, Composition and structure of gum Arabic in solution and at oil- water interfaces, Université de Toulouse, Institut National Polytechnique de Toulouse (INP Toulouse), Toulouse, 2018. 8. Bhat Younus Mohd, Dar Ali Taanver, Singh Rajendrajumar Laishram, Casein Proteins: Structural and Functional Aspects, in: Gigli Isabel (ed.), Milk Proteins - From Structure to Biological Properties and Health Aspects, INTECH, London, 2016, 3.-18. 9. Bretscher L.E., Holmagren S. K., Taylor K.M., Code for collagen’s stability deciphered, Nature, Vol. 6677, No. 392, 1998, 665.-667.

The application of radiation technology has proven to be a superior methodology compared to other techniques used for decontamination and/or preservation of cultural heritage in times of crisis. It is particularly suitable and effective for the prevention of large-scale biological degradation of works of art endangered by the war since a large number of objects needed to be processed in a short period. There is no other technology that can treat such large amounts of objects in a matter of hours. One of the most significant examples of the application of this technology in times of crisis is its use during the Croatian War of Independence from 1991- 1995. Wartime conditions, maintenance and preservation without continuity, relocations, and inadequate temporary storage facilities cause major deteriorations of cultural heritage. The war in Croatia seriously jeopardized Croatia’s cultural heritage. Rescue, evacuation and protection of cultural heritage affected by the war in Croatia was a serious challenge for many experts from various fields, as well as volunteers, involved in the protection of cultural goods. During the autumn of 1991, due to war destructions, conservation and restoration institutes began an extensive operation to save cultural heritage. Around 5000 objects, mostly wooden polychrome sculptures, paintings and parts of altars, were evacuated. In order to reduce the problem of large-scale biodegradation, the Croatian Conservation Institute decided to apply the radiation method to works of art using the irradiation device at the Ruđer Bošković Institute. This example of the use of the radiation method to rescue cultural heritage endangered by the war in Croatia was recognized by international experts as a particularly successful example of applying this method and is to this day presented as an example of the efficiency of this unique technique in times of crisis. 1. Katušin- Ražem, B., Braun, M., Ražem, D. Massive Preservation of War-Damaged Cultural Heritage Objects in Croatia by Irradiation. In: “Uses of Ionizing Radiation for Tangible Cultural Heritage Conservation”, IAEA Radiation Technology Ser. No. 6, IAEA, Vienna, 2017.

A convenient way to obtain a compact, flawless coating with nano-order thickness is by forming thin self-assembled molecular layers (SAMs). Crosslinking of the SAMs hardens the coatings, reduces penetration of external molecules, improves mechanical strength and chemical resistance, as well as other functional properties making such coatings more resistant and significantly extending their lifetimes. Radiation crosslinking refers to the process where high energy radiation, gamma-rays or fast electrons are used to induce a chemical reaction that results in formation of a 3D network. If for self-assembling is performed with an environment friendly compound like a fatty acid the use of the obtained coatings would be non-toxic and completely safe for the person applying the coating, as well as the person handling the coated object. Irradiation conditions are crucial for obtaining crosslinked coatings, but also other parts of the process can influence the outcoming properties of the coatings. The aim of this study is to determine the influence of the conditions in which the SAMs are formed on copper on the properties of the radiation crosslinked films used for protection of copper in atmospheric conditions: the influence of the formation of an oxide layer on which the coatings are formed, on the conditions of the self-assembling process from an ethanol solution, and the influence of drying after self-assembling. All these steps are performed prior to gamma irradiation. Elaidic acid, C₁₈H₃₄O₂, a trans-fatty acid, is used for preparation of the coatings on copper and the obtained crosslinked coatings protective properties are studied in a solution simulating atmospheric conditions. The investigations are performed by electrochemical techniques and by Attenuated total reflectance surface-enhanced infrared spectroscopy, ATR-SEIRAS. We thank the Croatian Science Foundation (HRZZ IP- 2020-02- 4344) for supporting the research.

