COLLAGEN AND HYALURONIC-ACID BASED POLYMERIC BLENDS AS DRUG-DELIVERY SYSTEMS FOR THE RELEASE OF PHYSIOLOGICAL CONCENTRATIONS OF GROWTH-HORMONE

Two synthetic polymers, poly(vinyl alcohol) (PVA) and poly(acrylic aci d) (PAA) were blended, in different ratios, with two biological polyme rs, collagen (C) and hyaluronic acid (HA). These blends were used to p repare two different materials, sponges and hydrogels, which were load ed with growth hormone (GH). The GH released, was monitored in vitro u sing a specific enzyme-linked immunoadsorbent (ELISA) assay. The resul ts show that GH is released in a dose-dependent manner, from HA/PAA sp onges and from HA/PVA and C/PVA hydrogels. The amount of GH released w as proportional to the percentage of the natural polymer (HA and C). T he release of GH from HA/PAA sponges was constant with time, whereas i n HA/PVA hydrogels it was linear for the first 3 days followed by a sl ower release. The GH release pattern in C/PVA hydrogels was different, with a slow release for the first 3 days followed by a more rapid rel ease. The concentrations of GH released from the materials were within a physiological range and sufficient to have a local effect on cellul ar proliferation. The effects of GH were tested in vitro using primary human osteoblast-like cells (HOBS) and measuring cell proliferation a nd alkaline phosphatase (ALP), a biochemical marker of HOB cell differ entiation.