4. Poly(NIPAAm) revisited - it has been 28 years since it was first proposed for use as a biomaterial: Original research article: Applications of thermally reversible polymers hydrogels in therapeutics and diagnostics, 1987; thermally reversible hydrogels: II. Delivery and selective removal of substances from aqueous solutions, 1986; a novel approach for preparation of pH-sensitive hydrogels for enteric drug delivery, 1991.