Amphiphilic cationic porphyrins have shown high potential in use as photosensitizers (PSs) for photodynamic therapy (PDT). Our research group has shown that compounds conjugated with long chain (C18) have an exceptional PDT effect compared to hydrophilic analogues on different tested cell lines. Unfortunately, highly effective amphiphilic compounds showed reduced selectivity to tumour cells, relatively high dark toxicity, and their aggregation was observed in high concentration. It must be kept in mind that the optimal ratio of hydrophilic and hydrophobic moieties is necessary to facilitate passage through the membrane bilayer, while maintaining good solubility in water and avoiding formation of aggregates that reduce the PDT effect. Chelation with Zn(II) alters the properties of free base porphyrins ; it changes lipophilicity of the compounds and may increase the lifetime of the excited triplet state (3PS*). The change also occurs in the absorbance spectra, as expected the number of Q bands reduces from four to two and there is a negligible absorption above 610 nm for these compounds to be efficiently activated with red. Therefore, we suggest photoactivation using LED based source of orange light, which better corresponds to the optical properties of Zn(II) porphyrins while maintaining good penetration through the tissue.In this work, we will present the synthesis of two groups of N- methylated tripyridylporphyrins, free base and chelated with Zn(II), both conjugated to alkyl chains of different length. Their photophysical and photochemical properties studied in different solvents, by laser flash photolysis (LFP) and timeresolved fluorescence spectroscopy (TRF) will be presented. The impact of small changes in chain length will also be evaluated in vitro, using MTT assay to detect cytotoxicity and measuring cellular uptake by using fluorescence microscopy on melanoma cells (MeWo) and human foreskin fibroblasts (HFF). To study the effect of the irradiation wavelength, the cytotoxicity of the compounds will be evaluated using red light (645 nm ; fluence rate 2.0 mW / cm2) and orange light (605 nm ; fluence rate 1.5 mW / cm2).

The aim of this study was to test gamma irradiation in reduction of aflatoxin B1 (AFB1) and ochratoxin A (OTA) toxicity. For this purpose, maize seeds samples contaminated with AFB1 (n=30) and dry-cured meat products contaminated with OTA (n=24) were investigated. Additionally, non-irradiated and gamma irradiated AFB1 and OTA standard solutions were tested for cytotoxicity and analyzed on LC-MS/MS. Gamma irradiation (5 and 10 kGy dose) reduced AFB1 level in maize seed samples for 35.1 to 98.6 %. In dry-cured meat samples gamma irradiation (up to 10 kGy dose) reduced OTA level for 17.70 to 33.66 %. Gamma irradiated AFB1 and OTA were less toxic to cells than non-irradiated mycotoxins, and resulted with reduced AFB1 and OTA level. In conclusion, gamma irradiation reduced AFB1 and OTA level in different commodities and their radiolytic products were less toxic, implying that gamma irradiation can be safely used for decontamination of mycotoxins in various feed and food.

A big part of our cultural heritage (CH) is made from natural materials which are very sensitive to surrounding conditions and thus get easily infected. Disinfection through ionizing radiation has been proven to be very effective, because it is based on electromagnetic radiation from radioactive 60Co, which causes chemical damage of DNA molecules of all biological pollutants, while on the other hand in most cases leaving the materials constituting the object intact. Contrary to all other methods gamma rays are highly penetrating acting on all pests present in the whole volume of a treated object in their whole life cycles ; from spores to grown pests. Among all the advantages of radiation technology it needs to be outlined that it is harmless for humans and damage of the material is minimal, when using optimal conditions. In the process of irradiating a CH object the most important parameter to pay special attention to is the irradiation dose. The used dose depends on the type and degree of contamination, the desired reduction of pests and their radio sensitivity, as well as type of material and its condition. It is necessary to apply the smallest possible dose for deactivation of biological contaminants, which should also be smaller than the dose that would induce any changes in the material or change its appearance. In this work, we investigated the influence of radiation on natural leather which is used for restoring leather book covers using gama rays. With this research, we wanted to investigate the effect ionizing radiation has on natural leather, treated and non-treated. The main objective was to determine can radiation technology be used for preservation of cultural heritage made of leather and in which conditions. Applying radiation to objects made of leather, such as clothing, book covers or furniture is still rare due to insufficient research into the effects of radiation on leather. This work investigates the effect of ionizing radiation on natural leather, unimpregnated and impregnated, in order to determine whether radiation technology can be used for protection and preservation of CH made from leather. Goatskin was used for the investigations with two types of common impregnation agents: Leather preservative and Talas SC600 preservative. The samples were tested by colorimetry and pH measurements, as well as FTIR. In the dose range used on cultural heritage at both investigated dose rates no observable changes were noticed, according to colorimetry, pH or FTIR.

