- Email: [email protected]
Chitosan and radiation chemistry
ARTICLE IN PRESS Radiation Physics and Chemistry 79 (2010) 272–275
Contents lists available at ScienceDirect
Radiation Physics and Chemistry journal homepage: www.elsevier.com/locate/radphyschem
Chitosan and radiation chemistry Andrzej G. Chmielewski n Institute of Nuclear Chemistry and Technology, Warsaw, Poland
a r t i c l e in f o
Keywords: Chitosan Radiation Gamma rays Electron beam Human health care
a b s t r a c t Chitosan as a raw material with special properties has drawn attention of scientists working in the field of radiation processing and natural polymer products development, and also of specialists working in the field of radiation protection and oncologists. Especially the applications concern reduced molecular weight chitosan which still retain its chemical structure; such form of the compound is fostering biological, physical and chemical reactivity of the product. Chitosan degrades into fragments under g-ray or electron beam irradiation. Antibacterial properties of the product are applied in manufacturing hydrogel for wound dressing and additional healing properties can be achieved by incorporating in the hydrogel matrix chitosan bonded silver clusters. Another possible application of chitosan is in reducing radiation damage to the radiation workers or radiation cured patients. In the case of radioisotopes oral or respiratory chitosan-based materials can be applied as chelators. Applications of chitosan in oncology are also reported. & 2009 Elsevier Ltd. All rights reserved.
1. Introduction
2. Chitosan modification by irradiation
Chitin is one of the most abundant natural biopolymer derived from exoskeletons of crustaceans. It can be also obtained from cell walls of fungi which becomes a basis for biotechnological production of this material. Chitosan is a product derived from N-deacetylation of chitin in the presence of hot alkali. The degree of deacetylation and the degree of polymerization (DP), which in turn decides molecular weight of polymer, are two important parameters dictating the use of chitosans in many applications, in pharmaceutical, cosmetics, biomedical, biotechnological, agricultural, food, and non-food industries as well (water treatment, paper, and textile) (Mourya and Inamdar, 2008). Chitosan nanoparticles have shown promise as carriers of anticancer drugs, antitumor genes, and other novel therapeutic agents. In addition, chitosan nanoparticles by themselves appear toxic to various types of malignant cells. The paper reviews research on radiationassisted development of materials based on chitosan and application of chitosan in radiation therapy and as an agent applied for radiological protection of the radiation workers and radiation-treated patients. This paper cover the well-known aspects of applications of radiation degraded chitosan and its derivatives and less known aspects of chitosan application of chitosan in radiooncology and radiological protection.
Commercially available chitosan possesses high molecular weight and low solubility in most solvents and this fact limits its applications. The solubility of chitosan can be improved by diminishing molecular weight (Mao et al., 2004). Low molecular weight chitosan can be prepared by chemical, radiation or enzymatic degradation of high molecular weight polymer (Wasikiewicz et al., 2005). Radiation is one of the most popular tools for modification of polysaccharides. For decreasing the polymerization degree combined chemical-radiation methods can also be used. Chitosan oligomers were obtained through irradiation of chitosan dissolved in acetic acid (Choi et al., 2002). Popular method is also chemical degradation with H2O2 which even in small quantity reduces gradually molecular weight of chitosan (Tian et al., 2004)
n
Corresponding author. E-mail address: [email protected]
0969-806X/$ - see front matter & 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.radphyschem.2009.11.002
2.1. Chitosan degradation by gamma ray irradiation The gamma rays degradation of chitosan was investigated by Choi et al. (2002). Chitosans were irradiated in acetic acid solution with different doses (2–200 kGy) of Co-60 gamma rays to investigate the yields of chitosan oligomers. From the viewpoint of practical utilization of radiation techniques to produce depolymerized chitosan, irradiation with 100 kGy is enough in the use of g-irradiation for degradation of chitosan (Zainol et al., 2009; Gryczka et al., 2009). Comparison of chitosan degradation and sodium alginate by gamma radiation (GD), sonochemical (USD) and ultraviolet (UVD) methods was performed by Wasikiewicz et al. (2005).Studies confirmed that the degradation
ARTICLE IN PRESS A.G. Chmielewski / Radiation Physics and Chemistry 79 (2010) 272–275
proceeds by breakage of glycosidic bonds, but in the case of USD it is governed by mechanical forces, whereas GD and UVD involve radical scission mechanism. The crystallinity of chitosan decreases with degradation, and the crystalline state of watersoluble chitosan is entirely different from that of water-insoluble chitosan.(Kang et al., 2007). 2.2. Chitosan degradation by electron beam irradiation Electron beam chitosan degradation was investigated by Chmielewski et al. (2007). Chitosan of average molecular weight Mw = 710,000 was degraded using radiation and combined chemical-radiation methods. Chitosan powder was irradiated in plastic bags with electron beam within the dose range 20–250 kGy. The MW decreased remarkably with increase in the dose, up to 200 kGy. There was no significant change in molecular weight for higher doses. Using H2O2 in the first stage of degradation can decrease the required dose of radiation and the product with lower crystalline phase content is obtained. 2.3. Chitosan grafting Chitosan has also been found to be a good candidate as a support material for gene delivery, cell culture and tissue engineering. For a breakthrough in utilization, graft copolymerization onto chitosan will be a key point, which will introduce the desired properties and enlarge the field of the potential applications of chitosan by choosing various types of side chains. such as grafting percentage and grafting efficiency, and the properties of grafted chitosan. The graft copolymerized chitosans find its potential applications in the field of drug delivery, tissue engineering, antibacterial, biomedical, metal adsorption and dye removal. Grafting of polystyrene onto chitin and chitosan using 60 Co g-irradiation at room temperature was investigated. The effects of various conditions such as adsorbed dose, solvent and oxygen on grafting were investigated. It was found that the grafting yield increased with increase in the absorbed dose. Others have also reported the radiation grafting of chitosan with N,N-dimethylaminiethylmethacrylate (DMAEMA) (Yilmaz et al., 2007). Studies were reported on graft polymerization of butyl acrylate onto chitosan by using g-irradiation (Yu et al., 2004). In this study, increasing grafting percentage was observed when the monomer concentration and total dose were increased or when the chitosan concentration and reaction temperature were increased. Review of the R&D works is presented by Jayakumara et al. (2005).
