PREPARATION OF CA-ALGINATE BIOPOLYMER BEADS AND INVESTIGATION OF THEIR DECORPORATION CHARACTERISTICS FOR 85 Sr, 238 U and 234 Th BY IN VITRO EXPERIMENTS Cem Gok 1,2,4, *, Udo Gerstmann 1,5 , Vera Ho ¨ llriegl 1,3 and Sule Aytas 2 1 Helmholtz-Zentrum Mu ¨nchen, German Research Center for Environmental Health, Institute of Radiation Protection, Ingolsta ¨dter Landstr. 1, 85764 Neuherberg, Germany 2 Ege University, Institute of Nuclear Sciences, 35100 Bornova, Izmir, Turkey 3 Department of Medical Radiation Physics and Diagnostics, Helmholtz-Zentrum Mu ¨ nchen, German Research Center for Environmental Health, Ingolsta ¨dter Landstr. 1, 85764 Neuherberg, Germany *Corresponding author: cemgok2005@gmail.com; cemgok@pau.edu.tr. Received September 27 2011, revised May 3 2012, accepted May 3 2012 The aim of this work was to investigatewhether Ca-alginate biopolymer beads (CaABBs) can be used to reduce the bioavail- ability of radionuclides in the gastrointestinal tract of humans. The uptake of strontium, uranium and thorium from a simu- lated gastrointestinal system was studied by in vitro techniques using CaABBs. This agent was prepared from Na-alginate through cross-linking with divalent calcium ions according to the egg-box model. The effects of process variables such as pH of the gastrointestinal juice, incubation time and solid-to-solution ratio for the removal of radionuclides from the gastrointes- tinal juice were investigated. The results suggest that CaABBs are a potent material for reducing the bioavailabilityof radio- nuclides with a high uptake efficiency in the gastrointestinal tract. INTRODUCTION In the case of accidental release of actinides in a nuclear facility or in the environment, internal con- tamination by either acute or chronic exposure has the potential to induce both radiological and chem- ical toxic effects. Incorporation by radioactive mater- ial occurs by three main routes: inhalation, ingestion and wound contamination. All the swallowed radio- active material, whether primarily from contami- nated food and water or secondarily from the respiratory tract, will enter the digestive tract, and will be handled like any other element. The uptake and the retention of a radionuclide are influenced by its portal of entry, chemistry, solubility, metabolism and particle size. Unlike some heavy metals, acti- nides are not known to play an essential role in the normal biochemical reactions occurring in living organisms, including plants, animals and humans. The basic principles of treatment are to reduce ab- sorption and internal deposition of radionuclides and to enhance excretion of absorbed contami- nants (1 – 6) . Persons internally contaminated with radionuclides are generally treated with metal chelat- ing agents for decorporation that bind to the radio- nuclides and are subsequently eliminated (7) . The most common agents used in decorpora- tion studies are diethylenetriaminepentaacetic acid (Ca- or Zn-DTPA) (8, 9) , octadentate hydroxypyridi- nonate (HOPO) (10, 11) , ethylenediaminetetraacetic acid (EDTA) and catecholate (CAM) (12) , prussian blue (13) , thiol chelating agents (14) , calixarenes (15) and phosphonic acids (16) . Chitosan (17) , a natural chelat- ing agent, was also used to reduce the bioavailability of radiostrontium in the gastrointestinal tract. However, these treatments are limited (7) . Hence, there is a need to find new and more effective radio- nuclide decorporation agents that are clinically acceptable. Another alternative, sodium alginate, is known to inhibit the absorption of ingested radiostrontium (18, 19) . However, sodium alginate is difficult to administer because of its high viscosity (17) . On the other hand, application of alginate as gel beads can solve this problem. Alginate and its derivatives can be readily modified chemically and made more suitable for use as decorporation agents for radionuclides. Owing to the simple preparation method, non-toxicity, highly effective and convenient properties that 4 Present address: Pamukkale University, Faculty of Science and Arts, Physics Department, 20070 Kinikli Campus, Denizli, Turkey. 5 Present address: German Federal Office for Radiation Protection, Ingolsta ¨dter Landstr. 1, 85764 Neuherberg, Germany. # The Author 2012. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com Radiation Protection Dosimetry (2013), Vol. 153, No. 1, pp. 47–55 doi:10.1093/rpd/ncs088 Advance Access publication 30 May 2012 by guest on December 27, 2012 http://rpd.oxfordjournals.org/ Downloaded from