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Thermoresponsive polymer micelles are promising drug and radionuclide carriers with a strong passive targeting effect into solid tumors. We have synthesized ABA triblock copolymers poly[2-methyl-2-oxazoline-block-(2-isopropyl-2-oxazoline-co-2-butyl-2-oxazoline)-block-2-methyl-2-oxazoline]. These polymers are molecularly dissolved in aqueous millieu below the cloud point temperature (CPT) of the thermoresponsive central block and above CPT form polymer micelles at CMC 5-10 × 10(-5) g · mL(-1) with diameter ≈200 nm. The phenolic moiety introduced into the copolymer allowed radionuclide labeling with iodine-125 ongoing in good yield with sufficient in vitro stability under model conditions.

We have developed a radiolabeling strategy for synthetic polymers based on the formation of azo dye usable for both covalent and chelating labeling modalities under mild conditions. Poly[N-(2-hydroxypropyl)methacrylamide] and poly(N-isopropyl acrylamide) were used as model polymers. N-methacryloyl tyrosinamide was introduced into the polymers and the phenolic moiety was then reacted with diazotized chelator precursors. The conjugates were radiolabeled with both the covalently bound (iodine-125) and chelated (indium-111) radionuclides in high yields and sufficient in vitro stability of the labels was proven., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

Novel polymer micelles, prepared by self-assembling thermoresponsive poly(N-isopropylacrylamide)-graft-poly[N-(2-hydroxypropyl)methacrylamide] copolymers with hydrolytically degradable N-glycosylamine groups between the polymer blocks are proposed for delivery of diagnostic and therapeutic radionuclides into solid tumors. The micelles are formed by fast heating of an aqueous solution of the copolymer to 37 degrees C. They have a hydrodynamic diameter of 128 nm (measured using dynamic light scattering) and slowly degrade during incubation in aqueous buffer at pH = 7.4. Labeling with both (131)I and (90)Y proceeds with high yields (>85%). The unlabeled polymers are not cytotoxic for any of the tested murine and human cell lines.