Both chemical and physical methods have been developed for the treatment and restoration of cultural heritage artefacts. However, chemical methods may leave undesirable chemicals, and the conventional physical methods generally use extreme conditions that are not suitable for some types of materials. Gamma irradiation has several advantages compared to conventional preservation methods, mainly related to safety both for the users and environment, efficiency, reliability, capacity, and, as mentioned, processing time. As the radiation technique has many advantages in the conservation treatment of cultural artefacts, the interest in radiation treatment has significantly increased worldwide in recent years. Radiation methods are effectively used in the Radiation Chemistry and Dosimetry Laboratory (RCDL) at the Ruđer Bošković Institute (RBI) in Zagreb, which has a long- lasting experience, especially in the application of irradiation for the preservation of cultural heritage objects.1 Numerous works of art have been successfully irradiated for disinfection purposes, such as wooden sculptures, church altars or their parts, artefacts from various museum collections, books, archival documents, musical instruments, ethnographic objects, archaeological findings and various historical collections. In order to increase the knowledge of the advantages and limitations of nuclear technology for cultural heritage applications, it is important to evaluate possible irreversible physical or chemical modifications induced by ionizing radiation on treated materials. So far, the results obtained have shown that radiation disinfection of cultural heritage can be successfully achieved and safely applied with no significant changes or modifications of the main properties of the constitutive materials of the processed objects. 1. Katušin-Ražem, B., Ražem, D., Braun, M. Irradiation treatment for the protection and conservation of cultural heritage artefacts in Croatia. Radiation Physics and Chemistry 78 (2009), 729-731.

Phthalimide is a versatile chromophore that has been utilized in a number of photochemical reactions, often giving complex molecules in the synthesis of natural products [1]. Among different photochemical processes known for the phthalimide chromophore, [2] it has been demonstrated that phthalimide in the triplet excited state undergoes facile electron transfer (ET) from good electron donors [3]. For example, such a photoinduced ET from carboxylate as an electron donor can initiate decarboxylation reaction, and plethora of different subsequent photochemical processes [4]. We have become interested in photodecarboxylation reactions of phthalimide derivatives and investigated a series of adamantylphthalimides 1-6 with different distance between the electron donor (carboxylate) and the acceptor (phthalimide) [5], as well as in the series of substituted phthalimides 6-11, or tetra- and pentapeptides 12-17 [6]. Herein we present results obtained by nanosecond laser flash photolysis (LFP), which allowed for the detection of the phthalimide triplet excited state and investigation of its reactivity. The results put in question if the triplet excited state detected by LFP is responsible for the observed photoinduced electron transfer reactivity.