3. Medical and health care applications Medicine, human health care and food safety are the most promising applications of chitosan. The foreseen or implemented products cover different fields of man health-related areas from food preservation, through cosmetics to drugs to radiopharmaceuticals manufacturing. 3.1. Health care products Controlled drug release: Graft copolymerization of acrylic acid (AA) and acrylamide (AAm) onto chitosan (CS) was carried out using gamma irradiation. The ability of the prepared copolymer intended to be used as gastric antibiotic delivery system was estimated using amoxicillin trihydrate as a model drug. Release of amoxicillin trihydrate from these investigated hydrogels was studied. For non-ionized drugs, such as amoxicillin trihydrate, the
273
electrostatic polymer/ polymer interactions take place between the cationic groups from CS and the anionic ones from PAA resulting in entrapping of the drug into the mesh space of the hydrogel. The non-ionized amoxicillin release was controlled by the swelling/eroding ratio (Taleb, 2008). With the purpose of obtaining a biocompatible and microbiologically safe matrix that could be simultaneously used as wound dressing material and controlled drug release system, membranes with different thicknesses and different contents in chitosan and hydroxyethyl methacrylate (HEMA) have been prepared by g-irradiation from a 60Co source. The amount of released drug was shown to be dependent on membranes network crosslinking due to composition, radiation and membrane thickness (Casimiro et al., 2007). Diet supplement: The influence of average molecular weight of chitosan in its fat-binding ability in vitro has been studied by using a biopharmaceutical model of the digestive tract. It was found that reduction in molecular weight leads to a significant increase in the amount of fat bound by 1 g of chitosan. Three physical methods of chitosan degradation, irradiation in dry state, irradiation in aqueous solution and sonication in aqueous solution, were tested. Radiation- or sonochemical treatment may be useful in improving fat-binding properties of chitosan as an active component of dietary food additives (CzechowskaBiskup et al., 2005). Artificial models of organs: Synthetic membranes as dermal equivalent can be applied in in vitro studies for developing new transdermal drugs or cosmetics. These membranes could be composed to mimic the dermis and seed cultivated keratinocytes as epidermal layer on it. The endothelial cells in growth to promote neovascularization and fibroblasts in growth to promote the substitution of this scaffold by natural components of the dermis. As, they can mimic the scaffold function of dermis, the membranes with biological interaction could be used for in vivo studies as dermal equivalent. For this application, poly(vinyl alcohol) (PVA) membranes crosslinked by gamma radiation were swelled with chitosan solution. PVA do not interact with the organism when implanted and is intended to mimic the mechanical characteristics of the dermal scaffold. The chitosan as a biocompatible biosynthetic polysaccharide was incorporated into PVA membranes to improve the organism response. Degradation of chitosan by the organism occurs preferably by hydrolysis or enzymatic action, for example, by lysozyme. For this purpose the swelling kinetic of PVA membranes with chitosan solution was performed and their degradation in vitro was verified (Rodas et al., 2005). Wound dressing: With the purpose of obtaining a biocompatible and microbiologically safe matrix that simultaneously could be used as wound dressing material and as a controlled drug release system, membranes with different thickness and different contents in chitosan and hydroxyethyl methacrylate (HEMA) have been prepared by g irradiation from a 60Co source. Antibiotic release experiments were performed before or after irradiation over amoxicillin loaded chitosan/pHEMA membranes in physiological saline solution. Results pointed out a fast amoxicillin release with similar release profile in all the studied membranes. The amount of released drug was shown to be dependent on membranes network crosslinking due composition, radiation and membrane thickness (Casimiro et al., 2007). In other studies, two-layer hydrogels which consisted of polyurethane membrane and a mixture of polyvinyl alcohol (PVA)/poly-N-vinylpyrrolidone(PVP)/glycerin/chitosan were made for a wound dressing. Polyurethane was dissolved in solvent; the polyurethane solution was poured on the mould, and then dried to make a thin membrane. Hydrophilic polymer solutions were poured on the polyurethane membranes. They
ARTICLE IN PRESS 274
A.G. Chmielewski / Radiation Physics and Chemistry 79 (2010) 272–275
were exposed to gamma irradiation or two steps of ‘freezing and thawing’ and gamma irradiation doses to make the hydrogels. The physical properties of hydrogels such as gelation and gel strength were seen to greatly improved when polyurethane membrane was used as a covering layer of hydrogel, and the evaporation speed of water in hydrogel was found to reduce (Park and Nho, 2003). Radiation sterilization: The response of chitosan to ionizing radiation is also important due to the fact that the products containing this polysaccharide are often sterilized with 25 kGy dose. It is well known that chitosan stops bleeding and this knowledge was the basis for development of the chitosan bandage. Each bandage is sealed in foil and sterilized by gamma radiation (Siekman, 2006). Electron beam has been applied for chitosan/soyabean protein isolate membranes for guided bone regeneration. Doses of 25, 50 and 100 kGy have been applied and no substantial changes in physico-chemical properties of the product were observed (Silva et al., 2004)
3.2. Food safety The antioxidant and antibacterial activities of chitosan are applied for food preservation and ensuring food safety. Gamma ray irradiation, especially for 20 kGy, of chitosan gives enough degradation to increase its antioxidant activity as a result of a change in molecular weight. Chitosan was irradiated in acetic acid solution (1%) with different doses (2–20 kGy) of Co-60 g-rays to investigate the enhancement of antioxidant activity of irradiated chitosan. Radical mediated lipid peroxidation inhibition, reducing power, superoxide anion radical and hydroxyl radical quenching assays were used for the evaluation of the antioxidant activity of irradiated chitosan (Feng et al., 2008). Other report concerns the production of irradiated chitosan and its novel use as a natural antioxidant for minimising lipid peroxidation of radiation-processed lamb meat. Antioxidant potential of chitosan isolated from shrimp waste was determined by the betacarotene bleaching assay and 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity. Irradiation of chitosan at 25 kGy dose of gamma radiation resulted in a six-fold increase in its antioxidant activity as compared to the non-irradiated chitosan as measured by DPPH assay. Similarly the reducing power of irradiated chitosan was 6-fold greater than that of autoclaved chitosan. The suitability of irradiated chitosan for controlling lipid oxidation of radiation-processed meat was also investigated. Irradiated chitosan when added to meat before radiation processing was found more effective in minimising lipid perioxidation, than non-irradiated chitosan (Kanatt et al., 2004). Chitosans with low molecular weight affect antioxidant activity in aqueous system and in apple juice. Antioxidant activity was determined, including those of DPPH radicals, hydrogen peroxide and superoxide anion radicals, and also of the metal ion chelating capacity. The preliminary in vitro results suggested that LMWC can increase antioxidant activity in apple juice (Chien et al., 2007). Degradated chitosan has better antibacterial activity in comparison to virgin one and it indicates it can be of use in applications in fruit preservation and its safety control. Chitosans showed higher antibacterial activities than chitosan oligomers and markedly inhibited growth of most bacteria tested although inhibitory effects differed with Mw of chitosan and bacterium. Chitosan generally showed stronger bactericidal effects with gram-positive bacteria than with gramnegative bacteria in the presence of 0.1% chitosan (Noa et al., 2002).
