The present invention relates to a sterile in situ cross-linkable polysaccharide compositions for augmenting, filling or replacing soft tissues in various cosmetic and therapeutic applications. The composition comprises a first polysaccharide derivative functionalized with a nucleophilic group and a second polysaccharide derivative functionalized with an electrophilic group. Said nucleophilic and electrophilic functional groups spontaneously form in situ covalent linkages following co-injection in the body of a patient, resulting in the formation of a cross-linked hydrogel at the site of co-injection.The present invention relates to a sterile in situ cross-linkable polysaccharide compositions for augmenting, filling or replacing soft tissues in various cosmetic and therapeutic applications. The composition comprises a first polysaccharide derivative functionalized with a nucleophilic group and a second polysaccharide derivative functionalized with an electrophilic group. Said nucleophilic and electrophilic functional groups spontaneously form in situ covalent linkages following co-injection in the body of a patient, resulting in the formation of a cross-linked hydrogel at the site of co-injection. The invention relates to the production of preparations for topical application for cosmetic or pharmaceutical products, characterized in that a mixture of 0.1-30% phsphatidylcholine, preferably hydrated, 0.5-50% vegetable oils and/or fats and/or waxes, 10-90% aquatic and/or aqueous plant extracts, 0.1-20% monosaccharides or polysaccharides is mixed and homogenized, preferably at a temperature of 40-90°C, then cooled to 10-40°C, and then bacterial and/or yeast cultures are added.La presente invención se relaciona con composiciones estériles de polisacáridos entrecruzables in situ para acrecentar, rellenar o reemplazar tejidos blandos en diversas aplicaciones cosméticas y terapéuticas. La composición comprende un primer derivado de polisacárido funcionalizado con un grupo n
