Abstract: Derivatives are synthesised of starting materials, usually polysaccharides, having sialic acid at the reducing terminal end, in which the reducing terminal unit is transformed into an aldehyde group. Where the polysaccharide has a sialic acid unit at the non-reducing end it may be passivated, for instance by converting into hydroxyl-substituted moiety. The derivatives may be reacted with substrates, for instance containing amine or hydrazine groups, to form non-cross-linked polysialylated compounds. The substrates may, for instance, be therapeutically useful drugs peptides or proteins or drug delivery systems.

Abstract: A polysialic acid compound is reacted with a hetero-bifunctional reagent to introduce a pendant functional group for site-specific conjugation to sulfhydryl groups, for instance side chains of cysteine units in drugs, drug delivery systems, proteins or peptides. The functional group is, for instance, an N-maleimide group.

Abstract: The present disclosure concerns biologically active materials, particularly materials that comprise a biodegradeable polymer linked to a biologically active agent. The disclosure further concerns materials known as polymer-drug conjugates that typically contain a therapeutic agent, for instance a bioactive cytotoxic drug linked to a polymer backbone. The linkage typically is a convalent linkage. However, in some embodiments the disclosure concerns other polymer conjugates including those where the biologically active agent is an imaging agent, such as a tyrosinamide, a diagnostic agent, or a targeting agent, such as biotin.