3.3. Applications in radiotherapy Radiation therapy has been used for the cancer treatment externally or internally. As selectivity is lacking, external therapy requires strong radiation dose and it causes dermal irritation and radiation effect of the normal tissues. 3.3.1. Radiopharmaceuticals There is interest in selectively targeting radionuclides to cancer cells in order to destroy them. The possibility to bind a radionuclide to chitosan resides in the chelating capacity of the latter as well as in its capacity to retain metal ions already in the form of complexes. Gadolinium neutron capture therapy (GdNCT) is a cancer therapy that utilizes g-rays emitted during the reaction 157Gd(n, g )158Gd to kill tumor cells. The bioadhesive characteristics of chitosan and its capacity to recognize, to a certain extent, the tumor cells prompted research on the delivery of Gd with the aid of chitosan.166Ho is utilized in medical radiotherapeutic applications due to its properties; emit bradiation and is characterized by 26.4 h half-life time value. The isotope is useful for imaging and can be used without external irradiation of other individuals. In addition, 166Ho has chemical characteristics suitable for labeling with bifunctional chelates. 166 Ho emits low-intensity and low-energy b-rays. MRI was used to demonstrate the effect of radiation synovectomy after the intra-articular injection of 166Ho-chitosan complex for the treatment of rheumatoid arthritis of the knee. The results of clinical studies strongly suggest that 166Ho is retained at the administration site only when it forms a chelate complex with chitosan (Ravi Kumar et al., 2004). Non-clinical and clinical studies of DW166HC, in which chitosan is chelated with 166-Holmium, as an anticancer agent for internal radiation therapy were performed: Reported results indicate strongly that DW166HC can be a highly effective and safe new radiopharmaceutical agent for internal radiation therapy against hepatoma (Ryu et al., 2000).
4. Radiation protection External and internal exposure to radiation concern mostly radiation-treated oncology patients and nuclear industry workers. Recently the international community is much concerned about possible dirty bomb use by terrorist organizations and is looking for possible precautionary measures. The analysis of radiolytic properties of chitosan has shown that this compound by free radical conversion up to the formation of some terminal products of chitosan radiolysis may protect DNA and membrane in irradiated cell (Pilipchatina and Sharpatyı, ˘ 2007). Some chitosan materials can be chemically modified to enhance their affinity to particular radionuclides. By binding to radionuclides, chitosan may suppress deposition in bones and critical organs like the liver and kidney, and accelerate removal from the body. Research is directed toward finding a natural chelator like chitosan that can safely and effectively rid the body of diverse radionuclides such as actinides, cobalt, strontium, and radium (PNNL, 2006)
5. Environmental applications Adsorption of Cr(VI) onto crosslinked chitosan synthesized by gamma irradiation in the presence of carbontetrachloride has been investigated. The adsorption behavior of crosslinked chitosan (CRC) and its hydrolysis product (CRCH) has been compared with native chitosan. The maximum adsorption of Cr(VI) on crosslinked chitosan gels occurs at pH 3. The most important
ARTICLE IN PRESS A.G. Chmielewski / Radiation Physics and Chemistry 79 (2010) 272–275
aspect of using crosslinked chitosan for treating the wastewater containing Cr(VI) is that after the Cr(VI) is loaded; the column can be easily regenerated and efficiently reused (Ramnani and Sabharwal, 2006).
6. Nuclear technology applications Chitosan derivatives can be applied as potential sorbents for uranium preconcentration. A chitosan resin derivatized with serine moiety (serine-type chitosan) was newly developed by using the crosslinked chitosan as a base material. The adsorption behavior of trace amounts of metal ions on the serine-type chitosan resin was systematically examined by packing it in a mini-column, passing a metal solution through it and measuring metal ions in the effluent by ICP-MS. Uranium in tap water could be determined by 10-fold preconcentration: analytical result was 1.46 7 0.02 ppt. The resin also was applied to the recovery of U in sea water: the recovery tests for artificial and natural sea water were 97.1% and 93.0%, respectively (Oshita et al., 2003).
7. Conclusions Radiation degradation, crosslinking and grafting of chitosan are one of the promising methods for byproduct development for medical and environmental applications. On the other hand, chitosan through its degradation mechanism can be applied to protect against radiation effects in living organisms. Most of the research results reported in this paper are from the basic laboratory studies. However, some applications have been already reported. These applications concern human health care and agricultural applications. However, environmental applications are also foreseen. Further optimization of the processes towards product manufacturing cost reduction are necessary. One way can be application of biotechnological processes for chitosan production and hybrid processes for this material degradation for final applications. References Casimiro, M.H., Gil, M.H., Leal, J.P., 2007. Drug release assays from new chitosan/ pHEMA membranes obtained by gamma irradiation. Nucl. Instrum. Methods Phys. Res. Sect. B 265, 406–409. Chien, Po-Jung, Sheu, Fuu, Wan-Ting, Huang, Min-Sheng, Su, 2007. Effect of molecular weight of chitosans on their antioxidative activities in apple juice. Food Chem. 102, 1192–1198. Chmielewski, A.G.,. Migdal, W., Swietoslawski, J., Swietoslawski, J., Jakubaszek, U. Tarnowski, T., 2007, Chemical-radiation degradation of natural oligoaminopolysaccharides for agricultural application. Radiat. Phys. Chem. 76, 18401842. Choi, Won-Seok, Ahn, Kil-Jin, Dong-Wook, Lee, Myung-Woo, Byun, Hyun-Jin, Park, 2002. Preparation of chitosan oligomers by irradiation. Polym. Degrada. Stab. 78, 533–538. Czechowska-Biskup, R., Rokita, B., Ulanski, P., Rosiak, J.M., 2005. Radiation-induced and sonochemical degradation of chitosan as a way to increase its fat-binding capacity. Nucl. Instrum. Methods Phys. Res. Sect. B 236, 383–390.
