Chain-extending poloxamers, thermoreversible hydrogels formed by them which include biological materials, and medicinal applications of same

A thermoreversible hydrogel composition comprising:

• a) a chain-extended poloxamer prepared by reacting at least one poloxamer with a diisocyanate, each of the at least one poloxamers comprising two poly(oxyethylene) blocks and one poly(oxypropylene) block, wherein the molecular weight of the poly(oxypropylene) block is greater than 2350 daltons, and further wherein if one of the at least one poloxamers has a molecular weight of at least 11,000 daltons and a proportion of polyethylene oxide exceeding 60%, at least two different poloxamers are reacted with the diisocyante;
• and
• b) a therapeutically effective amount of an active agent selected from the group consisting of an antibiotic active agent, an antimicrobial active agent, an antifungal active agent, a protein, a glucosaminoglycan, a lysozyme, a natural polyamino acid and a synthetic polyamino acid, and combinations thereof.