A versatile method for the conjugation of proteins and peptides to poly[2-(dimethylamino)ethyl methacrylate]

Random copolymers of 2-(dimethylamino) ethyl methacrylate (DMAEMA) with ami noethyl methacrylate (AEMA) were synthesized by radical polymerization. The amount of incorporated primary amino groups could be controlled by the fee d ratio of AEMA to DMAEMA, and was varied from 2 to 6 mol %. Subsequently, protected thiol groups were introduced in a derivatization step with N-succ inimidyl 3-(2-pyridyldithio)propionate (SPDP) and subsequent treatment with dithiothreitol (DTT). The obtained thiolated p(DMAEMA-co-AEMA) was conjuga ted to transferrin (Tf) or the F(ab') fragment of mAb 323/A3 via a disulfid e linkage. Moreover, the maleimide derivative of the nuclear localization s ignal (NLS) decapeptide Gly-Pro-Lys-Lys-Lys-Arg-Lys-Val-Glu-Asp-NH2 was cou pled to the thiolated polymer via a thioether linkage. The coupling efficie ncy, as determined by GPC (Tf), SDS-PAGE [F(ab')], or H-1 NMR (NLS peptide) was 90-95% for the Tf conjugate, and more than 95% for the F(ab') conjugat e and the NLS conjugate. The synthetic strategy described in this paper is a universal method for the preparation of conjugates of proteins and peptid es with pDMAEMA in particular. This method can possibly be used to synthesi ze protein-polymethacrylate conjugates in general.