275
Feng, Tao, Dua, Yumin, Li, Jin, Hu, Ying, Kennedy, J.F., 2008. Enhancement of antioxidant activity of chitosan by irradiation. Carbohydr. Polym. 73, 126–132. Gryczka, U., Dondi, D., Chmielewski, A.G., Migdal, W., Buttafava, A., Faucitano, A., 2009. The mechanism of chitosan degradation by gamma and e-beam irradiation. Radiat. Phys. Chem. 78 (7–8), 543–548. Jayakumara, R., Prabaharana, M., Reisa, R.L., Manoa, J.F., 2005. Graft copolymerized chitosan—present status and applications. Carbohydr. Polym. 62, 142–158. Kanatt, Sweetie R., Chander, Ramesh, Sharma, A., 2004. Effect of irradiated chitosan on the rancidity of radiation-processed lamb meat. Int. J. Food Sci. Technol. 39, 997–1003. Kang, Bin, Dai, Yao-dong, Zhang, Hai-qian, Da, Chen, 2007. Synergetic degradation of chitosan with gamma radiation and hydrogen peroxide. Polym. Degrada. Stab. 92, 359–362. Mao, S., Shuai, X., Unger, F., Simon, M., Bi, D., Kissel., T., 2004. The depolymerization of chitosan: effects on physicochemical and biological properties. Int. J. Pharm. 281, 45–54. Mourya, V.K., Inamdar, Nazma N., 2008. Chitosan-modifications and applications: opportunities galore. React. Funct. Polym. 68, 1013–1051. Noa, Hong Kyoon, Park, Na Young, Lee, Shin Ho, Meyers, S.P., 2002. Antibacterial activity of chitosans and chitosan oligomers with different molecular weights. Int. J. Food Microbiol. 74, 65–72. Oshita, Koji, Oshima, Mitsuko, Gao, Yunhua, Lee, Kyue-Hyung, Motomizu, Shoji, 2003. Synthesis of novel chitosan resin derivatized with serine moiety for the column collection/concentration of uranium and the determination of uranium by ICP-MS. Anal. Chim. Acta 480, 239–249. Pacific Northwest National Laboratory, 2006, September 19. Exoskeletons of Crabs and prawns may help reduce radiation poisoning. Science Daily. Retrieved June 14, 2008, /http://www.sciencedaily.com/releases/2006/09/060915202628. htmS. Park, Kyoung Ran, Nho, Young Chang, 2003. Synthesis of PVA/PVP hydrogels having two-layer by radiation and their physical properties. Radiat. Phys. Chem. 67 (3–4), 361–365. Pilipchatina, O.A., Sharpatyı˘, V.A., 2007. Free-radical mechanism of chitosan radiation degradation and problems of the chemical antiradiation protection. Radiat. Biol. Radioecol. 47 (6), 717. Ramnani, S.P., Sabharwal, S., 2006. Adsorption behavior of Cr(VI) onto radiation crosslinked chitosan and its possible application for the treatment of wastewater containing Cr(VI). React. Funct. Polym. 66 (9), 902–909. Ravi Kumar, M.N.V., Muzzarelli, R.A.A., Muzzarelli, C., Sashiwa, H., Domb, A.J., 2004. Chitosan chemistry and pharmaceutical perspectives. Chem. Rev. 104, 6017– 6084. Rodas, A.C.D., Ohnuki, T., Mathor, M.B., Lugao, A.B., 2005. Irradiated PVAl membrane swelled with chitosan solution as dermal equivalent. Nucl. Instrum. Methods Phys. Res. Sect. B 236, 536–539. Ryu, J.M., Chung, S.H., Oh, Y.H., Yoon, S.J., Lee, J.T., Lee, J.D., Han, K.H., Park, K.,B., Suzuki, Y., Momose, Y., 2000. Development of radiopharmaceutical DW166HC (holmium166-chitosan chelate compound) for anticancer agent. Cancer Detect. Prevent. 24 (Suppl. 1). Siekman, P.,2006. FSB Magazine, September 22. Silva, R.M., Lvira, C., Mano, J.F., Roman, J., San, Reis, R.L., 2004. Influence of b-radiation sterilisation in properties of new chitosan/soyabean protein isolate membranes for guided bone regeneration. J. Mater. Sci.: Mater. Med. 15, 523–5528. Taleb, Manal F.Abou, 2008. Radiation synthesis of polyampholytic and reversible pH responsive hydrogel and its application as drug. Delivery Syst. Polym. Bulletin 61, 341–351. Tian, F., Liu, Y., Hu, K., Zaho, B., 2004. Study on depolymeriztion behaviour of chitosan by hydrogen peroxide. Carbohydr. Polym. 57, 31–37. Wasikiewicz, J.M., Yoshii, F., Nagasawa, N., Wach, R.A., Mitomo, H., 2005. Degradation of chitosan and sodium alginate by gamma radiation, sonochemical and ultraviolet methods. Radiat. Phys. Chem. 73, 287–295. Yilmaz, E., Adali, T., Yilmaz, O., Bengisu, M., 2007. Grafting of poly(triethylene glycol dimethacrylate) onto chitosan by ceric ion initiation. React. Funct. Polym. 67 (1), 10–18. Yu, L., Li, L’Weian, Zh., 2004. A new hybrid nanocomposite prepared by graft copolymerization of butyl acrylate onto chitosan in the presence of organophilic montmorillonite. Radiat. Phys. Chem. 69 (6), 467–471. Zainol, I., Akil, H.Md., Mastor, A., 2009. Effect of g-irradiation on the physical and mechanical properties of chitosan powder. Mat. Sci. & Eng. C 29 (1), 292–297.
