Incorporation of proteins within alginate fibre-based scaffolds using a post-fabrication entrapment method

In this study, a physical entrapment process was explored for the incorporation of proteins within preformed fibrous alginates and the release profile was tuned by varying the processing parameters. The entrapment process was carried out in a series of aqueous solutions at room temperature and involved pre-swelling of the fibrous alginate within a Na(+)-rich solution, followed by exposure to the protein of choice and entrapping it by re-establishing cross-links of alginate with BaCl2. Entrapment and release of fluorescein isothiocyanate-labelled bovine serum albumin (FITC-BSA), a model protein, was studied. It was found that a sustained release of the incorporated protein in cell culture medium for about 6 days was achieved. The main factors determining the release profile included the NaCl/CaCl2 ratio in the pre-swelling solution, protein concentration, and the exposure time. To retard protein release, alginate fibres with entrapped FITC-BSA were processed together with poly(D, L-lactide) (PDLLA) into porous alginate fibre/PDLLA composites using supercritical CO2. In this manner, release of the protein for up to 3 months was achieved.