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Technetium-Labeled Compounds
Published in Garimella V. S. Rayudu, Lelio G. Colombetti, Radiotracers for Medical Applications, 2019
Suresh C. Srivastava, Powell Richards
The main source of technetium at present is the fission of uranium and it is recovered from the so-called waste products. Separation from the fission products and various actinides is effected by a number of methods — solvent extraction, ion exchange, precipitation, and distillation. Separation from rhenium is an important problem because of the similar chemistry of the two elements. Special methods have been devised to separate technetium from rhenium. Careful consideration must be given to the volatilization losses due to the formation of the heptoxide, Tc2O7, in many procedures. Boiling concentrated acid solutions can lead to vaporization losses of Tc2O7. As a result, initial dissolution of technetium compounds should either be carried out in dilute acids or the system should be capable of trapping the vapors. Alkaline fusion is a better method; either sodium peroxide or sodium carbonate-sodium nitrate mixtures can be employed. Alkaline peroxide is usually very effective in oxidizing and dissolving the sulfides and TcO2. The halides of technetium dissolve in water with decomposition, generally producing a precipitate of TcO2. Alkaline hydrogen peroxide is a good solvent for the halides. The metal is difficultly soluble in this reagent, but dissolves slowly in nitric acid or in dilute sulfuric acid containing cerie ion.
Paper 3 Answers
Published in James Day, Amy Thomson, Tamsin McAllister, Nawal Bahal, Get Through, 2014
James Day, Amy Thomson, Tamsin McAllister, Nawal Bahal
Disinfection is the elimination of most pathogenic agents but excluding bacterial spores: Chemical disinfectants Low level: kill most vegetative bacteria and viruses (e.g. alcohols and sodium hypochlorite (bleach)High level: those that kill spores (e.g. glutaraldehyde, sodium peroxide, chlorine)Pasteurization: hot water >77°C for at least 30 minutes.
Current advances in cell therapeutics: a biomacromolecules application perspective
Published in Expert Opinion on Drug Delivery, 2022
Samson A. Adeyemi, Yahya E. Choonara
To enhance the biological activity of the host, several in-depth experiments evaluated the in vitro [33] and in vivo [34] responses when diverse biomaterials were combined with alginate. For instance, while cell adhesion motifs are absent in native alginate, it is possible to conjugate RGD peptides to enhance cell adhesion [35]. Alginate degrades by alginase which is not produced in mammalians and biodegradation is possible through chemical modification of the polymeric chain. For example, mild oxidation of using sodium peroxide can alter the chemical composition resulting in biodegradation without interfering with gelation [36]. Similarly, studies have shown that gamma irradiation can manipulate the molecular weight distribution of alginate to refine its biodegradation kinetics [37]. In vitro dissolution of alginate hydrogels can also be facilitated by ion exchange in a buffer system. As a non-adhesive, alginate hydrogels can also produce switchable systems in combination with cell adhesive biomacromolecules such as collagen as a self-renewal permissive precursor to encapsulate human pluripotent stem cells[38]. Applications that have advanced from the use of alginate hydrogels as a protective barrier for cell therapeutics include treating brain tumours [39], immune-protection of pancreatic islet cells [4,40], cryopreservation [41] and to treat anaemia [42].