Contents lists available at ScienceDirect
Radiation Physics and Chemistry journal homepage: www.elsevier.com/locate/radphyschem
Chitosan and radiation chemistry Andrzej G. Chmielewski n Institute of Nuclear Chemistry and Technology, Warsaw, Poland
a r t i c l e in f o
Keywords: Chitosan Radiation Gamma rays Electron beam Human health care
a b s t r a c t Chitosan as a raw material with special properties has drawn attention of scientists working in the field of radiation processing and natural polymer products development, and also of specialists working in the field of radiation protection and oncologists. Especially the applications concern reduced molecular weight chitosan which still retain its chemical structure; such form of the compound is fostering biological, physical and chemical reactivity of the product. Chitosan degrades into fragments under g-ray or electron beam irradiation. Antibacterial properties of the product are applied in manufacturing hydrogel for wound dressing and additional healing properties can be achieved by incorporating in the hydrogel matrix chitosan bonded silver clusters. Another possible application of chitosan is in reducing radiation damage to the radiation workers or radiation cured patients. In the case of radioisotopes oral or respiratory chitosan-based materials can be applied as chelators. Applications of chitosan in oncology are also reported. & 2009 Elsevier Ltd. All rights reserved.
1. Introduction
2. Chitosan modification by irradiation
Chitin is one of the most abundant natural biopolymer derived from exoskeletons of crustaceans. It can be also obtained from cell walls of fungi which becomes a basis for biotechnological production of this material. Chitosan is a product derived from N-deacetylation of chitin in the presence of hot alkali. The degree of deacetylation and the degree of polymerization (DP), which in turn decides molecular weight of polymer, are two important parameters dictating the use of chitosans in many applications, in pharmaceutical, cosmetics, biomedical, biotechnological, agricultural, food, and non-food industries as well (water treatment, paper, and textile) (Mourya and Inamdar, 2008). Chitosan nanoparticles have shown promise as carriers of anticancer drugs, antitumor genes, and other novel therapeutic agents. In addition, chitosan nanoparticles by themselves appear toxic to various types of malignant cells. The paper reviews research on radiationassisted development of materials based on chitosan and application of chitosan in radiation therapy and as an agent applied for radiological protection of the radiation workers and radiation-treated patients. This paper cover the well-known aspects of applications of radiation degraded chitosan and its derivatives and less known aspects of chitosan application of chitosan in radiooncology and radiological protection.
Commercially available chitosan possesses high molecular weight and low solubility in most solvents and this fact limits its applications. The solubility of chitosan can be improved by diminishing molecular weight (Mao et al., 2004). Low molecular weight chitosan can be prepared by chemical, radiation or enzymatic degradation of high molecular weight polymer (Wasikiewicz et al., 2005). Radiation is one of the most popular tools for modification of polysaccharides. For decreasing the polymerization degree combined chemical-radiation methods can also be used. Chitosan oligomers were obtained through irradiation of chitosan dissolved in acetic acid (Choi et al., 2002). Popular method is also chemical degradation with H2O2 which even in small quantity reduces gradually molecular weight of chitosan (Tian et al., 2004)
n
Corresponding author. E-mail address: [email protected]
0969-806X/$ - see front matter & 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.radphyschem.2009.11.002
2.1. Chitosan degradation by gamma ray irradiation The gamma rays degradation of chitosan was investigated by Choi et al. (2002). Chitosans were irradiated in acetic acid solution with different doses (2–200 kGy) of Co-60 gamma rays to investigate the yields of chitosan oligomers. From the viewpoint of practical utilization of radiation techniques to produce depolymerized chitosan, irradiation with 100 kGy is enough in the use of g-irradiation for degradation of chitosan (Zainol et al., 2009; Gryczka et al., 2009). Comparison of chitosan degradation and sodium alginate by gamma radiation (GD), sonochemical (USD) and ultraviolet (UVD) methods was performed by Wasikiewicz et al. (2005).Studies confirmed that the degradation
ARTICLE IN PRESS A.G. Chmielewski / Radiation Physics and Chemistry 79 (2010) 272–275
proceeds by breakage of glycosidic bonds, but in the case of USD it is governed by mechanical forces, whereas GD and UVD involve radical scission mechanism. The crystallinity of chitosan decreases with degradation, and the crystalline state of watersoluble chitosan is entirely different from that of water-insoluble chitosan.(Kang et al., 2007). 2.2. Chitosan degradation by electron beam irradiation Electron beam chitosan degradation was investigated by Chmielewski et al. (2007). Chitosan of average molecular weight Mw = 710,000 was degraded using radiation and combined chemical-radiation methods. Chitosan powder was irradiated in plastic bags with electron beam within the dose range 20–250 kGy. The MW decreased remarkably with increase in the dose, up to 200 kGy. There was no significant change in molecular weight for higher doses. Using H2O2 in the first stage of degradation can decrease the required dose of radiation and the product with lower crystalline phase content is obtained. 2.3. Chitosan grafting Chitosan has also been found to be a good candidate as a support material for gene delivery, cell culture and tissue engineering. For a breakthrough in utilization, graft copolymerization onto chitosan will be a key point, which will introduce the desired properties and enlarge the field of the potential applications of chitosan by choosing various types of side chains. such as grafting percentage and grafting efficiency, and the properties of grafted chitosan. The graft copolymerized chitosans find its potential applications in the field of drug delivery, tissue engineering, antibacterial, biomedical, metal adsorption and dye removal. Grafting of polystyrene onto chitin and chitosan using 60 Co g-irradiation at room temperature was investigated. The effects of various conditions such as adsorbed dose, solvent and oxygen on grafting were investigated. It was found that the grafting yield increased with increase in the absorbed dose. Others have also reported the radiation grafting of chitosan with N,N-dimethylaminiethylmethacrylate (DMAEMA) (Yilmaz et al., 2007). Studies were reported on graft polymerization of butyl acrylate onto chitosan by using g-irradiation (Yu et al., 2004). In this study, increasing grafting percentage was observed when the monomer concentration and total dose were increased or when the chitosan concentration and reaction temperature were increased. Review of the R&D works is presented by Jayakumara et al. (2005).
