Physics And Chemistry Basis Of Biotechnology - De Cuyper - tiera.ru

Radioactive microspheres for medical applications
fine dispersion of albumin droplets then forms spherical and stable albumin particles
tightly enclosing the radioactive compounds after heating the mixture above 100 °C.
Microspheres made from or with proteins, such as the above albumin microspheres,
always contain tyrosine and histidine. Their phenol- and imidazole-rings can be easily
iodinated using methods such as the chloramine T, the iodogen, the Bolton-Hunter or
the iodo-bead method, to name just a few. A very good review that describes these
techniques in detail is available from Amersham [43]. Another way of achieving
iodinated microspheres is to radioiodinate the compound that will be incorporated into
the microspheres during their formation. Yang et al. made radioactive PLAmicrospheres
by first labelling the contrast agents ethyliopanoate and ethyldiatrizoate,
which were to be incorporated, with 131 I, dissolving them together with the polymer
PLA in methylene chloride and then preparing the microspheres by a solvent
evaporation method [44].
As with radioactive microspheres, radioactive liposomes can be made by adding
radioactive compounds during their formation. Unilamellar liposomes of 70 nm
diameter have been prepared by mixing the lipid-soluble radioactive complex
oxodichloroethoxy-bis-(triphenylphosphine) 186 rhenium(V) with phospholipids and the
detergent sodium deoxycholate, followed by detergent removal on a small gel filtration
column [45]. Such biocompatible 186 Re-liposomes can be used to deliver therapeutic
radiation doses for radiosynovectomy (see below).
Table 5. Methods of preparing radioactive microspheres in which radiolabelling is done
during formation of the microspheres.
Method of Labelling Examples Ref.
Colloid precipitation 99mTc sulphur colloid [39]
113mIn ferric hydroxide colloids [40]
165Dy-FHMA (~5 µm) [46]
Chromic [47]
Inclusion of radiolabelled
99m
Tc-HSA-gelatin microcapsules [48]
compound
131
I-ethyldiatrizoate-PLA microspheres [44]
125
I-iododeoxyuridine-PLGA microspheres [49]
125
I-HSA magnetic albumin microspheres [50]
32 Phosphate (1-2 µm)
Isotope exchange 211At-microspheres [34]
14 35 3 C-, S- and H-labeling [51]
Lipophilic inclusion
In situ production
186
Re/ 1 88 Re-triphenylphosphine-liposomes [45]
99m
Tc-Buckminster fullerenes (C60 or C80) or [52]
aggregates thereof (Technegas)
Abbreviations: FHMA = ferric hydroxide macroaggregates, HSA = human serum albumin
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