Copper is a malleable and ductile metal which is a very good conductor of both heat and electricity. Copper has low chemical reactivity. In moist air it slowly forms a greenish surface film called patina which protects the metal from further attack. Because of its advantages copper has a wide range of applications. To prolong the lifetime of copper made objects its surface is treated by different coatings, which are often not safe for the environment. Due to this reason new protective coatings are being developed for application on copper. Fatty acids are long chain molecules and non- toxic compounds with an affinity for self- assembling on metals. Once self-assembled on its surface the metal becomes hydrophobic. Thus, by blocking access for water to the surface the dissolution of the metal is disabled. If the fatty acid is unsaturated the film can be crosslinked by the use of gamma irradiation. Crosslinking makes the film more durable and stable. The protective efficiency of coatings developed this way depends on the type of fatty acid used, preparation conditions and environment the metal is exposed to. In this work the protective efficiency of coatings prepared from two different unsaturated fatty acids is compared: elaidic and linoelaidic acid. Both compounds are unsaturated trans fatty acids with 18 carbon atoms, where elaidic has one, while linoelaidic acid has two double bonds. The developed coatings were characterized by FTIR and goniometry. Their protective properties were investigated by electrochemical methods (potentiodynamic polarization and electrochemical impedance spectroscopy) in a solution simulating urban atmospheres. The optimal conditions for crosslinking were determined and the properties of the obtained coatings, as well as the properties of the non- crosslinked coatings were compared. The results have shown that both coatings offer good protective properties to copper in atmospheric conditions. For successful crosslinking a larger irradiation dose is needed in the case of linolelaidic acid.

The use of radiation treatment for preservation of cultural heritage has been growing in recent years. Its many advantages compared to classical treatment have attracted attention in many countries. Although the interest in this treatment has grown often conservators and restorers are sceptic towards the effect radiation has on the materials the object is made from. In many cases the object is made of multiple materials and these materials are mostly treated with different coatings or varnishes either to protect the object or to enhance its appearance. The wider use of this technique necessitates a multidisciplinary approach for effectively demonstrating that irradiation does not lead to unacceptable changes in the functional or decorative properties of the artefact as well does not compromise with the authenticity of the artefact. Leather is a common material used on cultural heritage, like books, furniture or clothing. The process for preparing leather is complex itself, and the restorers make the situation even more complicated when they additionally treat leather with preservatives. All these processes can have an impact when it comes to degradation by irradiation. In this work the impact irradiation and its conditions have on goatskin used for bookbinding was investigated. Pure goatskin, as well as goatskin treated by two different preservatives commonly used by book restorers was irradiated with different doses and dose rates. The samples were investigated by colorimetry and FTIR and their pH was monitored in the process. The results have shown that the type of preservative used does play a role when it comes to observing changes in irradiated goatskin, but the observable changes were noticed only at doses greater than the doses that are used for treating cultural heritage.

Human body is a corrosive media, thus implants when exposed to the human body are prone to corrosion. Implementation of fatty acids for protection of metals when exposed to the human body is a convinient method, since fatty acids are nontoxic i biodegradive. Crosslinking of fatty acids into polymer coatings improves their protective properties. This work presents the process of crosslinking the fatty acids on metals, and demonstrates the improved protective properties of the coatings.

Cultural heritage (CH) objects of organic origin are susceptible to degradation due to activity of various biological agents. The gamma irradiation method has already proved to be non-destructive and very effective method in saving CH objects. A CH object should be considered as a complex system with a lot of interfaces. Therefore, in the process of its protection, the interdisciplinary approach is necessary where, besides microbiological analysis, the impact of irradiation on the CH object components must be studied. Depending on radiation sensitivity of fungi 2 - 10 kGy is needed for fungal decontamination but lower dose can ensure satisfactory reduction of bioburden. However, for CH objects consisting of sensitive natural polymers, such as paper, textile and leather, it is crucial to apply the minimal dose which is still effective against biodeteriorating agents but does not affect the physical and chemical properties of the object. In this work the paper was used as the model system. The samples were inoculated with particular fungal species including primary (Aspergillus and Penicillium species), secondary (Cladosporium and Alternaria species) as well as tertiary colonizers (Fusarium species). After the irradiation at the Radiation Chemistry and Dosimetry Laboratory of the Ruđer Bošković Institute, plate count method was applied to determine the number of viable fungi and proper irradiation doses and dose rates that eliminate fungi, respectively. Impact of gamma irradiation on physico-chemical properties of the paper was performed by colorimetry and FTIR. This work will present a systematic overview of the required minimal doses for radiation treatment of the most common and specific microorganisms found on paper as based material of CH artefacts.