3. Medical and health care applications Medicine, human health care and food safety are the most promising applications of chitosan. The foreseen or implemented products cover different fields of man health-related areas from food preservation, through cosmetics to drugs to radiopharmaceuticals manufacturing. 3.1. Health care products Controlled drug release: Graft copolymerization of acrylic acid (AA) and acrylamide (AAm) onto chitosan (CS) was carried out using gamma irradiation. The ability of the prepared copolymer intended to be used as gastric antibiotic delivery system was estimated using amoxicillin trihydrate as a model drug. Release of amoxicillin trihydrate from these investigated hydrogels was studied. For non-ionized drugs, such as amoxicillin trihydrate, the
273
electrostatic polymer/ polymer interactions take place between the cationic groups from CS and the anionic ones from PAA resulting in entrapping of the drug into the mesh space of the hydrogel. The non-ionized amoxicillin release was controlled by the swelling/eroding ratio (Taleb, 2008). With the purpose of obtaining a biocompatible and microbiologically safe matrix that could be simultaneously used as wound dressing material and controlled drug release system, membranes with different thicknesses and different contents in chitosan and hydroxyethyl methacrylate (HEMA) have been prepared by g-irradiation from a 60Co source. The amount of released drug was shown to be dependent on membranes network crosslinking due to composition, radiation and membrane thickness (Casimiro et al., 2007). Diet supplement: The influence of average molecular weight of chitosan in its fat-binding ability in vitro has been studied by using a biopharmaceutical model of the digestive tract. It was found that reduction in molecular weight leads to a significant increase in the amount of fat bound by 1 g of chitosan. Three physical methods of chitosan degradation, irradiation in dry state, irradiation in aqueous solution and sonication in aqueous solution, were tested. Radiation- or sonochemical treatment may be useful in improving fat-binding properties of chitosan as an active component of dietary food additives (CzechowskaBiskup et al., 2005). Artificial models of organs: Synthetic membranes as dermal equivalent can be applied in in vitro studies for developing new transdermal drugs or cosmetics. These membranes could be composed to mimic the dermis and seed cultivated keratinocytes as epidermal layer on it. The endothelial cells in growth to promote neovascularization and fibroblasts in growth to promote the substitution of this scaffold by natural components of the dermis. As, they can mimic the scaffold function of dermis, the membranes with biological interaction could be used for in vivo studies as dermal equivalent. For this application, poly(vinyl alcohol) (PVA) membranes crosslinked by gamma radiation were swelled with chitosan solution. PVA do not interact with the organism when implanted and is intended to mimic the mechanical characteristics of the dermal scaffold. The chitosan as a biocompatible biosynthetic polysaccharide was incorporated into PVA membranes to improve the organism response. Degradation of chitosan by the organism occurs preferably by hydrolysis or enzymatic action, for example, by lysozyme. For this purpose the swelling kinetic of PVA membranes with chitosan solution was performed and their degradation in vitro was verified (Rodas et al., 2005). Wound dressing: With the purpose of obtaining a biocompatible and microbiologically safe matrix that simultaneously could be used as wound dressing material and as a controlled drug release system, membranes with different thickness and different contents in chitosan and hydroxyethyl methacrylate (HEMA) have been prepared by g irradiation from a 60Co source. Antibiotic release experiments were performed before or after irradiation over amoxicillin loaded chitosan/pHEMA membranes in physiological saline solution. Results pointed out a fast amoxicillin release with similar release profile in all the studied membranes. The amount of released drug was shown to be dependent on membranes network crosslinking due composition, radiation and membrane thickness (Casimiro et al., 2007). In other studies, two-layer hydrogels which consisted of polyurethane membrane and a mixture of polyvinyl alcohol (PVA)/poly-N-vinylpyrrolidone(PVP)/glycerin/chitosan were made for a wound dressing. Polyurethane was dissolved in solvent; the polyurethane solution was poured on the mould, and then dried to make a thin membrane. Hydrophilic polymer solutions were poured on the polyurethane membranes. They
ARTICLE IN PRESS 274
A.G. Chmielewski / Radiation Physics and Chemistry 79 (2010) 272–275
were exposed to gamma irradiation or two steps of ‘freezing and thawing’ and gamma irradiation doses to make the hydrogels. The physical properties of hydrogels such as gelation and gel strength were seen to greatly improved when polyurethane membrane was used as a covering layer of hydrogel, and the evaporation speed of water in hydrogel was found to reduce (Park and Nho, 2003). Radiation sterilization: The response of chitosan to ionizing radiation is also important due to the fact that the products containing this polysaccharide are often sterilized with 25 kGy dose. It is well known that chitosan stops bleeding and this knowledge was the basis for development of the chitosan bandage. Each bandage is sealed in foil and sterilized by gamma radiation (Siekman, 2006). Electron beam has been applied for chitosan/soyabean protein isolate membranes for guided bone regeneration. Doses of 25, 50 and 100 kGy have been applied and no substantial changes in physico-chemical properties of the product were observed (Silva et al., 2004)
3.2. Food safety The antioxidant and antibacterial activities of chitosan are applied for food preservation and ensuring food safety. Gamma ray irradiation, especially for 20 kGy, of chitosan gives enough degradation to increase its antioxidant activity as a result of a change in molecular weight. Chitosan was irradiated in acetic acid solution (1%) with different doses (2–20 kGy) of Co-60 g-rays to investigate the enhancement of antioxidant activity of irradiated chitosan. Radical mediated lipid peroxidation inhibition, reducing power, superoxide anion radical and hydroxyl radical quenching assays were used for the evaluation of the antioxidant activity of irradiated chitosan (Feng et al., 2008). Other report concerns the production of irradiated chitosan and its novel use as a natural antioxidant for minimising lipid peroxidation of radiation-processed lamb meat. Antioxidant potential of chitosan isolated from shrimp waste was determined by the betacarotene bleaching assay and 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity. Irradiation of chitosan at 25 kGy dose of gamma radiation resulted in a six-fold increase in its antioxidant activity as compared to the non-irradiated chitosan as measured by DPPH assay. Similarly the reducing power of irradiated chitosan was 6-fold greater than that of autoclaved chitosan. The suitability of irradiated chitosan for controlling lipid oxidation of radiation-processed meat was also investigated. Irradiated chitosan when added to meat before radiation processing was found more effective in minimising lipid perioxidation, than non-irradiated chitosan (Kanatt et al., 2004). Chitosans with low molecular weight affect antioxidant activity in aqueous system and in apple juice. Antioxidant activity was determined, including those of DPPH radicals, hydrogen peroxide and superoxide anion radicals, and also of the metal ion chelating capacity. The preliminary in vitro results suggested that LMWC can increase antioxidant activity in apple juice (Chien et al., 2007). Degradated chitosan has better antibacterial activity in comparison to virgin one and it indicates it can be of use in applications in fruit preservation and its safety control. Chitosans showed higher antibacterial activities than chitosan oligomers and markedly inhibited growth of most bacteria tested although inhibitory effects differed with Mw of chitosan and bacterium. Chitosan generally showed stronger bactericidal effects with gram-positive bacteria than with gramnegative bacteria in the presence of 0.1% chitosan (Noa et al., 2002).
