Preparation of tricalcium phosphate–calcium alginate composite flat sheet membranes and their application for protein release

Tricalcium phosphate–calcium alginate (TCP–CA) composite flat sheet membranes with the thickness of 150–200 μm were prepared by Ca²⁺ crosslinking of TCP and sodium alginate (SA) aqueous solution. The composite flat sheet membranes were characterized by SEM, FTIR, DSC and BET method. The mechanical properties of the membranes were tested with a tensile testing machine in wet form. Hemoglobin (HB) was immobilized in the following four matrices (1) HB was adsorbed onto the TCP powders directly, (2) HB and SA dissolved together, and then crosslinked by CaCl₂, (3) HB was pre‐adsorbed onto TCP powders, and then mixed with SA aqueous solution, finally crosslinked by CaCl₂, (4) HB and TCP powders were individually dispersed in the SA aqueous solution and then crosslinked by CaCl₂. The release behaviors of the four materials were investigated in phosphate buffer (pH = 6.86), Tris‐HCl solution (pH = 7.4) and NaCl solution (0.9 wt%). SEM observation showed that the TCP particles were well embedded and homogeneously distributed in the alginate matrix. DSC and FTIR indicated that there were additional interactions between the TCP and the polymer. TCP can improve the mechanical properties of CA membranes and the swelling ratio of TCP–CA membrane in NaCl solution decreased with the increase of TCP content. The sustained release behaviors of matrix 3 were shown in PBS, Tris‐HCl and NaCl solutions. POLYM. COMPOS., 36:1899–1906, 2015. © 2014 Society of Plastics Engineers