Sterilizacija je postupak u kojem se uništavaju svi mikroorganizmi pa i oni najrezistentniji poput bakterijskih spora. Kontrola sterilizacije provodi se fizikalnim, kemijskim i biološkim postupcima. Međutim, kemijski i fizikalni parametri sterilizacije ne pokazuju uspješnost procesa sterilizacije već potvrđuju da je materijal bio podvrgnut sterilizaciji odabranim postupkom. Jedna od najpouzdanijih, najprikladnijih i najjednostavnijih načina kojim se dokazuje učinkovitost sterilizacije je biološka kontrola. Jedna od često korištenih metoda za sterilizaciju različitih materijala i proizvoda poput medicinskog pribora za jednokratnu upotrebu, farmaceutskih sirovina, gotovih proizvoda i ambalaže je gama zračenje. To je efikasna, brza i sigurna metoda za inaktivaciju i eliminaciju svih bioloških kontaminanata u svim životnim ciklusima. U suradnji Nastavnog zavoda za javno zdravstvo Andrija Štampar i Instituta Ruđer Bošković provedeno je istraživanje djelotvornosti ionizirajućeg zračenja u postupku sterilizacije TSA i Sabouraud Dextrose agar Petrijevih zdjelica uz praćenje utjecaja gama zračenja na njihove fizikalno-kemijske parametre i mikrobiološke karakteristike u prisustvu bioloških indikatora koji sadrže spore Bacillus pumilus. Rezultati provedenih ispitivanja su pokazali da je primjena gama zračenja za postizanje sterilnih Petrijevih zdjelica kao gotovog proizvoda učinkovita budući su zahtjevi za sterilnost sukladno smjernicama EU i odgovarajućim europskim normama, u potpunosti zadovoljeni. Biološki indikatori koji su pritom bili upotrijebljeni dokazuju da su vegetativni oblici spora uništeni u procesu sterilizacije.

Poly(lactic acid) (PLA) intrigues many scientists, since it is known as a biodegradable polymer with one of the highest consumption volumes of the world. Due to its specific properties, especially those that make it ecologically acceptable, it has a wide application, from food packaging to medical implants. In this study, we used commercially available 3D printing filaments of PLA. The objective of this study was to investigate what type of structural changes are occurring by exposure of PLA to γ-radiation. The main point of our interest was the observation of radical formation and their stability as a function of time. Various total radiation doses were applied: starting from 25 kGy to 300 kGy. Electron spin resonance (ESR), a powerful tool in monitoring radicals, was used as the principal technique. FTIR spectroscopy was applied to check expected changes in vibrational spectra of the treated samples. ESR spectra measured immediately after the irradiation of PLA samples show a relatively strong signal. The radical concentration depends on the applied irradiation dose, while the spectral lineshape appears to be dose independent. Spectra of irradiated samples were compared to those of unirradiated PLA filaments. The loss of the ESR signal, directly related to the decrease of radical concentration, was monitored as a function of time for all applied radiation doses.. Differences in FTIR spectra of irradiated and unirradiated samples are reported and discussed. Results of spectroscopic measurements were supported by those obtained by other techniques.