3.3. Applications in radiotherapy Radiation therapy has been used for the cancer treatment externally or internally. As selectivity is lacking, external therapy requires strong radiation dose and it causes dermal irritation and radiation effect of the normal tissues. 3.3.1. Radiopharmaceuticals There is interest in selectively targeting radionuclides to cancer cells in order to destroy them. The possibility to bind a radionuclide to chitosan resides in the chelating capacity of the latter as well as in its capacity to retain metal ions already in the form of complexes. Gadolinium neutron capture therapy (GdNCT) is a cancer therapy that utilizes g-rays emitted during the reaction 157Gd(n, g )158Gd to kill tumor cells. The bioadhesive characteristics of chitosan and its capacity to recognize, to a certain extent, the tumor cells prompted research on the delivery of Gd with the aid of chitosan.166Ho is utilized in medical radiotherapeutic applications due to its properties; emit bradiation and is characterized by 26.4 h half-life time value. The isotope is useful for imaging and can be used without external irradiation of other individuals. In addition, 166Ho has chemical characteristics suitable for labeling with bifunctional chelates. 166 Ho emits low-intensity and low-energy b-rays. MRI was used to demonstrate the effect of radiation synovectomy after the intra-articular injection of 166Ho-chitosan complex for the treatment of rheumatoid arthritis of the knee. The results of clinical studies strongly suggest that 166Ho is retained at the administration site only when it forms a chelate complex with chitosan (Ravi Kumar et al., 2004). Non-clinical and clinical studies of DW166HC, in which chitosan is chelated with 166-Holmium, as an anticancer agent for internal radiation therapy were performed: Reported results indicate strongly that DW166HC can be a highly effective and safe new radiopharmaceutical agent for internal radiation therapy against hepatoma (Ryu et al., 2000).
4. Radiation protection External and internal exposure to radiation concern mostly radiation-treated oncology patients and nuclear industry workers. Recently the international community is much concerned about possible dirty bomb use by terrorist organizations and is looking for possible precautionary measures. The analysis of radiolytic properties of chitosan has shown that this compound by free radical conversion up to the formation of some terminal products of chitosan radiolysis may protect DNA and membrane in irradiated cell (Pilipchatina and Sharpatyı, ˘ 2007). Some chitosan materials can be chemically modified to enhance their affinity to particular radionuclides. By binding to radionuclides, chitosan may suppress deposition in bones and critical organs like the liver and kidney, and accelerate removal from the body. Research is directed toward finding a natural chelator like chitosan that can safely and effectively rid the body of diverse radionuclides such as actinides, cobalt, strontium, and radium (PNNL, 2006)
5. Environmental applications Adsorption of Cr(VI) onto crosslinked chitosan synthesized by gamma irradiation in the presence of carbontetrachloride has been investigated. The adsorption behavior of crosslinked chitosan (CRC) and its hydrolysis product (CRCH) has been compared with native chitosan. The maximum adsorption of Cr(VI) on crosslinked chitosan gels occurs at pH 3. The most important
ARTICLE IN PRESS A.G. Chmielewski / Radiation Physics and Chemistry 79 (2010) 272–275
aspect of using crosslinked chitosan for treating the wastewater containing Cr(VI) is that after the Cr(VI) is loaded; the column can be easily regenerated and efficiently reused (Ramnani and Sabharwal, 2006).
6. Nuclear technology applications Chitosan derivatives can be applied as potential sorbents for uranium preconcentration. A chitosan resin derivatized with serine moiety (serine-type chitosan) was newly developed by using the crosslinked chitosan as a base material. The adsorption behavior of trace amounts of metal ions on the serine-type chitosan resin was systematically examined by packing it in a mini-column, passing a metal solution through it and measuring metal ions in the effluent by ICP-MS. Uranium in tap water could be determined by 10-fold preconcentration: analytical result was 1.46 7 0.02 ppt. The resin also was applied to the recovery of U in sea water: the recovery tests for artificial and natural sea water were 97.1% and 93.0%, respectively (Oshita et al., 2003).
7. Conclusions Radiation degradation, crosslinking and grafting of chitosan are one of the promising methods for byproduct development for medical and environmental applications. On the other hand, chitosan through its degradation mechanism can be applied to protect against radiation effects in living organisms. Most of the research results reported in this paper are from the basic laboratory studies. However, some applications have been already reported. These applications concern human health care and agricultural applications. However, environmental applications are also foreseen. Further optimization of the processes towards product manufacturing cost reduction are necessary. One way can be application of biotechnological processes for chitosan production and hybrid processes for this material degradation for final applications. References Casimiro, M.H., Gil, M.H., Leal, J.P., 2007. Drug release assays from new chitosan/ pHEMA membranes obtained by gamma irradiation. Nucl. Instrum. Methods Phys. Res. Sect. B 265, 406–409. Chien, Po-Jung, Sheu, Fuu, Wan-Ting, Huang, Min-Sheng, Su, 2007. Effect of molecular weight of chitosans on their antioxidative activities in apple juice. Food Chem. 102, 1192–1198. Chmielewski, A.G.,. Migdal, W., Swietoslawski, J., Swietoslawski, J., Jakubaszek, U. Tarnowski, T., 2007, Chemical-radiation degradation of natural oligoaminopolysaccharides for agricultural application. Radiat. Phys. Chem. 76, 18401842. Choi, Won-Seok, Ahn, Kil-Jin, Dong-Wook, Lee, Myung-Woo, Byun, Hyun-Jin, Park, 2002. Preparation of chitosan oligomers by irradiation. Polym. Degrada. Stab. 78, 533–538. Czechowska-Biskup, R., Rokita, B., Ulanski, P., Rosiak, J.M., 2005. Radiation-induced and sonochemical degradation of chitosan as a way to increase its fat-binding capacity. Nucl. Instrum. Methods Phys. Res. Sect. B 236, 383–390.
