Process for the manufacture of sodium cellulose sulfate which can be used for micro-encapsulation

Method for the production of regio-selective substituted cellulose sulfate (CS) characterized by a combination of the following steps: a) swelling of native cellulose in a polar aprotic solvent; b) addition of a sulfating reagent and an acetylating reagent, for the simultaneous esterification and distribution of acetate groups and suIfate groups along and between the polymer chains; c) directly followed by a complete neutralization with a base, preferably sodium hydroxide, whereby the sulfate without cleaving the acetyl group is transferred into a sodium salt of the cellulose sulfate (SCS), whereby the directly following neutralization also avoids cleavage of acetate groups and consequently the degradation of the cellulose chains; and d) subsequent precipitation, deacetylation, washing and drying of the SCS, whereby the SCS is characterized by a solution viscosity, which is greater than 10 mPas at a concentration of 1% in water. Cellulose sulfate formed by this method is water-soluble and has an adjustable solution viscosity in aqueous solution, which makes it useful as an auxiliary material with ideal biological compatibility for biological and medical applications, in particular it is suitable for the encapsulation and immobilization of biological objects, e.g. tissue, cells, microorganisms, enzymes or viruses in microcapsules.