Abstract: Derivatives of PSAs are synthesised, in which a reducing and/or non-reducing end terminal sialic acid unit is transformed into a N-hydroxysuccinimide (NHS) group. The derivatives may be reacted with substrates, for instance substrates containing amine or hydrazine groups, to form non-cross-linked/crosslinked polysialylated compounds. The substrates may, for instance, be therapeutically useful drugs, peptides or proteins or drug delivery systems.

Abstract: Polydisperse and charged polysaccharides are fractionated into low polydispersity fractions (preferably having pd <1.1), each containing species within a narrow range of molecular weights. An aqueous solution of the polydisperse polysaccharides is contacted with an ion exchange resin in a column and the polysaccharides are subjected to selective elution by aqueous elution buffer. The selective elution consists of at least 3 sequential elution buffers having different and constant ionic strength and/or pH and in which the subsequent buffers have ionic strength and/or pH than those of the preceding step. The new preparations are particularly suitable for the production of PSA-derivatised therapeutic agents intended for use in humans and animals.

Abstract: An amine or hydrazide derivative of a sialic acid unit, e.g. in a polysaccharide, is reacted with a bifunctional reagent at least one of the functionalities of which is an ester of N-hydroxy succinimide, to form an amide or hydrazide product. The product has a useful functionality, which allows it to be conjugated, for instance to proteins, drugs, drug delivery systems or the like. The process is of particular utility for derivatising amine groups introduced in sialic acid terminal groups of polysialic acids.

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.