Absorption and release of protein from hydroxyapatite-polylactic acid (HA-PLA) membranes

Objectives: The aim of this study was to investigate the kinetics of protein interactions with a novel hydroxyapatite-polylactide (HA-PLA) composite membrane material. Methods: Trilayer PLA and HA-PLA composite membranes reinforced with PLA fibres were used to absorb and release protein which was measured by a BioRad assay. The proteins used were fetal calf serum and bovine serum albumin. PLA and HA-PLA composite films were manufactured to test permeability. Results: Maximal protein absorption was seen within 5 min of treating materials; a nearly 8-fold increase in total absorption was seen with HA-containing composites compared to those without HA. These also exhibited a more gradual and sustained release of protein for periods of up to 96 h, for example at 24 h protein concentrations released were 2.20 +/- 2.80 and 0.49 +/- 5.38 mu g/ml for membranes with and without HA respectively. In addition low pressure and temperature used during production of membranes also allowed greater and more sustained protein release. HA-PLA composite films also showed marked increased permeability compared to plain PLA films, for example after 24 h PLA only films 3.64 +/- 1.01 mu g/ml, PLA film with 25% HA: 44.99 +/- 35.61 mu g/ml, PLA film with 75% HA: 153.12 +/- 65.57 mu g/ml. Conclusions: The results demonstrate that these composite membranes rapidly absorb protein and that the absorbed protein is released slowly for periods of up to 96 h, dependent on constituents of the material and the manufacturing conditions. Incorporation of HA into these membranes was the key factor for improved protein kinetics and membrane permeability. (C) 2009 Elsevier Ltd. All rights reserved.