The panoramic 60Co source of the Ruđer Bošković Institute (RBI) is the only irradiation facility in Croatia suitable for a variety of applications: from medium range doses used in radiobiology and accident dosimetry to high doses used in radiation research and radiation processing. The operator of the facility, Radiation Chemistry and Dosimetry Laboratory enables an open access to a number of users working in diverse fields, from physics to biology, from arts to engineering, both from within and beyond the Institute. This policy enabled Croatian scientists to accomplish some important results using radiation in various fields in the past. The aim of the present work is to describe the irradiation facility, on account of its dosimetric calibration and details of the radiation field within the irradiation chamber. Dose mapping was performed primarily with an ethanol-chlorobenzene (ECB) dosimetry system containing five characteristic concentrations (4, 10, 20, 25 and 40 vol. % of chlorobenzene in 96 vol. % ethanol) [1, 2]. Several different dosimetry methods, including ionization chamber measurements, were used for precise dosimetric calibration of the source, which makes possible the calculation of dose received by samples of various compositions, sizes and shapes [3, 4]. All doses were expressed as “absorbed dose to water”, obtained from doses absorbed in ECB solutions multiplied with appropriate ratios of mass energy absorption coefficients for water and respective ECB formulations (ISO/ASTM, 2017). In this work we are presenting the results of the dosimetric calibration and examining the nature of dose distribution curves of the RBI cylindrical gamma ray panoramic source geometry. Also, we are presenting the results of the “transit dose” determinations (the dose absorbed during the movement of the source to and from its irradiation position). This dose has to be taken into consideration at doses lower than 10 Gy, i.e. mostly for experiments in radiobiology. References [1] D. Ražem et al., Consistency of ethanol- chlorobenzene dosimetry. Proceedings of IAEA Symposium on High-Dose Dosimetry, 1985, Vienna, 143-156. [2] S. Miljanić et al., Appl. Radiat. Isot., 1993, 44, 711-718. [3] Zs. Horváth et al., Radiochim. Acta 1970, 13, 150-152. [4] I. Dvornik, The ethanol-chlorobenzene dosimeter. In Manual on Radiation Dosimetry, (Eds. N.W. Holm and R.J. Berry) Marcel Dekker, New York, 1970, p.345.

Poly(lactic acid) (PLA) is a biodegradable polymer that has a wide application from food packaging to medical implants [1]. In this study, commercially available 3D printing (2.85 mm) PLA filaments was used to investigate the influence of high energy radiation on structural parameters. Samples were irradiated in a 60Co γ-source at room temperature in the presence of air, using a dose rate of 7, 94 Gy/s. Total irradiation doses were varied from 25 kGy to 300 kGy. Electron spin resonance (ESR), a powerful tool in radical detection, was used as the principal technique. FTIR spectroscopy was applied to investigate structural changes caused by irradiation, while the changes in mechanical behavior were investigated on a testing machine. Changes induced by samples irradiation, observed by ESR and FTIR spectroscopy as well as by mechanical measurements, will be reported and discussed, based on the results found in the literature [2, 3]. [1] L. T. Sin, A. R. Rahmat, W. A. W. A. Rahman (2012). Polylactic Acid: PLA Biopolymer Technology and Applications, Elsevier, Amsterdam, 2012. [2] P. Nugroho, H. Mitomo, F. Yoshii, T. Kume, Polym. Degrad. Stabil. 72 (2001) 337-343. [3] H. Y. Lin, S. Y. Tsai, H. T. Yu, C. P. Lin., J. Polym. Environ. 26 (2018) 122-131.

Metals have biomechanical properties which make them suitable as an implant material. They can be sterilized by the common sterilization procedures which makes them easy to use. Among the used metals stainless steel (SS) is the least corrosion resistant, and it is currently used for temporary implants only. Additional protection is needed to use SS in a larger variety of applications. Formation of a thin protective film on the metals surface is a good and practical way to enhance the metal’s natural protective properties. Fatty acids are non-toxic compounds which have an affinity for adsorbing on metals with one end of their molecules, the carboxyl group. The other end of fatty acids, the methyl group, has hydrophobic properties and when adsorbed on the metal surface it makes the whole surface of the metal appear hydrophobic. Thus by blocking access for water to the surface the dissolution of the metal is disabled. If the fatty acid is unsaturated the film can be polimerized by the use of gamma irradiation. Polimerization would make the film even more durable and stable. This would be a very convinient method of polimerization as implants are commonly sterilized by gamma irradiation and in this case both polimerization and sterilization could be done at the same time. In this work elaidic acid is applied by self- assembling on the surface of SS. This film is polimerized by gamma irradiation. The optimal conditions for the polimerization , as well as the corrosion resistance properties are investigated by electrochemical measurements. SEM is performed to analyse the structure of the metal's surface. FTIR analysis is performed to confirm polimerization occured. Contact angle measurements are performed to investigate the hydrophobic properties of the metal's surface.

