A series of boronated cationic copolymers, composed of different ratios of acrylamide, N-acryloyl-3-aminophenylboronic
acid and N-acryloyl-diaminoethane (the cationic moiety), were prepared with the intention of localizing
boron neutron capture therapy (BNCT) in experimentally induced
polyps on the
luminal side of the gut of the rat. The goals of this study were to: (a) test the effect of cationization of the boronated copolymers on their uptake by
polyps and normal adjacent epithelium; (b) compare the whole rat body distribution of
aminophenylboronic acid (APB) and polymeric APB after local application; (c) measure the effect of micro-environmental parameters such as pH, the presence of
mucin and
cations on the interaction between the APB-copolymers and the epithelium of the rat intestines. Direct analysis of tissue
boron levels showed that polymeric APB-uptake was higher in the
colonic polyps than in the surrounding normal tissues. Free APB, however, was found in similar quantities in both. When tested in the normal jejunum and colon of the rat, polymeric APB uptake was directly proportional to the molar content of the cationic monomer in the copolymers. The presence of
magnesium ions, free
boron cationic monomer and
mucin interfered with this uptake in a concentration-dependent manner. The uptake was pH-independent at pH 5, 7 and 10. APB accumulation in the colon
polyps was inversely proportional to the cationic monomer content in the copolymers, suggesting an increased amount of mucus around the
polyps, which probably impeded the electrostatic attachment of the
polymer to the malignant tissue. The use polymeric APB for targeting BNCT in perioperative treatment of
colorectal carcinoma is suggested, especially in the cases of microscopic residual disease after curative resection.