275
Feng, Tao, Dua, Yumin, Li, Jin, Hu, Ying, Kennedy, J.F., 2008. Enhancement of antioxidant activity of chitosan by irradiation. Carbohydr. Polym. 73, 126–132. Gryczka, U., Dondi, D., Chmielewski, A.G., Migdal, W., Buttafava, A., Faucitano, A., 2009. The mechanism of chitosan degradation by gamma and e-beam irradiation. Radiat. Phys. Chem. 78 (7–8), 543–548. Jayakumara, R., Prabaharana, M., Reisa, R.L., Manoa, J.F., 2005. Graft copolymerized chitosan—present status and applications. Carbohydr. Polym. 62, 142–158. Kanatt, Sweetie R., Chander, Ramesh, Sharma, A., 2004. Effect of irradiated chitosan on the rancidity of radiation-processed lamb meat. Int. J. Food Sci. Technol. 39, 997–1003. Kang, Bin, Dai, Yao-dong, Zhang, Hai-qian, Da, Chen, 2007. Synergetic degradation of chitosan with gamma radiation and hydrogen peroxide. Polym. Degrada. Stab. 92, 359–362. Mao, S., Shuai, X., Unger, F., Simon, M., Bi, D., Kissel., T., 2004. The depolymerization of chitosan: effects on physicochemical and biological properties. Int. J. Pharm. 281, 45–54. Mourya, V.K., Inamdar, Nazma N., 2008. Chitosan-modifications and applications: opportunities galore. React. Funct. Polym. 68, 1013–1051. Noa, Hong Kyoon, Park, Na Young, Lee, Shin Ho, Meyers, S.P., 2002. Antibacterial activity of chitosans and chitosan oligomers with different molecular weights. Int. J. Food Microbiol. 74, 65–72. Oshita, Koji, Oshima, Mitsuko, Gao, Yunhua, Lee, Kyue-Hyung, Motomizu, Shoji, 2003. Synthesis of novel chitosan resin derivatized with serine moiety for the column collection/concentration of uranium and the determination of uranium by ICP-MS. Anal. Chim. Acta 480, 239–249. Pacific Northwest National Laboratory, 2006, September 19. Exoskeletons of Crabs and prawns may help reduce radiation poisoning. Science Daily. Retrieved June 14, 2008, /http://www.sciencedaily.com/releases/2006/09/060915202628. htmS. Park, Kyoung Ran, Nho, Young Chang, 2003. Synthesis of PVA/PVP hydrogels having two-layer by radiation and their physical properties. Radiat. Phys. Chem. 67 (3–4), 361–365. Pilipchatina, O.A., Sharpatyı˘, V.A., 2007. Free-radical mechanism of chitosan radiation degradation and problems of the chemical antiradiation protection. Radiat. Biol. Radioecol. 47 (6), 717. Ramnani, S.P., Sabharwal, S., 2006. Adsorption behavior of Cr(VI) onto radiation crosslinked chitosan and its possible application for the treatment of wastewater containing Cr(VI). React. Funct. Polym. 66 (9), 902–909. Ravi Kumar, M.N.V., Muzzarelli, R.A.A., Muzzarelli, C., Sashiwa, H., Domb, A.J., 2004. Chitosan chemistry and pharmaceutical perspectives. Chem. Rev. 104, 6017– 6084. Rodas, A.C.D., Ohnuki, T., Mathor, M.B., Lugao, A.B., 2005. Irradiated PVAl membrane swelled with chitosan solution as dermal equivalent. Nucl. Instrum. Methods Phys. Res. Sect. B 236, 536–539. Ryu, J.M., Chung, S.H., Oh, Y.H., Yoon, S.J., Lee, J.T., Lee, J.D., Han, K.H., Park, K.,B., Suzuki, Y., Momose, Y., 2000. Development of radiopharmaceutical DW166HC (holmium166-chitosan chelate compound) for anticancer agent. Cancer Detect. Prevent. 24 (Suppl. 1). Siekman, P.,2006. FSB Magazine, September 22. Silva, R.M., Lvira, C., Mano, J.F., Roman, J., San, Reis, R.L., 2004. Influence of b-radiation sterilisation in properties of new chitosan/soyabean protein isolate membranes for guided bone regeneration. J. Mater. Sci.: Mater. Med. 15, 523–5528. Taleb, Manal F.Abou, 2008. Radiation synthesis of polyampholytic and reversible pH responsive hydrogel and its application as drug. Delivery Syst. Polym. Bulletin 61, 341–351. Tian, F., Liu, Y., Hu, K., Zaho, B., 2004. Study on depolymeriztion behaviour of chitosan by hydrogen peroxide. Carbohydr. Polym. 57, 31–37. Wasikiewicz, J.M., Yoshii, F., Nagasawa, N., Wach, R.A., Mitomo, H., 2005. Degradation of chitosan and sodium alginate by gamma radiation, sonochemical and ultraviolet methods. Radiat. Phys. Chem. 73, 287–295. Yilmaz, E., Adali, T., Yilmaz, O., Bengisu, M., 2007. Grafting of poly(triethylene glycol dimethacrylate) onto chitosan by ceric ion initiation. React. Funct. Polym. 67 (1), 10–18. Yu, L., Li, L’Weian, Zh., 2004. A new hybrid nanocomposite prepared by graft copolymerization of butyl acrylate onto chitosan in the presence of organophilic montmorillonite. Radiat. Phys. Chem. 69 (6), 467–471. Zainol, I., Akil, H.Md., Mastor, A., 2009. Effect of g-irradiation on the physical and mechanical properties of chitosan powder. Mat. Sci. & Eng. C 29 (1), 292–297.