Production, Characterization, and Investigation of Shape Memory Properties of Iron and Boron Doped Hydroxyapatite‐Polycaprolactone Membranes

ABSTRACT

In this study, multifunctional poly(ε‐caprolactone) (PCL)‐based composite membranes incorporating borate (BO ₃ ³⁻ ) and iron (Fe ³⁺ ) co‐doped hydroxyapatite (FeBHA) were developed. FeBHA powders were synthesized via a microwave‐assisted precipitation method, and composite membranes were fabricated using a nonsolvent‐induced phase separation technique with HA loadings of 10, 15, and 30 wt%. Structural analyses showed that B and Fe addition was accompanied by composition‐dependent changes in HA crystallinity and particle morphology, while the HA phase was preserved. Incorporation of HA into the PCL matrix increased membrane hydrophilicity, as reflected by higher water uptake values. Cytotoxicity tests showed that HA‐based powders supported cell adhesion, although excessive iron incorporation led to a concentration‐dependent decrease in cell viability. Among the compositions, PCL/0.05FeBHA (15%) and PCL/0.10FeBHA (15%) exhibited the most balanced physicochemical and biological performance. DSC analysis revealed only minor changes in the melting transition of PCL, with composite membranes exhibiting melting temperatures ( T _m ) between 60.98°C and 62.50°C. Shape‐memory tests confirmed a thermally activated response, with PCL/0.05FeBHA (15%) exhibiting a shape‐fixing ratio of 89.3% ± 1.6% and recovery ratios of 37.5% ± 0.5% and 45.3% ± 1.5% after the first and third cycles, respectively, whereas PCL/0.10FeBHA (15%) reached the highest recovery ratio after three cycles (47.5% ± 2.6%). Direct cytotoxicity studies with Saos‐2 cells revealed that PCL/0.10FeBHA (15%) significantly enhanced cell viability and proliferation compared with pure PCL and other compositions. Osteogenic activity was also improved, as demonstrated by increased alkaline phosphatase activity. Overall, the developed PCL/FeBHA membranes combine enhanced bioactivity, improved cellular response, and shape memory functionality, highlighting their potential as multifunctional biomaterials for bone tissue engineering (BTE).