One of the largest health issue in modern society is increased frequency of hard tissues chronic diseases. Often the only treatment of such diseases is implementation with the aim to regenerate damaged or diseased tissue. Considering that the main inorganic component of hard tissue is biological apatite, form of calcium phosphate (CaP), composite materials based on calcium phosphate and different inorganic nanomaterials attracts attentions as possible new and innovative implant materials. Among different nanomaterials, TiO2 nanomaterials stand out because they can improve mechanical properties of CaP. Albumine is one of three soluble proteins which adsorbs on the surface of implant materialsright after its implantation and affect their behavior in vivo. But, its role in formation of calcium phosphates on titanium implants is still not clarified. Therefore, the aim of this study is to investigate the adsorption of bovine serum albumin (BSA) on nanocomposites of calcium phosphate (CaP) and TiO2 nanoparticles (CaP/TiNP) or nanotubes (CaP/TiNT). In order to do that, the kinetics of BSA adsorption kinetics of BSA adsorption on TiO2 nanoparticles (TiNP), titanate nanotubes (TiNT), calcium deficient hydoxiapatite (CaDHA) obtained in control system, CaP/TiNP and CaP/TiNT was measured in situ on UV/VIS scanning spectrophotomer. Samples obtained after adsorption were filtered and given for further analysis which included Fourier- transform infrared apectroscopy (FTIR), powder x-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of kinetics measurements were modeled using kinetics models of pseudo-first, pseudo-second rate and interparticle diffusion model. From the results of various kinetic models, the adsorption kinetics were found to follow pseudo-second- order rate kinetic model for CaP/TiNT nanocomposites, respectively pseudo-second- order rate and interparticle diffusion model for CaP/TiNP nanocomposites. Results obtained from FTIR, XRD and SEM analysis showed that albumin did not influence the composition and solid phase morphology

Great amounts of books and different documents are important cultural heritage artifacts, and thus preserving paper based objects is an important mission in the community dealing with cultural heritage. Paper is a versatile material formed from wood pulp or plant fiber and its use goes back to the 2nd century BC. It is a cellulose based material often contaminated by fungi, especially if stored in inadequate conditions, i.e. in moist atmospheres. The use of gamma irradiation for decontamination of cultural heritage is increasing in the past years because of the many advantages of this method compared to the classical treatments for decontamination. Its use on paper based materials is also increasing. It is known that cellulose is degraded by ionizing irradiation, but at which doses and in which conditions is precisely distinguished. In this work we investigated the changes induced by gamma irradiation on paper, and the influence of different irradiation conditions. We investigated different doses commonly used for decontamination of cultural heritage, but also different dose rates and conditions like irradiation of paper in air, pre-autoclaved and pre-vacuumed paper, to determine the influence of such conditions on the irradiation process. The visual changes were investigated by colorimetry, while the changes in the chemical composition were investigated by Fourier-transform infrared spectroscopy. The obtained results have shown that the dose rate under which irradiation is performed makes an important impact on the preservation of paper when it is irradiated in air, i.e. higher dose rates should be applied to preserve the paper. Vacuuming of the paper did not show a difference compared to paper irradiated in air, but decontaminating (autoclaving) did. Namely, the paper that is microbiologically contaminated shows a visual change at lower doses than the non-contaminated paper. These findings are new in literature since most investigations and thus the recommendations for the use of different doses are determined on non-contaminated paper, while our results have shown that these observations are not the same as in real conditions.